The satellite image composite of insular Southeast Asia was produced from satellite data acquired by the VEGETATION sensor (VGT) on board the SPOT4 satellite. In four spectral bands and at a spatial resolution of about one square kilometre (112º -1) the sensor provides an almost daily coverage of the whole region (94ºE - 155ºE, 20Nº-12ºS).
In order to cope with the problem of persistent haze and cloud cover in this region and to obtain a reasonably cloud and haze free regional image composite, all available VGT 10-day standard composites of the months of April to September 1998, March to November 1999 and January to March 2000 had to be utilized.
Image composition consisted of: (i) the elimination of pixels affected by clouds, haze and sensor errors from the S10 composites (empirically defined thresholds in the blue band >7.5% and in the short wave infrared (SWIR) band <6% of reflection factor), (ii) the generation of monthly image composites (pixel selection by the minimum SWIR value), (iii) the generation of annual composites for data sets of the years 1998,1999 and 2000 with a pixel selection by the minimum value in the near infrared (NIR) band, and (iv) the combination of these annual composites to the final satellite image composite.
The composite is displayed in natural false colour, where the Red/Green/Blue components correspond to the VGT spectral bands SWIR/NIR/ Red. Due to the pixel selection procedure evergreen tropical forests (dark green) could be well separated from regrowth and bush (green), from mixed agricultural land - including rubber and oil palm plantations (yellowish green), from other dry cropland and grassland (pink, dark pink). Burnt areas in the lowlands of Sumatra, Borneo and New Guinea (mainly burnt in late 1998) were enhanced and appear in intensive red colours, similar to the sparse alpine grasslands and rocks at high altitudes of New Guinea.
For more information on this topic, please contact Hans-Jürgen Stibig>
Mapping of the tropical forest cover of insular Southeast Asia from SPOT4-Vegetation images, Stibig, H-J., Beuchle, R. and F. Achard, 2003. International Journal of Remote Sensing, 24(18), 3651-3662.
Forest cover of insular southeast Asia mapped from recent satellite images of coarse spatial resolution, Stibig, H-J. and Malingreau, J.P. 2003, Ambio, 32(7), 469-475.
Forest cover map of insular Southeast Asia at 1:5 500 000 Stibig, H-J., Beuchle, R, and Janvier, P. 2002, Publications of the European Communities, EUR 20129 EN, European Commission, Luxembourg.