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- classification over the selected zones 
(ISOCLUS MLC); 
- modal filtering to eliminate the "striping" 
noise - fig.10; 
  
Fig.10. Landsat MSS 6 image of the sudied area. 
- Sobel edge detection (SOBEL), fig.11; 
- thresholding the edge detected features into a 
bitmap (THR); 
  
Figll. Sobel edge detection filter on the filtered classified image 
(Landsat MSS). 
- encoding the obtained bitmap into an image 
channel (MAP), showing the isodensity lines - 
fig.12. 
- In order to monitor the morphological changes of 
the Sacalin Island, the Landsat MSS - 1975 and 
Landsat TM - 1989, have been fusioned with the 
SAR - PRI - 1993. The principal components were 
extracted from the four MSS bands, in order to 
better visualise the shape of the Sacalin Island. It 
can be easily observed how the island has thickened 
In ime, due to sediment depositing - fig.7 a and 
fig.7b; fig.12 a and fig 12 b. 
561 
- Significant results are obtained in monitoring the 
pollution: 
- a proliferation of phytoplancton algae took 
place in 1975 (mainly Exuviela cordata - 40-50 
mil/1); this phenomenon - biological pollution type 
"red blossoming" may be clearly observed on the 
Landsat data of 16.06.1975  (fig.13). The 
phenomenon began to decrease in July, fact which 
was confirmed by the Landsat image of 25.07.1975. 
During the cold season of 1976 a new wide-spread 
"red blossoming" occurred - this time due to 
diatomee (Scetanema - more than 60 mil/l) which 
may be clearly seen on Landsat data of 26.02.1976 - 
band 4,5. 
- The Landsat MSS & TM recordings on bands 5 
and 7 show the successive stage of the evolution of 
the Danube Delta, clearly marking the seperation 
between the fluviatile delta and the marine delta; 
  
Fig.12. Monitoring the morphological changes of  Sacalin 
Island,between 1975 and 1993 Landsat MSS first principal 
component(1975-right) and SAR-ERS-1(1993-left) images. 
- In order to monitor the beach evolution and to 
establish the maximum instability areas, field 
surveyings have been performed, landmark on 
coastal zone and measurements on profiles, airborne 
and some correlations with space data, allowing us 
to monitor the sediment discharge and depositing 
regime in the sea, near the Danube mouths. 
5. SOME PROPOSALS FOR FURTHER 
DEVELOPMENTS: 
- Completing and perfecting our "in-situ" 
radiometric targenting system, mainly for the radar 
data. There is an obvious need to adapt the classical 
(conventional) measurements to the specific remote 
needs, for static objects-phenomena, as well as for 
slow, respective rapid variable in time ones. 
- Also a sustained activity of standardisation should 
take place, for the expertise, compatibilisation and 
complementarity of data, their fusion and 
integration, thus allowing the interchange between 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996