[GRASSLIST:2151] Where's the data within a cell?

Rich Shepard rshepard at appl-ecosys.com
Wed Jul 25 17:49:12 EDT 2001

  In GRASS raster maps, where in a cell is the geographical location? Is it
in the center? The lower, left corner? The upper, left corner?

  This can certainly make a difference, especially when cell size is 30 m or
greater. It also matters when converting data from one format to another.
For example, when I wrote a program several years ago to convert ARC/Info
grid files to ASCII x, y, z files, I had to assume that the northing,
easting was in the lower, left corner because I could find nothing to tell
me differently. But, if GRASS holds the location in the center of the cell,
then such translated data could be off by 15 m. That's a lot, even for the
real world.



Dr. Richard B. Shepard, President

                       Applied Ecosystem Services, Inc. (TM)
            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
                 Making environmentally-responsible mining happen.

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