An outlier correction procedure and its application to areal surface data measured by optical instruments

An outlier correction procedure for areal surface topography data based on surrounding data for outlier detection and correction is reviewed. The outlier detection is based on the median relative height of the surrounding data within a defined detection window. The threshold value is calculated from a cumulative probability curve of the medians of all data points. The detection window size is selected based on the size of the largest outlier cluster observed on the topography data. The application of the procedure to dental implant surface topography data measured by a confocal laser scanning microscope shows excellent outlier removal compared to typical filtering methods. The procedure only affects outliers, and the information on normal data points remains unchanged. The application to topography data from 21 repeated measurements of a deterministic measuring standard shows great improvement in accuracy and repeatability of surface roughness parameters. The flexibility of the outlier correction procedure is observed through its application to several types of topography data from various types of optical surface measurement systems.