Remote sensing as the name defines itself is an art of sensing or knowing about an article, region or area from distance remote beyond normal visible and audible reach.
This technical art started with taking photograph of a region by cameras fixed or hanging in flying aeroplanes. These photo graphs are called aerial photographs. The operation is called aerial survey. The aeroplane flies taking traverses on equi distance and fixed lines on the meridian which is called “SWATH”. The automatic camera attached to the aeroplane takes continuous photograph of the region coming under its coverage. Later on these photographs are arranged according to specified codification for further use in the field of surveys of Engineering, Agriculture, Geology, Forestry and Environmental Science.
With advancement of space science and launching of specified satellite, this science has improved a lot. The digital auto cameras are fixed in the orbiting satellite which takes continuous photographs of the objects and areas coming within its range.These images are enlarged into slides and photo plates. This is called satellite imagery.
To make these images informative, one has to execute different processes with them through a number of instruments. Some of the important instruments are mirror stereoscope, illuminative magnifier, pocket stereoscope, Digital Planimeter, Parallax Bar, Procom and Enlarger.
By using these applications one can have clear idea of continents, measurement of heights over a three dimensional profile of landmarks. Flood plains of river basin, view of draught hit area, areas hit by natural calamities, areas hit by forest fire and mining disaster. It is also used for Environmental Monitoring and helps in study of changes in land profile , changes in vegetation and agriculture profile , water reservoir location and water quality monitoring . With the advent of digital image processing facility, now it has become possible to analyse the images in three dimensional format, in less time and with freedom of more and more manipulation to bring out more accurate study results.