Gis App 6

Gis Gis is a system for capturing, storing, analyzing and managing data and associated attributes which are spatially referenced to the earth. In the strictest sense, it is a computer system capable of integrating, storing, editing, analyzing, sharing, and displaying geographically-referenced information. In a more generic sense, GIS is a tool that allows users to create interactive queries (user created searches), analyze the spatial information, edit data, maps, and present the results of all these operations. Geographic information science is the science underlying the geographic concepts, applications and systems, taught in degree and GIS Certificate programs at many universities Geographic Information System (GIS) is a computer based information system used to digitally represent and analyse the geographic features present on the Earth' surface and the events (non-spatial attributes linked to the geography under study) that taking place on it. The meaning to represent digitally is to convert analog (smooth line) into a digital form. Geographic information system technology can be used for scientific investigations, resource management, asset management, Environmental Impact Assessment, Urban planning, cartography, criminology, history, sales, marketing, and logistics Data representation GIS data represents real world objects (roads, land use, elevation) with digital data. Real world objects can be divided into two abstractions: discrete objects (a house) and continuous fields (rain fall amount or elevation). There are two broad methods used to store data in a GIS for both abstractions: Raster and vector Raster Raster data type consists of rows and columns of cells where in each cell is stored a single value. Raster data are can be images (raster images) with each pixel (or cell) containing a color value. Additional values recorded for each cell may be a discrete value, such as land use, a continuous value, such as rainfall, or a null value if no data is available. While a raster cell stores a single value, it can be extended by using raster bands to represent RGB (red, green, blue) colors, colormaps (a mapping between a thematic code and RGB value), or an extended attribute table with one row for each unique cell value. The resolution of the raster data set is its cell width in ground units Raster data is stored in various formats; from a standard file-based structure of TIF, JPEG, etc. to binary long object (BLOB) data stored directly in a relational database management system (RDBMS) similar to other vector-based feature classes. Database storage, when properly indexed, typically allows for quicker retrieval of the raster data but can require storage of millions of significantly-sized records. Vector

Vector data type uses geometries such as points, lines (series of point coordinates), or polygons, also called areas (shapes bounded by lines), to represent objects. Examples include property boundaries for a housing subdivision represented as polygons and well locations represented as points. Vector features can be made to respect spatial integrity through the application of topology rules such as 'polygons must not overlap'. Vector data can also be used to represent continuously varying phenomena. Contour lines and triangulated irregular networks (TIN) are used to represent elevation or other continuously changing values. TINs record values at point locations, which are connected by lines to form an irregular mesh of triangles. The face of the triangles represent the terrain surface. Advantages and disadvantages There are advantages and disadvantages to using a raster or vector data model to represent reality. Raster data sets record a value for all points in the area covered which may require more storage space than representing data in a vector format that can store data only where needed. Raster data also allows easy implementation of overlay operations, which are more difficult with vector data. Vector data can be displayed as vector graphics used on traditional maps, whereas raster data will appear as an image that may have a blocky appearance for object boundaries. Vector data can be easier to register, scale, and re-project. This can simplify combining vector layers from different sources. Vector data are more compatible with relational database environment. They can be part of a relational table as a normal column and processes using a multitude of operators. Remotely sensed data also plays an important role in data collection and consist of sensors attached to a platform. Sensors include cameras, digital scanners and LIDAR, while platforms usually consist of aircraft and satellites. Raster-to-vector translation Data restructuring can be performed by a GIS to convert data into different formats. For example, a GIS may be used to convert a satellite image map to a vector structure by generating lines around all cells with the same classification, while determining the cell spatial relationships, such as adjacency or inclusion More advanced data processing can occur with image processing, a technique developed in the late 1960s by NASA and the private sector to provide contrast enhancement, false colour rendering and a variety of other techniques including use of two dimensional Fourier transforms. Since digital data are collected and stored in various ways, the two data sources may not be entirely compatible. So a GIS must be able to convert geographic data from one structure to another Projection:

Projection is a fundamental component of map making. A projection is a mathematical means of transferring information from a model of the Earth, which represents a threedimensional curved surface, to a two-dimensional medium—paper or a computer screen. Different projections are used for different types of maps because each projection particularly suits certain uses. For example, a projection that accurately represents the shapes of the continents will distort their relative sizes. See Map projection for more information A map projection is any method used in cartography (mapmaking) to represent the twodimensional curved surface of the earth or other body on a plane. The term "projection" here refers to any function defined on the earth's surface and with values on the plane, and not necessarily a geometric projection. Flat maps could not exist without map projections, because a sphere cannot be laid flat over a plane without distortions. One can see this mathematically as a consequence of Gauss's Theorema Egregium. Flat maps can be more useful than globes in many situations: they are more compact and easier to store; they readily accommodate an enormous range of scales; they are viewed easily on computer displays; they can facilitate measuring properties of the terrain being mapped; they can show larger portions of the earth's surface at once; and they are cheaper to produce and transport. These useful traits of flat maps motivate the development of map projections. The digital elevation model, consisting of surface elevations recorded on a 30-meter horizontal grid, shows high elevations as white and low elevation as black. Need of GIS? Many professionals, such as foresters, urban planners, and geologists, have recognized the importance of spatial dimensions in organising & analysing information. Whether a discipline is concerned with the very practical aspects of business, or is concerned with purely academic research, geographic information system can introduce a perspective, which can provide valuable insights as 1. 70% of the information has geographic location as it's denominator making spatial analysis an essential tool. 2. Ability to assimilate divergent sources of data both spatial and non-spatial (attribute data). 3. Visualization Impact 4. Analytical Capability 5. Sharing of Information Factors Aiding the rise of GIS. 

Revolution in Information Technology. • • •

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Computer Technology. Remote Sensing. Global Positioning System.

Communication Technology.

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Rapidly declining cost of Computer Hardware, and at the same time, exponential growth of operational speed of computers. Enhanced functionality of software and their user-friendliness. Visualizing impact of GIS corroborating the Chinese proverb "a picture is worth a thousand words." Geographical feature and data describing it are part of our everyday lives & most of our everyday decisions are influenced by some facet of Geography

Advantages of GIS The Geographic Information System has been an effective tool for implementation and monitoring of municipal infrastructure. The use of GIS has been in vogue primarily due to the advantage mentioned below:    

Planning of project Make better decisions Visual Analysis Improve Organizational Integration

Planning Of Project Advantage of GIS is often found in detailed planning of project having a large spatial component, where analysis of the problem is a pre requisite at the start of the project. Thematic maps generation is possible on one or more than one base maps, example: the generation of a land use map on the basis of a soil composition, vegetation and topography. The unique combination of certain features facilitates the creation of such thematic maps. With the various modules within GIS it is possible to calculate surface, length, width and distance. Making Decisions The adage "better information leads to better decisions" is as true for GIS as it is for other information systems. A GIS, however, is not an automated decision making system but a tool to query, analyze, and map data in support of the decision making process. GIS technology has been used to assist in tasks such as presenting information at planning inquiries, helping resolve territorial disputes, and siting pylons in such a way as to minimize visual intrusion. Visual Analysis Digital Terrain Modeling (DTM) is an important utility of GIS. Using DTM/3D modeling, landscape can be better visualized, leading to a better understanding of certain relations in the landscape. Many relevant calculations, such as (potential) lakes and water volumes, soil erosion volume (Example: landslides), quantities of earth to be moved (channels, dams, roads, embankments, land leveling) and hydrological modeling becomes easier. Not only in the previously mentioned fields but also in the social sciences GIS can prove extremely useful. Besides the process of formulating scenarios for an Environmental Impact Assessment, GIS can be a valuable tool for sociologists to analyze administrative data such as population distribution, market localization and other related features. Improving Organizational Integration Many organizations that have implemented a GIS have found that one of its main benefits is improved management of their own organization and resources. Because GIS has the ability to link data sets together by geography, it facilitates interdepartmental information sharing and communication. By creating a shared database one department can benefit from the work of another--data can be collected once and used many times. As communication increases among individuals and departments, redundancy is reduced, productivity is enhanced, and overall organizational efficiency is improved. Thus, in a utility

company the customer and infrastructure databases can be integrated so that when there is planned maintenance, affected people can be informed by computer-generated letters.

