Hello GRASS users,
I have done some experiments about what happens to raster maps when you
change the resolution of your region and then run r.resample.
I work in a Lat/Lon projection and normally use a resolution of 15 seconds.
In a 1x1 minute area, there are sixteen 15 second raster cells.
I changed my resolution to 30 seconds (so there are now four 30 second raster c
ells)
then ran r.resample on my map.
This is what my map looked like at a resolution of 15 seconds:
|----|----|----|----|41:01N
| 1 | 2 | 3 | 4 |
|----|----|----|----|41:00:45N
| 5 | 6 | 7 | 8 |
|----|----|----|----|41:00:30N
| 9 | 10 | 11 | 12 |
|----|----|----|----|41:00:15N
| 13 | 14 | 15 | 16 |
|----|----|----|----|41:00N
This is what I thought my result would be at 30 seconds:
(take the value of the upper-left cell out of the center four)
|---------|---------|41:01N
| | |
| 1 | 3 |
| | |
|---------|---------|41:00:30N
| | |
| 9 | 11 |
| | |
|---------|---------|41:00N
But, what I got was this:
|---------|---------|
| | |
| 6 | 8 |
| | |
|---------|---------|
| | |
| 14 | 16 |
| | |
|---------|---------|
Can anyone explain why GRASS used the bottom-right cell out of the center four
and not the upper-left cell?
I can't find any reference of what GRASS does an any manual, but I've read on t
his
user group that it takes the upper-left cell.
Any help would be sincerely appreciated.
Thanks so much.
Julie Daniel
Physical Scientist
National Weather Service
(301) 713-1669
email: julied@lionheart.ssmc.noaa.gov