Airphoto, Photo Index, and LANDSAT images.
Boundary lines are marked on the factor overlay where tonal and topographic changes
occur. These changes often occur at slope breaks, where the one landform surface
interfaces with another. These topo/tonal breaks enable the analyst to visualize boundary
lines for separating the landforms. While observing stereoscopically the relief-change
location, the analyst will note contrasting light to dark tones that represent changes in
vegetative cover. It is useful to observe the mosaic and topographic maps alternately for
these tonal/topo markings.
Tonal conditions should be noted on the photo index while marking boundaries to
separate landforms. Flat, generally level, or low relief terrain is characterized by dark
tones. The irregular surfaces of both wooded and urban terrain assist in the search for
landform boundaries. The irregular-relief indicates and elevated landscape. Dark-light
tones, and slope-break tone contrasts are indicative of relief difference in the predominant
features.
Source: Terrain analysis procedural guide for surface configuration, US Army engineer
topographic laboratories, p. 5-5