Schetselaar, Ernst
(Green Vegetation Index) (B4 — B3) / (B4+B3). All values greater than zero, i.e. high GVI were
included in the mask. The traverse lines represented 62,263 training pixels. The unmasked regions
totaled 3,732,893 pixels. Using these values the training set accounted for less then 1.7 96 of the
training area. The total field magnetic data were processed to generate an apparent susceptibility map.
This procedure essentially converts the total field measurements in a map representation of
magnetization, provided that the magnetic anomalies arise from vertical prisms with the same depth to
their tops and the same depth extent (Milligan and Gunn, 1997). Although these conditions are
obviously violated in the area of study, the reduction to the pole and downward continuation filters
involved in generating such a representation more likely yield patterns that match with surface geology
patterns in comparison to the total magnetic field representation.
Figure-4 Summary of data sets used in the classification. A) Traverse lines, B) 1:100 000 geological
map data. Detailed geology is displayed with shaded DEM. C) Landsat 5 — TM represented as linearly
stretched colour composite using RGB bands 751. D) Total Field Magnetic data. Blues represent
potential field lows and reds delineate highs.
aom A 30 Km A
30 Km A | 30 Km À
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.