Distress Signal.docx

Distress signal From Wikipedia, the free encyclopedia

Jump to navigationJump to search "Call for help" redirects here. For the TV show, see Call for Help. A distress signal or distress call is an internationally recognized means for obtaining help. Distress signals are communicated by transmitting radio signals, displaying a visually observable item or illumination, or making a sound audible from a distance. A distress signal indicates that a person or group of people, ship, aircraft, or other vehicle is threatened by serious and/or imminent danger and requires immediate assistance.[1]:PCG D−3 Use of distress signals in other circumstances may be against local or international law. An urgency signal is available to request assistance in less critical situations. In order for distress signalling to be the most effective, two parameters must be communicated:  

Alert or notification of a distress in progress Position or location (or localization or pinpointing) of the party in distress.

For example, a single aerial flare alerts observers to the existence of a vessel in distress somewhere in the general direction of the flare sighting on the horizon but extinguishes within one minute or less. A hand-held flare burns for three minutes and can be used to localize or pinpoint more precisely the exact location or position of the party in trouble. An EPIRB both notifies or alerts authorities and at the same time provides position indication information. Contents [hide] 

     

1Maritime distress signals o 1.1Automated radio signals o 1.2Use of Mayday o 1.3Unusual or extraordinary appearance o 1.4Inverted flags o 1.5Device loss and disposal 2Aviation distress signals 3Mountain distress signals 4Ground distress beacons 5See also 6References 7External links

Maritime distress signals[edit] Distress signals at sea are defined in the International Regulations for Preventing Collisions at Sea and in the International Code of Signals. Mayday signals must only be used where there is grave and imminent danger to life. Otherwise, urgent signals such as pan-pan can be sent. Most jurisdictions have large penalties for false, unwarranted or prank distress signals. Distress can be indicated by any of the following officially sanctioned methods:

Distress Signals

Smoke signal

 

       

Transmitting a spoken voice Mayday message by radio over very high frequency channel 16 (156.8 MHz) and/or high frequency on 2182 kHz Transmitting a digital distress signal by activating (or pressing) the distress button (or key) on a marine radio equipped with Digital Selective Calling (DSC) over the VHF (channel 70) and/or HF frequency bands. Transmitting a digital distress signal by activating (or pressing) the distress button (or key) on an Inmarsat-C satellite internet device Sending the Morse code group SOS (▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄) by light flashes or sounds Burning a red flare (either hand-held or aerial parachute flare) Launching distress rockets Emitting orange smoke from a canister Showing flames on the vessel (as from a burning tar barrel, oil barrel, etc.) Raising and lowering slowly and repeatedly both arms outstretched to each side Making a continuous sound with any fog-signalling apparatus



Firing a gun or other explosive signal at intervals of about a minute

 

Flying the international maritime signal flags NC Displaying a visual signal consisting of a square flag having above or below it a ball or anything resembling a ball (round or circular in appearance)

A floating man-overboard pole or dan buoy can be used to indicate that a person is in distress in the water and is ordinarily equipped with a yellow and red flag (international code of signals flag "O") and a flashing lamp or strobe light. In North America, marine search and rescue agencies in Canada and the United States also recognize certain other distress signals:  

