Tham khảo tài liệu 'robotic subsurface mapping using gpr part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | smallest error are merged together. To compute the matching error we fit the points in both regions to a plane using least square error fitting technique and compute the maximum absolute deviation of the points from the plane. After combining a pair of regions we compute the new match error values between the new region and all its connected neighbouring regions. Then we repeat the whole process until the smallest match error is larger than a threshold. At the beginning of the merging process each region contains only a single point so it is possible to merge two regions which have a total of two point. In this case and in the case where the combined region has less than 3 non-coaxial points we fit the points to a line instead of a plane to avoid ill defined computation. We also have another constraint during the merging process. The planes can not have an elevation angle larger than half of the beamwidth because if a reflector is tilted at a larger angle it will not be detected. When the smallest match error is larger than a preset threshold the plane segmentation phase ends and the quadratic patch segmentation phase begins. At this point the reflection points have been grouped into planes. In the next phase the planes are combines into quadratic patches. We chose quadratic patches because it models the reflection profile from a flat cylindrical and spherical reflector pretty accurately. We begin this phase by examining all the connected planes in the mesh. If a pair of planes can be combined to make a concave surface we disconnect the pair in the mesh so that the planes can not be directly merged together. This is to prevent the construction of concave quadratic patches. Once this is done we begin to compute the match errors of combining every pair of connected regions into quadratic patches. As in the planes segmentation phase we use a least square fitting technique to fit the points in the two regions into a quadratic patch. The match error measurement is the .
