DIGITAL GEOMETRIC RECTIFICATION OF 50NAR IMAGES 
WITH INTERFEROMETRIC METHODS 
Dieter Kolouch 
Institute for Photogrammetry and Engineering Surveys 
University of Hannover 
Federal Republic of Germany 
Commission Il! 
ABSTRACT 
The knowledge of bottom topography of our oceans is one of the assumptions for engineer- 
ing and marine geology. Especially in shallow coastal areas, however, topography is fre- 
quently changed by storms and tidal currents. Short-time surveying repetitions are ne- 
cessary for up-to-date information. The employment of echo-sounders, which can take 
one depth-profile at time, means a great expense for this work. This paper presents a new 
system called Interferometric Side-Scan-Bonar (18858), that records images with fringe 
pattern, which are geometrically related to several depth profiles. The evaluation of 
these data is done by digital image processing methods with respect to a geometrical mo- 
del for the recording situation. Necessary additional data for outer orientation as rota- 
tion and positioning of the sensor are taken into account. 
1. Introduction 
Side-Scan-Bonar is nowadays an operational underwater system for sea-floor mapping. The 
system containing transducers for sound propagation is towed by ship and transmits 
acoustic pulses orthogonal to the towing direction. The emitted acoustic field is verti- 
cally wide open and horizontally narrow bound, which has the effect that each single 
pulse only "sounds" a small sea-floor strip. The reflections from the sea-bottom (echos] 
are received by the same transducers and recorded in an image line, wherein the position 
of an image point corresponds to the target range (determined by signal running time) 
and the point density to the echo intensity. By towing the sensor and pulsewise repetition 
of transmitting and receiving sound an images is built up line by line. 
  
Fig.1: Side-Scan-Sonar System (EG+G)