Application Of Remote Sensing In Topographic And Land Cover Mapping

FACULTY OF GEOINFORMATION SCIENCE AND ENGINEERING SGS 1523 REMOTE SENSING APLICATIONS ON TOPOGRAPHIC AND LAND COVER MAPPING

Dr. BAHARIN BIN AHMAD

MOHD FARID BIN FAUZI AG090090 900707-03-5463

September 7,

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INTRODUCTION TOPOGRAPHY Topography is come from Greek words τόπος topo-, which mean place, and γράφω graphia, that’s bring the meaning of writing. Based on this word, topography mean the study of Earth's surface shape and features or those of planets, moons, and asteroids. It is an art or practice of graphic delineation in detail usually on maps or charts of natural and man-made features of a place or region especially in a way to show their relative positions and elevations. Topography specifically involves the recording of relief or terrain, the three-dimensional quality of the surface, and the identification of specific landforms. In modern usage,it been generate in electronic form and presented on a map by a variety of techniques, including contour lines, Hypsometric tints and relief shading. Topographic maps usually portray both natural and manmade features. They show and name works of nature including mountains, valleys, plains, lakes, rivers, and vegetation. They also identify the principal works of man, such as roads, boundaries, transmission lines, and major buildings. The wide range of information provided by topographic maps make them extremely useful to professional and recreational map users alike. Topographic maps are used for engineering, energy exploration, natural resource conservation, environmental management, public works design, commercial and residential planning, and outdoor activities like hiking, camping, and fishing.

LAND COVER MAPPING Land cover is important for many scientific, resource management and policy purposes and for a range of human activities. It can be define as key for environmental information. It is an important determinant of land use and thus of value of land to the society. Land cover varies at a range of spatial scales from local to global, and at temporal frequencies of days to millennia. As the need for environmental planning and management became important, an accompanying call for land cover information emerged in parallel. Land cover actually is a product of remote sensing, initially through aerial photography. We can find the population of plant in certain place through land cover mapping. Usually, people use land cover mapping to see the change in population and growth in certain place. We can also determine the effect of land use or human activities to the environment especially the plant population.

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REMOTE SENSING Remote sensing can be defined as the acquisition and recording information about an object without being in direct contact with that object. Based on that definition, we can conclude that aerial photogrametry, sounders(used in ocean topography) and even data from satellite are also remote sensing. Mapping process actually use remote sensing technique long time ago. The modern remote sensing started in 1858 when Gaspard-Felix Tournachon first took aerial photographs of Paris from a hot air balloon. It is actually very simple method in remote sensing like in photography, but as we want to determine in detail on spatial, spectral and other properties, many innovation have been added to get and ideal instrument to give more data to us. Nowadays, remote sensing mostly used the data from the satellite. This is because the data is very easy to get. The development of artificial satellites in the latter half of the 20th century allowed remote sensing to progress to a global scale as of the end of the cold war. Instrumentation aboard various Earth observing and weather satellites such as Landsat, the Nimbus and more recent missions such as RADARSAT and UARS provided global measurements of various data for civil, research, and military purposes. Space probes to other planets have also provided the opportunity to conduct remote sensing studies in extraterrestrial environments, synthetic aperture radar aboard the Magellan spacecraft provided detailed topographic maps of Venus, while instruments aboard SOHO allowed studies to be performed on the Sun and the solar wind, just to name a few examples.

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Figure 1: Operation date for different remote sensing platform. A mark change occurred about 1960 when spaceborne platform become operational.

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PREVIOUSLY IN TOPOGRAPHIC AND LAND COVER Previously in topographic and land survey mapping, surveyor use direct or terrestrial survey technique which need them to go to the field to make survey. They use traversing, triangulation and trilateration for horizontal positioning and for vertically, they use geodetic levelling, trigonometric heighting, barometric levelling and tilting.

Diagram 1 : traversing technique which been used in terrestrial survey. Traverse networks involved placing the survey stations along a line or path of travel, and then using the previously surveyed points as a base for observing the next point.

Diagram 2: Geodetic labeling for vertical positioning.