Components of GIS GIS constitutes of five key components:     

Hardware Software Data People Method

Hardware It consists of the computer system on which the GIS software will run. The choice of hardware system range from 300MHz Personal Computers to Super Computers having capability in Tera FLOPS. The computer forms the backbone of the GIS hardware, which gets it's input through the Scanner or a digitizer board. Scanner converts a picture into a digital image for further processing. The output of scanner can be stored in many formats e.g. TIFF, BMP, JPG etc. A digitizer board is flat board used for vectorisation of a given map objects. Printers and plotters are the most common output devices for a GIS hardware setup. Software GIS software provides the functions and tools needed to store, analyze, and display geographic information. GIS softwares in use are MapInfo, ARC/Info, AutoCAD Map, etc. The software available can be said to be application specific. When the low cost GIS work is to be carried out desktop MapInfo is the suitable option. It is easy to use and supports many GIS feature. If the user intends to carry out extensive analysis on GIS, ARC/Info is the preferred option. For the people using AutoCAD and willing to step into GIS, AutoCAD Map is a good option. Data Geographic data and related tabular data can be collected in-house or purchased from a commercial data provider. The digital map forms the basic data input for GIS. Tabular data related to the map objects can also be attached to the digital data. A GIS will integrate spatial data with other data resources and can even use a DBMS, used by most organization to maintain their data, to manage spatial data. People GIS users range from technical specialists who design and maintain the system to those who use it to help them perform their everyday work. The people who useGIS can be broadly classified into two classes. The CAD/GIS operator, whose work is to vectorise the map objects. The use of this vectorised data to perform query, analysis or any other work is the responsibility of a GIS engineer/user. Method And above all a successful GIS operates according to a well-designed plan and business rules, which are the models and operating practices unique to each organization. There are various techniques used for map creation and further usage for any project. The map creation can either be automated raster to vector creator or it can be manually vectorised using the scanned images. The source of these digital maps can be either map prepared by any survey agency or satellite imagery

GIS Applications Computerized mapping and spatial analysis have been developed simultaneously in several related fields. The present status would not have been achieved without close interaction between various fields such as utility networks, cadastral mapping, topographic mapping, thematic cartography, surveying and photogrammetery remote sensing, image processing, computer science, rural and urban planning, earth science, and geography. The GIS technology is rapidly becoming a standard tool for management of natural resources. The effective use of large spatial data volumes is dependent upon the existence of an efficient geographic handling and processing system to transform this data into usable information. The GIS technology is used to assist decision-makers by indicating various alternatives in development and conservation planning and by modelling the potential outcomes of a series of scenarios. It should be noted that any task begins and ends with the real world. Data are collected about the real world. Of necessity, the product is an abstraction; it is not possible (and not desired) to handle every last detail. After the data are analysed, information is compiled for decision-makers. Based on this information, actions are taken and plans implemented in the real world.

Major areas of application 

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Different streams of planning Urban planning, housing, transportation planning architectural conservation, urban design, landscape. Street Network Based Application It is an addressed matched application, vehicle routing and scheduling: location and site selection and disaster planning. Natural Resource Based Application Management and environmental impact analysis of wild and scenic recreational resources, flood plain, wetlands, acquifers, forests, and wildlife. View Shed Analysis Hazardous or toxic factories siting and ground water modelling. Wild life habitat study and migrational route planning. Land Parcel Based Zoning, sub-division plans review, land acquisition, environment impact analysis, nature quality management and maintenance etc. Facilities Management Can locate underground pipes and cables for maintenance, planning, tracking energy use.

GIS in agriculture GIS is used in a variety of agricultural applications such as managing crop yields, monitoring crop rotation techniques, and projecting soil loss for individual farms or entire agricultural regions. GIS in business A GIS is a tool for managing business information of any kind according to where it's located. You can keep track of where customers are, site businesses, target marketing campaigns, optimize sales territories, and model retail spending patterns. A GIS gives you that extra advantage to make you and your company more competitive and successful.

A GIS enables you to better understand and evaluate your data by creating graphic displays using information stored in your database. With a GIS, you can change the display of your geographic data by changing the symbols, colors, or values in the database tables. GIS in electric/gas utilities Cities and utilities use GIS every day to help them map and inventory systems, track maintenance, monitor regulatory compliance, or model distribution analysis, transformer analysis, and load analysis. GIS in the environment GIS is used every day to help protect the environment. As an environmental professional, you can use GIS to produce maps, inventory species, measure environmental impact, or trace pollutants. The environmental applications for GIS are almost endless. GIS in forestry Today, managing forests is becoming a more complex and demanding challenge. With GIS, foresters can easily see the forest as an ecosystem and manage it responsibly. GIS in geology Geologists use GIS every day in a wide variety of applications. You too can use GIS to study geologic features, analyze soils and strata, assess seismic information, or create 3dimensional displays of geographic features. GIS in hydrology You can use GIS to study drainage systems, assess groundwater, and visualize watersheds, and in many other hydrologic applications. GIS in land use planning People use GIS to help visualize and plan the land use needs of cities, regions, or even national governments. GIS in local government People in local government use GIS every day to help them solve problems. Often the data collected and used by one agency or department can be used by another. GIS in mapping Mapping is an essential function of a GIS. People in a variety of professions are using GIS to help others understand geographic data. You don't have to be a skilled cartographer to make maps with a GIS. GIS in the military Military analysts and cartographers use GIS in a variety of applications such as creating basemaps, assessing terrain, and aiding in tactical decisions. GIS in risk management

A GIS can help with risk management and analysis by showing you which areas will be prone to natural or man-made disasters. Once identified, preventive measures can be developed that deal with the different scenarios. GIS in Site Planning People around the world use GIS to help them locate sites for new facilities or locate alternate sites for existing facilities. GIS in transportation GIS can be used to help you manage transportation infrastructure or help you manage your logistical problems. Whether monitoring rail systems and road conditions or finding the best way to deliver your goods or services, GIS can help you. GIS in the water/wastewater industry People in the water/wastewater industry use GIS with the planning, engineering, operations, maintenance, finance, and administration functions of their water/wastewater networks. Global Positioning System Introduction The Global Positioning System (GPS) is a burgeoning technology, which provides unequalled accuracy and flexibility of positioning for navigation, surveying and GIS data capture. The GPS NAVSTAR (Navigation Satellite timing and Ranging Global Positioning System) is a satellitebased navigation, timing and positioning system. The GPS provides continuous threedimensional positioning 24 hrs a day throughout the world. The technology seems to be beneficiary to the GPS user community in terms of obtaining accurate data upto about100 meters for navigation, metre-level for mapping, and down to millimetre level for geodetic positioning. The GPS technology has tremendous amount of applications in GIS data collection, surveying, and mapping. Geopositioning -- Basic Concepts By positioning we understand the determination of stationary or moving objects. These can be determined as follows: 1. In relation to a well-defined coordinate system, usually by three coordinate values and 2. In relation to other point, taking one point as the origin of a local coordinate system. The first mode of positioning is known as point positioning, the second as relative positioning. If the object to be positioned is stationary, we term it as static positioning. When the object is moving, we call it kinematic positioning. Usually, the static positioning is used in surveying and the kinematic position in navigation. GPS - Components and Basic Facts The GPS uses satellites and computers to compute positions anywhere on earth. The GPS is based on satellite ranging. That means the position on the earth is determined by measuring the distance from a group of satellites in space. The basic principle behind GPS are really simple, even though the system employs some of the most high-tech equipment ever developed. In order to understand GPS basics, the system can be categorised into FIVE logical Steps

1. Triangulation from the satellite is the basis of the system. 2. To triangulate, the GPS measures the distance using the travel time of the radio message. 3. To measure travel time, the GPS need a very accurate clock. 4. Once the distance to a satellite is known, then we need to know where the satellite is in space. 5. As the GPS signal travels through the ionosphere and the earth's atmosphere, the signal is delayed. To compute a positions in three dimensions. We need to have four satellite measurements. The GPS uses a trigonometric approach to calculate the positions, The GPS satellites are so high up that their orbits are very predictable and each of the satellites is equipped with a very accurate atomic clock. Components of a GPS The GPS is divided into three major components   

The Control Segment The Space Segments The User Segment

The Control Segment The Control Segment consists of five monitoring stations (Colorado Springs, Ascesion Island, Diego Garcia, Hawaii, and Kwajalein Island). Three of the stations (Ascension, Diego Garcia, and Kwajalein) serve as uplink installations, capable of transmitting data to the satellites, including new ephemerides (satellite positions as a function of time), clock corrections, and other broadcast message data, while Colorado Springs serves as the master control station. The Control Segment is the sole responsibility of the DoD who undertakes construction, launching, maintenance, and virtually constant performance monitoring of all GPS satellites. The DOD monitoring stations track all GPS signals for use in controlling the satellites and predicting their orbits. Meteorological data also are collected at the monitoring stations, permitting the most accurate evaluation of tropospheric delays of GPS signals. Satellite tracking data from the monitoring stations are transmitted to the master control station for processing. This processing involves the computation of satellite ephemerides and satellite clock corrections. The master station controls orbital corrections, when any satellite strays too far from its assigned position, and necessary repositioning to compensate for unhealthy (not fully functioning) satellites. The Space Segment The Space Segment consists of the Constellation of NAVASTAR earth orbiting satellites. The current Defence Department plan calls for a full constellation of 24 Block II satellites (21 operational and 3 in-orbit spares). The satellites are arrayed in 6 orbital planes, inclined 55 degrees to the equator. They orbit at altitudes of about 12000, miles each, with orbital periods of 12 sidereal hours (i.e., determined by or from the stars), or approximately one half of the earth's periods, approximately 12 hours of 3-D position fixes. The next block of satellites is called Block IIR, and they will provide improved reliability and have a capacity of ranging between satellites, which will increase the orbital accuracy. Each satellite contains four precise atomic clocks (Rubidium and Cesium standards) and has a microprocessor on board for limited self-monitoring and data processing. The satellites are equipped with thrusters which can be used to maintain or modify their orbits. The User Segment The user segment is a total user and supplier community, both civilian and military. The User Segment consists of all earth-based GPS receivers. Receivers vary greatly in size and

