> Lisa Mcculler (mcculler@vinny.cecer.army.mil ) writes on 16 Jul 93:
> >Can you in GRASS not only get the distance between two points but
> >also a true <aircraft> heading?  If so, is it an easy process?
> 
> It's my understanding, from recent discussion on the programmer's
> list, that it is not currently possible to do this (in a general way)
> in GRASS programs. If it is, could someone please explain how?
> 
My first approach would be to use the coordinates of the two points
to calculate dx and dy (or dN and dE), then use trigonometry (you
know, the stuff with sinuses and arctangents etcetera) to calculate
the angle of the vector between the two points. Shouldn't be too
difficult to get a true heading out of this. My second approach 
would be to wonder why the Grass programmers do not consider this a
solution, and to suppose that the curviness of the earth probably 
messes up the cleanest of calculations...


----\_\_\_--\_----\_------\_-------------------- P. Martijn van Leusen -------- 
     \_   \_ \_\_\_\_      \_        Dept of Pre- and Protohistoric Archaeology
      \_\_\_  \_ \_ \_      \_        University of Amsterdam, The Netherlands
       \_      \_    \_ \_\_ \_               martijn@scanner.frw.uva.nl
--------\_------\_----\_--\_--\_\_\_\_-----------------------------------------

