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REMOTE SENSING APPLICATION

Remote sensing become potential and indispensable tools for solving many problems of civilengineering.

Remote sensing observations provides data on earths resources in a spatial format

In structural engineering:

Fiber Optic Sensor

Any device in which variations in the transmitted power or the rate of Transmission of Light in opticalFiber are the means of measurement or control. Fibers can be used to measure temperature,pressure, strain, voltage, current, liquid level, rotation and particle velocity. The small size and the factthat no electrical power is needed at the remote location gives the fiber optic sensor advantages toconventional electrical sensor in certain applications. Fibers can be used to measure temperature,pressure, strain, voltage, current, liquid level, rotation and particle velocity. The small size and the factthat no electrical power is needed at the remote location gives the fiber optic sensor advantages toconventional electrical sensor in certain applications.

Structural Health Monitoring (SHM) provides designers with feedback ofstructural performance, assisting in development of structures with higher utilityand lower manufacturing costs. Structural Health Monitoring nowadayscontinues to advance from conventional strain gauges to FBG Fibre OpticSensors (FOS) and major breakthroughs in wireless remote monitoring. Fibreoptic sensors use optical wavelength of fibre Bragg grating to measurement,

temperature and strain. FOS has many advantages over the traditional electricalsystem such as: Suitable for long -term permanent SHM: monitor structure during constructionstage and whole lifespan as well No calibration needed One cable can have hundreds of the sensors Simple installation Cable can r un kilometres, no length limit Fibre optic sensors use light signal - no electrical sparking, intrinsically safe Gauge length can be few metres long to measure global behaviours of structures Suitable for both static and dynamic measurement The primary of monitoring is to ensure the longevity and safety of the structureas well as optimizing its management. To implement corrective measures andmaintenance action, monitoring must be enable the timely detection of anycondition or behaviour that could deteriorate the structure, deem it unsafe or

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potentially results in its failure.The monitoring programme plays a fundamental role during the construction

phase as it enables the verification of design hypotheses and construction processes, affecting, in some cases, the construction rate of the structures andoverall quality. Most defects are introduced already at the time of construction.Monitoring also allows performance evaluation of new materials andtechnologies used in bridge construction and rehabilitation. This objective iseasily achieved with fibre optic sensors since these sensors effectively integratein new materials such as fibrereinforced polymer composite.Furthermore, fibre optic sensors adapt perfectly to long-term monitoring of

bridges behaviour as well as short-term monitoring of bridges dynamic behaviour under traffic load.

Finally, monitoring can be used as a tool for supervised lifetime extension of bridges approaching the end of their life or in need of major repair. It ensuresthat such bridges are operated safely while allowing the postponement of majorinvestments and traffic disruption.

b- Town Planning and Urban Development:To achieve the objectives of making metropolis cities more livable and ofinternational standard, a co-coordinated and integrated approach among the

various agencies involved in urban development and provision of services areneeded including participatory process in planning and implementation at local

body levels. As well as to have planned and organized disposal of populationthrough growth centres, which will acts as counter-magnets to the cities growth.This growth may not able to withstand the existing infrastructure, traffic, road,drainage and utility networks etc. Advance urban planning is required for a

planned development of the area for which up to date real time and accurateinformation are the vital important. Geographical Information system& Remote Sensing is inevitable technology in the development of nationalInfrastructure and planning and they provide solution related to manyenvironmental.

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Applications of Remote SensingIn civil engineering, remote sensing is used to gain data regarding the earth. Remote sensingcollects 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

InvestigationsSite investigations in general require topographical and geological information. Remotesensing 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. Geologicalconsiderations also matter and include data regarding the different soil and rock typespresent at a site.In selecting river-crossing sites for bridges and pipelines, an important consideration is thestability of slopes leading down to and up from the water crossing. Such slopes includeriverbanks, terrace faces and valley wall. History of river erosion and sedimentation would giveclues needed for locating the sites where scour is likely to occur. High spatial resolution satellitedata with stereo vision capability can facilitate depth perception in the above saidinvestigations and also for regional planning of large commercial airports, harbors, industrial

towns and recreational sites.Terrain Mapping and AnalysisAssessment of the performance of the terrain for specific developmental activities can bemade through terrain evaluation. For this, terrain information can be acquired from RS dataand by generating the Digital Terrain Model (DTM). A DTM is an ordered array of numbersrepresenting the spatial distribution of terrain characteristics stored in a computer so as toenable the determination of any quantitative data pertaining to terrain. DTM facilitatesinvestigation of a number of alternative horizontal and vertical alignments of canals, roads,pipelines or corridors for different construction projects. In an engineering construction likedam, the knowledge of material comprising the terrain is essential for proper planning,location, construction and maintenance of engineering facilities. For computation ofhydrograph parameters like peak runoff rate, time of concentration and time to peak, theheight 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 EngineeringBy analyzing multi-date RS data, it would be possible to monitor the effects of damconstruction. Remotely sensed data of pre and post dam construction can reveal the forestand other land at different water levels. This would also help in preliminary investigation offinding suitable areas for human resettlement.

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To study the feasibility of inter basin transfer of surplus flood flows, RS data can be costeffective. In large area reconnaissance studies, various technically feasible and economicallyviable alternatives in locating surplus flow diversion routes to water deficient basins can bearrived at. Also, reservoir sites to store the surplus flows in these basins could be identified. Suchprojects of large dimensions require considerations of land use / land cover, soil andgeological mapping, terrain evaluation, construction material inventory etc. the latter are

derived from satellite remote sensing data of particular resolution depending upon the scaleon which such information is required.The water storage built in through reservoirs, tanks, etc., are often reduced due tosedimentation. Remotely sensed data can be used to monitor the water bodies over time andassess the silting condition. In case of gauged reservoirs of medium to large sizes, RS data canprovide an assessment of sediment volume and reduction in the capacity of sediment volumeand 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 ofland and water resources. The RS based input integrated with ground based informationthrough GIS is useful for broad reconnaissance level interpretation of land capability, irrigationsuitability, potential land use, water harvesting areas, monitoring the effects of soil and waterconservation measures, estimation of run off and sediment yields and monitoring land usechange including land degradation.The commercial areas of irrigation projects are fed by different sources of irrigation likereservoir, tanks, ponds and wells. Assessment of command areas and crops would be highlyuseful in water release policy or conjunctive use of water in the overall project commandarea. Satellite data has been advantageously used to obtain such information on surfaceirrigation projects.In case of floods, appropriate flood management work has to be executed to reduce thedamages and utilize the floodwaters. For this purpose satellite RS provides comprehensive,reliable and timely information (multi-date) on flood inundated and drainage congestedareas, extent of damage to crops, structure etc. river configuration, silt deposits andvulnerable 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 ofwater resources. It is well proven in exploring ground water prospect zones. Potential groundwater areas cannot be seen directly on satellite images but they can be identified by thephysical changes the formation of an aquifer has on the visible surface.Sediment pollution is often clearly depicted on aerial and space images. Materials that formfilms on the water surface, such as oil films, can also be detected through the use of aerialand satellite images.RS can also be used to identify potential fishing zones in coastal areas.