Difference between revisions of "Import TRMM"

From GRASS-Wiki
Jump to: navigation, search
m (Getting rotated maps in TRMM-HDF?)
m (Getting rotated maps in TRMM-HDF?)
 
Line 28: Line 28:
 
These are rotated and need to be rotated back. The (properly oriented) binary grids are much easier to handle than the original HDF files.
 
These are rotated and need to be rotated back. The (properly oriented) binary grids are much easier to handle than the original HDF files.
  
See also {{AddonCmd|r.flip|version=7}}
+
See also [[AddOns/GRASS7/raster#r.flip]]
  
 
[[Category: FAQ]]
 
[[Category: FAQ]]
 
[[Category: Import]]
 
[[Category: Import]]

Latest revision as of 02:06, 25 September 2014

TRMM data are usually delivered in a specific HDF format which is (partially) supported from GDAL 1.8+ (so, r.in.gdal would in theory work, see also below for rotation problem).

However, it is easier to get instead binary grids from here:

ftp://disc2.nascom.nasa.gov/data/TRMM/Gridded/3B43_V6/

The format is explained here. Hence, to import gridded TRMM into a Lat-long location with is done via

# generally
r.in.bin -f -b north=50 south=-50 east=180 west=-180 rows=400 cols=1440 ....

e.g.

r.in.bin -f -b input=3B43.100101.6.precipitation.bin output=3B43.100101.6.precipitation \
         north=50 south=-50 east=180 west=-180 rows=400 cols=1440

Optionally convert then from mm/hr to some other time unit.

Getting rotated maps in TRMM-HDF?

The TRMM 3B43 HDF files are rotated by 90° (clockwise), so north is right and west is up. The included datasets "precipitation" and "error" can be dumped from the HDF files to a binary or ASCII file with the "hdp" tool which should be on any system that has the HDF4 library installed.

Rotate "precipitation" with

 hdp dumpsds -r 4 -d -o <outfile> -b <TRMM_3B43.hdf>

and "error" with

 hdp dumpsds -r 5 -d -o <outfile> -b <TRMM_3B43.hdf>

These are rotated and need to be rotated back. The (properly oriented) binary grids are much easier to handle than the original HDF files.

See also AddOns/GRASS7/raster#r.flip