Geographic boundaries in GRASS raster/vector files
rshepard at appl-ecosys.com
Sat Apr 8 09:38:35 EDT 2000
On Fri, 7 Apr 2000, Eric G . Miller wrote:
> There's no difference between corners and edges. Other software just
> takes the least/greatest values for min(x,y),max(x,y) to form the
> bounding box -- grass refers to edges. So you just take the extrema and
> use them as your edges. You might add a little to get an even cell
> size. Maybe make a MASK layer to block out those areas outside your
> area of interest -- you could use an SPC boundary map to create one.
I suspected as much, thank you for confirming it. Now for the translation:
north = max(y)
south = min(y)
west = min(x)
east = max(x)
> I've yet to get the State of California (as a whole) to fit in a UTM
> projection ;-). So, we use an Albers Equal Area Projection.
Well, we all know that California is different. :-)
Almost all of our projects are small. I think the largest area covered 440
acres. *Our* problem is finding data of sufficiently large scale to provide
the detail we need. Well, ... actually, when it comes to in-river work,
we've covered several miles all at once. But, nothing state-wide so far.
We are preparing some demos which cover the entire Willamette River
valley, a linear distance of about 150 miles. I know that somewhere there is
a dividing line between the Oregon North Zone and the Oregon South Zone in
the State Plane Coordinates system, but I don't know just were it is. Both
Oregon and Washington handle the problem of two zones by projecting one onto
the other. Hey, that works for us, too!
Dr. Richard B. Shepard, President
Applied Ecosystem Services, Inc. (TM)
Making environmentally-responsible mining happen. (SM)
2404 SW 22nd Street | Troutdale, OR 97060-1247 | U.S.A.
+ 1 503-667-4517 (voice) | + 1 503-667-8863 (fax) | rshepard at appl-ecosys.com
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