Abstract:
The wide acceptance of Digital Elevation Models (DEMs) for many applications, has resulted in the need for newer high-resolution DEMs to allow for the modelling of complex environments. To accurately model these environments, analysis of potential inaccuracies is beneficial for all applications of DEMs. DEMs provide a vital instrument for various modelling applications such as hydrological, coastal flooding, landform, and other such analysis. The capability to accurately model both landscape forms and processes in a relatively short amount of time provides an unprecedented ability and accuracy to environmental planning. The satellite-derived DEMs produced by Vricon and TanDEM-X, present exceptional accuracy and resolution for topographical data in the Western Pacific region. Given that this is a first, several significant issues have arisen related to potential influences on the accuracy and validity of the satellite-derived DEMs, i.e. to assess how features such as vegetation and land-cover may affect accuracy. To achieve this, a PPK-GPS was employed to collect positional site data with cm-level precision, and a SenseFLY Ebee Drone was used to produce a Digital Surface Model (DSM) of a selected site. This data, when compared to the satellite-derived DEMs in software such as ArcGIS, will allow for an analysis of accuracy. There are expectations that inaccuracies within the DEMs will arise due to the negative influence of eight identified categories of vegetation and land-cover in Palau. The PPK survey of Palau has resulted in 339 unique positional data points over the eight land cover types. It has been concluded, through the acquisition and analysis of topographical data points, that the unique Land Cover Types have negatively influenced DEM accuracy, slope has likely had little to no influence of DEM accuracy, and vertical features do have a horizontal influence on the scale of meters. Through the extraction of accurate elevation data from satellite imagery such as DEMs in remote areas of the Pacific, we can begin to assist in the future environmental planning for these Pacific island nations, around such problems as sea level rise and hydrological modelling.