Fundamentals of Soil Science (1+1)

Introduction

Definition:

Aerial photography is defined as the science of obtaining photographs from the air using various platforms, mostly aircraft, for studying the surface of the earth . The pictures taken by camera fitted in an aircraft and flying over the predetermined height, depending on the scale of aerial photography and focal length of camera.

• Aerial photographs gives a bird’s eye view of large areas.
• The sun provides the source of energy ( electromagnetic radiations or EMR ) and the photosensitive film acts as a sensor to record the images.
• Variations in the grey tones of the various images in a photograph indicate different amounts of energy reflected from the objects as recorded on the film.
• The photographs contain 50 to 65 percent overlap which is essential for stereoscopic viewing and analysis of stereo pairs.
• The aerial photographs ranging in scale from 1:8000 to 1: 60,000 are used in different types of soil surveys.
• In soil survey , we mostly use panchromatic black and white air photos taken with a black and white film. In these photographs, there are many shades of grey colour.
• Black and white air photos can indicate a lot of information about land forms, vegetation, human interference as well as soils. Natural colour and infrared film are also used for aerial photography, especially for forest areas to discreminate forest types/ species.
• Many landforms – terraces, flood plains, sand dunes, coastal plains, plateaus, paleochannels, hills, valleys and mountain can be recognized on the photographs based on their shapes, relative heights and slopes. Difference in tones or colour may also reflect soil differences.
• When we look at an aerial photograph , we can see various objects of different sizes and shapes. Some of these objects may be readily identifiable while others may not be, depending on the interpreter’s perception and experience.
• Individual objects like trees, houses, roads, foot paths, field boundaries, lakes, river courses etc, are imaged clearly depending on the scale of photographs. These ‘landmarks’ serve as effective reference point or local control points that facilitates a soil surveyor in orientation and navigation during the field work and in demarcating boundaries of high local accuracy.
• Base maps for publication can be prepared from aerial photographs economically and in reasonable time.