complexity, though the basic design is rather simple. The typical receiver is composed of an antenna and preamplifier, radio signal microprocessor, control and display device, data recording unit, and power supply. The GPS receiver decodes the timing signals from the 'visible' satellites (four or more) and, having calculated their distances, computes its own latitude, longitude, elevation, and time. This is a continuous process and generally the position is updated on a second-by-second basis, output to the receiver display device and, if the receiver display device and, if the receiver provides data capture capabilities, stored by the receiver-logging unit. GPS Positioning Types Absolute Positioning The mode of positioning relies upon a single receiver station. It is also referred to as 'stand-alone' GPS, because, unlike differential positioning, ranging is carried out strictly between the satellite and the receiver station, not on a ground-based reference station that assists with the computation of error corrections. As a result, the positions derived in absolute mode are subject to the unmitigated errors inherent in satellite positioning. Overall accuracy of absolute positioning is considered to be no greater than 50 meters at best by Ackroyd and Lorimer and to be + 100 meter accuracy by the U.S. Army Corps of Engineers. Differential Positioning Relative or Differential GPS carries the triangulation principles one step further, with a second receiver at a known reference point. To further facilitate determination of a point's position, relative to the known earth surface point, this configuration demands collection of an errorcorrecting message from the reference receiver. Differential-mode positioning relies upon an established control point. The reference station is placed on the control point, a triangulated position, the control point coordinate. This allows for a correction factor to be calculated and applied to other roving GPS units used in the same area and in the same time series. Inaccuracies in the control point's coordinate are directly additive to errors inherent in the satellite positioning process. Error corrections derived by the reference station vary rapidly, as the factors propagating position errors are not static over time. This error correction allows for a considerable amount of error of error to be negated, potentially as much as 90 percent

GPS setu Factors that affect GPS There are a number of potential error sources that affect either the GPS signal directly or your ability to produce optimal results: 

Number of satellites - minimum number required: You must track atleast four common satellites - the same four satellites - at both the reference receiver and rover for either DGPS or RTK solutions. Also to achieve centimeter -level accuracy, remember you must have a fifth satellite for on-the fly RTK initialization. This extra satellite adds a check on the internal calculation. Any additional satellites beyond five provide even more checks, which is always useful.

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Multipath - reflection of GPS signals near the antennae: Multipath is simply reflection of signals similar to the phenomenon of ghosting on our television screen. GPS signals may be reflected by surfaces near the antennae, causing error in the travel time and therefore error in the GPS positions.

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Ionosphere - change in the travel time of the signal: Before GPS signals reach your antenna on the earth, they pass through a zone of charged particles called the ionosphere, which changes the speed of the signal. If your reference and rover receivers are relatively close together, the effect of ionosphere tends to be minimal. And if you are working with the lower range of GPS precisions, the ionosphere is not a major consideration. However if your rover is working too far from the reference station, you may experience problems, particularly with initializing your RTK fixed solution.

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Troposphere - change in the travel time of the signal: Troposphere is essentially the weather zone of our atmosphere, and droplets of water

vapour in it can effect the speed of the signals. The vertical component of your GPS answer (your elevation) is particularly sensitive to the troposphere. 

Satellite Geometry - general distribution of the satellites: Satellite Geometry - or the distribution of satellites in the sky - effects the computation of your position. This is often referred to as Position Dilution of Precision (PDOP). PDOP is expressed as a number, where lower numbers are preferable to higher numbers. The best results are obtained when PDOP is less than about 7. PDOP is determined by your geographic location, the time of day you are working, and any site obstruction, which might block satellites. You can use planning software to help you determine when you'll have the most satellites in a particular area. When satellites are spread out, PDOP is Low (good). When satellites are closer together, PDOP is High (weak).

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Satellite Health - Availability of Signal: While the satellite system is robust and dependable, it is possible for the satellites to occassionally be unhealthy. A satellite broadcasts its health status, based on information from the U.S. Department of Defense. Your receivers have safeguards to protect against using data from unhealthy satellites.

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Signal Strength - Quality of Signal : The strength of the satellite signal depends on obstructions and the elevation of the satellites above the horizon. To the extent it is possible, obstructions between your GPS antennae and the sky should be avoided. Also watch out for satellites which are close to the horizon, because the signals are weaker.

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Distance from the Reference Receiver : The effective range of a rover from a reference station depends primarily on the type of accuracy you aere trying to achieve. For the highest real time accuracy (RTK fixed), roveres should be within about 10-15 Km (about 6-9 miles) of the reference station. As the range exceeds this recommended limit, you may failto initialize and be restricted to RTK float solutions (decimeter accuracy).

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Radio Frequency (RF) Interference: RF interference may sometimes be a problem both for your GPS reception and your radio system. Some sources of RF interference include: •

Radio towers

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Transmitters

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Satellite dishes

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Generators

One should be particularly careful of sources which transmit either near the GPS frequencies (1227 and 1575 MHz) or near harmonics (multiples) of these frequencies. One should also be aware of the RF generated by his own machines.

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Loss of Radio Transmission from Base: If, for any reason, there is an interruption in the radio link between a reference receiver and a rover, then your rover is left with an autonomous position. It is very important to set up a network of radios and repeaters, which can provide the uninterrupted radio link needed for the best GPS results.

Reference Station Equipment:   

GPS receiver GPS antenna Radio and antenna, Power supply, & Cables

Radios We have seen that each GPS rover must receive information from the reference station to achieve accurate positions. To maintain constant communication between your reference station and rover, you need these items at the reference station and at each rover:   

Radio Radio Antenna Cables

The radios are cabled directly into the GPS receiver. Power may be provided to the radio through the GPS receiver. At the reference site, GPS data is broadcast through the radio. At the rover site, the reference GPS data is received by the radio and routed into the rover receiver, where it is processed together with rover's GPS data/ The rover radio can also draw power from the GPS receiver. Repeater Radios: If, for any reason, the reference station transmission cannot reach your rovers, then you must use one or more repeaters. A repeater relays the data from your reference or another repeater. The maximum number of repeaters you can use depends on your type of radio. Repeaters differ from your reference and rover radios in two important ways: they must have their own source of power, and they can be moved as the needs change. The radios draw very low power, but they require uninterrupted power. Because repeaters may need to be moved to accommodate your needs, batteries or compact solar power units are normally used. Frequency and Bandwidth: Most radios used in GPS fall within one of the following frequency ranges:   

150-174 MHz (VHF) 406-512 MHz (UHF) 902-928 MHz (spread spectrum)

The lower-frequency radios (150-174 MHZ) tend to have more power, due to design and legal issues (not Physics), However, the bandwidth, which determines the amount of data you can transmit, is narrower in these lower ranges (also due to design, not physics). In the nominal 450 MHz and 900 MHz ranges, the bandwidth is wider. This has positive effects both on the amount of data transmitted and on the number of repeaters possible within the radio network. Radio Range To guarantee steady, uninterrupted transmission over the radio, one should be aware of some of the factors that affect the radio's effective range.

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Antenna Height: raising the radio antenna is the easiest and most effective way to increase range. Antenna design: radiating patterns vary, depending on the antenna design. For best performance, be sure you understand how yoour antenna transmits signals. Cable length and type: radio signals suffer loss in cables, so keep the length to a minimum. If you must use long cables, use low-loss cables. Output power: doubling output power does not double your effective range. Be sure one understands the relationship between power and gain before the best system is decided. Obstructions: Buildings, walls and even the machines can block or interrupt radio transmission. The repeaters should be carefully used to help minimize the effect of obstructions.