Diagram 3: Vertical positioning by using trigonometrical heighing Diagram 4: Long ago, surveyors totally use triangulation technique in making map. They take the data from benchmark (point that surveyors made into which an angle-iron could be placed to bracket ("bench") a leveling rod, thus ensuring that the leveling rod can be

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repositioned in exactly the same place in the future.) and then bring it to their temporary benchmark and their field study.

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In terrestrial survey, they use many instrument such as theodolite, electronic distance metre (EDM), total station, dumpy level and other instrument. Surveyor take long time to finish their surveying job because of the physical aspect on the place. For example; it is hard to find the coverage of Bruguiera sp. In mangrove swamp due to the difficulties to go to that place and how to use all those equipment at that place. The other thing is surveying project on that time need a lot of many because it is costly. They need to consider for the food, petrol or diesel and other important thing that needed during making the project.

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TECHNOLOGY OF REMOTE SENSING Coarse-spatial resolution meteorological satellite data have been available since the 1960s but civilian remote sensing of the Earth’s surface from space only began in 1972. This is after the launcing of Earth Series Satellite which conduct the data of earth obvservation for remote sensing. On that time, the satellite image only produce data at medium spatial resolutions which is only 250 metres spatial resolution. Year by year, we can see the improve in satellite remote sensing. We can now get data from satellite platforms with a large number of sensor such as in Terra and ENVISAT and data with higher spatial resolution like from IKONOS and Quickbird. The production of satellite being increasing and it is being estimate that about 100 new satellite now been launced between 1996 and 2006. Even develop country just like our country have launched their own remote sensing satellite for their own reason. Most of the people get the data from Landsat series(multispectral and thematic mapper), SPOT, MODIS and IKONOS. That is because this satellite have the latest technology and given better data for spatial resolution, spectral resolution, temporal resolution, and radiometric resolution. The most popular satellite data is from French satellite SPOT(Satellite Pour l'Observation de la Terre) that was initiated by the CNES (Centre national d'études spatiales — the French space agency) in the 1970s and was developed in association with the SSTC (Belgian scientific, technical and cultural services) and the Swedish National Space Board (SNSB). Instead of having good resolution (10 metre spatial resolution), it also have two sensor which can scanning two images on the same time. It is good for those who want to get real-time data but you must pay for it. That is believed that there is satellite which is more ideal than that and being used by certain country for their military and other function only for them. Diagram 4: SPOT 5 satellite for remote sensing studies

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Diagram 5: IKONOS satellite which give until 0.6 metre spatial resolution.

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REMOTE SENSING IN TOPOGRAPIC MAPPING Previously, we have been told about the definition of topography. As we know, mapping shows the detail of the physical geography of the ground data. It shows not only naturally covered object but also human-made features. The important thing in a topographic map are imaginary latitude and longitude that is important to determine the place of object on the ground. The cross point between both latitude and longitude is call coordinate. Due to the latitude and latitude coordinate system, each point will have only one coordinate. This coordinate can easily been found by using Global Positioning System (GPS) which is also categorized as remote sensing. The other usage of remote sensing is to draw a map correct to the ground. There will be some error due to carelessness of the surveyor who conduct the project. By using remote sensing, the data shows correctly the position of certain object on the ground. The data from satellite or aerial photogrammetry can gives us the differences of height on the ground. This differences shown clearly in those data obtained. In case of difficulties of field study, remote sensing can help to determine and study the dangerous place or place that cannot been reach by the human. From above, we can take all the data including places that is not easy to determine. There is many ways to studied certain place data such as by using geometrical correction. The data from the satellite been corrected by using polynomial formula.

Diagram 3: the image that being captured by using aerial photogrammetry (above) is then being change to topographic map (below). It gives exact position of the point or object on the ground. [REMOTE SENSING APPLICATION IN TOPOGRAPHIC AND LAND COVER MAPPING]

