The same principles hold true in ground observation. Without clear shadows such as these, it is extremely difficult for an aerial photo interpreter to identify certain objects. From the air, shadows often reveal more than the shape of the object itself. Monument is over 500 feet high. Shine alone can betray the best camouflage.
Tone is the relative shade of gray in which objects appear on an aerial panchromatic photograph.
Shine is the flashing of light reflected from a smooth surface. By the addition of texturing material a smooth or shiny surface may be made to produce a dark tone or value in a photograph. The height and distance of an aerial observer from an object determine what he can see and identify. As a general rule, contrasting objects are seen from the air, under ideal conditions, at a scale of 1 foot per thousand feet of elevation. For example, an object 2 feet in size can be seen at 2,000 feet, if the observer knows where to look for it.