Iterative point matching for registration of free-form curves and surfaces
Zhengyou Zhang
Develops an efficient iterative point matching algorithm for registering 3D free-form curves and surfaces that accelerates closest-point search via k-D trees and dynamically filters outliers and occlusions using distance statistics for accurate rigid motion estimation.
The article addresses the challenge of precisely aligning successive 3D visual maps captured by stereo systems on a moving vehicle in rugged terrain. Accurate registration supports vehicle localization, error correction in stereo reconstruction, and construction of a global digital elevation map.
The work set out to develop and test a fast heuristic algorithm that refines an initial rough motion estimate into a precise 3D rigid transformation between two free-form point sets.
The approach iteratively matches each point in the first set to its nearest neighbor in the second set, discards implausible pairings through statistical analysis of distances, and solves for the motion that minimizes the sum of squared distances. The method was evaluated on both synthetic curves with controlled noise levels and real stereo reconstructions of a chair scene and a rock field.
The algorithm converges in 10-40 iterations, reduces average point distance to a few centimeters, and remains accurate even when 10-20 percent of points are outliers or occluded. Rotation and translation errors stay below 5 percent on noisy synthetic data and produce visually consistent alignment on real scenes. A coarse-to-fine sampling strategy cuts runtime by more than half with negligible loss of precision.
These results show that reliable registration of arbitrary shapes is possible without extracting geometric primitives, enabling practical visual navigation and large-scale map building. The technique is faster than global matching methods yet more robust than differential approaches that require very small motion.
Implementations should adopt the non-symmetric matching criterion for speed-critical use and combine the algorithm with a coarse global search when initial motion uncertainty exceeds roughly 20 degrees. Further work is needed to incorporate per-point uncertainty and to segment scenes containing multiple independently moving objects.
The main limitations are dependence on a reasonable starting estimate to avoid local minima, the need to tune one distance threshold to data resolution, and the assumption that the scene is largely static between views. Results are consistent across dozens of trials, yet readers should verify performance on their specific sensor noise characteristics before operational deployment.
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