We propose a systematic approach for registering cross-source point clouds that come from different kinds of sensors. This task is especially challenging due to the presence of significant missing data, large variations in point density, scale difference, large proportion of noise, and outliers. The robustness of the method is attributed to the extraction of macro and micro structures. Macro structure is the overall structure that maintains similar geometric layout in cross-source point clouds. Micro structure is the element (e.g., local segment) being used to build the macro structure. We use graph to organize these structures and convert the registration into graph matching. With a novel proposed descriptor, we conduct the graph matching in a discriminative feature space. The graph matching problem is solved by an improved graph matching solution, which considers global geometrical constraints. Robust cross source registration results are obtained by incorporating graph matching outcome with RANSAC and ICP refinements. Compared with eight state-of-the-art registration algorithms, the proposed method invariably outperforms on Pisa Cathedral and other challenging cases. In order to compare quantitatively, we propose two challenging cross-source data sets and conduct comparative experiments on more than 27 cases, and the results show we obtain much better performance than other methods. The proposed method also shows high accuracy in same-source data sets.
One of the mathematical tools typically used for registration is Mutual Information (MI), which catches the non-linear correlations between the point clouds and the geometric properties of the target surface. The authors in @cite_8 use ICP and mutual information (MI) to build one-to-one correspondence between an magnetic resonance (MR) surface and laser-scanned cortical surface; however, this method is highly dependent on initialization and overlap rate. The work in @cite_28 registers unstructured 3D point clouds by using K-means to form a set of codewords and using an estimator to optimize the MI value to obtain the final rigid relations. Cross correlation of the horizontal cross section images of the two point clouds is used in @cite_20 to coarsely register the point clouds, and ICP is then used to refine the coarse results. These MI-based methods perform poorly when data is missing because it make the MI of two point clouds originally not the same.
@cite_28 @cite_20 @cite_8
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This paper reports a novel mutual information (MI) based algorithm for automatic registration of unstructured 3D point clouds comprised of co-registered 3D lidar and camera imagery. The proposed method provides a robust and principled framework for fusing the complementary information obtained from these two different sensing modalities. High-dimensional features are extracted from a training set of textured point clouds (scans) and hierarchical k-means clustering is used to quantize these features into a set of codewords. Using this codebook, any new scan can be represented as a collection of codewords. Under the correct rigid-body transformation aligning two overlapping scans, the MI between the codewords present in the scans is maximized. We apply a James-Stein-type shrinkage estimator to estimate the true MI from the marginal and joint histograms of the codewords extracted from the scans. Experimental results using scans obtained by a vehicle equipped with a 3D laser scanner and an omnidirectional camera are used to validate the robustness of the proposed algorithm over a wide range of initial conditions. We also show that the proposed method works well with 3D data alone. Abstract. Registration of point clouds is a necessary step to obtain a complete overview of scanned objects of interest. The majority of the current registration approaches target the general case where a full range of the registration parameters search space is assumed and searched. It is very common in urban objects scanning to have leveled point clouds with small roll and pitch angles and with also a small height differences. For such scenarios the registration search problem can be handled faster to obtain a coarse registration of two point clouds. In this paper, a fully automatic approach is proposed for registration of approximately leveled point clouds. The proposed approach estimates a coarse registration based on three registration parameters and then conducts a fine registration step using iterative closest point approach. The approach has been tested on three data sets of different areas and the achieved registration results validate the significance of the proposed approach. An inter-modality registration algorithm that uses textured point clouds and mutual information is presented within the context of a new physical-space to image-space registration technique for image-guided neurosurgery. The approach uses a laser range scanner that acquires textured geometric data of the brain surface intraoperatively and registers the data to grayscale encoded surfaces of the brain extracted from gadolinium enhanced MR tomograms. Intra-modality as well as inter-modality registration simulations are presented to evaluate the new framework. The results demonstrate alignment accuracies on the order of the resolution of the scanned surfaces (i.e. submillimetric). In addition, data are presented from laser scanning a brain's surface during surgery. The results reported support this approach as a new means for registration and tracking of the brain surface during surgery.