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X1=a0+a1x1+a2y1+a3x1y1+a4y1 2 +a5x12 Y1=b0+b1x1+b2y1+b3x1y1+b4y1 The of the point is determined using GPS by going to field study. 2 coordinate +b5x12point or known as ground control point (GCP) is three; but for more Minimum accurate geometrical correction, there need more GCPs as we can reduce the error using 2nd,3rd,4th and so on degree of polynomial formula. From this, we can get true to scale data and of course, the area, length and other information can easily get. In distance area, it is not easy to find the accurate distance between the places especially from the mainland to the island. By remote sensing, we can get almost accurate distance from the data obtained from the satellite and have been corrected by using those formula above. As the satellite or aerial photogrammetry images are being captured or scanned far above the earth surface, it covered larger area; and for the satellite data, although it covered larger area, but it also give out the higher resolution data that can determine easily by researcher. Actually, the remote sensing for topography is by using Light Detection and Ranging (LIDAR). Aircraft is the best platform to use this method. LIDAR is an optical remote sensing technology that measures range or other information of a distant target by measuring the properties of scattered light. The distance to an object or surface being determined by using the laser pulses. Similar to radar technology which uses radio waves, which is light but not in the form of visible spectrum, the range to an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal. Interferometric Synthetic Aperture Radar (IFSAR). This geodetic method uses two or more synthetic aperture radar (SAR) images to generate maps of surface deformation or digital elevation using differences in the phase of the waves returning to the satellite. It is categories as active remote sensing as the antenna transmits radiation which is then reflected from the target, as opposed to passive sensing where the reflections detected come from ambient illumination. Topographic mapping is not only mean for the land shapes, elevation and height but also covered volcano topographic and ocean topographic. Ocean topography is not easy to find without using remote sensing technique. In remote sensing, we use sounder to determine the distance between the sounder to the sea-floor. The sounder transmit sound wave to

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the sea-floor and receive it back. That’s mean the sounder has both transmitter and receiver. The distance between the sounder and sea-floor distance is determine based on the delay time for the sound wave to reflected back to the sounder. The wave velocity is fixed but the delay time is based on its distance travel. Not only sounder has this function. Ship also have this distance measurement equipment. They use SONAR as to determine the sea-floor shape and elevation. Beside that, those ship also use SONAR whether for fishing or military uses. (determining the present of submarines) Why the ocean topography is important? It is nothing to use for those who did not use the ocean; but for those who relate with ocean, ocean topography is very important. They can prevent the collision between their ship and the rock or sea-floor. Not only that, they also use it to control the type of fish that they want to catch. It is actually based on the habitat of the fish whether in deep or shallow sea.

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REMOTE SENSING IN LAND COVER MAPPING Land cover mapping is play a big role to the earth. As modern world has been created, the natural resources management should be handle by human. Human life is related to nature and nature also relate to human. It is like one interaction between all living organism on the earth. As a consequence of steady population growth, commercial and residential development in the We do land cover mapping to manage our resources, manage the land use, plan what to do with the resources, town planning and the most impotant thing maintain the balance of nature. How remote sensing helps us in land cover mapping? By using remote sensing, we can easily classify the resources on the ground for which the area covered with. We can determine the land cover due to digital number (DN) classification technique. Digital number of different object might have different number. It is based on how the electromagnetic radiation from the sun (passive remote sensing) or satellite(active remote sensing) itself being reflected back by the object. If you using data of Landsat TM, you can use seven different bands to study the differences between object on the ground. For example; when you studied about plant or vegetative covering, you can use band 3,4 and 5. Those bands can easily differentiate the different type of vegetative.

Diagram 7: it is good if using satellite image to make the land cover mapping because it cover larger area and with higher spatial resolution. Yokohama picture by IKONOS satellite with 1 metre spatial resolution

The differences also can be determine by using certain combination of RGB(red, blue and green combination). It gives different colour of the studied

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are if it is not the same type of object or species. This process is important to determine the differences between one covering area with another.

Table 1: The function of different wavelength in order to differentiate area.

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DIAGRAM 8: how to classify object due to its digital number. We can determine the class of object by minimum distance to means classified survey(top-left), nearest neigbour classification (bottom-right), maximum likehood classification strategy(bottom-left) and parallelepiped classification strategy (top-right). The three point will easily classify.

We can use false-colour composite in determining the covered area of certain species or type of land cover because there is only a little bit different between species especially for vegetation if we use the true-colour composite. In true-colour, it will show green and light green but in falsecolour it will show different solor light dark green and pink.

