Interpretation of Aerial Photographs

One of the most effective tools that the geographer can use for the interpretation of the landscape is the aerial photograph.

The benefits of using aerial photographs are many:

When a scene is being viewed through an aerial photo, there is an immediate feeling of "naturalness", for the images can be intuitively understood by the observer
The topographic map is the result of a selective process with symbols representing selected real world features. Many facets of the landscape have to be omitted. This selectively is achieved at the expense of complex reality which is the forte of aerial photography
Aerial Photographs do not suffer from problems of human error in the way that maps sometimes do.

Whereas maps have symbols with an established meaning, aerial photos have different tones and patterns which must be distinguished and given a meaning by the interpreter.

SIZE- In using this property of an object, the photo interpreter must use an object or shape he/she recognizes and from this absolute size other objects can be placed into their relative size brackets.
SHAPE - Of all the properties in this list, shape is frequently the factor that provides the key evidence for the interpreter. This is especially the case with respect to landform interpretation where the external form of a feature is its identifying mark.
TONE - This property of a photograph is a result of the different light reflectivity of the surfaces that compose the earth's crust. No feature has a constant tone, for this will vary with the reflectivity of the object, the weather, the angle of light on an object and moisture content of the surface. The sensitivity of the response of tone to all the aforementioned variables makes it a very discriminating factor. Slight changes in the natural landscape are more easily comprehended because of tonal variations.
PATTERN - The spatial distribution of man-made or natural objects is frequently a vital clue to their identity.
TEXTURE - This is a difficult property to describe, but it is essentially a way of characterizing the smoothness or coarseness of the image on the photo. Texture involves the total sum of tone, shape pattern and size, which together give the interpreter an intuitive feeling for the landscape being analyzed. This property is not one that can be pegged down accurately, in definitional terms, but is nevertheless vital to the understanding of aerial photographs.