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

[Rich Shepard]

On Wed, 17 Feb 2010, Hamish wrote:

> Markus is right, you need a new location with meters as the native unit,
> and reproject into it ... because the map data's internal coordinates
> will still be in feet even if you manually change the location to think
> the general unit is meters.

Hamish, et al.:

   Thinking about this over night I see that reprojecting to a new location
is the solution.

   I posted the metadata and r.info results in an earlier response to Markus.

> Is it just the single DEM raster in this location? If so, you might try
> running r.region to re-position the array in space + resolution.

   Unfortunately, it's all Oregon data. Why the state's chosen projection is
described in mixed units I've no idea (and they may not, either). Attached
are the metadata for both the DEM (which is at 10m resolution) and all other
(vector) data.

> If you did change the location's native units, they'd be in decameters not
> meters, right?

   I don't think so.

   In retrospect, I used the values in the DEM metadata and in the vector
metadata and mixed meters and feet. I believe that re-importing all DEM data
into a new location where I convert the e-w and n-s resolutions to 10.0
meters will fix the issue. I don't know if I need to reproject the vector
files, too, since v.info shows nothing about units.

   I'm open to suggestions and advice.

Rich
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