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Figure 2: false-colour image

Figure 3: true-colour image

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The are other factor that can help us in determination of vegetation species: 1. Size 2. Shape 3. Texture 4. Colour 5. Shadow If we know the angle of the sun, we can also measure the height of the tree just from satellite data without go to the field study. Remote sensing is important in land cover mapping because it can decrease the cost for the project. As we know, this project is costly if did not use remote sensing technology. Previously, people take long time to discover the population of vegetation in the forest because they need to every inch of the jungle but by using remote sensing, you just go to certain place on that jungle and then you can get the whole land covered of the jungle.

To make sure the land cover mapping is in a perfect condition, the characteristic of the remote sensed data should be suitable and matching with the study area. A land cover classification system which can effectively employ orbital and high altitude remote sensor data should meet the following criteria 1. The minimum level of interpretation accuracy in the identification of land use and land cover categories from remote sensor data should be at least 85 percent. 2. The accuracy of interpretation for the several categories should be about equal. 3. Repeatable or repetitive results should be obtainable from one interpreter to another and from one time of sensing to another. 4. The classification system should be applicable over extensive areas. 5. The categorization should permit vegetation and other types of land cover to be used as surrogates for activity.

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6. The classification system should be suitable for use with remote sensor data obtained at different times of the year. 7. Effective use of subcategories that can be obtained from ground surveys or from the use of larger scale or enhanced remote sensor data should be possible. 8. Aggregation of categories must be possible. 9. Comparison with future land use data should be possible. 10. Multiple uses of land should be recognized when possible.

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LIMITATION IN REMOTE SENSING Remote sensing is not magic. We also need to go to the field to find certain data. That because we can classify thing but do not know what is it, so we need to know what is it. Remote sensing also can have error due to atmosphere that surround around the earth. Those particle cause scattering and reflection of EMR that will cause error. The EMR reflected or scattered from the neighboring place also effect the image. The satellite also can uncalibrated when being used for a long time. So, the image produce might be not the same in ratio or image might be poor. The mistake in choosing data will also increase the cost for each project.

CONCLUSION We must choose the ideal way to do something. As in topographic and land cover mapping, it is shown that is easy if we use the remote sensing technique so why should we ignore it. But, if we making mistakes in choosing data then our project will cost more than traditional way. We must combine the remote satellite data and land survey data because each data should have their own error. Combination of data will make our result is more accurate.

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REFERENCE Books: Lillesand, T.M & R.W. Keifer, 1987. Remote sensing and image interpretation. Second edition. J. Wiley & Sons, Inc. Buiten, H.J. & J.G.P.W. Clevers, 1993. Land observation by remote sensing: Theory and Applications. English version. Gordon and Breach Science Publishers Gibson, P.J. & C.H. Power, 2000. Introductory remote sensing: principles and concepts. Routledge,NY

Journal: Riffat Naseem Malik & Syed Zahoor Hussain, 2006. Land-cover mapping: a remote sensing approach. Department of Biological Sciences, Quad-i-Azam University, Islamabad, Pakistan. Thurston Regional Planning Council, July 2001. Land cover mapping of Thurston county: methodology and applications International Journal of Remote Sensing, November 2008. Volume 29, Issue 22

Website: • • • • • • • • •

http://www.remotesensing.gov.my/tmsPUBLISHER/images/default/publication _3rdmicrowave/3rdmicrowave_paper9.pdf (27 August 2009) http://www.gisdevelopment.net/technology/ip/techip011.htm (27 August 2009) http://www.usgcrp.gov/usgcrp/ProgramElements/land.ht (27 August 2009) http://www.pakbs.org/pjbot/PDFs/38(3)/PJB38(3)559.pdf (27 August 2009) http://www.trpc.org/resources/landcoverreport02_02_05.pdf (27 August 2009) http://www.trpc.org/resources/sample.pdf (27 August 2009) http://en.wikipedia.org/wiki/Triangulation (1 September 2009) http://en.wikipedia.org/wiki/Topography (1 September 2009) http://www.merriam-webster.com/dictionary/topography (1 September 2009)

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http://en.wikipedia.org/wiki/SPOT_(satellites) 2009) http://en.wikipedia.org/wiki/Remote_sensing 2009) http://en.wikipedia.org/wiki/Image_registration September 2009)

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