Grounding The radio antenna may be a target for lightning. To avoid damage, you may wish to ground your reference station antenna. GPS Applications One of the most significant and unique features of the Global Positioning Systems is the fact that the positioning signal is available to users in any position worldwide at any time. With a fully operational GPS system, it can be generated to a large community of likely to grow as there are multiple applications, ranging from surveying, mapping, and navigation to GIS data capture. The GPS will soon be a part of the overall utility of technology. There are countless GPs applications, a few important ones are covered in the following passage. Surveying and Mapping The high precision of GPS carrier phase measurements, together with appropriate adjustment algorithms, provide an adequate tool for a variety of tasks for surveying and mapping. Using DGPs methods, accurate and timely mapping of almost anything can be carried out. The GPS is used to map cut blocks, road alignments, and environmental hazards such as landslides, forest fires, and oil spills. Applications, such as cadastral mapping, needing a high degree of accuracy also can be carried out using high grade GPS receivers. Continuous kinematic techniques can be used for topographic surveys and accurate linear mapping. Navigation Navigation using GPS can save countless hours in the field. Any feature, even if it is under water, can be located up to one hundred meters simply by scaling coordinates from a map, entering waypoints, and going directly to the site. Examples include road intersections, corner posts, plot canters, accident sites, geological formations, and so on. GPS navigation in helicopters, in vehicles, or in a ship can provide an easy means of navigation with substantial savings. Remote Sensing and GIS It is also possible to integrate GPS positioning into remote-sensing methods such as photogrammetry and aerial scanning, magnetometry, and video technology. Using DGPS or kinematic techniques, depending upon the accuracy required, real time or post-processing will provide positions for the sensor which can be projected to the ground, instead of having ground control projected to an image. GPS are becoming very effective tools for GIS data capture. The GIS user community benefits from the use of GPS for locational data capture in various GIS applications. The GPS can easily be linked to a laptop computer in the field, and, with appropriate software, users can also have all their data on a common base with every little distortion. Thus GPS can help in several aspects of construction of accurate and timely GIS databases. Geodesy Geodetic mapping and other control surveys can be carried out effectively using high-grade GPs

equipment. Especially when helicopters were used or when the line of sight is not possible, GPS can set new standards of accuracy and productivity. Military The GPS was primarily developed for real time military positioning. Military applications include airborne, marine, and land navigation. Future of GPS Technology Barring significant new complications due to S/A (Selective Availability) from DOD, the GPS industry is likely to continue to develop in the civilian community. There are currently more than 50 manufacturers of GPs receivers, with the trend continuing to be towards smaller, less expensive, and more easily operated devices. While highly accurate, portable (hand-held) receivers are already available, current speculation envisions inexpensive and equally accurate 'wristwatch locators' and navigational guidance systems for automobiles. However, there is one future trend that will be very relevant to the GIS user community, namely, community base stations and regional receive networks, as GPS management and technological innovations that will make GPS surveying easier and more accurate.

www.gps.gov/

GPS The Global Positioning System (GPS) is a U.S. space-based radionavigation system that provides reliable positioning, navigation, and timing services to civilian users on a continuous worldwide basis -- freely available to all. For anyone with a GPS receiver, the system will provide location and time. GPS provides accurate location and time information for an unlimited number of people in all weather, day and night, anywhere in the world The GPS is made up of three parts: satellites orbiting the Earth; control and monitoring stations on Earth; and the GPS receivers owned by users. GPS satellites broadcast signals from space that are picked up and identified by GPS receivers. Each GPS receiver then provides three-dimensional location (latitude, longitude, and altitude) plus the time. Individuals may purchase GPS handsets that are readily available through commercial retailers. Equipped with these GPS receivers, users can accurately locate where they are and easily navigate to where they want to go, whether walking, driving, flying, or boating. GPS has become a mainstay of transportation systems worldwide, providing navigation for aviation, ground, and maritime operations. Disaster relief and emergency services depend upon GPS for location and timing capabilities in their life-saving missions. Everyday activities such as banking, mobile phone operations, and even the control of power grids, are facilitated by the accurate timing provided by GPS. Farmers, surveyors, geologists and countless others perform their work more efficiently, safely, economically, and accurately using the free and open GPS signals. What is GPS?

The Global Positioning System (GPS) is a U.S.-owned utility that provides users with positioning, navigation, and timing (PNT) services. This system consists of three segments: the space segment, the control segment, and the user segment. The U.S. Air Force develops, maintains, and operates the space and control segments. The space segment consists of a nominal constellation of 24 operating satellites that transmit one-way signals that give the current GPS satellite position and time. The control segment consists of worldwide monitor and control stations that maintain the satellites in their proper orbits through occasional command maneuvers, and adjust the satellite clocks. It tracks the GPS satellites, uploads updated navigational data, and maintains health and status of the satellite constellation. The user segment consists of the GPS receiver equipment, which receives the signals from the GPS satellites and uses the transmitted information to calculate the user’s three-dimensional position and time. GPS Services GPS satellites provide service to civilian and military users. The civilian service is freely available to all users on a continuous, worldwide basis. The military service is available to U.S. and allied armed forces as well as approved Government agencies A variety of GPS augmentation systems and techniques are available to enhance system performance to meet specific user requirements. These improve signal availability, accuracy, and integrity, allowing even better performance than is possible using the basic GPS civilian service The outstanding performance of GPS over many years has earned the confidence of millions of civil users worldwide. It has proven its dependability in the past and promises to be of benefit to users, throughout the world, far into the future The Future of GPS The United States is committed to an extensive modernization program, including the implementation of a second and a third civil signal on GPS satellites. The second civil signal will improve the accuracy of the civilian service and supports some safety-of-life applications. The third signal will further enhance civilian capability and is primarily designed for safety-of-life applications, such as aviation.

Positioning, Navigation, and Timing Policy U.S. law and policy on GPS emphasize continuity of service, open access to civil signals, and technological leadership. In 1996, the United States issued a national policy statement on the management and use of space-based positioning, navigation and timing services, which include GPS and augmentations. It underscored the dual use (civilian-military) nature of GPS and established a joint civil-military national management structure to oversee its operation U.S. policy was expanded in 2004 in response to changing international conditions and the incredible growth in the types and complexities of GPS applications. This policy reaffirms the United States commitment to provide reliable civil space-based positioning, navigation, and timing services through GPS on a continuous, worldwide basis -- freely available to all. The policy also calls for improving the performance of GPS and cooperating with other nations. GPS Augmentations To meet the specific user requirements for positioning, navigation, and timing (PNT), a number of augmentations to the Global Positioning System (GPS) are available. An augmentation is any system that aids GPS by providing accuracy, integrity, reliability, availability, or any other improvement to positioning, navigation, and timing that is not inherently part of GPS itself. Such augmentations include, but are not limited to: Nationwide Differential GPS System (NDGPS): The NDGPS is a groundbased augmentation system operated and maintained by the Federal Railroad Administration, U.S. Coast Guard, and Federal Highway Administration, that provides increased accuracy and integrity of the GPS to users on land and water. Modernization efforts include the High Accuracy NDGPS (HA-NDGPS) system, currently under development, to enhance the performance and provide 10 to 15 centimeter accuracy throughout the coverage area. NDGPS is built to international standards, and over 50 countries around the world have implemented similar systems Wide Area Augmentation System (WAAS): The WAAS, a satellite-based augmentation system operated by the U.S. Federal Aviation Administration (FAA), provides aircraft navigation for all phases of flight. Today, these capabilities are broadly used in other applications because their GPS-like signals can be processed by simple receivers without additional equipment. Using International Civil Aviation Organization (ICAO) standards, the FAA continues to work with other States to provide seamless services to all users in any region. Other ICAO standard space-based augmentation systems include: Europe's European Geostationary Navigation Overlay System (EGNOS), India's GPS and Geo-Augmented Navigation System (GAGAN), and Japan's Multifunction Transport Satellite (MTSAT) Satellite Augmentation System (MSAS). All of these

international implementations are based on GPS. The FAA will improve the WAAS to take advantage of the future GPS safety-of-life signal and provide better performance and promote global adoption of these new capabilities Continuously Operating Reference Station (CORS): The U.S. CORS network, which is managed by the National Oceanic & Atmospheric Administration, archives and distributes GPS data for precision positioning and atmospheric modeling applications mainly through post-processing. CORS is being modernized to support real-time users Global Differential GPS (GDGPS): GDGPS is a high accuracy GPS augmentation system, developed by the Jet Propulsion Laboratory (JPL) to support the real-time positioning, timing, and orbit determination requirements of the U.S. National Aeronautics and Space Administration (NASA) science missions. Future NASA plans include using the Tracking and Data Relay Satellite System (TDRSS) to disseminate via satellite a real-time differential correction message. This system is referred to as the TDRSS Augmentation Service Satellites (TASS) International GNSS Service (IGS): IGS is a network of over 350 GPS monitoring stations from 200 contributing organizations in 80 countries. Its mission is to provide the highest quality data and products as the standard for Global Navigation Satellite Systems (GNSS) in support of Earth science research, multidisciplinary applications, and education, as well as to facilitate other applications benefiting society. Approximately 100 IGS stations transmit their tracking data within one hour of collection There are other augmentation systems available worldwide, both government and commercial. These systems use differential, static, or real-time techniques U.S. Policy on International Cooperation The U.S. Space-Based Positioning, Navigation, and Timing Policy underscores the importance that all global navigation satellite systems and their augmentations be compatible with GPS The agreement in 2004 between the United States and the European Union (E.U.) on GPS and Galileo recognized the benefits of interoperable systems. The parties agreed to pursue a common, open, civil signal on both Galileo and future GPS satellites, in addition to ongoing cooperation on the GPS-based EGNOS augmentation system. The United States has a long cooperative relationship with Japan on GPS. In addition to the Multifunction Transport Satellite (MTSAT) Satellite Augmentation System (MSAS), the parties are working towards developing a GPS-compatible regional satellite "mini-" constellation known as the Quasi Zenith Satellite System (QZSS).

