In this paper

an adaptive morphological filter was developed to detect nonground LIDAR points in urban area

based on the continuous region detection and a hierarchical recognition mechanism.First

all continuous regions are labeled

and major ground points are detected by the characteristics of spread and continuity.Second

detached ground points are recognized by the quality of continuity and normalized height.Third

the height within objects occupied regions is calculated by linear interpolation and smoothness.Three datasets from three urban areas

are selected in the test

with different point densities and landscape complexities.Qualitative and quantitative analyses have indicated that this filter could remove most nonground points effectively in moderate complex urban environments

with the advantages of automatic window size determination and outliers detection.