Sea marker dye White high intensity strobe light flashing at 60 times per minute

Automated radio signals[edit] In addition, a distress can be signaled using automated radio signals such as a Search and Rescue Transponder (SART) which responds to 9 GHz radar signal, or an Emergency Position-Indicating Radio Beacon (EPIRB) which operates in the 406 MHz radio frequency. EPIRB signals are received and processed by a constellation of satellites known as COSPAS-SARSAT. Older EPIRBs which use 121.5 MHz are obsolete. Many regulators require vessels which proceed offshore to carry an EPIRB. Many EPIRBs have an in-built Global Positioning System receiver. When activated these EPIRBs rapidly report the latitude and longitude of the emergency accurate to within 120m. The position of non-GPS EPIRBs is determined by the orbiting satellites, this can take ninety minutes to five hours after activation and is accurate to within 5 km. Marine safety authorities recommend the use of GPSequipped EPIRBs.[2] A miniaturised EPIRB capable of being carried in crew members' clothing is called a Personal Locator Beacon (PLB). Regulators do not view them as a substitute for a vessel's EPIRB. In situations with a high risk of "man overboard", such as open ocean yacht racing, PLBs may be required by the event's organisers. PLBs are also often carried during risky outdoor activities upon land. EPIRBs and PLBs have a unique identification number (UIN or "HexID"). A purchaser should register their EPIRB or PLB with the national search and rescue authority; this is free in most jurisdictions. EPIRB registration allows the authority to alert searchers of the vessel's name, label, type, size and paintwork; to promptly notify next-of-kin; and to quickly resolve inadvertent activations. A DSC radio distress signal can include the position if the lat/long are manually keyed into the radio or if a GPS-derived position is passed electronically directly into the radio.

Use of Mayday[edit] A Mayday message consists of the word "mayday" spoken three times in succession, which is the distress signal, followed by the distress message, which should include:     

Name of the vessel or ship in distress Her position (actual, last known or estimated expressed in lat./long. or in distance/bearing from a specific location) Nature of the vessel distress condition or situation (e.g. on fire, sinking, aground, taking on water, adrift in hazardous waters) Number of persons at risk or to be rescued; grave injuries Type of assistance needed or being sought



Any other details to facilitate resolution of the emergency such as actions being taken (e.g. abandoning ship, pumping flood water), estimated available time remaining afloat

Unusual or extraordinary appearance[edit]

HMS Romney aground off the Texelin 1804. In Richard Corbould's print, Romney's blue ensign at the stern is shown inverted, as a sign of distress

When none of the above-described officially sanctioned signals are available, attention for assistance can be attracted by anything that appears unusual or out of the ordinary, such as a jib sail hoisted upside down. During daylight hours when the sun is visible, a heliograph mirror can be used to flash bright, intense sunlight. Battery-powered laser lights the size of small flashlights (electric torches) are available for use in emergency signalling.

Inverted flags[edit] For hundreds of years inverted national flags were commonly used as distress signals.[3] However, for some countries’ flags it is difficult (e.g., Spain, South Korea, the UK) or impossible (e.g., Japan, Thailand, and Israel) to determine whether they are inverted. Other countries have flags that are inverses of each other; for example, the Polish flag is white on the top half and red on the bottom, while Indonesia's and Monaco's flags are the opposite—i.e., top half red, bottom half white. A ship flying no flags may also be understood to be in distress.[4] If any flag is available, distress may be indicated by tying a knot in it and then flying it upside-down, making it into a wheft.[5]

Device loss and disposal[edit] To avoid pointless searches some devices must be reported when lost. This particularly applies to EPIRBs, life buoys, rafts and devices marked with the vessel's name and port. Expired flares should not be set off, as this indicates distress. Rather, most port authorities offer disposal facilities for expired distress pyrotechnics. In some areas special training events are organised, where the flares can be used safely. EPIRBs must not be disposed of into general waste as discarded EPIRBs often trigger at the waste disposal facility. In 2013 the majority of EPIRB activations investigated by the Australian Maritime Safety Authority were due to the incorrect disposal of obsolete 121.5 MHz EPIRB beacons.[6]

Aviation distress signals[edit] Radio beacon of distress

MENU 0:00

Modulation of a radio beacon of distress on 121,5 MHz and 243 MHz. (Radio triangulation)

Problems playing this file? See media help.

