Fundamentals of Soil Science (1+1)

Classification

Classification of aerial photography:

On the basis of scale:

• Large scale : Between 1:5,000 and 1: 20,000
• Medium scale: Between 1: 20,000 and 1:50,000
• Small scale : Smaller than 1:50,000

On the basis of tilt:

• Vertical : When the tilt is within 3 ( nealy vertical)
• Oblique: Low oblique ( horizon does not appear but tilt is more than 30)
• Horizontal or terrestial: Camera axis is kept horizontal

On the basis of angular coverage:

• Narrow angle : Angle of coverage less than 500
• Normal angle : Angle of coverage less than 600
• Wide angle : Angle of coverage less than 900
• Super-wide angle : Angle of coverage less than 1200

On the basis of film:

• Black and white panchromatic
• Black and white infrared
• Colour
• Colour infra-red/ false colour

Application of aerial photography:

Mapping: This is a valuable tool for soil mapping. It has been found to be fast, accurate, indispensable in inaccessible areas and cost effective in the long run.

Interpretation: Photointerpretation has revolutionalised the method of data collection in various disciplines. It is greatly reduced the field work and thereby the cost. The information is reliable and acceptance for most studies such as in the fields of geology, water resources, geomorphology, hydrogeology, forestry and ecology, soil surveys and urban and regional planning.

Map substitute: In a situation where there are no adequate large scale maps available, aerial photographs can serve as map substitutes in the form of photomaps.

Limitations:

• Elevations are not shown on the photographs.
• Scale is not precisely uniform and the differences of scale between adjoining photographs create some problems in matching and transferring of soil boundaries.
• Distance and directions can not be measured as accurately as on topographical maps.