Remote Sensing and GIS - 1

Hi friends, this is the time for us to know something about remote sensing and GIS and their application in civil engineering. Whatever may be the project that you are taking, you first need a map of the area before you could survey it to know all the topographical and geological features of that area. Inorder to survey in a more effiicient and easy manner, we civil engineers go for remote sensing and GIS.

Inorder to make the article a readable one, I have planned to post it in parts. This is the first part.

First of all, let us know what remote sensing actually means. It is the method of acquiring the information about an object without having any physical contact with it. It can be done through the sensors attached to the satellite. There are two types of sensors used in this process namely the active and passive sensors. The passive sensors are engaged with the job of detecting the reflected rays(sunlight, infra red, etc), while on the other hand the active sensors emit certain energy and locates the object in terms of height, speed, direction, etc.

Remote sensing data provides spatial information about the earth's resources, GIS relates the different spatial data and their attribute data so as to use them in various fields of civil engineering. The details collected from remote sensing includes hydrology, terrain, land use, drainage, etc. These details can be integrated in GIS to solve many problems in civil engineering.

 

 

The basic principle of remote sensing

Some current uses of GIS and Remote Sensing in civil projects are housing, sanitation, power, water supply, disposal of effluents, urban growth, irrigation project design and planning, new road alignment etc. For this Remote sensing and GIS are used to generate development models by integrating the information on natural resources, demographic and socio -economic data in a GIS domain with satellite data.

Primary concept of GIS

The above figure shows the primary concept of GIS. This is the way the sptial data acquired through the remote sensing is split in GIS for various or specific purposes. GIS is a software that enables us to get answers for a set of questions like 'what is the drainage pattern of the area?, what are the catchment area available?, etc. For this purpose there are three views of GIS namely - The database view, the map view and the model view.

The Database view
A GIS is a unique kind of database of the world—a geographic database (geo database). It is an "Information System for Geography." Fundamentally, a GIS is based on a structured database that describes the world in geographic terms.

The database view

The  Map view
A GIS is a set of intelligent maps and other views that show features and feature relationships on the earth's surface. Maps of the underlying geographic information can be constructed and used as "windows into the database" to upport queries, analysis, and editing of the information.

The Map view

The Model view
A GIS is a set of information transformation tools that derive new geographic datasets from existing datasets. These geo-processing functions take information from existing datasets, apply analytic functions, and write results into new derived datasets.

The model view

References
 http://fosetonline.org/Academicmeet/C&A/APPLICATION%20OF%20REMOTE%20SENSING%20AND%20GIS%20IN%20CIVIL%20ENGINEERING.pdf