Print this pageHigh-Pass Band 
Filter
of the Southern African Landscape
Paul J. Markwick and Vasil Lefterov
GETECH, Leeds, United Kingdom
The image being presented demonstrates a visualisation technique for picking out the main imbalances in the landscape of Southern Africa. The image processing and presentation has all been performed in GIS.
A 50km low-pass filter has been applied to the SRTM30 Digital Elevation Model and the difference between the derived mean enveloping surface and the topography is plotted. Essentially this produces a high-pass band filter
of the landscape.
To aid visualisation, the colour scheme is biased towards the biggest differences, highlighting discontinuities in the landscape with wavelengths of less than 50km. Examples of the imbalances, which can be seen on the map, include: drainage response to recent tectonic events, rift shoulders and incised rivers.
AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas