An evaluation of the accuracy of the ASTER GDEM and the role of stack number: a case study of Nisiros Island, Greece

Abstract

A reference digital elevation model (RDEM) produced by the Hellenic Military Geographical Service (HMGS) (Athens, Greece) is used to assess the vertical accuracy of the ASTER (advanced spaceborne thermal emission and reflection radiometer) global digital elevation model (GDEM) for a small volcanic island, Nisiros, in south-east Greece. The overall vertical accuracy of the GDEM is within the root mean square error (RMSE) specified by the ASTER DEM Working Group. Despite this, ASTER GDEM is a product with variable vertical accuracy depending on the number of scenes (stack number (SN)) per grid point used for the computation of elevation. The exposure (SN) of a physiographic region to ASTER sensors seems to be elevation- and slope-dependent in this particular study area. The difference between the GDEM and RDEM may partly be explained by the fact that GDEM is a digital surface model and thus the variable landcover heights introduce additional error in accuracy estimates.