Outlier detection using LAD method in cadastral coordinate transformation

Abstract

There are two coordinate systems with different geodetic datum in Taiwan region, i.e., TWD67 (Taiwan Datum, 1967) and TWD97 (Taiwan Datum, 1997). In order to maintain the consistency of cadastral coordinates, it is necessary to transform one coordinate system to another. However, no matter what transformation method was used, the most fundamental influence of accuracy is the quality of data itself. The LAD (Least Absolute Deviations) method was affected by nearly very little or none from blunders. Thus, LAD method, used for parameters estimation, has been successfully used for outlier measurements detection. Therefore, in order to ensure not only the quality of cadastral coordinate data but also the accuracy of cadastral coordinate transforming, this study will take the Least Absolute Deviations method for parameter estimation and outlier detection. The proposed algorithms and the detailed test results will be presented in this paper.