[GRASS-dev] [GRASS GIS] #2349: CELL raster format: make ZLIB level 3 standard compression instead of RLE

[GRASS GIS]

#2349: CELL raster format: make ZLIB level 3 standard compression instead of RLE
-------------------------------------+--------------------------------------
 Reporter:  neteler                  |       Owner:  grass-dev@…              
     Type:  enhancement              |      Status:  new                      
 Priority:  blocker                  |   Milestone:  7.0.0                    
Component:  Raster                   |     Version:  svn-releasebranch70      
 Keywords:  compression, r.compress  |    Platform:  All                      
      Cpu:  Unspecified              |  
-------------------------------------+--------------------------------------

Comment(by neteler):

 It seems that the NULL file is not compressed (file "cell_misc/null").
 According to

 http://lists.osgeo.org/pipermail/grass-user/2010-January/054216.html

 it is one bit (null/non-null) for each cell. It looks like this:

 {{{
 [neteler at giscluster modis_lst_reconstructed_europe_daily]$ hexdump
 cell_misc/lst_2002_196_average/null | head
 0000000 ffff ffff ffff ffff ffff ffff ffff ffff
 *
 0000ad0 ffff ffff ffff ffe0 ffff ffff ffff ffff
 0000ae0 ffff ffff ffff ffff ffff ffff ffff ffff
 *
 00015a0 ffff ffff ffff ffff ffff ffff e0ff ffff
 00015b0 ffff ffff ffff ffff ffff ffff ffff ffff
 *
 0002080 ffff ffff ffe0 ffff ffff ffff ffff ffff
 0002090 ffff ffff ffff ffff ffff ffff ffff ffff
 ...
 }}}

 For our 12829 daily min/average/max MODIS LST maps covering Europe, the
 null files
 consume a lot of space:

 {{{
 [neteler at giscluster cell_misc]$ du -hs .
 621G    .
 }}}

 Question: Would it be possible to compress also the null files, even with
 just a
 weak compression?

-- 
Ticket URL: <http://trac.osgeo.org/grass/ticket/2349#comment:12>
GRASS GIS <http://grass.osgeo.org>