Extracting a Topographic Index for Modelling Global Scale Processes from Low Resolution Digital Elevation Models.

A. Skellern, M. J. Kirkby and P. E. Kneale
School of Geography, University of Leeds, Leeds LS2 9JT, United Kingdom

This paper describes the extraction of a topographic index from digital elevation models (DEMs) at a range of different resolutions, derived from high resolution (50m - 100m) DEMs of areas of England, Spain and USA. Comparison of each different resolution DEM and the summary statistics of an extracted topographic index allows an assessment to be made as to the applicability of extracting a similar index at the global scale.

The high resolution DEMs are degraded within a geographic information system (GIS) to a range of resolutions, 150m, 750m, 4050m, 11250m and 20250m. The resulting low resolution DEMs give a similar resolution to that found with many global DEMs available today, such as ETOP05 and DTM5 (5 minute latitude/longitude grid). A comparison of the extracted index provides a method of parameterizing its extraction from coarse resolution global scale DEMs. This would allow the modelling of processes at the global scale, that require the effect of topography to be included.

The paper then goes on to describe, with illustrations from a particular application, that of modelling global peat distributions, how this has been achieved.