Comparative Analysis of IDW and Spline in Generation of Digital Elevation Models from Airborne LiDAR in Bare Lands

Fahmy F. F. Asal
Page No. 81-92

Light Detection and Ranging (LiDAR) is a recently established remote sensing technology, however
its capabilities have not been fully exploited. Airborne Laser Scanning (LiDAR) is characterized by
high density of point measurements that can be utilized in creation of digital elevation model
(DEM) with levels centimetre accuracy. Since LiDAR measurements are always in discrete point
data format, there is always a need for interpolation operations in order to create a continuous
surface forming a DEM. As different interpolation techniques are expected to provide different
quality DEMs it has been important to analyze the outcomes from those techniques. This research
is focused towards evaluation of DEMs generated from raw airborne LiDAR measurements in bare
lands using the Inverse Distance Weighting (IDW) and the spline interpolation approaches. A
sample of raw LiDAR data for Gilmer county, USA has been exploited in the study. Digital
elevation models have been generated from the data using IDW and spline approaches using a
specialized spatial analysis system. A well designed group of qualitative and quantitative analysis
tests have been exploited in the analysis of the generated DEMs. The analysis has shown that the
spline approach has provided DEM of more corrugated surface, coarser tones and coarser texture
compared to the DEM produced by the IDW algorithm. Also, IDW DEM possesses statistical
quantities that are close to their correspondings of the raw LiDAR data while the spline DEM has
statistical values with noticeable deviations from those of the raw LiDAR data. Additionally, spline
DEM has provided corrugated contour lines in addition to numbers of tinny closed contour lines
that could be spikes while the IDW has provided smoother contour lines with absence of any spikes.
Finally, the slope map from IDW LiDAR DEM has shown fine tones, smooth texture and regular
patterns referring to a terrain of gently varied slopes while the spline LiDAR DEM has interpreted
coarser tone, coarser texture and disturbed patterns referring to corrugated slopes of the terrain.
Key words:- DTM/DEM/DSM, IDW, Spline, LiDAR, Airborne Laser Scanning, Spatial analysis.