1. A method executed in instructions on a computing device for estimating the value of an attribute at a principal point, the method comprising: identifying one or more secondary points where sample elevation data of the ground below vegetation canopy was obtained that are within a predetermined distance to the principal point; sequentially selecting the one or more secondary points identified as being within the predetermined distance to the principal point; for each secondary point selected: allocating a masking zone to the selected secondary point, the masking zone defining a geographic area that originates from the selected secondary point, the masking zone being more distant from the principal point than the location of the selected secondary point; determining whether a more distant secondary point is within the geographic area defined by the masking zone allocated to the selected secondary point; if the more distant secondary point is inside the geographic area defined by the masking zone, discarding the elevation data associated with the more distant secondary point relative to secondary points that are outside the geographic area defined by the masking zone when estimating the elevation of the ground at the principal point; and calculating an estimate of the elevation at the principal point, the calculation using a weighted mean parameter to assign significance to secondary points that are not inside a masking zone without employing a gap probability function to return signals of LiDAR data having a reflectance value that is above a threshold indicative of ground terrain.