The United States is also consulting closely with India on its development of its GAGAN space-based augmentation system, and with the Russian Federation on compatibility and interoperability between GPS and Russia's satellite navigation system, GLONASS. The U.S. Department of Defense also cooperates with numerous countries to ensure that GPS provides military space-based PNT service and interoperable user equipment to its coalition partners around the world. Space-based PNT services must serve global users with transparent interfaces and standards. The U.S. policy is to provide space-based PNT services on a continuous worldwide basis, freely available to all for civil, commercial, and scientific uses, and provide open, free access, to information necessary to develop and build equipment to use these services Applications Timing In addition to longitude, latitude, and altitude, the Global Positioning System (GPS) provides a critical fourth dimension – time. Each GPS satellite contains multiple atomic clocks that contribute very precise time data to the GPS signals. GPS receivers decode these signals, effectively synchronizing each receiver to the atomic clocks. This enables users to determine the time to within 100 billionths of a second, without the cost of owning and operating atomic clocks Precise time is crucial to a variety of economic activities around the world. Communication systems, electrical power grids, and financial networks all rely on precision timing for synchronization and operational efficiency. The free availability of GPS time has enabled cost savings for companies that depend on precise time and has led to significant advances in capability For example, wireless telephone and data networks use GPS time to keep all of their base stations in perfect synchronization. This allows mobile handsets to share limited radio spectrum more efficiently. Similarly, digital broadcast radio services use GPS time to ensure that the bits from all radio stations arrive at receivers in lockstep. This allows listeners to tune between stations with a minimum of delay Companies worldwide use GPS to time-stamp business transactions, providing a consistent and accurate way to maintain records and ensure their traceability. Major investment banks use GPS to synchronize their network computers located around the world. Large and small businesses are turning to automated systems that can track, update, and manage multiple transactions made by a global network of customers, and these require accurate timing information available through GPS

The U.S. Federal Aviation Administration (FAA) uses GPS to synchronize reporting of hazardous weather from its 45 Terminal Doppler Weather Radars located throughout the United States Instrumentation is another application that requires precise timing. Distributed networks of instruments that must work together to precisely measure common events require timing sources that can guarantee accuracy at several points. GPSbased timing works exceptionally well for any application in which precise timing is required by devices that are dispersed over wide geographic areas. For example, integration of GPS time into seismic monitoring networks enables researchers to quickly locate the epicenters of earthquakes and other seismic events Power companies and utilities have fundamental requirements for time and frequency to enable efficient power transmission and distribution. Repeated power blackouts have demonstrated to power companies the need for improved time synchronization throughout the power grid. Analyses of these blackouts have led many companies to place GPS-based time synchronization devices in power plants and substations. By analyzing the precise timing of an electrical anomaly as it propagates through a grid, engineers can trace back the exact location of a power line break Some users, such as national laboratories, require the time at a higher level of precision than GPS provides. These users routinely use GPS satellites not for direct time acquisition, but for communication of high-precision time over long distances. By simultaneously receiving the same GPS signal in two places and comparing the results, the atomic clock time at one location can be communicated to the other. National laboratories around the world use this "common view" technique to compare their time scales and establish Coordinated Universal Time (UTC). They use the same technique to disseminate their time scales to their own nations New applications of GPS timing technology appear every day. Hollywood studios are incorporating GPS in their movie slates, allowing for unparalleled control of audio and video data, as well as multi-camera sequencing. The ultimate applications for GPS, like the time it measures, are limitless As GPS becomes modernized, further benefits await users. The addition of the second and third civilian GPS signals will increase the accuracy and reliability of GPS time, which will remain free and available to the entire world Benefits Widespread availability of atomic clock time, without the atomic clocks Precise synchronization of communications systems, power grids, financial networks, and other critical infrastructure

More efficient use of limited radio spectrum by wireless network Improved network management and optimization, making traceable time tags possible for financial transactions and billi Communication of high-precision time among national laboratories using “common view” techniques Roads and Highways It is estimated that delays from congestion on highways, streets, and transit systems throughout the world result in productivity losses in the hundreds of billions of dollars annually. Other negative effects of congestion include property damage, personal injuries, increased air pollution, and inefficient fuel consumption The availability and accuracy of the Global Positioning System (GPS) offers increased efficiencies and safety for vehicles using highways, streets, and mass transit systems. Many of the problems associated with the routing and dispatch of commercial vehicles is significantly reduced or eliminated with the help of GPS. This is also true for the management of mass transit systems, road maintenance crews, and emergency vehicles GPS enables automatic vehicle location and in-vehicle navigation systems that are widely used throughout the world today. By combining GPS position technology with systems that can display geographic information or with systems that can automatically transmit data to display screens or computers, a new dimension in surface transportation is realized A geographic information system (GIS) stores, analyzes, and displays geographically referenced information provided in large part by GPS. Today GIS is used to monitor vehicle location, making possible effective strategies that can keep transit vehicles on schedule and inform passengers of precise arrival times. Mass transit systems use this capability to track rail, bus, and other services to improve on-time performance Many new capabilities are made possible with the help of GPS. Instant car pools are feasible since people desiring a ride can be instantly matched with a vehicle in a nearby area Using GPS technology to help track and forecast the movement of freight has made a logistical revolution, including an application known as time-definite delivery. In time-definite delivery, trucking companies use GPS for tracking to guarantee delivery and pickup at the time promised, whether over short distances or across time zones. When an order comes in, a dispatcher punches a computer function, and a list of trucks appears on the screen, displaying a full array of

detailed information on the status of each of them. If a truck is running late or strays off route, an alert is sent to the dispatcher Many nations use GPS to help survey their road and highway networks, by identifying the location of features on, near, or adjacent to the road networks. These include service stations, maintenance and emergency services and supplies, entry and exit ramps, damage to the road system, etc. The information serves as an input to the GIS data gathering process. This database of knowledge helps transportation agencies to reduce maintenance and service costs and enhances the safety of drivers using the roads Research is underway to provide warnings to drivers of potential critical situations, such as traffic violations or crashes. Additional research is being conducted to examine the potential for minimal vehicle control when there is a clear need for action, such as the pre-deployment of air bags. The position information provided by GPS is an integral part of this research GPS is an essential element in the future of Intelligent Transportation Systems (ITS). ITS encompasses a broad range of communications-based information and electronics technologies. Research is being conducted in the area of advanced driver assistance systems, which include road departure and lane change collision avoidance systems. These systems need to estimate the position of a vehicle relative to lane and road edge with an accuracy of 10 centimeters With the continuous modernization of GPS, one can expect even more effective systems for crash prevention, distress alerts and position notification, electronic mapping, and in-vehicle navigation with audible instructions Benefits Higher levels of safety and mobility for all surface transportation system users More accurate position determination to provide greater passenger information More effective monitoring to ensure schedule adherence, creating a transit system more responsive to transportation users needs Better location information with electronic maps to provide in-vehicle navigation systems for both commercial and private users Increased efficiencies and reduced costs in surveying roads Space Earth orbit The Global Positioning System (GPS) is revolutionizing and revitalizing the way nations operate in space, from guidance systems for crewed vehicles to the

management, tracking, and control of communication satellite constellations, to monitoring the Earth from space. Benefits of using GPS include: Navigation solutions -- providing high precision orbit determination, and minimum ground control crews, with existing space-qualified GPS units Attitude solutions -- replacing high cost on-board attitude sensors with low-cost multiple GPS antennae and specialized algorithms Timing solutions -- replacing expensive spacecraft atomic clocks with low-cost, precise time GPS receivers Constellation control -- providing single point-of-contact to control for the orbit maintenance of large numbers of space vehicles such as telecommunication satellites Formation flying -- allowing precision satellite formations with minimal intervention from ground crews Virtual platforms -- providing automatic "station-keeping" and relative position services for advanced science tracking maneuvers such as interferometry Launch vehicle tracking -- replacing or augmenting tracking radars with higher precision, lower-cost GPS units for range safety and autonomous flight termination The moon, mars and beyond The U.S. vision for space exploration, being implemented by the National Aeronautics and Space Administration (NASA), includes developing innovative technologies, knowledge, and infrastructures for returning to the Moon and preparing the way for future human missions to Mars and beyond. The vision will stimulate new research that will literally become the final frontier in navigation. Drawing on the experience with GPS, one could imagine creating a GPS-like network of satellites around the Moon and Mars. A Lunar or Martian network could provide an integrated communications and navigation infrastructure to support exploration and science missions both in lunar orbit and on the surface of the Moon and Mars. NASA is also studying the utility of placing GPS-like beacons on satellites destined for the Sun-Earth Lagrangian points. Geodetic reference points could be established at these locations to support the future exploration of the Solar System Benefits Providing high precision positioning with minimum ground control

