Introduction to remote sensing

Abstract

Remote sensing consists of gathering information about objects and features without placing instruments in contact with them. The sensors are placed on aircraft or spacecraft platforms and the earth’s surface surveyed for its natural resources. Electromagnetic radiation (EMR) in the visible, infrared and microwave bands are employed, mostly solar radiation or natural emissions. The interactions of EMR with the objects are impressed as "signatures" on the reflected, scattered, transmitted or emitted EMR. The sensors employed are (i) cameras with normal or special films sensitive to infrared, (ii) electro-optical systems in the scanning mode using solid state detectors, (iii) imaging tubes and devices and (iv) microwave systems which can gather data even when clouds intervene. The data gathered with the sophisticated systems are converted into imagery or directly processed on electronic computers. The processed data are then interpreted in terms of known ground truths or 'EMR signatures' of the objects. Remote sensing has wide applications in agriculture, forestry, geology, hydrology cartography and oceanography.