d) Vegetation patterns reflect both regional and local climatic conditions.
Locally, a small difference in soil moisture condition is often detected by a corresponding change of vegetation; this is very useful in landslide investigations. For example, areas of wet vegetation, represented on the photographs by dark spots or "tails", are a clue to seepage on slopes.
Orchards are often located on well-drained soils.
Cultural patterns reflect how humans adjust to the natural terrain, on which they live and work. An understanding of these patterns and the reasons for their presence can be valuable indicators of soil type, moisture and other characteristics, e.g., drainage ditches indicate a high water table, vertical cuts along highways indicate the presence of bedrock, sloping cuts are typical of unconsolidated materials.
In addition, some other important features are:
Texture is the frequency of tonal changes within an aerial photograph that arise when a number of features are viewed together.
Shadows of objects aid in their identification.
Size of an object is a function of photo scale. The sizes of objects can be estimated by comparing them with objects for which the size is known.
THE ANALYSIS PROCEDURE DESCRIBED ABOVE IS SYSTEMATICALLY RECORDED ON A PHOTO-INTERPRETATION CHART. FIG. 1 SHOWS SUCH A CHART ON WHICH FEATURES FOR A NUMBER OF ROCK TYPES ARE GIVEN AS A GUIDE.
A BLANK CHART IS PROVIDED FOR YOU TO RECORD OBSERVATIONS.