WHAT IS AERIAL PHOTO INTERPRETATION ?

AERIAL   PHOTO    INTERPRETATION ?

It is defined as an act of examining photographic images and judging their significance. This includes interpreter and photograph
1. Interpreter:

• Good vision
• Well-trained for photo interpreter
• Sufficient experience of doing the work successfully
• Good knowledge of locality and type of forest present there
• Good power of concentration and great deal of patience

2. Photographs: Photographs should be of high quality and free from defects

Elements of aerial photo interpretation

It is done on the basis of following pictorial elements:

1. Tone: Tone refers to the relative brightness of objects on photographs. On B/W photographs, tone varies from white (1) to black (10) with various shade of grey in between. The tone of an object provides more information than any other single element of object recognition. Young stands are lighter compared to mature stands. The phenological changes such leaf fall, new flush of leaves, flowering and fruiting also affect tone of trees’ spps on APs.
2. Size: The size of an object image depends upon the object’s size, scale of photograph and resolve power of camera. The minimum size of object to be visible on APs should be about 1/20th minimum. A super highway should not be confused with rural road, a small residence with an apparent building, etc.The size of the crowns and their heights often give a good indication for identification of certain species when other pictorial elements, i.e. tone may not differentiate them from other species.
3. Shape: Shape refers to the general form or outline of individual objects eg. roads, building, rivers, trees, etc.The shape of a tree crown is important in identification of the species. Most conifers and young broadleaved species have an ovate shaped while those of mature broadleaved species are dome shaped crowns (circular).
4. Texture: Texture is the degree of coarseness or smoothness of an image and is dependent on shape, size, tone, scale, sun elevation as well as reflection properties of the objects. In forestry, smooth texture is often associated with young trees and coarser texture with older trees. It is more useful in interpretation of larger groups of objects like tree stands. Branching habit and age of trees decide the texture of trees.
5. Location or site: As different species are found in different places under the influence of locality factors, location or site is helpful in identifying species, egridges and slopes are covered by coniferous in hills whereas, nallahand valleys covered by broadleaved species. In plain, only certain species are found while in hills, other certain species are found, eg. Fir, spruce, chirpineand deodar occur in certain elevation and on certain aspects.
6. Association: Association refers to occurrence of certain features in relation to others. Some tree species are so closely associated that each helps to confirm the presence of others. Certain tree species can be identified by recognition of other species, which grow together, eg. Khairand Sisooare associated with fresh alluvial deposits in riverainareas.
7. Shadow: Shadow of objects falling on ground gives an indication of objects. It depends on the time of photography and direction of flight. Shadow of the trees falling on ground help in identification of species as they give an indication of the shape of the crown. Wind, however, affects the shadows and makes identification difficult
8. Pattern: Pattern refers to the spatial arrangement of objects like orchard, plantation, etc is a characteristics of man made objects. Those can be easily separated from natural objects such as natural forest, ridges, drainage, which have random pattern.It describes the regularity and characteristics arrangement of different shades of tone or texture in a photograph.