[GRASS-dev] r.watershed question
Michael Barton
michael.barton at asu.edu
Sat Dec 20 02:15:21 EST 2008
Should r.watershed be giving negative accumulation values? I ran it on
the spearfish 30m DEM and got results that are increasingly positive
downstream for one drainage (as I would expect) and increasingly
negative downstream for other drainages (I would not expect this). Do
I misunderstand what accumulation is supposed to do?
Here is r.info for the results.
r.info atest_rwaccum
+
----------------------------------------------------------------------------+
| Layer: atest_rwaccum Date: Sat Dec 20 00:08:40
2008 |
| Mapset: PERMANENT Login of Creator:
cmbarton |
| Location:
Spearfish60_test |
| DataBase: /Users/Shared/
grassdata |
| Title: Watershed accumulation: overland flow that traverses
each cell ( |
| Timestamp:
none |
|
----------------------------------------------------------------------------|
|
|
| Type of Map: raster Number of Categories:
81709 |
| Data Type:
CELL |
| Rows:
466 |
| Columns:
633 |
| Total Cells:
294978 |
| Projection: UTM (zone
13) |
| N: 4928000 S: 4914020 Res:
30 |
| E: 609000 W: 590010 Res:
30 |
| Range of data: min = -90540 max =
81709 |
|
|
| Data
Source: |
|
elevation
.dem at PERMANENT |
|
|
|
|
| Data
Description: |
| generated by
r.watershed |
|
|
|
Comments
: |
| Processing mode: All in
RAM |
|
|
| r.watershed elevation="elevation.dem at PERMANENT"
accumulation="atest_\ |
| rwaccum"
memory=300 |
|
|
+
----------------------------------------------------------------------------+
(Sat Dec 20 00:09:19 2008) Command finished (0 sec)
I am running this on my Mac using GRASS 6.4SVN from 10 December. If
there was a major bug fix since that date, I can recompile tomorrow.
Michael
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