Vertical exaggeration refers to the common practice in topographic profiles of different horizontal and vertical scales. It is expressed as a number, the ratio of the vertical to horizontal scale, and is almost always greater than 1. Over a long profile, if the same scale were used the differences in elevation would be very small compared to the distances involved and the profile would appear flat. The resulting scene would not look at all like the human eye perceives terrain; we overestimate slopes and the vertical dimension of topography.
|Vertical exaggeration x40. Note that this profile is about 1100 km long, and the vertical scale is about 12 km in total, so that the ratio between the two is about 100 to 1. If the profile were drawn to be 1000 pixels wide, it should be only 10 pixels high to have correct scaling.|
|Vertical exaggeration x10.|
|Vertical exaggeration x5. Note that we are still a long way from a 1:1 scaling, and already we think the profile is essentially flat.|
MICRODEM automatically suggests a vertical exaggeration; the user must consider that exaggeration can make slight slopes into cliffs. The suggested vertical exaggeration is the largest that will fit on the screen if the profile goes through the maximum elevation in the data set and the base of the profile is the minimum elevation. (If a default option is selected, the computer will find the elevation range within the smallest square that contains the view). Selecting a larger vertical exaggeration should be done with care, generally only if you do not check for the extreme values first and only after drawing a profile and finding it to lack sufficient vertical exaggeration. You can always select a smaller vertical exaggeration, but may get pancake topography. Vertical exaggeration is necessary to interpret line of sight profiles, but must be considered before jumping to conclusions about trafficability up slopes.
A true scale profile is only possible over short distances with very steep topography.
Last revision 2/27/2016