Large Scale Assessment of Free Global DEMs Through the Google Earth Engine Platform

The aim of this study is to compare and analyze the accuracy of freely available global DEMs. Four DEMs generated using optical and SAR satellite imagery - ASTER GDEM, SRTM DEM, ALOS AW3D30, Tandem-X 90m - were analyzed over the territories of four U.S. states (approximately 927000 km
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) that are characterized by different morphologies and land covers. The accuracy assessment procedure was implemented within the Google Earth Engine (GEE) platform, designed to manage and analyze Geo Big Data. The outcomes highlight a good agreement among the statistical parameters at a global level for each wide area analyzed. The accuracy, as expected, decreases with the increase of the slopes, and ALOS AW3D30 displays the overall best performance, with an accuracy ranging between 2.5 m in flat areas and about 10 m in hilly/mountainous areas.