ASTER GDEM v2

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) has been operated onboard Terra’s spacecraft since 1999. The ASTER imaging system comprises two telescopes; one with nadir angle and another with backward-angle, enabling along-track stereoscopic data acquisition with a horizontal ground sampling distance of about 15 meters. High-resolution global DEMs have been generated from the ASTER stereoscopic data sets, representing the top of terrain features (digital surface model) of the Earth. Two DEM versions have been released by The Ministry of Economy, Trade, and Industry (METI) of Japan and the United States National Aeronautics and Space Administration (NASA), GDEMv1 in 2009 and the improved version GDEM v2 in 2011. The release of the newest ASTER version, ASTER GDEM v3, is expected for 2018. ASTER GDEM v2 is the newest version. This dataset was generated from 1.5 million scenes of the L1A product from the ASTER instrument acquired between 2000 until 2010 using stacking methods. GDEM v2 covers Earth’s land surfaces between 83° North and 83° South with a spatial resolution of 1 arc-second (approximately 30 meters), and a coverage of about 99% of Earth’s land areas (see figure here ). Compared to GDEM v1, the development of v2 mainly focusses on the incorporation of newer ASTER data (from September 2008 until October 2010, valued at 260.000 additional scenes) and improving resolution by decreasing the window size (from nine-by-nine pixel to five-by-five pixel), and partial removal of biases and artefacts (e.g., clouds). The ASTER GDEM v2 dataset is divided into 1° x 1° geographic latitude and longitude tiles (3601 columns and 3601 rows at 1 arc-sec resolution), that have a typical file size of 12 MB in GeoTIFF (.tif) format. The entire model totals to 271 GB data (26702 tiles) globally. One tile contains two types of data layers; the elevations (.dem) and quality assurance (.num). The quality assurance layer represents the number of stacked scenes or which reference data was used in the particular pixel. The absolute vertical accuracy of ASTER elevations has been assessed to be about ~17 meters at 95% confidence level. Geodetic information: The ASTER GDEM v2 DEMs are vertically referenced to the EGM96 geoid and horizontally referenced to the WGS84 (World Geodetic System 1984). Further notes: The ASTER data set can be considered as a digital surface model (DSM), representing heights of the bare ground where vegetation cover or buildings are absent, and otherwise provides heights of the surface objects (e.g. vegetation). The ASTER GDEM v2 still contains a number of artefacts (e.g., steps/stripes, spikes) that may be an issue for some applications. Data access: Homepage of ASTER GDEM dataset is https://asterweb.jpl.nasa.gov/gdem.asp , with data searching function available on NASA Reverb ( http://reverb.echo.nasa.gov/reverb/ ), LP DAAC Global Data Explorer ( http://gdex.cr.usgs.gov/gdex/ ) and Japanese ASTER GDEM page ( http://www.jspacesystems.or.jp/ersdac/GDEM/E/index.html ). Users can utilize ASTER GDEM data without any charge, as long as it is used for given societal benefit areas which defined by GEOSS (global Earth Observation System of System). References: JAXA, ASTER Global DEM (ASTER GDEM) Quick Guide for V2, available on http://www.jspacesystems.or.jp/ersdac/GDEM/ver2Validation/GDEM_QuickGuide2.pdf Tachikawa, T, Masami Hato, Manabu Kaku and Akira Iwasaki. Characteristics of ASTER GDEM Version 2, IGARSS, July 2011. Available on http://www.jspacesystems.or.jp/ersdac/GDEM/ver2Validation/IGARSS2011_Proceedings_GDEM2.pdf ASTER GDEM Validation Team, ASTER Global Digital Elevation Model Version 2 – Summary of Validation Results, available on http://www.jspacesystems.or.jp/ersdac/GDEM/ver2Validation/Summary_GDEM2_validation_report_final.pdf