Zuxun Zhang
The LPA, where the house may be exist, can be extracted.
Besides, the extraction can be by mathematical morphology: A simple low-pass filtering is used for DSM first. Then,
the algorithm of extracting the peak point by mathematical morphology is adopted to extract all local peak-points of 3d
DSM. The LPA is generated by region growing, based on the peak-points as the seeds. Finally, the boundary of LPA is
extracted by edge following algorithm. The result is similar as the heuristic searching mentioned above.
3 Boundary Extraction and 3D Reconstruction of Regular House
3.1 Extracting for Roof of the Simple Regular House
The extraction of the roof boundary is the so-called feature extraction by considering the intrinsic properties of the
house structures. It is well know that roof is consisting of boundaries, which are straight lines usually. Therefore
extraction of the straight lines is a major component of it. However, the structure of the house roof is complicated and
of various types. It’s hard to give a general description of roofs’ intrinsic properties. Thus, it is difficult to give a general
extraction algorithm of the house boundary extraction. Hereafter, we only discuss the boundary extraction of simplest
regular house with the widest application. That is the boundary extraction of the roofs with flattop and fastigium house.
The method discussed in the paper is composed of two parts: a). Image processing, which includes straight-line
extraction and area construction. b). Perceptual organization, which consists of organizing the fragmented and low-level
information into higher level descriptions (Hericsson 1995). As shown in Figure 3. First, extract straight lines (Figure
3.b) from image windows (Figure 3.a) partitioned from original images. Analyze these broken straight lines and remove
those not orienting to the housing main direction and fragmented lines (Figure 3.c). Extend the lines and compute their
intersections to construct an area (Figure 3.d). Give a comprehensive analysis of the information about the straight lines
and the area. Branch the areas and then merge them to acquire the boundary of the flat top house (Figure 3.f).
O
Figure 3. Extraction procedure of flattop
The algorithm of flattop extraction, mentioned above, is also suitable for the extraction of "L" shaped houses, as shown
in Figure 4. Above scheme can be alternated and extended in order to apply to fastigium house. Considering the fact
that fastigium house generally has its main direction, the lines in the main direction can firstly be extracted and then the
lines nearly perpendicular to them section by section. The extraction result of fastigium house is shown in Figure 5.
1018 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000.
