2) Water Quality 
Water quality assessment requires the detection and measurement 
of pollution sources and the mixing of pollutants. By remote 
sensing this is generally possible for visible pollutants such 
as sewage and bulk oil. 
Non-visible pollution of a chemical nature can only be 
detected and traced by an indicator such as a dye-tracer or 
by temperature difference. Both types of indicators have been 
used in experiments in the Wilhelmshaven area. With Rhodamin- 
dye a chemical plant discharge was investigated and thermal 
contrasts served to trace the discharge of a paper plant and 
a thermal power plant. 
The power plant investigations were combined with a test 
on the accuracy of water temperaturg measurement by 
remote sensing. Using the thermal M S-Scanner data 
directly, without corrections yielded RMS errors of + 1,5% 
at check points. An atmospheric model, taking into account 
meteorological measurements of air temperature and humidity 
during the data acquisition period resulted in RMS errors of 
* 0,4 C. If, finally, water temperature measurements were used 
at few control points RMS errors od + 0,2 C were obtained at 
check points, after application of an interpolation procedure 
according to a low order polynomial. 
3) Tidal flat classification 
  
Both non-supervised and supervised classification attempts 
have been made for tidal land, trying to separate the most impor- 
tant tidal land classes by the usual multivariate procedures. 
As usual in classification, difficulties were encountered in the 
definition of classes by radiometric properties. On the other 
hand it was difficult to find suitably pure sample areas for con- 
ducting supervised classification. Particularly for low resolution 
Landsat-images in 4 channels (pixel size 80 m) and for medium reso- 
lution M S- images in 11 channels (pixel 4 m) the classification 
results were poorer than for 3-color separated aerial color photo- 
graphs (pixel size o,4 m), despite the fact that for the color 
photos the spectral channels were very wide and overlapping. 
4. Sonar Imaging 
Into the uses of remote sensing in coastal areas, there 
should also be included such non-classical RS devices as the 
underwater sonar. 
Its geometry and its imaging problems are similar to those 
of SLAR. Geometry is the lesser problem. It can be taken care 
of if the sensor movements are accurately known. 
  
    
   
    
  
  
    
  
   
     
   
     
   
   
    
   
  
   
  
   
   
    
   
    
  
   
  
   
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