International Archives of Photogrammetry and Remote Sensing, Vol. 32, Part 7-4-3 W6, Valladolid, Spain, 3-4 June, 1999 
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The examples shown and discussed have been selected for 
demonstrating the principle of DTM integration based on 
wavelets and give some first ideas about the accuracy behaviour 
of the integration approach on different scales. But without 
doubt, more comprehensive investigations have to follow to 
support these first results. 
5. CONCLUSIONS 
In this paper, we presented a concept for the integration of 
DTMs which differ in scale. The basic idea of the concept is to 
use wavelets for representing DTMs on multiple scales. The 
generation of a multiscale representation is obtained by wavelet 
decomposition of the high resolution DTM. For merging two 
DTMs, the DTM representations on the same scale or resolution 
level are introduced into a weighted least squares fit. With 
wavelet reconstruction, the integrated DTM estimates on all 
finer scales are obtained. 
Some examples are investigated to demonstrate the applicability 
of the proposed wavelet approach and the first experiments with 
the developed routines show that the errors of the fused 
estimates at the fine scale have been reduced. This basically 
confirms our a priori expectation for the integration result. 
Further investigations have to follow. In particular, DTMs with 
given ground truth should be taken into account to rigorously 
assess the overall accuracy improvement. Comparison with 
other methods would be also quite interesting. Further, little 
attention has been paid to the wavelet itself. The standard 
wavelets, like Haar and Daubechies, are only two among a lot of 
others, even though they excel because they are simple, 
orthogonal, have compact support, certain smoothness and other 
beneficial properties. 
Finally, the merging by simple least squares weighting might be 
replaced by more sophisticated DTM interpolation schemes. 
Even though these aspects have no impact on the basic concept, 
they have to be taken into account in future experimental 
investigations. 
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