Replacing high cost, and high mass, on-board sensors

Aviation Aviators throughout the world use the Global Positioning System (GPS) to increase the safety and efficiency of flight. With its accurate, continuous, and global capabilities, GPS offers seamless satellite navigation services that satisfy many of the requirements for aviation users. Space-based position and navigation enables three-dimensional position determination for all phases of flight from departure, en route, and arrival, to airport surface navigation. The trend toward an Area Navigation concept means a greater role for GPS. Area Navigation allows aircraft to fly user-preferred routes from waypoint to waypoint, where waypoints do not depend on ground infrastructure. Procedures have been expanded to use GPS and augmented services for all phases of flight. This has been especially true in areas that lack suitable ground based navigation aids or surveillance equipment New and more efficient air routes made possible by GPS are continuing to expand. Vast savings in time and money are being realized. In many cases, aircraft flying over data-sparse areas such as oceans have been able to safely reduce their separation between one another, allowing more aircraft to fly more favorable and efficient routes, saving time, fuel, and increasing cargo revenue Improved approaches to airports, which significantly increase operational benefits and safety, are now being implemented even at remote locations where traditional ground-based services are unavailable. In some regions of the world, satellite signals are augmented, or improved for special aviation applications, such as landing planes during poor visibility conditions. In those cases, even greater precision operations are possible The good news for the aviation community is that GPS is being constantly improved and modernized. A main component of the ongoing civilian modernization effort is the addition of two new signals. These signals complement the existing civilian service. The first of these new signals is for general use in non-safety critical applications. The second new signal will be internationally protected for aviation navigational purposes. This additional safety-of-life civilian signal will make GPS an even more robust navigation service for many aviation applications The second safety-of-life signal will enable significant benefits above and beyond the capabilities of the current GPS services. The availability of this signal offers increased instrument approach opportunity throughout the world by making the use of dual-frequency avionics possible. Dual frequency means that errors that

occur in the signals due to disturbances in the ionosphere can be significantly reduced through the simultaneous use of two signals. This will improve the overall system robustness, to include accuracy, availability, and integrity, and will allow a precise approach capability with little or no ground infrastructure investment Reliance on GPS as the foundation for today and tomorrow's air traffic management system is a major part of many national plans. Those aviation authorities that are moving forward with GPS have observed and documented reductions in flight time, workload, and operating costs for both the airspace user and service provider. GPS also serves as an essential component for many other aviation systems, such as the Enhanced Ground Proximity Warning System (EGPWS) that has proven successful in reducing the risk of Controlled Flight into Terrain, a major cause of many aircraft accidents Benefits Continuous, reliable, and accurate positioning information for all phases of flight on a global basis, freely available to all Safe, flexible, and fuel-efficient routes for airspace service providers and airspace users Potential decommissioning and reduction of expensive ground based navigation facilities, systems, and services Increased safety for surface movement operations made possible by situational awareness Reduced aircraft delays due to increased capacity made possible through reduced separation minimums and more efficient air traffic management, particularly during inclement weather Increased safety-of-life capabilities such as EGPWS Agriculture The development and implementation of precision agriculture or site-specific farming has been made possible by combining the Global Positioning System (GPS) and geographic information systems (GIS). These technologies enable the coupling of real-time data collection with accurate position information, leading to the efficient manipulation and analysis of large amounts of geospatial data. GPS-based applications in precision farming are being used for farm planning, field mapping, soil sampling, tractor guidance, crop scouting, variable rate applications, and yield mapping. GPS allows farmers to work during low visibility field conditions such as rain, dust, fog, and darkness

In the past, it was difficult for farmers to correlate production techniques and crop yields with land variability. This limited their ability to develop the most effective soil/plant treatment strategies that could have enhanced their production. Today, more precise application of pesticides, herbicides, and fertilizers, and better control of the dispersion of those chemicals are possible through precision agriculture, thus reducing expenses, producing a higher yield, and creating a more environmentally friendly farm Precision agriculture is now changing the way farmers and agribusinesses view the land from which they reap their profits. Precision agriculture is about collecting timely geospatial information on soil-plant-animal requirements and prescribing and applying site-specific treatments to increase agricultural production and protect the environment. Where farmers may have once treated their fields uniformly, they are now seeing benefits from micromanaging their fields. Precision agriculture is gaining in popularity largely due to the introduction of high technology tools into the agricultural community that are more accurate, cost effective, and user friendly. Many of the new innovations rely on the integration of on-board computers, data collection sensors, and GPS time and position reference systems Many believe that the benefits of precision agriculture can only be realized on large farms with huge capital investments and experience with information technologies. Such is not the case. There are inexpensive and easy-to-use methods and techniques that can be developed for use by all farmers. Through the use of GPS, GIS, and remote sensing, information needed for improving land and water use can be collected. Farmers can achieve additional benefits by combining better utilization of fertilizers and other soil amendments, determining the economic threshold for treating pest and weed infestations, and protecting the natural resources for future use GPS equipment manufacturers have developed several tools to help farmers and agribusinesses become more productive and efficient in their precision farming activities. Today, many farmers use GPS-derived products to enhance operations in their farming businesses. Location information is collected by GPS receivers for mapping field boundaries, roads, irrigation systems, and problem areas in crops such as weeds or disease. The accuracy of GPS allows farmers to create farm maps with precise acreage for field areas, road locations and distances between points of interest. GPS allows farmers to accurately navigate to specific locations in the field, year after year, to collect soil samples or monitor crop conditions Crop advisors use rugged data collection devices with GPS for accurate positioning to map pest, insect, and weed infestations in the field. Pest problem areas in crops can be pinpointed and mapped for future management decisions and input recommendations. The same field data can also be used by aircraft sprayers, enabling accurate swathing of fields without use of human “flaggers” to

guide them. Crop dusters equipped with GPS are able to fly accurate swaths over the field, applying chemicals only where needed, minimizing chemical drift, reducing the amount of chemicals needed, thereby benefiting the environment. GPS also allows pilots to provide farmers with accurate maps Farmers and agriculture service providers can expect even further improvements as GPS continues to modernize. In addition to the current civilian service provided by GPS, the United States is committed to implementing a second and a third civil signal on GPS satellites. The first satellite with the second civilian signal was launched in 2005. The new signals will enhance both the quality and efficiency of agricultural operations in the future Benefits Precision soil sampling, data collection, and data analysis, enable localized variation of chemical applications and planting density to suit specific areas of the field Accurate field navigation minimizes redundant applications and skipped areas, and enables maximum ground coverage in the shortest possible tim Ability to work through low visibility field conditions such as rain, dust, fog and darkness increases productivity Accurately monitored yield data enables future site-specific field preparation Elimination of the need for human "flaggers" increases spray efficiency and minimizes over-spray Marine The Global Positioning System (GPS) has changed the way the world operates. This is especially true for marine operations, including search and rescue. GPS provides the fastest and most accurate method for mariners to navigate, measure speed, and determine location. This enables increased levels of safety and efficiency for mariners worldwide It is important in marine navigation for the ship's officer to know the vessel's position while in open sea and also in congested harbors and waterways. While at sea, accurate position, speed, and heading are needed to ensure the vessel reaches its destination in the safest, most economical and timely fashion that conditions will permit. The need for accurate position information becomes even more critical as the vessel departs from or arrives in port. Vessel traffic and other waterway hazards make maneuvering more difficult, and the risk of accidents becomes greater

Mariners and oceanographers are increasingly using GPS data for underwater surveying, buoy placement, and navigational hazard location and mapping. Commercial fishing fleets use GPS to navigate to optimum fishing locations, track fish migrations, and ensure compliance with regulations An enhancement to the basic GPS signal known as Differential GPS (DGPS) provides much higher precision and increased safety in its coverage areas for maritime operations. Many nations use DGPS for operations such as buoy positioning, sweeping, and dredging. This enhancement improves harbor navigation Governments and industrial organizations around the world are working together to develop performance standards for Electronic Chart Display and Information Systems, which use GPS and/or DGPS for positioning information. These systems are revolutionizing marine navigation and are leading to the replacement of paper nautical charts. With DGPS, position and radar information can be integrated and displayed on an electronic chart, forming the basis of the Integrated Bridge System which is being installed on commercial vessels of all types GPS is playing an increasingly important role in the management of maritime port facilities. GPS technology, coupled with geographic information system (GIS) software, is key to the efficient management and operation of automated container placement in the world's largest port facilities. GPS facilitates the automation of the pick-up, transfer, and placement process of containers by tracking them from port entry to exit. With millions of container shipments being placed in port terminals annually, GPS has greatly reduced the number of lost or misdirected containers and lowered associated operation costs. GPS information is embedded within a system known as the Automatic Identification System (AIS) transmission. The AIS, which is endorsed by the International Maritime Organization, is used for vessel traffic control around busy seaways. This service is not only vital for navigation, but is increasingly used to bolster the security of ports and waterways by providing governments with greater situational awareness of commercial vessels and their cargo. AIS uses a transponder system that operates in the VHF maritime band and is capable of communicating ship to ship as well as ship to shore, transmitting information relating to ship identification, geographic location, vessel type, and cargo information -- all on a real-time, wholly automated basis. Because the ship's GPS position is embedded in these transmissions, all essential information about vessel movements and contents can be uploaded automatically to electronic charts. The safety and security of vessels using this system is significantly enhanced Finally, with the modernization of GPS, mariners can look forward to even better service. In addition to the current GPS civilian service, the United States is

