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 
  
  
1328 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.