Figure 4. 
Edge detection with Sobel kernel upon 
frame from LANDSAT - TM august 1989 
recording, containing Sachalin Island, before 
(a) and after - (b) principal component 
transform. 
These images are processed by Manuel 
VAIS using ERDAS- IMAGINE in a 
professional stage at Remote Sensing and 
GIS Laboratory from Department‘ of 
Geography - Nottingham University, under 
tutorial of the professor Paul M. Mather. 
  
Intemational Archives of Photogrammetry and Remote 
  
  
Sensing. Vol.