[GRASS-user] V.distance

Markus Neteler neteler at osgeo.org
Wed Jan 9 03:35:36 EST 2008


On Jan 8, 2008 11:54 PM, Richard Chirgwin <rchirgwin at ozemail.com.au> wrote:
> What algorithm does V.distance use for calculations?

For cartesian coordinate systems it currently uses 2D/3D Pythagoras.
 Vect_line_distance() in
 http://trac.osgeo.org/grass/browser/grass/trunk/lib/vector/Vlib/line.c

For LatLong it uses geodesic distance calculation (reference):
  Vect_line_geodesic_length() in
  http://trac.osgeo.org/grass/browser/grass/trunk/lib/vector/Vlib/line.c
 which calls
  http://trac.osgeo.org/grass/browser/grass/trunk/lib/gis/geodist.c

Markus

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