Orientation and Free Network Theory of Satellite CCD Line-Scanner Imagery 
Atsushi Okamoto, Kyoto University 
Susumu Hattori, Fukuyama University 
Hiroyuki Hasegawa, PASCO Corporation 
Tetsu Ono, Kyoto University 
COMMISSION III 
KEY WORDS: Satellite CCD Line-Scanner Imagery, Affine Transformation, Iterative Approach, 
Free Network Analysis 
ABSTRACT 
In 1992 Okamoto et al. proposed an orientation theory of satellite CCD line-scanner imagery based on affine 
transformation. However, in order to employ this orientation approach, the central-perspective satellite CCD 
line-scanner images are required to be transformed into affine ones and this image transformation cannot be 
performed without errors due to height differences in the terrain. Therefore, the original orientation method could be 
applied only for the case where the terrain was hilly and the image transformation errors were negligibly small. In 
this paper, we will first present an iterative orientation method of satellite CCD line-scanner imagery where the 
image transformation errors are corrected.by using the ground height information obtained in the previous iteration 
step. Tests with many simulation models clarified that two iteration steps are quite enough to remove the image 
transformation errors, even when height differences in the terrain exceed 4,000 meters. Next, the free network theory 
of satellite CCD line-scanner imagery is constructed, because this problem is becoming of greater importance for the 
precise analysis of satellite CCD line-scanner imagery having very high ground resolution (1m - 4m) which may 
appear in a few years. 
INTRODUCTION 
The general orientation theory of satellite CCD 
line-scanner imagery such as SPOT imagery can 
rigorously be constructed based on  projective 
transformation. However, this theory itself is of little 
practical use, because the attained accuracy is rather low 
due to very high correlations among the orientation 
parameters. In order to overcome this difficulty, an 
orientation theory of one-dimensional affine images was 
derived by Okamoto et al. in 1992, which can be 
applied for the analysis of satellite CCD line-scanner 
imagery by transforming the central-perspective images 
into affine ones. However, this image transformation 
cannot be performed without errors due to height 
differences in the terrain. Therefore, a correction 
technique of the image transformation errors is required 
to be developed to employ the orientation method using 
affine transformation for the analysis of satellite CCD 
line-scanner imagery of mountainous terrain where the 
image transformation errors are not negligibly small. 
Also, this problem can be overcome by introducing an 
iterative orientation approach using affine transfor- 
mation, where the image transformation errors are 
corrected by using the ground height information 
obtained in the previous iteration step. 
Very little has been written that provides a general and 
rigorous approach to the free network analysis of 
satellite CCD  line-scanner imagery, though this 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996 
problem is becoming of greater importance for the 
precise analysis of forthcoming satellite CCD 
line-scanner imagery having very high ground 
resolution (Im - 4m). However, if the orientation 
problem of overlapped images is solved and the 
geometrical characteristics of the one-to-one 
correspondence relating the model and object spaces are 
clarified, we can easily find linearly independent free 
network vectors required for obtaining unbiased 
solutions with minimum variance. In the general 
orientation problem of one-dimensional affine images, 
the absolute orientation can be expressed by a 
two-dimensional affine transformation having six 
independent coefficients and the equation of the 
photographing plane in the object space coordinate 
system. Thus, in the free network analysis of satellite 
CCD line-scanner imagery, we need nine linearly 
independent vectors which can be given by linearizing 
the one-to-one correspondence between the model and 
object spaces. 
In this paper, the general orientation problem of 
one-dimensional affine images is first briefly discussed. 
Then, the transformation of central-perspective 
line-scanner images into affine ones is described with 
correction of the image transformation errors, and 
simulation results of the proposed iterative orientation 
approach are discussed. Regarding the free network 
analysis of satellite CCD line-scanner imagery, the nine 
linearly independent vectors are given and the practical 
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