Remote sensing and it's applications
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Remote sensing uses electromagnetic radiation to obtain information about objects without direct contact. It has many applications in civil engineering including regional planning, terrain mapping, water resources engineering, transportation analysis, and landslide studies. Remote sensing data is collected spatially and converted to geospatial data through GIS systems. This data provides valuable terrain, geological, and land use information useful for site investigations, infrastructure planning and development, monitoring of dams, reservoirs, and flooding, mineral exploration, urban development, and construction of protective structures.
Remote sensing and it's applications
- 1. Remote Sensing: Applications in Civil engineering GIS: Assignment-1 Waleed Liaqat 122 – A Submitted to: Engr M. Zaheer
- 2. What is Remote Sensing? Remote sensing (RS) is a method of obtaining information from distant objects without direct contact. This is possible due to the existence or the generation of force fields between the sensing device and the sensed object. Usable force fields are mechanical waves in solid matter (seismology) or in liquids (sound waves). But the principal force field used in remote sensing is that of electromagnetic energy. The emission of electromagnetic waves is suitable for directional separation. Thus, images of the radiation incident on a sensor may be generated and analyzed. Remote sensing has a lot of applications in engineering particularly in civil engineering. One of the most common forms of remote sensing in civil engineering is photogrammetry i.e. the use of photographs to gain knowledge regarding photographed objects and entities. In civil engineering projects, Remote sensing techniques can become potential and indispensable tools. Various civil engineering application areas include regional planning and site investigation, terrain mapping and analysis, water resources engineering, town planning and urban infrastructure development, transportation network analysis, landslide analysis, etc. Figure shows use of electromagnetic radiation in remote sensing.
- 3. Applications of Remote Sensing In civil engineering, remote sensing is used to gain data regarding the earth. Remote sensing collects data in spatial form. In case of the earth, the data collected is called geospatial data. This is then converted to valuable information through a geo-informatics system (GIS). Some of the applications of RS in civil engineering are: Regional Planning and Site Investigations Site investigations in general require topographical and geological information. Remote sensing data allows such information to be obtained. In case of dam site investigation e.g., information on topography such as type of terrain (hilly or plain) is essential. Geological considerations also matter and include data regarding the different soil and rock types present at a site. In selecting river-crossing sites for bridges and pipelines, an important consideration is the stability of slopes leading down to and up from the water crossing. Such slopes include riverbanks, terrace faces and valley wall. History of river erosion and sedimentation would give clues needed for locating the sites where scour is likely to occur. High spatial resolution satellite data with stereo vision capability can facilitate depth perception in the above said investigations and also for regional planning of large commercial airports, harbors, industrial towns and recreational sites. Terrain Mapping and Analysis Assessment of the performance of the terrain for specific developmental activities can be made through terrain evaluation. For this, terrain information can be acquired from RS data and by generating the Digital Terrain Model (DTM). A DTM is an ordered array of numbers representing the spatial distribution of terrain characteristics stored in a computer so as to enable the determination of any quantitative data pertaining to terrain. DTM facilitates investigation of a number of alternative horizontal and vertical alignments of canals, roads, pipelines or corridors for different construction projects. In an engineering construction like dam, the knowledge of material comprising the terrain is essential for proper planning, location, construction and maintenance of engineering facilities. For computation of hydrograph parameters like peak runoff rate, time of concentration and time to peak, the height and slope information derived from Digital Elevation Model (DEM) are useful. Remote sensing based inventory of construction material such as boulders, quarry rock, sand – clay mixtures etc. would help to locate suitable sites of construction materials. Water Resources and Hydrological Engineering By analyzing multi-date RS data, it would be possible to monitor the effects of dam construction. Remotely sensed data of pre and post dam construction can reveal the forest and other land at different water levels. This would also help in preliminary investigation of finding suitable areas for human resettlement.
