The raster resolution for the rainfall data was 0.25 degrees, or about
27 km. per pixel. So each pixel covers about 750 sq.km. The column with
the precip_sum will be mm/raster cell, or mm over an area of 750,000,000
sq.m.
Does that make more sense?
On 06/22/2010 03:57 PM, Sandile Gumede wrote:
It's in mm/hr.
Are these values normal, to me it seems like big values because they
are ranging from 2000-4500, see below I just copied a few:
120795|4076||1|4076|4076|0|4076|0|0|0|4076
120796|4080||1|4080|4080|0|4080|0|0|0|4080
120797|4084||1|4084|4084|0|4084|0|0|0|4084
120798|4088||1|4088|4088|0|4088|0|0|0|4088
120799|4092||1|4092|4092|0|4092|0|0|0|4092
120800|4096||1|4096|4096|0|4096|0|0|0|4096
120801|4100||1|4100|4100|0|4100|0|0|0|4100
120802|4104||1|4104|4104|0|4104|0|0|0|4104
120803|4108||1|4108|4108|0|4108|0|0|0|4108
120804|4112||1|4112|4112|0|4112|0|0|0|4112
120805|4116||1|4116|4116|0|4116|0|0|0|4116
120806|4120||1|4120|4120|0|4120|0|0|0|4120
120807|4124||1|4124|4124|0|4124|0|0|0|4124
120808|4128||1|4128|4128|0|4128|0|0|0|4128
120809|4144||1|4144|4144|0|4144|0|0|0|4144
120810|4148||1|4148|4148|0|4148|0|0|0|4148
120811|4152||1|4152|4152|0|4152|0|0|0|4152
120812|4156||1|4156|4156|0|4156|0|0|0|4156
2010/6/22 Micha Silver <[email protected] <mailto:[email protected]>>
On 22/06/2010 13:08, Sandile Gumede wrote:
Thanks, I finally got the results.
That's good to hear.
Now the question I would like to ask is that, from these columns
I got the values but which unit are these values are measured? Is
it (mm) or ?
Well, that depends on the units of the raster. If the raster
values are mm. then each column represents mm per *raster cell*.
So if you have a rainfall raster with values in mm., and
resolution of 10 meters, then the numbers in the columns are
mm/100sq.m.
--
Micha
On Sat, Jun 19, 2010 at 9:57 PM, Micha Silver <[email protected]
<mailto:[email protected]>> wrote:
Hello Sandile:
I tried to duplicate your steps and it seems to work for me.
Here's what I did:
wget
ftp://trmmopen.gsfc.nasa.gov/pub/gis/3B42RT.2010032900.1day.tif
wget
ftp://trmmopen.gsfc.nasa.gov/pub/gis/3B42RT.2010032900.1day.tfw
gdalinfo 3B42RT.2010032900.1day.tif
Driver: GTiff/GeoTIFF
Files: 3B42RT.2010032900.1day.tif
3B42RT.2010032900.1day.tfw
Size is 1440, 480
Coordinate System is `'
Origin = (-180.000000000000000,60.000000000000000)
Pixel Size = (0.250000000000000,-0.250000000000000)
....
---- Note: no projection info above ----
---- Now I use the -projwin option of gdal_translate to
select a small window
gdal_translate -a_srs EPSG:4326 -projwin 34.0 33.0 36.0 29.0
3B42RT.2010032900.1day.tif rainfall_il.tif
---- GEOGCS entry now shows 4326 ----
g.mapset map=ASTER_DEM loc=WGS84
----- A location setup as EPSG:4326----
r.in.gdal israel.tif out=rainfall_il
r.univar rainfall_il
100%
total null and non-null cells: 77760000
total null cells: 0
Of the non-null cells:
----------------------
n: 77760000
minimum: 0
maximum: 34
range: 34
mean: 0.364583
mean of absolute values: 0.364583
standard deviation: 3.45241
variance: 11.9192
variation coefficient: 946.948 %
sum: 28350000
----- Now using an existing catchment vector map ----
v.rast.stats vect=arava_wsheds rast=rainfall_il colpre=precip
v.info <http://v.info> -c arava_wsheds
Displaying column types/names for database connection of layer 1:
INTEGER|cat
CHARACTER|label
DOUBLE PRECISION|area_km
INTEGER|precip_n
DOUBLE PRECISION|precip_min
DOUBLE PRECISION|precip_max
DOUBLE PRECISION|precip_range
DOUBLE PRECISION|precip_mean
DOUBLE PRECISION|precip_stddev
DOUBLE PRECISION|precip_variance
DOUBLE PRECISION|precip_cf_var
DOUBLE PRECISION|precip_sum
---- and some values ----
v.db.select arava_wsheds
cat|label|area_km|precip_n|precip_min|precip_max|precip_range|precip_mean|precip_stddev|precip_variance|precip_cf_var|precip_sum
21|Jordan|1055.231692|2|0|0|0|0|0|0||0
19|Hidan|987.811979|2|0|0|0|0|0|0||0
28|Og|124.122969|||||||||
36|Zarqa|273.606213|||||||||
24|Kidron|122.460114|||||||||
9|Darga|289.012122|||||||||
6|Arugot|236.365116|1|0|0|0|0|0|0||0
26|Mujib|1277.546513|2|0|0|0|0|0|0||0
---- (Many catchments have 0 or no value because of the small
region I chose. The global data is 1/4 degree resolution and
my region is only 2 deg E-W.)----
HTH...
