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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