- 4. To study the feasibility of inter basin transfer of surplus flood flows, RS data can be cost effective. In large area reconnaissance studies, various technically feasible and economically viable alternatives in locating surplus flow diversion routes to water deficient basins can be arrived at. Also, reservoir sites to store the surplus flows in these basins could be identified. Such projects of large dimensions require considerations of land use / land cover, soil and geological mapping, terrain evaluation, construction material inventory etc. the latter are derived from satellite remote sensing data of particular resolution depending upon the scale on which such information is required. The water storage built in through reservoirs, tanks, etc., are often reduced due to sedimentation. Remotely sensed data can be used to monitor the water bodies over time and assess the silting condition. In case of gauged reservoirs of medium to large sizes, RS data can provide an assessment of sediment volume and reduction in the capacity of sediment volume and reduction in the capacity of the reservoir. Characterization of water bodies in terms of geological, geomorphological, hydro geological, soil and land use / land cover parameters carried out using RS data enables conservation of land and water resources. The RS based input integrated with ground based information through GIS is useful for broad reconnaissance level interpretation of land capability, irrigation suitability, potential land use, water harvesting areas, monitoring the effects of soil and water conservation measures, estimation of run off and sediment yields and monitoring land use change including land degradation. The commercial areas of irrigation projects are fed by different sources of irrigation like reservoir, tanks, ponds and wells. Assessment of command areas and crops would be highly useful in water release policy or conjunctive use of water in the overall project command area. Satellite data has been advantageously used to obtain such information on surface irrigation projects. In case of floods, appropriate flood management work has to be executed to reduce the damages and utilize the floodwaters. For this purpose satellite RS provides comprehensive, reliable and timely information (multi-date) on flood inundated and drainage congested areas, extent of damage to crops, structure etc. river configuration, silt deposits and vulnerable areas of bank erosion. This data is used for construction of protective structures. Satellite derived snow cover assessment is being extensively used as an important input in snow melt runoff prediction models to assist in multipurpose reservoir operations. Image interpretation can be used in a variety of ways to help monitor the quality, quantity of water resources. It is well proven in exploring ground water prospect zones. Potential ground water areas cannot be seen directly on satellite images but they can be identified by the physical changes the formation of an aquifer has on the visible surface. Sediment pollution is often clearly depicted on aerial and space images. Materials that form films on the water surface, such as oil films, can also be detected through the use of aerial and satellite images. RS can also be used to identify potential fishing zones in coastal areas.
- 5. Town Planning And Urban Development The unprecedented growth of urbanization in many countries across the globe has given rise to problems of housing, sanitation, power, water supply, disposal of effluents and environmental pollution. Systematic mapping and periodic monitoring of urban land use is therefore necessary for proper planning, management and policy making (with the help of RS and GIS optimal master plan for development and management of urban settlements can be prepared). For sustainable development of urban clusters, optimal urban land use plans and resources development models need to be generated by integrating the information on natural resources, demographic and socio – economic data in a GIS domain with the currently available satellite data. Mining and Mineral Exploration: RS data allows identification of mineral deposits in remote areas. Once a mineral deposit is identified, mining techniques are discussed. RS data gives us suitable data regarding the geological and the topographical conditions in which the mineral resource exists and this helps in planning of the mining operation particularly in tunnel engineering. Also as mentioned above minerals such as oil, limestone etc. have important uses in manufacturing of materials for civil engineering projects and so locating their deposits is essential and RS data can help us do that economically. Transportation Network Analysis With the help of high spatial resolution data, mapping of road and rail network can be accomplished. This facilitates in deciding optimal routing for transport of construction materials. Even, identification of village roads is possible in certain cases. RS data can also be used in construction of roadways and other forms of transport systems. Landslide Studies Landslides are the most common and recurring hazards in mountainous areas causing enormous loss of life and property every year. The parameters that contribute directly or indirectly include lithology and structure, landform, slope, aspect, relief, vegetation cover, climatic and human activities. Information on these aspects can be collected and integrated for preparing a landslide hazard zone map that can be done through RS. This allows for construction of protection facilities.