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of this particular study area. A sensor is needed that is able to 
detect land cover changes, in particular deforestation, with 
lower spatial resolution than the AIRSAR sensor, but with more 
bands and more polarizations than the ERS-1 sensor. Especially 
bands with larger wavelengths are needed to improve the 
accuracy of the classification of secondary vegetation. 
Another possibility can be using high spatial resolution data to 
derive information (e.g. the location of recently cut areas) and 
to correct misclassification. Therefore, it is recommended to 
include the AIRSAR data in the ERS-1 monitoring system 
proposed by Bijker (1997) in regular intervals either at the 
initial stage and/or at a later stage. It can be expected that the 
location of those classes, which could not be detected properly 
in the ERS-1 images, such as secondary forest and recently cut 
areas, becomes known and so the accuracy of later ERS-1 
classifications will be improved by including this knowledge. 
Nevertheless, field observations should still be included, 
specifically in areas showing non-conformity between high and 
lower spatial resolution data. 
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ACKNOWLEDGEMENTS 
The authors would like to thank Marcela Quifiones and Dirk 
Hoekman for providing their AIRSAR data and classification. 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004