distance calculations
Michael Shapiro
shapiro at zorro.cecer.army.mil
Wed Aug 4 21:49:25 EDT 1993
In <9308010329.AA07425 at brier.ecn.purdue.edu> mccauley at ecn.purdue.edu (Darrell McCauley) writes:
>I'm trying to do distance calculations. Here's a full sample
>program:
>#include <math.h>
>#include "gis.h"
>int main (argc, argv)
> char **argv;
> int argc;
>{
> double x1=8.0,y1=7.0,x2=6.0,y2=5.0;
> G_gisinit (argv[0]);
> printf ("projection: %d\n", G_begin_distance_calculations());
> printf ("G_distance: %g\n", G_distance (x1,y1,x2,y2));
> printf (" hypot: %g\n", hypot (x1-x2,y1-y2));
>}
>Is there any thing wrong with this? I run this simple
>program under (x,y), LL, and utm, I get the same answers:
> GRASS 4.1 > simple
> projection: 0
> G_distance: 8
> hypot: 2.82843
>(that is, except for the projection). A distance of 8 is clearly
>wrong.
Declare: double G_distance();
I probably forgot to put this declaration into "gis.h"
--
Michael Shapiro shapiro at zorro.cecer.army.mil
U.S. Army CERL (217) 373-7277
P.O. Box 9005
Champaign, Ill. 61826-9005
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