ACE2: The New Global Digital Elevation Model

Abstract

Detailed accurate Digital Elevation Model (DEM) data have historically not been available on other than a regional scale, and often have uncertainties in both vertical and horizontal precision. This paper presents the results of a global assessment of the unique Shuttle Radar Topographic Mission (SRTM) DEM using more than 100 million height datapoints derived from ERS1, ERS2, Topex, EnviSat and Jason-1 radar altimeter data, retracked using an expert system approach. This paper outlines the retracking approach taken to derive heights from the altimeter waveforms and describes the methodology for fusion of these data with the SRTM dataset, correcting errors in the SRTM heights and providing accurate measurements beyond the SRTM latitude limit, to produce a full global DEM. Of particular interest, the unique ability of radar altimeters to provide very precise vertical measurements has allowed the correction of vertical offsets to better than 1 m within ACE2, and has also allowed identification of horizontal misplacements. As part of this development, a detailed quality matrix is being generated, to give users information both on the data source of each pixel, and an assessment of the vertical precision of the measurement. It is this detailed global assessment of quality that makes the ACE2 development both unique and of special value for a range of geodetic applications. The first full release of ACE2 is scheduled for later in 2008. © Springer-Verlag Berlin Heidelberg 2010.