The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
Figure 6. The fire product 
Another product available at a 15 minutes interval is the Land 
Surface Temperature (LST), generated by the LandSAF (Meteo 
Portugal, http://landsaf.meteo.pt). The data is compressed and 
delivered in a HDF5 format. Using FWtools version 2.1.0 
(http://fwtools.maptools.org) the HDF can be converted to 
ILWIS and additional script routines are incorporated to attach 
the proper projection information to the northern and southern 
African windows, glue to maps to cover the whole continent, 
convert the data to temperature in degree Celsius and finally re 
assigns the pixels covered by water and clouds. The import 
procedure starts with a decompression which is facilitated using 
bzip2 (http://www.bzip.org/downloads.html) from within the 
batch routine. An example of the imported product is given in 
figure 7. More LandS AF products are to be expected in the 
future (e.g. an évapotranspiration product) which can 
subsequently be imported anticipating only slight adaptations to 
the batch routine developed for the LST product. 
Figure 7: Land Surface Temperature 
Other import routines developed deal with the Low Rate Image 
Transmission data (LRIT) in the GEONETCast data stream 
from the so called foreign satellites. An example is given in 
figure 8, displaying a global mosaic of images taken from 
GOES-West, GOES-East, MSG, Meteosat-7 and MTSAT-1R. 
The radiometry of GOES is also handled to convert the 
respective spectral channels in albedo and temperature. First the 
data received via GEONETCast is decompressed, the segments 
of the images are glued together and the data is imported, the 10 
bit data of GOES is transformed to 16 bit prior to import. 
Within a three hour period global composites can be made of 
images acquired by these geostationary satellites. 
Figure 8: Foreign Satellite thermal infrared global composite 
5. PRODUCTS FROM EXTERNAL DATA PROVIDERS 
IN GEONETCAST 
Already for some time a number of derived products based on 
the SPOT Vegetation Instrument are disseminated via 
GEONETCast. At a 10 day interval several of the Vegetation 
for Africa products can be received. The free VGTExtract tool 
(http://www.vgt4africa.org) can be used to unzip the data, 
transform it e.g. into an ENVI hdr file using the appropriate 
calibration coefficients (VGT4Aftrica User Manual, 2006). But 
the VGT products can also be directly imported into ILWIS 
using batch routines to decompress the files (using pkunzip, 
available at: http://www.freewarehof.org/olhof.html), read the 
HDF4 formatted data (using the FWtools utility as described 
above) and transforming the data into the appropriate units and 
assigning the projection information. Figure 9 shows a number 
of decadal products from VGT4Africa. 
Figure 9: VGT4Africa products in GEONETCast 
(A): Normalised Difference Vegetation index, (B): Normalised 
Difference Water Index, (C): Vegetation Production Indicator, 
(D): Dry Matter Productivity 
The NDVI is calculated by comparing the visible and near- 
infrared sunlight reflected by the surface. The NDWI is a 
dimensionless index that indicates the presence or absence of 
water on the surface and is calculated by comparing the 
shortwave and near-infrared sunlight reflected by the surface. 
The VPI is used to assess the overall vegetation condition and is 
a categorical type of difference vegetation index, whereby the 
actual NDVI is referenced against the NDVI percentiles (in 5 
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