LEFT IMAGE RIGHT IMAGE 
with ST',ST" ... starting wrong match point locations 
AAT... intermediate match point locations (possible side maximum) 
Ce. correct match point locations 
e nhe Din _ DR (18) 
TYL DY, , TYR DYg 
FIGURE 4. Movement of match points along "relief" lines 
This step ratio can be considered constant for a specific image location, since the Z-derivatives 
are practically constant throughout the iterations as we explained before. That means that if the 
left patch moves with step S, at a point A”, then the right patch must move with step Sp 2 S, /R 
at point A". Thus, a side-maximum can be selected only if it falls at one of the "fixed step ratio" 
point pairs (e.g. A'- A’ ) of the relief lines. This means that the probability of hitting a 
side-maximum is even smaller than in the epipolar correlation case, since the transfomations of 
the patches are not only along lines but they must additionally satisfy the "step conditions". 
4.9 CPU Time 
Average CPU time per point is listed in Tables 1 and 2. On the average 1 sec per iteration is 
needed for 152 patches on a VAX 11/750. The main portion of the time required in each iteration 
is for the formation of the normal matrix and secondly for resampling the gray values. Image 
processing modules and array processors can considerably speed up the computations, 
especially since most of them are of simple algorithmic structure. 
5. CONCLUSIONS 
The above mentioned results can be summarized as follows: 
* The geometric constraints should be treated as stochastic variables with large weight. Their 
use increases the reliability of the match (probability of side-maxima is strongly reduced). 
- 295 =