Updated December 1998
by R. Drigo, Shaheduzzaman, M. Lorenzini
35 pp, 6 plates, 10 tables
RSC Series No. 61, FAO, Rome 1991.
Data from SPOT satellite in the form of multispectral (XS) and panchromatic (PAN) imagery with 20 and 10 m resolution respectively have been used for mapping Sylhet forest resources with the support of considerable field data and partial I.R. photo coverage at 1:50,000 scale.
The analysis of XS data and production of False Colour Composite (FCC) through appropriate enhancements and the comparison with panchromatic films have been the object of a study tour to Remote Sensing Centre FAO Rome.
Considering the complex, broken topography of the area and the limited dynamic range of SPOT multispectral (XS) data, digital classifications were tried but subsequently rejected with the consideration that a visual integrated interpretation could bring more reliable results.
In most cases the NDVI (Normalized Difference Vegetation Index) ratio-band combined with the other two visible bands proved most effective for species differentiation and reduction of topographic shadow effects.
Hardcopies of FCC with best enhancements for selected forest areas have been produced with a scale of 1:50,000 and interpreted in combination with panchromatic stereo-pairs having the same scale.
Panchromatic stereo-pairs have shown very high interpretability mainly due to high resolution and discernible vegetation texture.
Cost and performance analysis indicates that second generation high resolution satellite data such as TM, Russian satellite and SPOT (specially in PAN mode) represent a viable alternative to small scale aerial photography for intermediate forest resources assessment and monitoring for management applications.
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