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Scan Matching |
[Frueh and Zakhor, MFI 2001]
Given two overlapping horizontal laser scans taken at times t1 and t2, an estimation for their relative pose can be obtained by scan matching. Two scans are automatically matched together by optimizing a quality function.
1.) Two scans S1 and S2 are drawn in the same coordinate system:
2.) A quality of match function Q is maximized by varying position parameters (translation (du, dv) and a rotation dphi):
3.) The optimal parameters are found after the two scans are matched:
4. Performing a scan match for every pair of subsequent scans, we obtain a series of relative position estimates (="steps") to be concatenated to an "initial path".
(click on picture to enlarge)
Although the initial path estimate is locally fairly accurate, traveling for several hundred meters inevitably results in an error accumulation and hence a significantly erroneous global pose. We have developed global correction methods to overcome this problem.