//---------------------------------------------------------------
//                              CalcHeightDelta
//
//  General: This function calculates the height delta between two
//           geographic points based on the class's carpet of heights
//
//  Paramters: 
//          Point1: first point (in)
//          Point2: second point (in)
//          
//  Return Value: The height difference between the two points
//
//---------------------------------------------------------------
// programmer: Yossi Humus
// Date: October, 1978