[GRASS-user] Raster resolution problems

[Hanlie Pretorius]

Hi,

I'm using GRASS6.4SVN on Windows XP.

I want to import TRMM precipitation data into a GRASS projected
(Transverse Mercator) location. I have previously successfully import
this data to a GCS (WGS84) location using the procedure at
http://grass.osgeo.org/wiki/Import_XYZ.

My problem is the grid resolution. The TRMM grid consists of 0.25°
squares, but projected they have different sizes. Here is the output
from v.report (area in km2) for a vector layer with the TRMM grid
squares, projected into the Transverse Mercator location:

-----
cat|LabelX|LabelY|LblOffsetX|LblOffsetY|Label|gRow|gColumn|RowCol|area
5|28.25|-28.75|-20|-20|28.25||||677.428350142518
11|28.5|-28.5|-20|-20|28.5||||678.961903132767
6|28.25|-28.5|-20|-20|28.25||||679.002141385312
1|28|-28.5|-20|-20|28||||679.062503849138
12|28.5|-28.25|-20|-20|28.5||||680.522519692921
7|28.25|-28.25|-20|-20|28.25||||680.563040996854
2|28|-28.25|-20|-20|28||||680.623828116383
13|28.5|-28|-20|-20|28.5||||682.070220966439
8|28.25|-28|-20|-20|28.25||||682.111024322052
3|28|-28|-20|-20|28||||682.172234597964
14|28.5|-27.75|-20|-20|28.5||||683.604982570918
9|28.25|-27.75|-20|-20|28.25||||683.646066944101
4|28|-27.75|-20|-20|28||||683.70769882544
15|28.5|-27.5|-20|-20|28.5||||685.126780361735
10|28.25|-27.5|-20|-20|28.25||||685.168144684034
-----

The projected grid 'squares' vary in size from 677km2 to 685km2. So
how am I supposed to set the resolution of the region when I do the
import?

(I previously tried to reproject the TRMM data from the GCS location
to the Transverse Mercator location, but then I ran into the same
problem - resolution.

Any ideas?

Thanks
Hanlie