Full text: XVIIIth Congress (Part B7)

  
The results from the neural network part in phase 2 and 
the comparisons here are given for the same two groups 
of stands. Stands that are "spectral" homogenetic have a 
lower correct classification rate of 34-53% compared with 
the 70-95% for the statistical classification . Some of the 
"spectral" heterogeneous stands are better classified with 
the neural network, but they still have too low 
classification rate (4-43%) to be compared with the 5-30% 
in phase 1. 
After the object-classification of the stands the differences 
are smaller. For the homogeneous stands two were 
changed from the correct classes. But for the 
heterogeneous stands a few more stands were put into the 
correct super class with the neural network classification. 
In the low-productive forest area none of the methods are 
useful depending on the dominating background- 
reflection. Small stands are another group that are not 
suitable for this kind of classification with the sensors we 
have available today. 
5. CONCLUSIONS AND REMARKS 
The results do not indicate that neural network classifier 
would be useful enough to this kind of forest stand 
classification. Especially when considering the problem of 
setting the variables for a non-specialist, the time 
consumption and the lack of confidence in the results 
when the behavior sometimes seems to be unpredictable. 
Out of 17 tests with larger neural networks (with 50 to 
100 nodes and from 30 minutes to 50 hours iteration 
tme) only two seem to reach some kind of global 
minimum. The other test ends up with a high average 
system error. For the best training results there are no 
intermediary results stored so it had not been tested to see 
if it was overtrained as is indicated by [Skidmore et al. 
1994] among others. 
ACKNOWLEDGEMENTS 
Special thanks are directed to the initiator of the project 
Assistant Professor Asbjórn Kjellsen, North-Trgndelag 
College for his encouraging support. 
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996 
 
	        
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