1. Introduction
A large proportion of volcanic research and risk mitigation
is underpinned by the availability of reliable topographic
data. For example, state-of-the-art methods to delineate
areas at risk at active volcanoes include the use of computer
models that simulate the path of volcanic flows over digital
representations of the local topography, or digital elevation
models (DEMs) (e.g. Ishihara et al., 1990; Schilling, 1998).
The reliability of such studies are aided or hindered by the
resolution and quality of the DEM available (Stevens et al.,
2002), and also on whether the data are up-to-date, a
particular concern at active volcanoes, where significant
terrain alteration accompanies many eruptions.