Fig. 1. Flow of building feature information extraction

Fig. 2. Process of extracting vertical contour points. (a) Horizontal section (different colors represent different sections); (b) calculation of the difference of adjacent horizontal angle; (c) vertical contour point extraction

Fig. 3. Process of extracting horizontal contour points. (a) Vertical section (different colors represent different sections); (b) calculation of the vertical angle difference of adjacent points; (c) extraction of horizontal contour points

Fig. 4. Extraction of minimum bounding rectangle size

Fig. 5. Building 1. (a) Point cloud model; (b) removing distant noise; (c) removing near noise

Fig. 6. Building 2. (a) Point cloud model; (b) removing distant noise; (c) removing near noise; (d) removing internal noise

Fig. 7. Building 3. (a) Point cloud model; (b) removing distant noise; (c) removing near noise; (d) removing internal noise

Fig. 8. Experimental results of building 1 pre-processed by proposed algorithm. (a) Pre-processed data; (b) horizontal section; (c) vertical section; (d) all extracted contour points; (e) window and door contour points; (f) overall contour points of the building

Fig. 9. Experimental results of building 2 pre-processed by proposed algorithm. (a) Pre-processed data; (b) horizontal section; (c) vertical section; (d) all extracted contour points; (e) window and door contour points; (f) overall contour points of the building

Fig. 10. Experimental results of building 3 pre-processed by proposed algorithm. (a) Pre-processed data; (b) horizontalsection; (c) vertical section; (d) all extracted contour points; (e) window and door contour points; (f) overall contourpoints of the building

Fig. 11. Relationship of slice density and other parameters. (a) Relation between slice time and slice times; (b) relationship between extraction time and slice times; (c) relationship between extraction accuracy and slice times