committed to implementing two additional civilian signals. Access to the new signals will mean increased accuracy, more availability, and better integrity for all users Benefits Allows access to fast and accurate position, course, and speed information, saving navigators time and fuel through more efficient traffic routing Provides precise navigation information to boaters Improves precision and efficiency of buoy positioning, sweeping, and dredging operations Enhances efficiency and economy for container management in port facilities Increases safety and security for vessels using the AIS Rail Rail systems in many parts of the world use the Global Positioning System (GPS) in combination with various sensors, computers, and communication systems to improve safety, security, and operational effectiveness. These technologies help to reduce accidents, delays, operating costs, and dangerous emissions, while increasing track capacity, customer satisfaction, and cost effectiveness. Integral to the efficient operation of rail systems is the requirement for accurate, real-time position information of locomotives, rail cars, maintenance-of-way vehicles, and wayside equipment Ensuring high levels of safety, improving the efficiency of rail operations, and expanding system capacity are all key objectives of today’s railroad industry. Unlike most other modes of transportation, there is little flexibility in managing rail traffic. Most rail systems are comprised of long stretches of a single set of tracks. Trains bound for thousands of destinations must simultaneously share the use of these single line tracks Precise knowledge of where a train is located is essential to prevent collisions, maintain smooth flow of traffic, and minimize costly delays due to waiting for clearance for track use. Only the skill of the crews, accurate timing, a dynamic dispatching capability, and a critical array of “meet and passes” locations on short stretches of parallel tracks, allow rail dispatchers to guide their trains safely through. It is therefore critical for safety and efficiency reasons to know the position and performance of these trains both individually and system-wide

GPS also contributes to dependable scheduling through train location awareness, enhancing connectivity with other modes of transportation, such as rail station to airport transfers An enhancement to the basic GPS signal known as Differential GPS (DGPS) improves accuracy and safety within its coverage areas. The enhanced position information enables the dispatcher to determine on which of two parallel tracks a train is located. When coupled with other location and navigation devices to account for time in tunnels, behind hills, and other obstructions, DGPS can provide a reliable and accurate position-locating capability for rail traffic management systems Differential GPS is an essential element of the Positive Train Control (PTC) concept being adopted in many parts of the world. This concept involves providing precise railroad position information to sophisticated command and control systems to produce the best operating plan to include varying train speed, re-routing traffic, and safely moving maintenance crews onto and off tracks. A PTC system can track the location and speed of a train more accurately than was previously possible, providing train movement information to rail management personnel who can then enforce speeds and limits of authority, as necessary. By providing better tracking of train location and speed, PTC increases operational efficiency, allows higher track capacity, enhances crew, passenger, and cargo safety, and also results in a safer environment for personnel working on the track Differential GPS can also aid in surveying and mapping track structure for maintenance and future system planning. By using DGPS, one can precisely locate mileposts, signal masts, switch points, bridges, road crossings, signal equipment, etc. GPS can satisfy the high level of accuracy needed for operation in terminal areas and rail yards, where dozens of tracks may run in parallel Finally, with the modernization of GPS, rail operators can look forward to providing better service. In addition to the current GPS civilian service, the United States is committed to implementing two additional civilian signals. Access to the new signals will mean increased accuracy, more availability, and better integrity for all users. Benefits Enhanced levels of safety Increased capacity and efficiency for all rail users. Dependable schedule and equipment location awareness

Improved track, traffic, and train sensor information that flows together and produces a constantly updated plan to manage operations Increased situational awareness for improved safety of trains and maintenance crews Environment To sustain the Earth’s environment while balancing human needs requires better decision making with more up-to-date information. Gathering accurate and timely information has been one of the greatest challenges facing both government and private organizations that must make these decisions. The Global Positioning System (GPS) helps to address that need Data collection systems provide decision makers with descriptive information and accurate positional data about items that are spread across many kilometers of terrain. By connecting position information with other types of data, it is possible to analyze many environmental problems from a new perspective. Position data collected through GPS can be imported into geographic information system (GIS) software, allowing spatial aspects to be analyzed with other information to create a far more complete understanding of a particular situation than might be possible through conventional means Aerial studies of some of the world’s most impenetrable wilderness are conducted with the aid of GPS technology to evaluate an area’s wildlife, terrain, and human infrastructure. By tagging imagery with GPS coordinates it is possible to evaluate conservation efforts and assist in strategy planning Some nations collect and use mapping information to manage their regulatory programs such as the control of royalties from mining operations, delineation of borders, and the management of logging in their forests GPS technology supports efforts to understand and forecast changes in the environment. By integrating GPS measurements into operational methods used by meteorologists, the atmosphere’s water content can be determined, improving the accuracy of weather forecasts. In addition, the proliferation of GPS tidal tracking sites, and improvement in estimating the vertical component of a site’s position from GPS measurements, present a unique opportunity to directly observe the effects of ocean tides GPS receivers mounted on buoys track the movement and spread of oil spills. Helicopters use GPS to map the perimeter of forest fires and allow efficient use of fire fighting resources The migratory patterns of endangered species, such as the mountain gorillas of Rwanda, are tracked and mapped using GPS, helping to preserve and enhance declining populations

In earthquake prone areas such as the Pacific Rim, GPS is playing an increasingly prominent role in helping scientists to anticipate earthquakes. Using the precise position information provided by GPS, scientists can study how strain builds up slowly over time in an attempt to characterize, and in the future perhaps anticipate, earthquakes Another benefit to using GPS is timeliness with which critical products can be generated. Because GPS data are in a digital form available at all times and in all parts of the world, they can be captured and analyzed very quickly. This means that it is possible for analysis to be completed in hours or days rather than weeks or months, thus ensuring that the final product is timelier. With the rapid pace of change in the world today, these savings in time can be critical The modernization of GPS will further enhance the support of GPS technology to the study and management of the world’s environment. The United States is committed to implementing two additional civilian signals that will provide ecological and conservation applications with increased accuracy, availability, and reliability. Tropical rain forest ecology, for example, will benefit from the increased availability of GPS within heavy foliage areas and the reduction of spatial error in fine-scale vegetation mapping Benefits GPS data collection systems complemented with GIS packages provide a means for comprehensive analysis of environmental concerns Environmental patterns and trends can be efficiently recognized with GPS/GIS data collection systems, and thematic maps can be easily created GPS data can be quickly analyzed without the preliminary requirement for field data transcription into a digitized form Accurate tracking of environmental disasters such as fires and oil spills can be conducted more efficiently Precise positional data from GPS can assist scientists in crustal and seismic monitoring Monitoring and preservation of endangered species can be facilitated through GPS tracking and mapping public safety and disaster relief A critical component of any successful rescue operation is time. Knowing the precise location of landmarks, streets, buildings, emergency service resources, and disaster relief sites reduces that time -- and saves lives. This information is critical to disaster relief teams and public safety personnel in order to protect life

and reduce property loss. The Global Positioning System (GPS) serves as a facilitating technology in addressing these needs GPS has played a vital role in relief efforts for global disasters such as the tsunami that struck in the Indian Ocean region in 2004, Hurricanes Katrina and Rita that wreaked havoc in the Gulf of Mexico in 2005, and the Pakistan-India earthquake in 2005. Search and rescue teams used GPS, geographic information system (GIS), and remote sensing technology to create maps of the disaster areas for rescue and aid operations, as well as to assess damage Another important area of disaster relief is in the management of wildfires. To contain and manage forest fires, aircraft combine GPS with infrared scanners to identify fire boundaries and “hot spots.” Within minutes, fire maps are transmitted to a portable field computer at the firefighters’ camp. Armed with this information, firefighters have a greater chance of winning the battle against the blaze In earthquake prone areas such as the Pacific Rim, GPS is playing an increasingly prominent role in helping scientists to anticipate earthquakes. Using the precise position information provided by GPS, scientists can study how strain builds up slowly over time in an attempt to characterize, and in the future perhaps anticipate, earthquakes Meteorologists responsible for storm tracking and flood prediction also rely on GPS. They can assess water vapor content by analyzing transmissions of GPS data through the atmosphere GPS has become an integral part of modern emergency response systems -whether helping stranded motorists find assistance or guiding emergency vehicles As the international industry positioning standard for use by emergency and other specialty vehicle fleets, GPS has given managers a quantum leap forward in efficient operation of their emergency response teams. The ability to effectively identify and view the location of police, fire, rescue, and individual vehicles or boats, and how their location relates to an entire network of transportation systems in a geographic area, has resulted in a whole new way of doing business. Location information provided by GPS, coupled with automation, reduces delay in the dispatch of emergency services. Incorporation of GPS in mobile phones places an emergency location capability in the hands of everyday users. Today’s widespread placement of GPS location systems in passenger cars provides another leap in developing a comprehensive safety net. Today, many ground and maritime vehicles are equipped with autonomous crash sensors and GPS. This information, when coupled with automatic communication systems, enables a call for help even when occupants are unable to do so

