An Improved Digital Elevation Model of the Prince Edward Island Group
by Combining InSAR and C-band SRTM Data.

T.C.K. Bermon, S.A. Briels, R.F. Hanssen
	
This study investigates improvements in spatial resolution of C-band
Shuttle Radar Topography Mission (SRTM) Digital Elevation Model's
(DEM's) by substituting ENVISAT ASAR interferometric data. This is
applied for the Prince Edward Island Group, two islands in the Indian
Ocean of which no high resolution digital topographic information is
available. A single ENVISAT ASAR image pair is used to estimate height
deviations from SRTM. The image pair showed incoherent areas due to
snow accumulation and steep terrain slopes. In the residual phase
between ASAR and SRTM a spatially correlated signal is present. This
is expected to be dominated by atmospheric influence and could cause
single point height errors up to 49 meter. For points relatively close
together, the 90% error in height difference is smaller than the 90%
height error of SRTM (16 meter). Over approximately 65% of the area
the spatial resolution is improved from 90 meter (SRTM) to 20 meter
(ENVISAT ASAR). This technique could also be applied to reduce SRTM
DEM height error variance by using spatially filtered ASAR
data. Substitution of ENVISAT ASAR data proved to be a useful
technique to improve SRTM DEM resolution and is applicable all over
the world.