A further improvement on conventional photography has been achieved in the recent technique of remote sensing which involves simultaneous sensing in several bands of the electromagnetic spectrum in contrast to sensing in only the visible band of the spectrum as in conventional photography. Much useful information, of value to botanists, geologists, environmental biologists and soil scientists, has already been obtained by the use of two new remote sensing techniques, viz., infrared surveying and radar mapping. Some of the practical results obtained by the use of these techniques are described in Morris and Martin-Kaye (1973). Recently, automated computer processing techniques have been developed which use data acquired from overhead multispectral scanners and spectral pattern recognition algorithms to classify surface materials on the ground. The capability to classify surface vegetation from aircraft and satellite data in densely forested areas, such as the Himalayas, allows the assessment of many environmental parameters since vegetation is a sensitive indicator of its environment.
Remote sensing techniques have also proven useful in identifying various conations of soil such as top soil, scraped soil, etc. Remote sensing has been employed to study the effects of air pollution (especially S02) on vegetation. Infrared colour photography is used for mapping and for detecting disease in trees and crops as well as for locating the extent of thermal pollution in rivers etc.