Irmela HERZOG1 | Alden YÉPEZ2
(1The Rhineland Commission for Archaeological Monuments and Sites, Bonn, Germany | 2Universidad Católica del Ecuador, Quito, Ecuador)

Abstract:
Digital elevation models (DEMs) are an important basis for many archaeological GIS studies like predictive modelling, visibility and least-cost path analysis (LCPA). Twelve years ago Willem Beex held a workshop on the use and abuse of DEMs in Vienna, but lately hardly any archaeological GIS study refers to his paper in the CAA 2003 proceedings though the problems connected with DEM use have not decreased with increasing availability of DEM data. Issues are DEM resolution as well as horizontal and vertical accuracy, interpolation methods based on irregularly distributed measurements or points derived from contour lines, and the impact of these issues on derived variables like slope and aspect. The poster will discuss these issues referring to DEM applications in Ecuador’s highlands. A high resolution DEM with 1 m contour lines is available for the pyramids and burial mounds in Cochasquí but covers only part of the study area. For our visibility study, we tried to seamlessly combine this DEM with lower resolution data after identifying the more accurate of the two available lower resolution DEMs. DEM data also plays an important role in our landscape analysis of the Quijos and Cosanga study area. Our first analysis mainly relied on freely available ASTER satellite data, with only low vertical accuracy in some areas. It turned out that the topographic data recorded during a survey project and the ASTER DEM did not fit well, i.e. some river stretches flowed upslope, so that some adjustments with respect to horizontal accuracy were necessary. We alternatively used the SRTM data, with lower resolution but higher accuracy. Recently, digital contour line data became available from the Ecuadorian Ordnance Survey and a DEM was derived from this data. The poster will compare the three DEMs with respect to the outcome of slope, aspect and LCPA.

Keywords: digital elevation models, Ecuador, least-cost path analysis