The density and
qualitative evaluation of resulting DEMs suggests that 0.5mDEMs are
sufficiently well resolved for the local binning scheme. Four shots per
squaremetermatches the number of nodes in a 0.5mDEM. Using the
local binning approach which we implemented including IDW (Kim
et al., 2006) the question becomes, what is the optimal search radius
for the favored IDW method? If there are no laser returns within the
search radius, the DEMnode at that location is returned as null (holes
in the images in Fig. 3). As the search radius increases, the number of
nulls goes down rapidly and asymptotically approach someminimum
defined by anomalously large areas of no returns