[GRASSLIST:7089] d.measure in feet or meters?

GRASS GRASS user
1

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

Thanks,

David
--
David Finlayson
Marine Geology & Geophysics
School of Oceanography
Box 357940
University of Washington
Seattle, WA 98195-7940
USA

Office: Marine Sciences Building, Room 112
Phone: (206) 616-9407
Web: http://students.washington.edu/dfinlays

2

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
msurements.c.

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.

Hamish