[GRASS-user] Projection Units and Values Negatively Affect r.topidx Results

[Rich Shepard]

On Thu, 18 Feb 2010, Markus Metz wrote:

> Wouldn't make sense, 32.82281055 international feet are about 10.12
> meters. I guess your projection is missing the information about how to
> convert feet to meters. In proj4 lingo that would be +to_meter=0.3048. The
> problem could be that for your dem, the horizontal units are
> Planar_Distance_Units: User_Defined_Unit and not international feet (this
> problem might originate from using ESRI software to generate the source
> data but that's a wild guess and doesn't help you much).

Markus,

   I agree that the planar distance units appear to be the source of the
problem (and it would not surprise me if that originates with ESRI), which
leaves the same question yet to be answered: how do I fix this? What do I
need to do to make GRASS accept meters as the defined units and ensure that
the projection transformation converts all measurements from international
feet to meters?

   The attempts to convert the DEMs seem to recognize this issue:

Input Projection Parameters:  +proj=lcc +lat_1=43 +lat_2=45.5 +lat_0=41.75
+lon_0=-120.5 +x_0=400000.00000000 +y_0=0 +no_defs +a=6378137
+rf=298.257222101 +nadgrids=/usr/local/grass-6.4.0svn/etc/nad/WO
Input Unit Factor: 0.3048

Output Projection Parameters:  +proj=lcc +lat_1=43 +lat_2=45.5 +lat_0=41.45
+lon_0=-120.5 +x_0=400000 +y_0=0 +no_defs +a=6378137 +rf=298.257222101
+nadgrids=/usr/local/grass-6.4.0svn/etc/nad/WO
Output Unit Factor: 1

Notice that the input parameters have a unit factor to convert from feet to
meters, yet the error is still thrown that "Input raster map is outside
current region".

Rich