The modernization of GPS will further facilitate disaster relief and public safety services. The addition of new civil signals will increase accuracy and reliability all over the world. In short, GPS modernization translates to more lives saved and faster recovery for victims of global tragedies Benefits Deliver disaster relief to areas in a more timely and accurate manner, saving lives and restoring critical infrastructure Provide position information for mapping of disaster regions where little or no mapping information is available Enhance capability for flood prediction and monitoring of seismic precursors and events Provide positional information about individuals with mobile phones and in vehicles in case of emergency Surveying and mapping As technology evolves and expands throughout the world, the surveying and mapping community is steadily redefining the tools required to increase productivity and obtain highly accurate data Using the near pinpoint accuracy provided by the Global Positioning System (GPS) with ground augmentations, highly accurate surveying and mapping results can be rapidly obtained, thereby significantly reducing the amount of equipment and labor hours that are normally required of other conventional surveying and mapping techniques. Today it is possible for a single surveyor to accomplish in one day what used to take weeks with an entire team. GPS is unaffected by rain, wind, or reduced sunlight, and is rapidly being adopted by professional surveyors and mapping personnel throughout the world GPS provides accurate three-dimensional positioning information for natural and artificial features that can be displayed on maps and models of everything in the world - mountains, rivers, forests, endangered animals, precious minerals and many other resources. GPS position information for these features serves as a prime input to geographic information systems (GIS), that assemble, store, manipulate, and display geographically referenced information GPS has played a vital role in relief efforts for global disasters such as the tsunami that struck in the Indian Ocean region in 2004, Hurricanes Katrina and Rita that wreaked havoc in the Gulf of Mexico in 2005, and the Pakistan-India earthquake in 2005. Search and rescue teams used GPS position information to create maps

of the disaster areas for rescue and aid operations, as well as to help assess damage Throughout the world, government agencies, scientific organizations, and commercial operations are using the surveys and maps deriving from GPS and GIS for timely decision-making and wiser use of resources. Any organization or agency that requires accurate location information can benefit from the efficiency and productivity provided by the positioning capability of GPS Unlike traditional techniques, GPS surveying is not bound by constraints such as line-of-sight visibility between reference stations. Also, the spacing between stations can be increased. The increased flexibility of GPS also permits survey stations to be established at easily accessible sites rather than being confined to hilltops as previously required Remote GPS systems may be carried by one person in a backpack, mounted on the roof of an automobile, or fastened atop an all-terrain vehicle to permit rapid and accurate field data collection. With a GPS radio communication link, realtime, continuous centimeter-level accuracy makes possible a productivity level that is virtually unattainable using optical survey instruments With the modernization of GPS even further enhancements are in the works. In addition to the current GPS civilian service, the United States is committed to implementing two additional civilian signals. The extra signals will, for example, provide a means for correcting errors caused by the ionosphere, thus improving positioning accuracy. The new signals will also improve the availability and overall integrity of the system for all users Benefits Provides significant productivity gains over traditional surveying by eliminating many of its inherent limitations, such as the requirement for a line of sight between surveying points Provides accurate positioning of natural and artificial features that can be used to create maps and models that are used for a wide range of services such as disaster relief and public safety Gives decision-makers timely and valuable information for wise use of resources Yields highly accurate surveying results in real-time at the centimeter-level Allows surveyors to work uninterrupted in periods of poor weather conditions or reduced sunlight Recreation

The Global Positioning System (GPS) has eliminated many of the hazards associated with common recreational activities by providing a capability to determine a precise location. GPS receivers have also broadened the scope and enjoyment of outdoor activities by simplifying many of the traditional problems, such as staying on the “correct trail” or returning to the best fishing spot. Outdoor exploration carries with it many intrinsic dangers, one of the most important of which is the potential for getting lost in unfamiliar or unsafe territory. Hikers, bicyclists, and outdoor adventurers are increasingly relying on GPS instead of traditional paper maps, compasses, or landmarks. Paper maps are often outdated, and compasses and landmarks may not provide the precise location information necessary to avoid venturing into unfamiliar areas. In addition, darkness and adverse weather conditions may also contribute to imprecise navigation results GPS technology coupled with electronic mapping has helped to overcome much of the traditional hardships associated with unbounded exploration. GPS handsets allow users to safely traverse trails with the confidence of knowing precisely where they are at all times, as well as how to return to their starting point. One of the benefits is the ability to record and return to waypoints. Similarly, fishermen typically use GPS signals as a means to continually stay apprised of location, heading, bearing, speed, distance-to-go, time-to-go, chart plotting functions, and most importantly, returning to a location where the fish are plentiful An advantage in newer GPS receivers is the capability to transfer data to and from a computer. Outdoor enthusiasts can download waypoints from an exciting adventure and share them. An example of this is a web site based in Malaysia dedicated to GPS for mountain biking enthusiasts. Riders post waypoint files marking their favorite rides allowing other riders to try out the trails Golfers use GPS to measure precise distances within the course and improve their game. Other applications include skiing, as well as recreational aviation and boating GPS technology has generated entirely new sports and outdoor activities. An example of this is geocaching, a sport which rolls a pleasurable day’s outing and a treasure hunt into one. Another new sport is geodashing, a cross-country race to a predefined GPS coordinate GPS modernization efforts, designed to enhance more serious applications than recreation have provided direct and indirect benefits to the user. Various GPS augmentation systems that were developed in several countries for commerce and transportation are also being widely used by outdoor enthusiasts for recreational purposes. Modernization plans for GPS will result in even greater reliability and availability for all users, such as under a denser forest cover -- just the environment in which many adventurers most need this capability

Benefits Highly accurate all-weather positioning information using GPS receivers helps outdoor adventurers with safer exploration anywhere in the world Ability to return to favorite fishing spots, trails, campsites or other locations with precision year after year, despite changing terrain conditions New and interesting activities (based solely on the capabilities of GPS) are developed every day by outdoor enthusiasts and shared with others Relatively small, portable, and affordable handsets can be used for multiple types of recreation activities

http://en.wikipedia.org/wiki/Global_Positioning_System The Global Positioning System (GPS) is the only fully functional Global Navigation Satellite System (GNSS). Utilizing a constellation of at least 24 medium Earth orbit satellites that transmit precise microwave signals, the system enables a GPS receiver to determine its location, speed/direction, and time Developed by the United States Department of Defense, it is officially named NAVSTAR GPS (Contrary to popular belief, NAVSTAR is not an acronym, but simply a name given by Mr. John Walsh, a key decision maker when it came to the budget for the GPS program[1]). The satellite constellation is managed by the United States Air Force 50th Space Wing. The cost of maintaining the system is approximately US$750 million per year,[2] including the replacement of aging satellites, and research and development. Despite these costs, GPS is free for civilian use as a public good GPS has become a widely used aid to navigation worldwide, and a useful tool for mapmaking, land surveying, commerce, and scientific uses. GPS also provides a precise time reference used in many applications including scientific study of earthquakes, and synchronization of telecommunications networks Simplified method of operation A GPS receiver calculates its position by measuring the distance between itself and three or more GPS satellites. Measuring the time delay between transmission and reception of each GPS microwave signal gives the distance to each satellite, since the signal travels at a known speed. These signals also carry information about the satellites' location and general system health (known as almanac and ephemeris). By determining the position of, and distance to, at least three satellites, the receiver can compute its position using trilateration.[3] Receivers typically do not have perfectly accurate clocks and therefore track one or more additional satellites, using their atomic clocks to correct the receiver's own clock error

Applications The Global Positioning System, while originally a military project, is considered a dualuse technology, meaning it has significant applications for both the military and the civilian industry Military Concerning military applications, GPS allows accurate targeting of various military weapons including ICBMs, cruise missiles and precision-guided munitions. It is used to navigate and coordinate the movement of troops and supplies The GPS satellites also carry nuclear detonation detectors, which form a major portion of the United States Nuclear Detonation Detection System. Civilian Many civilian applications benefit from GPS signals, using one or more of three basic components of the GPS; absolute location, relative movement, time transfer The ability to determine the receiver's absolute location allows GPS receivers to perform as a surveying tool or as an aid to navigation. The capacity to determine relative movement enables a receiver to calculate local velocity and orientation, useful in vessels or observations of the Earth. Being able to synchronize clocks to exacting standards enables time transfer, which is critical in large communication and observation systems. An example is CDMA digital cellular. Each base station has a GPS timing receiver to synchronize its spreading codes with other base stations to facilitate inter-cell hand off and support hybrid GPS/CDMA positioning of mobiles for emergency calls and other applications Finally, GPS enables researchers to explore the Earth environment including the atmosphere, ionosphere and gravity field. GPS survey equipment has revolutionized tectonics by directly measuring the motion of faults in earthquakes To help prevent civilian GPS guidance from being used in an enemy's military or improvised weaponry, the US Government controls the export of civilian receivers. A US-based manufacturer cannot generally export a GPS receiver unless the receiver contains limits restricting it from functioning when it is simultaneously (1) at an altitude above 18 kilometers (60,000 ft) and (2) traveling at over 515 m/s (1,000 knots