--
Micha
On 06/17/2010 12:50 PM, Sandile Gumede wrote:
Hi
It is still giving me -NULL value error.
Do you think maybe its the way I downloaded my rainfall
data? This is the site where I downloaded my data sets_
ftp://trmmopen.gsfc.nasa.gov/pub/gis/ _and this data covers
the whole world, the only thing I did was to clip a specific
region (using coordinates) that is in South Africa to do my
analysis. I used a bash script to download and project the
data, see below:
#!/bin/bash
wget
ftp://trmmopen.gsfc.nasa.gov/pub/gis/3B42RT.2010032900.1day.tif
wget
ftp://trmmopen.gsfc.nasa.gov/pub/gis/3B42RT.2010032900.1day.tfw
gdal_translate -of GTiff -co "PROFILE=GeoTIFF" -co
"INTERLEAVE=PIXEL" -co "COMPRESS=LZW" -co "TILED=YES" -a_srs
EPSG:4326 -a_ullr 18.2987501 -33.6795831 19.1712501
-34.3487498 3B42RT.2010032900.1day.tif TRMMLast1day.tif
On Thu, Jun 17, 2010 at 8:41 AM, Sandile Gumede
<[email protected] <mailto:[email protected]>> wrote:
Hi
It is still giving me -NULL value error.
Do you think maybe its the way I downloaded my rainfall
data? This is the site where I downloaded my data sets_
ftp://trmmopen.gsfc.nasa.gov/pub/gis/ _and this data
covers the whole world, the only thing I did was to clip
a specific region (using coordinates) that is in South
Africa to do my analysis. I used a bash script to
download and project the data, see below:
#!/bin/bash
wget
ftp://trmmopen.gsfc.nasa.gov/pub/gis/3B42RT.2010032900.1day.tif
wget
ftp://trmmopen.gsfc.nasa.gov/pub/gis/3B42RT.2010032900.1day.tfw
gdal_translate -of GTiff -co "PROFILE=GeoTIFF" -co
"INTERLEAVE=PIXEL" -co "COMPRESS=LZW" -co "TILED=YES"
-a_srs EPSG:4326 -a_ullr 18.2987501 -33.6795831
19.1712501 -34.3487498 3B42RT.2010032900.1day.tif
TRMMLast1day.tif
2010/6/15 Micha Silver <[email protected]
<mailto:[email protected]>>
On 15/06/2010 14:35, Sandile Gumede wrote:
Hi
If I run g.region rast=rainfall -p, I get:
OK, what you've done here is change the current
region to match the raster "rainfall".
Can you now try:
v.rast.stats -c vect=catchments rast=rainfall
pref=precip
projection: 3 (Latitude-Longitude)
zone: 0
datum: wgs84
ellipsoid: wgs84
north: 33:40:46.49916S
south: 34:20:55.49928S
west: 18:17:55.50036E
east: 19:10:16.50036E
nsres: 0:00:05.01875
ewres: 0:00:02.18125
rows: 480
cols: 1440
cells: 691200
and If I run r.univar rainfall, I get the following
output:
100%
total null and non-null cells: 691200
total null cells: 0
Of the non-null cells:
----------------------
n: 691200
minimum: 0
maximum: 3094
range: 3094
mean: 22.0228
mean of absolute values: 22.0228
standard deviation: 76.1639
variance: 5800.94
variation coefficient: 345.841 %
sum: 15222164
On Tue, Jun 15, 2010 at 12:22 PM, Hamish
<[email protected] <mailto:[email protected]>> wrote:
Micha wrote:
> 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,
that is perfectly normal for a lat/lon map away
from the equator.
longitude scales a cos(lat).
> (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...)
the results of:
g.region -p rast=mapname
r.univar mapname
could help.
Hamish
--
Kind Regards
TS Gumede
CSIR, Meraka Institute
072 258 1650
This mail was received via Mail-SeCure System.
--
Micha Silver
http://www.surfaces.co.il/
Arava Development Co. +972-52-3665918
--
Kind Regards
TS Gumede
CSIR, Meraka Institute
072 258 1650
--
Kind Regards
TS Gumede
CSIR, Meraka Institute
072 258 1650
This mail was received via Mail-SeCure System.
--
Micha Silver
Arava Development Co. +972-52-3665918
http://surfaces.co.il
--
Kind Regards
TS Gumede
CSIR, Meraka Institute
072 258 1650
This mail was received via Mail-SeCure System.
--
Micha Silver
http://www.surfaces.co.il/
Arava Development Co. +972-52-3665918
--
Kind Regards
TS Gumede
CSIR, Meraka Institute
072 258 1650
This mail was received via Mail-SeCure System.
--
Micha Silver
http://www.surfaces.co.il/
Arava Development Co. +972-52-3665918
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