The civilian aircraft emergency frequency for voice distress alerting is 121.5 MHz. Military aircraft use 243 MHz (which is a harmonic of 121.5 MHz, and therefore civilian beacons transmit on this frequency as well). Aircraft can also signal an emergency by setting one of several special transponder codes, such as 7700. The COSPAS/SARSAT signal can be transmitted by an Electronic Locator Transmitter or ELT, which is similar to a marine EPIRB on the 406 MHz radio frequency. (Marine EPIRBs are constructed so as to float, while an aviation ELT is constructed so as to be activated by a sharp deceleration and is sometimes referred to as a Crash Position Indicator or CPI). A "triangular distress pattern" is a rarely used flight pattern flown by aircraft in distress but without radio communications. The standard pattern is a series of 120° turns.

Mountain distress signals[edit] The recognised mountain distress signals are based on groups of three, or six in the UK and the European Alps. A distress signal can be three fires or piles of rocks in a triangle, three blasts on a whistle, three shots from a firearm, or three flashes of a light, in succession followed by a one-minute pause and repeated until a response is received. Three blasts or flashes is the appropriate response. In the Alps, the recommended way to signal distress is the Alpine distress signal: give six signals within a minute, then pause for a minute, repeating this until rescue arrives. A signal may be anything visual (waving clothes or lights, use of a signal mirror) or audible (shouts, whistles, etc.). The rescuers acknowledge with three signals per minute. In practice either signal pattern is likely to be recognised in most popular mountainous areas as nearby climbing teams are likely to include Europeans or North Americans. To communicate with a helicopter in sight, raise both arms (forming the letter Y) to indicate "Yes" or "I need help," or stretch one arm up and one down (imitating the letter N) for "No" or "I do not need help". If semaphore flags are available, they can possibly be used to communicate with rescuers.

Ground distress beacons[edit] The COSPAS-SARSAT 406 MHz radio frequency distress signal can be transmitted by hikers, backpackers, trekkers, mountaineers and other ground-based remote adventure seekers and personnel working in isolated backcountry areas using a small, portable Personal Locator Beacon or PLB.

Navigation light From Wikipedia, the free encyclopedia Combined green and red navigation light at the bow of a sailboat

A navigation light, also known as a running or position light, is a source of illumination on a vessel, aircraft or spacecraft. Navigation lights give information on a craft's position, heading, and status. Their placement is mandated by international conventions or civil authorities. Navigation lights are not intended to provide illumination for the craft making the passage, only for other craft to be aware of it.

Marine navigation lights[edit] In 1838 the United States passed an act requiring steamboats running between sunset and sunrise to carry one or more signal lights; color, visibility and location were not specified. In 1848 the United Kingdom passed regulations that required steam vessels to display red and green sidelights as well as a white masthead light. In 1849 the U.S. Congress extended the light requirements to sailing vessels. In 1889 the United States convened the first International Maritime Conference to consider regulations for preventing collisions. The resulting Washington Conference Rules were adopted by the U.S in 1890 and became effective internationally in 1897. Within these rules was the requirement for steamships to carry a second mast head light. The international 1948 Safety of Life at Sea Conference recommended a mandatory second masthead light solely for power driven vessels over 150 feet in length and a fixed sternlight for almost all vessels. The regulations have changed little since then.[1] The International Regulations for Preventing Collisions at Sea established in 1972 stipulates the requirements for the navigation lights required on a vessel.

Basic lighting[edit]

Basic lighting configuration. 2=a vessel facing directly towards observer; 4=vessel facing away from the observer.

To avoid collisions, vessels mount navigation lights that permit other vessels to determine the type and relative angle of a vessel, and thus decide if there is a danger of collision. In general sailing vessels are required to carry a green light that shines from dead ahead to 2 points (22 1⁄2°) abaft[note 1] the beam on the starboard side (the right side from the perspective of someone on board facing forward), a red light from dead ahead to two points abaft the beam on the port side (left side) and a white light that shines from astern to two points abaft the beam on both sides. Power driven vessels, in addition to these lights, must carry either one or two (depending on length) white masthead lights that shine from ahead to two points abaft the beam on both sides. If two masthead

lights are carried then the aft one must be higher than the forward one.[2] Hovercraft at all times and some boats operating in crowded areas may also carry a yellow flashing beacon for added visibility during day or night.

