[GRASSLIST:7104] Re: d.measure in feet or meters?
hamish_nospam at yahoo.com
Thu Jun 9 22:42:25 EDT 2005
> I have a location projected to U.S. State plane feet. This projection
> uses the U.S. foot for distance. When I use the d.measure tool it
> returns the units in meters. Are the units really in meters or are
> they feet and mislabeled to meters?
> I noticed that under my location directory there is a file called
> PROJ_UNITS that has the following:
> unit: USfoot
> units: USfeet
> meters: 0.30480060960121920243
d.measure calls both G_begin_distance_calculations() and G_distance() in
lib/gis/distance.c shows that G_begin_distance_calculations() does this:
factor = G_database_units_to_meters_factor();
and then G_distance runs this:
factor * hypot (e1-e2,n1-n2);
So it should be correct. Try throwing up a scalebar with d.barscale (-f)
and measure against that to test.
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