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

[Hamish]

Markus:
> > I think that a change of the base unit of a location requires a new
> > location and reprojection of the data. I may be wrong, though.

Rich:
>   Should I join the proj4 mail list and ask there? I'd
> sure like to resolve this issue quickly.

it's a question of GRASS DataBase setup, nothing to do with geodesy, so
I doubt the proj4 list could help much.

what format is the original source dataset? can you post what gdalinfo
says about it?


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.

rule of thumb: libgis is rather good at what it does, I would not try
and outsmart it by editing these things by hand.

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.

"d.grid -w" overlay as a quick & dirty way to verify you got everything
right.

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


Hamish