Lights of special significance[edit] In addition to red, white and green running lights, a combination of red, white and green Mast Lights placed on a mast higher than all the running lights, and viewable from all directions, may be used to indicate the type of craft or the service it is performing. See "Quick Guide" in external links. 



Ships at anchor display one or two white anchor lights (depending on the vessel's length) that can be seen from all directions. If two lights are shown then the forward light is higher than the aft one. Boats classed as "small" are not compelled to carry navigation lights and may make use of a handheld torch.

Satellite navigation From Wikipedia, the free encyclopedia

Jump to navigationJump to search For satellite navigation in automobile navigation systems, see Automotive navigation system. A satellite navigation or satnav system is a system that uses satellites to provide autonomous geospatial positioning. It allows small electronic receivers to determine their location (longitude, latitude, and altitude/elevation) to high precision (within a few metres) using time signals transmitted along a line of sight by radio from satellites. The system can be used for providing position, navigation or for tracking the position of something fitted with a receiver (satellite tracking). The signals also allow the electronic receiver to calculate the current local time to high precision, which allows time synchronisation. Satnav systems operate independently of any telephonic or internet reception, though these technologies can enhance the usefulness of the positioning information generated. A satellite navigation system with global coverage may be termed a global navigation satellite system (GNSS). As of December 2016, only the United States' Global Positioning System (GPS), Russia's GLONASS, China's BeiDou Navigation Satellite System (BDS) and the European Union's Galileo are global operational GNSSs. The European Union's Galileo GNSS is scheduled to be fully operational by 2020.[1] China is in the process of expanding its regional BeiDou Navigation Satellite System into the global BeiDou-2 GNSS by 2020.[2] India, France and Japan are in the process of developing regional navigation and augmentation systems as well. Global coverage for each system is generally achieved by a satellite constellation of 18–30 medium Earth orbit (MEO) satellites spread between several orbital planes. The actual systems vary, but use orbital inclinationsof >50° and orbital periods of roughly twelve hours (at an altitude of about 20,000 kilometres or 12,000 miles).

Classification[edit] Satellite navigation systems that provide enhanced accuracy and integrity monitoring usable for civil navigation are classified as follows:[3] 

GNSS-1[citation needed] is the first generation system and is the combination of existing satellite navigation systems (GPS and GLONASS), with Satellite Based Augmentation Systems (SBAS) or Ground Based Augmentation Systems (GBAS). In the United States, the satellite based component is the Wide Area Augmentation System (WAAS), in Europe it is the European



    

 

Geostationary Navigation Overlay Service (EGNOS), and in Japan it is the Multi-Functional Satellite Augmentation System (MSAS). Ground based augmentation is provided by systems like the Local Area Augmentation System (LAAS).[citation needed] GNSS-2[citation needed] is the second generation of systems that independently provides a full civilian satellite navigation system, exemplified by the European Galileo positioning system. These systems will provide the accuracy and integrity monitoring necessary for civil navigation; including aircraft. This system consists of L1 and L2 frequencies (in the L band of the radio spectrum) for civil use and L5 for system integrity. Development is also in progress to provide GPS with civil use L2 and L5 frequencies[4], making it a GNSS-2 system.¹[citation needed] Core Satellite navigation systems, currently GPS (United States), GLONASS (Russian Federation), Galileo (European Union) and Compass (China). Global Satellite Based Augmentation Systems (SBAS) such as Omnistar and StarFire. Regional SBAS including WAAS (US), EGNOS (EU), MSAS (Japan) and GAGAN (India). Regional Satellite Navigation Systems such as China's Beidou, India's NAVIC, and Japan's proposed QZSS. Continental scale Ground Based Augmentation Systems (GBAS) for example the Australian GRAS and the joint US Coast Guard, Canadian Coast Guard, US Army Corps of Engineers and US Department of Transportation National Differential GPS (DGPS) service. Regional scale GBAS such as CORS networks. Local GBAS typified by a single GPS reference station operating Real Time Kinematic (RTK) corrections.

