Fig. 1. Main processes of volume measurement based on improved point cloud slicing method

Fig. 2. Point cloud data acquisition of spatial objects. (a) Multi-view point cloud data; (b) point cloud model

Fig. 3. Diagram of point cloud data slicing. (a) Side view of Stanford Bunny and some slicing positions on it; (b) contour boundary points in slicing layers

Fig. 4. Diagram of segmentation based on euclidean clustering (z=-7.52 mm). (a) Contour boundary points and initial polygon in slicing layers; (b) classification results; (c) generation of contour polygons after classification; (d) side length frequency distribution histogram of this polygon; (e) a partial enlarged drawing of Fig. (d)

Fig. 5. Schematic diagram of some points (like point 5) being missed during the two-way nearest point search

Fig. 6. Diagram of polygon splitting and recombination method. (a) Split into multiple polylines; (b)recombination into individual contour boundary polygons

Fig. 7. Analysis of inclusion relationships between multi-contour boundary polygons in cross-section. (a) Position information of boundary polygons; (b) tree structure; (c) chain table; (d) cross-section region (shaded part)

Fig. 8. Test data. (a) Three-dimensional surface model of Stanford Bunny; (b)(c) physical objects, point cloud data, and surface models of Happy Buddha, and Lucy

Fig. 9. Comparison and analysis of multi-contour boundary segmentation results of different slicing positions (along z-axis) of Stanford Bunny. (a) Sorting results of the two-way nearest points search; (b) results of the SEC method; (c) results of the PSR method

Fig. 10. Comparison and analysis of multi-contour boundary segmentation results of different slicing positions (alonge y-axis) of Happy Buddha. (a) Sorting results of the two-way nearest points search; (b) results of the SEC method; (c) results of the PSR method

Fig. 11. Comparison and analysis of multi-contour boundary segmentation results of different slicing positions (along z-axis) of Lucy. (a) Sorting results of the two-way nearest points search; (b) results of the SEC method; (c) results of the PSR method

Fig. 12. Comparison and analysis of cross-sectional area results of different slicing layers at Stanford Bunny. (a) Area of each boundary polygon; (b) accuracy of cross-sectional area results

Fig. 13. Comparison and analysis of the cross-sectional area results of different slicing layers at Happy Buddha and Lucy. (a)(c) Area of each boundary polygon; (b)(d) accuracy of cross-sectional area results

Fig. 14. Comparison and analysis of volume measurement results of three datasets with different slicing intervals. (a)(c)(e) Accuracy of volume results; (b)(d)(f) calculation time