
Help on CalcHeight:
===================

After loading an RPC file, click on the bottom of
a vertical structure to set the base height and then
shift-click on the top of the structure. Press
the CALC button to display the structure's height,
latitude, longitude and base elevation. The number
in brackets next to the height is the minimum distance 
(in pixels) between the top pixel and a vertical line 
through the bottom pixel. It should be of the order of 1 
or less.

If no DEM is loaded, the base elevation is the average
value for the whole scene. 

If a DEM is used, the base elevation is taken from it.
The latitude and longitude are then orthorectified values.