History and theory[edit]

Ground based radio navigation has long been practiced. The DECCA, LORAN, GEE and Omega systems used terrestrial longwave radio transmitters which broadcast a radio pulse from a known "master" location, followed by a pulse repeated from a number of "slave" stations. The delay between the reception of the master signal and the slave signals allowed the receiver to deduce the distance to each of the slaves, providing a fix. The first satellite navigation system was Transit, a system deployed by the US military in the 1960s. Transit's operation was based on the Doppler effect: the satellites travelled on well-known paths and broadcast their signals on a well-known radio frequency. The received frequency will differ slightly from the broadcast frequency because of the movement of the satellite with respect to the receiver. By monitoring this frequency shift over a short time interval, the receiver can determine its location to one side or the other of the satellite, and several such measurements combined with a precise knowledge of the satellite's orbit can fix a particular position. Satellite orbital position errors are induced by variations in the gravity field and radar refraction, among others. These were resolved by

a team led by Harold L Jury of Pan Am Aerospace Division in Florida from 1970-1973. Using realtime data assimilation and recursive estimation, the systematic and residual errors were narrowed down to a manageable level to permit accurate navigation. [5] Part of an orbiting satellite's broadcast included its precise orbital data. In order to ensure accuracy, the US Naval Observatory (USNO) continuously observed the precise orbits of these satellites. As a satellite's orbit deviated, the USNO would send the updated information to the satellite. Subsequent broadcasts from an updated satellite would contain its most recent ephemeris. Modern systems are more direct. The satellite broadcasts a signal that contains orbital data (from which the position of the satellite can be calculated) and the precise time the signal was transmitted. The orbital ephemeris is transmitted in a data message that is superimposed on a code that serves as a timing reference. The satellite uses an atomic clock to maintain synchronization of all the satellites in the constellation. The receiver compares the time of broadcast encoded in the transmission of three (at sea level) or four different satellites, thereby measuring the time-of-flight to each satellite. Several such measurements can be made at the same time to different satellites, allowing a continual fix to be generated in real time using an adapted version of trilateration: see GNSS positioning calculation for details. Each distance measurement, regardless of the system being used, places the receiver on a spherical shell at the measured distance from the broadcaster. By taking several such measurements and then looking for a point where they meet, a fix is generated. However, in the case of fast-moving receivers, the position of the signal moves as signals are received from several satellites. In addition, the radio signals slow slightly as they pass through the ionosphere, and this slowing varies with the receiver's angle to the satellite, because that changes the distance through the ionosphere. The basic computation thus attempts to find the shortest directed line tangent to four oblate spherical shells centred on four satellites. Satellite navigation receivers reduce errors by using combinations of signals from multiple satellites and multiple correlators, and then using techniques such as Kalman filtering to combine the noisy, partial, and constantly changing data into a single estimate for position, time, and velocity.

Comparison of geostationary, GPS, GLONASS, Galileo, Compass (MEO), International Space Station, Hubble Space Telescope and Iridium constellation orbits, with the Van Allen radiation belts and the Earth to scale.[a] The Moon's orbit is around 9 times larger than geostationary orbit.[b] (In the SVG file, hover over an orbit or its label to highlight it; click to load its article.)

launched GNSS satellites 1978 to 2014

GPS[edit] Main article: Global Positioning System The United States' Global Positioning System (GPS) consists of up to 32 medium Earth orbit satellites in six different orbital planes, with the exact number of satellites varying as older satellites are retired and replaced. Operational since 1978 and globally available since 1994, GPS is currently the world's most utilized satellite navigation system.

