This paper presents a thorough investigation on integrating slope map on the existing progressive morphological filtering algorithm for ground point’s extraction. The existing filtering algorithm employs constant slope value for the entire area. The slope map is either generated from field collected elevation data or ground point obtained from initial filtering of airborne LiDAR data. The filtering process has been performed with recursive mode and it stops after the results of the filtering does not show any improvement and the DTM error larger than the previous iteration. The results show that both data used for slope map generation have decreasing pattern of DTM error with increasing in filtering iteration. The spatially-distributed slope map has significantly improved the quality of the DTM compared to the results of filtering based on a constant slope value