SATK2. Exercise 3. Special image-processing procedures. 
The introductory topic in this exercise is the transformation 
from RGB colour-space to IHS colour-space. ALGEBRA is the 
ERDAS function which is used to demonstrate this. The "Result 
Screen-Image" in Figure 6a shows an original SPOT XS 
subscene, the components I, H and S after the transformation 
and also the result of an IHS2RGB transformation when the 
original image is used as input. The sixth image in Figure 6a 
is the result of an IHS2RGB transformation of the IHS image. 
This result is thus the same as the original RGB-image. 
  
  
Display of original and [HS-transformed SPOT XS 
data. 
  
Figure 6b. Merging of SPOT XS with SPOT PA data. 
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In the second part of the exercise the knowledge about the IHS 
transformation obtained in the first part, is applied to the 
generation of a combined SPOT XS/PA image. In this process 
image to image rectification is included. It is in this connection 
necessary to determine both sets of GCP coordinates directly in 
the images. Figure 6b shows the "Result Screen-Image" from 
this part of the exercise. It is realized that PC-ERDAS (not 
even Version 7.5) is ideal for a task like this. 
In the last part a digital mosaic shall be made from two slightly 
overlapping Landsat MSS subscenes. Important functions used 
in this procedure are DIGSCRN, CUTTER and STITCH. Due 
to different dates of acquisition, the radiometric properties of 
the two subscenes are different. HSTMATCH is therefore used 
to complete the production of the mosaic. Figure 6c shows the 
result. 
  
Figure 6c. Mosaicing of Landsat MSS subscenes. 
SATK2. Exercise 4. Colour-hardcopy production, Unsuper- 
vised classification (Clustering) and Field-control (Collection 
of ground-truth). 
The digital image used in this exercise is a subset of a level 2B 
(precision-corrected) multispectral SPOT-scene which covers an 
area in Valle in Setesdal in south Norway. This area has been 
chosen for the exercise because a privately owned consulting 
company (VIAK) in collaboration with a research foundation 
(Telemarksforskning) has produced a vegetation-map of the 
area based on the same set of data.