International Archives of Photogrammetry and Remote Sensing, Vol. 32, Part 7-4-3 W6, Valladolid, Spain, 3-4 June, 1999 
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Fig. 3. Integration result of both smooth DTMs. The integrated estimates at multiple scales are plotted. 
low resolution level. This is because the accuracy of the second 
DTM is higher than the accuracy of the first one. The computed 
reconstruction using the information of the two DTMs in each 
experiment can be seen in Figures 3 and 5, respectively. 
Already visually a reduction of the noise in the integrated 
DTMs can be observed. This means, that, independently of the 
terrain type, the second, lower resolution DTM with the more 
precise height values in its raster points contributes through the 
wavelet reconstruction in such a way that the noisy high 
resolution DTM after integration receives a significant 
improvement on all scale levels. For the wavelet transform, 
Daubechies wavelets of order 2 (Daubechies, 1992) are used, 
even though the use of the simpler Haar wavelet (which in 
general lacks smoothness) would not result in a visually 
recognisable difference. 
Fig. 4. Experiment with undulating terrain. Plotted is the high resolution DTM with three coarser scale levels.