[GRASS-user] v.rast.stats

GRASS GRASS user
1

Hi,

After running v.rast.stats vect=catchments rast=rainfall colprefix=precip, I ran v.info -c catchments and I got 9 new columns:
precip_min, precip_max, precip_ran, precip_mean, precip_std, precip_var, precip_cf_, precip_sum,…,precip_per.

How do I then be able to see how much rain has fallen in each catchment(polygon), and which direction is the water flowing?

–
Kind Regards
TS Gumede
CSIR, Meraka Institute
072 258 1650

2

Hi,

After running v.rast.stats vect=catchments rast=rainfall colprefix=precip, I ran v.info -c catchments and I got 9 new columns:
precip_min, precip_max, precip_ran, precip_mean, precip_std, precip_var, precip_cf_, precip_sum,…,precip_per.

How do I then be able to see how much rain has fallen in each catchment(polygon), and which direction is the water flowing?

v.db.select catchments column=precip_sum

If you display the stream network over the catchments, and use the “display=shape,dir” option to d.vect then you’ll see small arrows along the streams indicating direction of flow.

··· 
-- 
Micha Silver
Arava Development Co. +972-52-3665918
[http://surfaces.co.il](http://surfaces.co.il)
3

(back on the ML)

Hi Sandile:
The error is popping up, apparently, because of the strange “-NULL” value. What is -NULL??
Can you display the rainfall raster? Does it look OK (some value everywhere?)

Perhaps run a check on the original rainfall.tif with gdalinfo to see what range of values it is showing? Then do r.info rainfall to show what range the GRASS raster has.

··· 
-- 
Micha Silver
[http://www.surfaces.co.il/](http://www.surfaces.co.il/)
Arava Development Co.  +972-52-3665918
4

if I run r.info -g rainfall, I get:

north=-33.679583
south=-34.34875
east=19.17125
west=18.29875

and if I run v.info -g catchments, I get:

north=-33.6795831
south=-34.3487498
east=19.1712501
west=18.2987501
top=0.000000
bottom=0.000000

OK, now we see that the regions are identical.
I’d like to see also the full output of
r.info rainfall
(it will give the max-min values of the raster) and also the output of
gdalinfo rainfall.tif (the original tiff file)
Perhaps then we can understand where the -NULL values are from?

··· 
-- 
Micha Silver
[http://www.surfaces.co.il/](http://www.surfaces.co.il/)
Arava Development Co.  +972-52-3665918
5

Hello Sandile
(Please keep messages on the list- maybe others can help…)

Hi

Below is the output of r.info rainfall

Type of Map: raster Number of Categories: 1020
Data Type: CELL
Rows: 480
Columns: 1440
Total Cells: 691200
Projection: Latitude-Longitude
N: 33:40:46.49916S S: 34:20:55.49928S Res: 0:00:05.01875
E: 19:10:16.50036E W: 18:17:55.50036E Res: 0:00:02.18125
Range of data: min = 0 max = 1020

The only unusual thing I notice above is that the resolution settings for the raster are different N-S and E-W. This came from the original tiff (see below) which also has rectangular pixels, and your use of the “-o” option when importing.
I wonder if that’s what is causing your problems with v.rast.stats?? (the v.rast.stats module creates a temp raster at the current region’s resolution settings, which might be different from this rainfall raster’s rectangular resolution…)

Please give us the output of g.region -p.

Perhaps someone with more experience can answer: If v.rast.stats runs using a raster with resolution different from the current region settings what will happen?

Regards,
Micha

··· 
-- 
Micha Silver
[http://www.surfaces.co.il/](http://www.surfaces.co.il/)
Arava Development Co.  +972-52-3665918