Problem when loading GRASS 6 raster with large integer values

On Tue, 16 Sep 2008, Rainer M Krug wrote:

Hi

when I try to import a raster layer from grass with large integer
values, I get wrong values in R (see below). When I change the
datatype in GRASS to double, it works.

The underlying r.out.bin exports CELL rasters as short integers using two
bytes only, and the 6.3 version of the module has no option or flag for
setting this differently. So conversion to DCELL (or FCELL) is the only fix.

Roger

Thanks,

Rainer



GRASS 6.3.0 (grass):~/Documents/Projects/AlienSpread/R > r.stats -c
input=tmpDispLocal
100%
0 39798
11 831
58 78
105 38
242 1652
889 816
2205 294
2310 56
3315 1171
4935 116
7875 9
8085 67
11550 6
13010 299
24675 2
30135 425
47702 1
48510 981
103635 1255
165375 8
177797 160
177870 6
379995 324
606375 8
662970 292
1416345 445
2260125 41
* 50661
[Raster MASK present]


BUT:

   seeds <- readRAST6(

+                        "tmpDispLocal",
+                        ignore.stderr=!Debug
+                        )
Creating BIL support files...
Header File =

/home/rkrug/Documents/Projects/AlienSpread/R/../grass/simulation/.tmp/ecolmod/tmpDispLocal.hdr
World File =

/home/rkrug/Documents/Projects/AlienSpread/R/../grass/simulation/.tmp/ecolmod/tmpDispLocal.wld
Exporting raster as integer values (bytes=2)
Using the current region settings...
north=6247000.000000
south=6195000.000000
east=270200.000000
west=251000.000000
r=520
c=192

table(seeds[[1]])

-31233 -27437 -25447 -18811 -18738 -17834 -17026 -13221      0     11
58
   8   1255    445    160      6      1    981    324  39798    831     78
 105    242    889   2205   2310   3315   4935   7610   7875   8085  11550
  38   1652    816    294     56   1171    116    292      9     67      6
13010  16551  24675  30135  31901
 299      8      2    425     41

Additional info:

GRASS 6.3.0 (grass):~/Documents/Projects/AlienSpread/R > r.info
map=tmpDispLocal

+----------------------------------------------------------------------------+
| Layer:    tmpDispLocal                   Date: Tue Sep 16 16:45:35 2008
   |
| Mapset:   simulation                     Login of Creator: rkrug
  |
| Location: grass
   |
| DataBase: /home/rkrug/Documents/Projects/AlienSpread/R/..
   |
| Title:     ( tmpDispLocal )
   |
| Timestamp: none
   |

|----------------------------------------------------------------------------|
|
   |
|   Type of Map:  raster               Number of Categories: 2260125
  |
|   Data Type:    CELL
  |
|   Rows:         520
   |
|   Columns:      192
   |
|   Total Cells:  99840
   |
|        Projection: UTM (zone -34)
   |
|            N:    6247000    S:    6195000   Res:   100
  |
|            E:     270200    W:     251000   Res:   100
  |
|   Range of data:    min = 0  max = 2260125
  |
|
   |
|   Data Description:
   |
|    generated by r.mapcalc
   |
|
   |
|   Comments:
   |
|    round(tmpDisp * 0.300000)
  |
|
   |

+----------------------------------------------------------------------------+

[Raster MASK present]
GRASS 6.3.0 (grass):~/Documents/Projects/AlienSpread/R >

--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no