Figure 2. Top left part of the nadir channel: a) original, b) as a) 
after contrast enhancement to show the noise, C) after 
preprocessing. 
from the expected nominal orbits or the ephemeris data. Twelve 
absolute constraints are enforced in order to keep projection 
centres moving strictly along appropriate elliptical orbital 
segments. Thus, linear and quadratic rates of change in X, Y, Z, 
which are eventually used as given values, are calculated. The 
minimum number of full control points is 4 for the linear model 
of attitude changes and 6 for the quadratic. 
  
112 
Figure 3. In a) part of the original nadir image. In b) after 
preprocessing. 
  
Figure 4. Good [a), b)] and poor [c), d)] definition control point 
in nadir and fore preprocessed images respectively. 
Kratky also provides direct projection equations from one space 
to another (two image spaces, object space) by means of 
polynomial mapping functions (PMFs). The PMFs consist of 3rd 
- 4th degree polynomials with 11 - 16 terms, whereby the object 
space is reduced to two dimensions by extracting the elevation, 
i.e. the elevation Z is an independent parameter connecting all 
three 2D spaces. The polynomial coefficients are estimated by 
least squares adjustment after the sensor orientation is estimated 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996 
  
  
  
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