GLONASS[edit] Main article: GLONASS The formerly Soviet, and now Russian, Global'naya Navigatsionnaya Sputnikovaya Sistema, (GLObal NAvigation Satellite System or GLONASS), is a space-based satellite navigation system that provides a civilian radionavigation-satellite service and is also used by the Russian Aerospace Defence Forces. GLONASS has full global coverage with 24 satellites.

Galileo[edit] Main article: Galileo (satellite navigation) The European Union and European Space Agency agreed in March 2002 to introduce their own alternative to GPS, called the Galileo positioning system. Galileo became operational on 15 December 2016 (global Early Operational Capability (EOC)) [6] At an estimated cost of €3 billion,[7] the system of 30 MEO satellites was originally scheduled to be operational in 2010. The original year to become operational was 2014.[8] The first experimental satellite was launched on 28 December 2005.[9] Galileo is expected to be compatible with the modernized GPS system. The receivers will be able to combine the signals from both Galileo and GPS satellites to greatly increase the accuracy. Galileo is expected to be in full service in 2020 and at a substantially higher cost.[1] The main modulation used in Galileo Open Service signal is the Composite Binary Offset Carrier (CBOC) modulation.

BeiDou-2[edit] Main article: BeiDou Navigation Satellite System China has indicated their plan to complete the entire second generation Beidou Navigation Satellite System (BDS or BeiDou-2, formerly known as COMPASS), by expanding current regional (AsiaPacific) service into global coverage by 2020.[2] The BeiDou-2 system is proposed to consist of 30 MEO satellites and five geostationary satellites. A 16-satellite regional version (covering Asia and Pacific area) was completed by December 2012.

Regional navigation satellite systems[edit] BeiDou-1[edit]

Main article: Beidou Navigation Satellite System Chinese regional (Asia-Pacific, 16 satellites) network to be expanded into the whole BeiDou-2 global system which consists of all 35 satellites by 2020.

NAVIC[edit] Main article: NAVIC The NAVIC or NAVigation with Indian Constellation is an autonomous regional satellite navigation system developed by Indian Space Research Organisation (ISRO) which would be under the total control of Indian government. The government approved the project in May 2006, with the intention of the system completed and implemented on 28 April 2016. It will consist of a constellation of 7 navigational satellites.[10] 3 of the satellites will be placed in the Geostationary orbit (GEO) and the remaining 4 in the Geosynchronous orbit(GSO) to have a larger signal footprint and lower number of satellites to map the region. It is intended to provide an all-weather absolute position accuracy of better than 7.6 meters throughout India and within a region extending approximately 1,500 km around it.[11] A goal of complete Indian control has been stated, with the space segment, ground segment and user receivers all being built in India.[12] All seven satellites, IRNSS-1A, IRNSS1B, IRNSS-1C, IRNSS-1D, IRNSS-1E, IRNSS-1F, and IRNSS-1G, of the proposed constellation were precisely launched on 1 July 2013, 4 April 2014, 16 October 2014, 28 March 2015, 20 January 2016, 10 March 2016 and 28 April 2016 respectively from Satish Dhawan Space Centre.[13][14] The system is expected to be fully operational by August 2016.[15]

QZSS[edit] Main article: Quasi-Zenith Satellite System The Quasi-Zenith Satellite System (QZSS), is a proposed four-satellite regional time transfer system and enhancement for GPS covering Japan, and the Asia-Oceania regions. QZSS services are available on a trial basis as of January 12, 2018, and are scheduled to be launched in November 2018. The first satellite was launched in September 2010.[16]

Comparison of systems[edit] System

Owner

Coverage

Coding

BeiDou

Galileo

GLONAS S

GPS

NAVIC

QZSS

China

EU

Russia

United States

India

Japan

Regional (Global by 2020)

Global by 2020

Global

Global

Regional

Regional

CDMA

CDMA

FDMA

CDMA

CDMA

CDMA

Orbital altitude

Period

21,150 km (13,140 mi)

