[GRASS-user] Filling Null values in a MODIS image

[Hanlie Pretorius]

Hi,

I have a MODIS land cover image that contains NULL values according to r.univar:
-----
r.univar map=modis_land_cover_type1_2001_primary at PERMANENT
total null and non-null cells: 41884
total null cells: 17145
-----

So, I tried to fill it with r.fillnulls and I get the following:
-----
r.fillnulls input=MCD12Q1.A2001001.005_land_cover_type1 at PERMANENT
output=MCD12Q1.A2001001.005_land_cover_type1_filled
Locating and isolating NULL areas...
Reading input raster map <r_fillnulls_1911 at PERMANENT>...
Writing output raster map <r_fillnulls_1911.buf>...
Creating interpolation points...
Extracting points...
Building topology for vector map <vecttmp_fillnulls_1911>...
Registering primitives...
0 primitives registered
0 vertices registered
Building areas...
0 areas built
0 isles built
Attaching islands...
Attaching centroids...
Number of nodes: 0
Number of primitives: 0
Number of points: 0
Number of lines: 0
Number of boundaries: 0
Number of centroids: 0
Number of areas: 0
Number of isles: 0
r.to.vect complete.
Interpolating 0 points
Not sufficient points to interpolate. Maybe no hole(s) to fill in the
current map region?
Removing raster <MASK>
Removing raster <r_fillnulls_1911>
Removing raster <r_fillnulls_1911.buf>
Removing raster <r_fillnulls_1911_filled>
Raster map <r_fillnulls_1911_filled> not found
<r_fillnulls_1911_filled> nothing removed
Removing vector <vecttmp_fillnulls_1911>
(Wed Aug  4 10:18:22 2010) Command finished (0 sec)
-----

Output of g.region -p:
-----
g.region -p rast=modis_land_cover_type1_2001_primary at PERMANENT res=0.00423094
projection: 3 (Latitude-Longitude)
zone:       0
datum:      wgs84
ellipsoid:  wgs84
north:      27:19:08.833466S
south:      28:30:53.475952S
west:       28:03:57.840271E
east:       28:41:37.727966E
nsres:      0:00:15.210751
ewres:      0:00:15.269511
rows:       283
cols:       148
cells:      41884
-----

Output of r.info:
-----
r.info map=modis_land_cover_type1_2001_primary at PERMANENT
 +----------------------------------------------------------------------------+
 | Layer:    modis_land_cover_type1_2001_p  Date: Thu Jul 29 15:17:55 2010
 | Mapset:   PERMANENT                      Login of Creator: hanlie
 | Location: world_wgs84
 | DataBase: /media/0847147784/grassdata
 | Title:     ( MCD12Q1.A2001001.005_land_cover_type1 )
 | Timestamp: none
 |----------------------------------------------------------------------------
 |
 |   Type of Map:  raster               Number of Categories: 14
 |   Data Type:    CELL
 |   Rows:         11957
 |   Columns:      6277
 |   Total Cells:  75054089
 |        Projection: Latitude-Longitude
 |            N: 27:19:08.833466S    S: 28:30:53.475952S   Res: 0:00:00.36001
 |            E: 28:41:37.727966E    W: 28:03:57.840271E   Res: 0:00:00.36002
 |   Range of data:    min = 1  max = 14
 |
 |   Data Description:
 |    generated by r.in.gdal
 |
 |   Comments:
 |    r.in.gdal input="F:\Hanlie\UCT\M.Sc\Data\modis\MOD12Q1\MCD12Q1.A2001\
 |    001.h20v11.005.2009342153812_land_cover_type1.tif" output="MCD12Q1.A\
 |    2001001.005_land_cover_type1"
 |
 +----------------------------------------------------------------------------+


I have tried to see the NULLS by displaying everything in white,
except for NULLS displayed in red, but I didn't see anything.

Does anyone know how I can find out if there are actually NULL value
and where they are?

Thanks
Hanlie