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Figure 11. The ultimate edges 
6. CONCLUSION 
In order to make full use of the complementary advantages of 
the LIDAR data and aerial images, a new adaptive method of 
building edge detection by fusion of the two data sources is 
proposed in this paper. Firstly, the objects and ground are 
separated by a filter based on morphological gradient. The non 
building objects are removed by mathematical morphology and 
region growing. Secondly, the aerial image is smoothed by 
Gaussian convolution, and the gradients of the image are 
calculated. Finally, the edge buffer areas are created in image 
space by the edge points of the individual roof patch. The pixels 
with local maximal gradient in the buffer area are judged as the 
candidate edge. The ultimate edges are determined through 
fusing the edges in image and the roof patch by morphological 
operation. The experimental results show that the method is 
adaptive for various building shapes. The merits of the two data 
sources are employed efficiently during the building edge 
detection. The ultimate edges are closed and thin with one-pixel 
width, which are very suitable for subsequent building 
modelling. 
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ACKNOWLEDGEMENTS 
The research is supported by 973 Program (No.2006CB701304) 
and NCET program (No. NCET—06—0619). 
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