Why Aerial Survey is Consider as a Reliable Technique for the Study of Natural Resources?

In keeping with the growing realization of the adverse effects of soil erosion, deforestation, pollution, etc., on our natural resources, considerable progress has been made in recent years in devising suitable techniques for the periodi­cal preparation of inventories of such resources.

Until recently, much of this information used to be compiled at ground level but the trend has now shifted to the use of aerial survey as a more effective method. Aerial survey is now regarded as a reliable technique for the study of natural resources.

Various kinds of sophisticated photographic equipment and techniques have been employed in such aerial surveys and one that has proved particularly valuable is the technique of low-level stereophotography (Grimes and Hubbard, 1972).

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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.