[GRASS-user] region settings

[Daniel Lee]

Hi Janet,

2012/8/9 Janet Choate <jsc.eco at gmail.com>

> i reprojected to utm with r.proj, that worked great.  however, i'm still a
> bit worried about the resolution.  after i reprojected to utm, the region
> settings now show the nsres/ewres to be approx 1.0 and not 30.  i can
> aggregate up to 30 - but i'm worried if i do so.  should i trust that it is
> really 1 meter?  i requested 1 arc second data (30m) from NED, but it is
> possible i ended up with 1m.  do you know if there is any way to tell if
> the data is really 1m or already at 30m - other than with g.region?


I'm not sure on that one. It could be that you've got the wrong data.
However, reprojecting using r.proj takes the region settings of the target
mapset. Therefore if had a resolution of 1 m beforehand, the source maps
will have been resampled to 1 m while reprojecting (the default method is
nearest neighbor).

I would zoom in and take a look at the data using the measuring tool. If it
looks like it's been resampled from 30m to 1m (especially using nearest
neighbor), then that's probably what happened ;)

There's a great help text on reprojecting rasters in the manual of r.proj.
If you're wanting to look at it on the web, check it out here:
http://grass.osgeo.org/manuals/html70_user/r.proj.html
For some reason, when I google r.proj I get two versions of the manual. The
second one with the link is the one I find more helpful because it has code
in it that you can pretty much cut and paste into your GRASS environment.

Best,
Daniel
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