5. Data Processing 
  
The developed hardware requipment for synchronous interferometric and standard sonar 
imaging allows in combination with the introduced software package the determination 
of discrete three-dimensional coordinates from two-dimensional image coordinates. These 
data can be used for further processing with different aimes. This can be the interpola- 
tion of a Digital Terrain Model (DTM) with following automatical depth-line plotting. 
Figure 14 shows an example, which was processed from only one short interferometric 
side-scan-sonar record. 
d + 
tin 2) 
on 
requencies 
noise than 
as designed 
main was tested 
+ 
  
Fig.14: Automatically processed sea-map (plotting with TASH, Kruse. 1980) 
On the other hand the data obtained can be used for the rectification of the standard sonar 
image. 
As mentioned before interferometric and standard sonar images are recorded synchroneous- 
ly. Therefore the image coordinates in the digital raster correspond to each other. Re- 
ferring to equations (B) and (7) horizontal distances Y', and water depth Zr, are determined 
from discrete image coordinates for the interferometric pattern in each single image line. 
To rectify the standard image in such a way that all image points are represented in an 
horizontal plane the Z' - and Y' -coordinates must be transformed from the "dynamic" sensor 
system to the "static" sensor system. If correction by image line by image line is intended 
only rolling in o has to be taken into account. That is a simple coordinate transformation 
c profile 
an automa- Wn = Zh, cos - YA -sinu (9) 
irs and 
V Zu sino -* YH-cosu (10) 
The now horizontal distances Vr correspond to the measured image coordinates in the 
standard image and an orthophoto can be processed by using these passpoints by simple li- 
near and polynomial interpolation line by line. Figure 15 shows this processing from the 
original sound image using the interferometric pass point information to a ground range 
representation with depth lines in overlay.