12.63 h (12 h 38 min)

Revolutio ns 17/9 per sidere al day

Number of satellites

5 geostationary orbit (GEO) satellites, 30 medium Earth orbit (MEO) satellites

19,130 k m (11,890 mi)

20,180 km (12,540 mi )

36,000 km (22,000 mi)

11.26 h 14.08 h (14 h (11 h 5 min) 16 min)

11.97 h (11 h 58 min)

1436.0m (IRNSS-1A) 1436.1m (IRNSS-1B) 1436.1m (IRNSS-1C) 1436.1m (IRNSS-1D) 1436.1m (IRNSS-1E) 1436.0m (IRNSS-1F) 1436.1m (IRNSS-1G)

17/10

2

23,222 km (14,429 mi)

24 by design, 14 operational, 4 commissioni ng, 30 operational satellites budgeted

17/8

28 (at least 24 by design) including:[ 17]

24 operation al 2 under check by the satellite prime contracto r 2 in flight

3 geostationary orbit (GEO) satellites, 31 (at least 5 24 by geosynchrono design)[18] us (GSO) medium Earth orbit (MEO) satellites

32,000 km (20,000 mi )

In 2011 the Governme nt of Japan has decided to accelerate the QZSS deployme nt in order to reach a 4-satellite constellati on by the late 2010s,

tests phase

while aiming at a final 7satellite constellati on in the future

Frequenc y

1.561098 GHz ( B1) 1.589742 GHz ( B1-2) 1.20714 GHz (B 2) 1.26852 GHz (B 3)

1.164– 1.215 GHz (E5a and E5b) 1.260– 1.300 GHz (E6) 1.559– 1.592 GHz (E2-L1-E11)

Around 1.602 GH z (SP) Around 1.246 GH z (SP)

Status

22 satellites operational, 40 additional satellites 20162020

18 satellites operational 12 additional satellites 2017-2020

Operation Operationa al l

Precision

System

10m (Public) 0.1m (Encrypted)

BeiDou

1m (Public) 0.01m (Encrypted)

Galileo

4.5m – 7.4m

GLONAS S

1.57542 G Hz (L1 signal) 1.2276 GH z (L2 signal)

15m (Without DGPS or WAAS)

GPS

1176.45 MHz( L5 Band) 2492.028 MHz (S Band)

7 satellites fully operational

10m (Public) 0.1m (Encrypted)

NAVIC

1m (Public) 0.1m (Encrypte d)

QZSS

Augmentation[edit] GNSS augmentation is a method of improving a navigation system's attributes, such as accuracy, reliability, and availability, through the integration of external information into the calculation process, for example, the Wide Area Augmentation System, the European Geostationary Navigation Overlay Service, the Multi-functional Satellite Augmentation System, Differential GPS, GPS Aided GEO Augmented Navigation (GAGAN) and inertial navigation systems.

DORIS[edit] Main article: DORIS (geodesy) Doppler Orbitography and Radio-positioning Integrated by Satellite (DORIS) is a French precision navigation system. Unlike other GNSS systems, it is based on static emitting stations around the world, the receivers being on satellites, in order to precisely determine their orbital position. The system may be used also for mobile receivers on land with more limited usage and coverage. Used with traditional GNSS systems, it pushes the accuracy of positions to centimetric precision (and to millimetric precision for altimetric application and also allows monitoring very tiny seasonal changes of Earth rotation and deformations), in order to build a much more precise geodesic reference system.[19]

Low Earth orbit satellite phone networks[edit] The two current operational low Earth orbit satellite phone networks are able to track transceiver units with accuracy of a few kilometers using doppler shift calculations from the satellite. The coordinates are sent back to the transceiver unit where they can be read using AT commands or a graphical user interface.[20][21] This can also be used by the gateway to enforce restrictions on geographically bound calling plans.