Helena Mitasova, Bill Brown, Lubos Mitas
University of Illinois at Urbana-Champaign
The DEM for this section was about 10,000x10,000 rows/cols at 2.5m resolution. When such a large file is displayed on a screen, only about every 10th pixel is used and the data look great. However, when we zoomed in so that every pixel is used, the data are really noisy with vertical relative elevation of the "bumps" at about 2-3m.
zoomed-in view of IFSAR imagery
IFSAR DEM rendered at 2.5m resolution with no
vertical exageration (this is what you should be seing in reality)
different view of the same DEM subset
zoomed-in into area with the small pond displayed with mask showing the areas with no data (water, shadow)
same area with colored version of imagery draped over
the terrain
We have experimented with various approaches to removal of noise with some promissing results illustrated by the following images. (read more in email)
original 2.5m resolution IFSAR DEM
5m contours from the original 2.5m resolution IFSAR DEM
smoothed DEM A
smoothed DEM B
the data which we currently have for this area
(resampled from the 100m resolution DEM). Colors indicate the shift
in elevation
Comparison of the smoothed IFSAR data and our current elevation data shows that the IFSAR data (even after a significant smoothing) provide much more detail about the terrain in the study area. However, to find an appropriate level of smoothing comparison with at least a small set of more accurate data is needed.
