For each maximum image coordinate yg in each single image line xy water 
    
  
depth Z, and horizontal distance Yn can be determined using the equations 
(1) and (2) with reference to the sensors origin: 
where R = 
n 
m,' = 
n = 
D = 
X = 
  
Ra fie À n° . NG 
in? PU TEE (1) 
1/2 
2 D.2 
ue (2) 
me YA = range in space 
scale in transmitting direction 
number of the fringe order 
distance of the transducers 
wave-length 
These coordinates are used as input for three-dimensional space coordinate 
determination. This works 
in a reference system with respect to the dyna- 
mic towing situation, where in sensor movement and positioning are taken 
into account. Basis for a successful processing is the automatic detection 
of the fringe pattern image coordinates in each single line. 
3. Direction Dependent Filtering 
  
As mentioned above the recorded images are seriously contaminated due to 
the high amplification of 
the echo signals. This prevents automatic 
determination of interference image coordinates in the original images. 
  
Fig. 3: 
Densitometric Image 
Profile