Photo Gray Tones
The gray tones depicted on panchromatic air photos are the result of surface spectral
reflectance variations. These variations result from terrain factors including soil color and
texture, vegetative cover, soil moisture, and slope/aspect. Every landform has an
observable distribution of gray tones, which is a manifestation of the surface conditions
on the landform. A given distribution of gray tones may or may not be a definitive
identifier of a landform. The gray tones may be an indicator in certain situations. For
example, two landforms which can be indicated by photo gray tones are the mottled gray
tone of a young glacial ground moraine and the dull uniform gray tone in large field
patterns representing glacial lakebeds. A typical description is “light tones occur on
cultivated open areas, dark tones where tree covered.”
Source: Terrain analysis procedural guide for surface configuration, US Army engineer
topographic laboratories, p. 5-12