U.S. Releases Enhanced Shuttle Land Elevation Data
On September 23, 2014, the White House announced that the highest-resolution topographic data generated from NASA's Shuttle Radar Topography Mission (SRTM) in 2000 will be released globally over the next year. The announcement was made at the United Nations Heads of State Climate Summit in New York.
Previously, SRTM data for regions outside the United States were sampled for public release at 3 arc-seconds, which is 1/1200th of a degree of latitude and longitude, or about 90 meters (295 feet). The new data are being released with a 1 arc-second, or about 30 meters (98 feet), sampling that reveals the full resolution of the original measurements. Data for most of Africa and its surrounding areas were released with the announcement. The next release is planned for later in 2014, and it is expected to include all of South America plus North America south of the United States.
See full caption at the Photojournal PIA04965.
See the full JPL Release 2014-321.
See an index map of the newly available full-resolution data.
The new data are available for download from the USGS EROS Data Center - see Public Data Distribution for details.
Below, shaded relief images of deeply eroded volcanic terrain in northeast Tanzania demonstrate the improved nature of the highest-resolution SRTM data now being released. The image at left has data samples spaced every 90 meters (295 feet); the image at right has samples spaced every 30 meters (98 feet).
Credit: NASA/JPL-Caltech/National Geospatial Intelligence Agency
Click on the image for a detailed comparison, including an animation
Void-Filled "SRTM Plus" Released (SRTM NASA V3)
NASA has released a void-filled version of the Shuttle Radar Topography Mission digital elevation model, known as "SRTM Plus" or SRTM NASA Version 3. SRTM Plus uses SRTM Version 2 (see below) where the radar interferometric method was successful (not void). Most voids are filled with elevation data from the ASTER GDEM2 (Global Digital Elevation Model Version 2). ASTER is a sensor on NASA's Terra satellite that uses stereoscopic imaging to measure elevations via optical parallax where not obscured by clouds. Additional void filling of small areas used the GMTED2010 elevation model compiled by the US Geological Survey. SRTM Plus was produced under NASA's "Making Earth System Data Records for Use in Research Environments" (MEaSUREs) Program.
The elevation models and related products are available from NASA's Land Processes Distributed Active Archive Center (LPDAAC) at:
SRTM Plus is currently available globally at 3-arc-seconds (about 90-meters) pixel spacing. Release at 1-arc-second (about 30-meter) pixel spacing is expected to follow regional releases of other SRTM products during 2014-2015.
NASADEM: What's Next with SRTM
Engineers and scientists at JPL are currently working on a complete reprocessing of the original SRTM radar data in order to produce an improved near-global digital elevation model (DEM) to be called NASADEM. As with SRTM Plus, this work is funded under NASA's "Making Earth System Data Records for Use in Research Environments" (MEaSUREs) Program. In brief, the expected improvements include (1) fine vertical adjustments within and among individual shuttle data takes via reference to precise ICESat (Ice, Cloud, and land satellite) laser profiles, (2) void reduction via improved radar interferometric processing, (3) use of better fill data in the remaining voids, especially ASTER GDEM3 when available, and (4) improved quality assessments and adjustments. This project is scheduled for completion in early 2017, but we expect to release interim products in 2015 and 2016.
An edited version of "The Shuttle Radar Topography Mission, Rev. Geophys., 45, RG2004, doi:10.1029/2005RG000183" was recently released. See the SRTM Bibliography for further information.
SRTM Accuracy Report
JPL has released the full SRTM accuracy report. It's available in the SRTM Bibliography. A condensed version was published in the March 2006 issue of Photogrammetric Engineering and Remote Sensing, which is devoted to SRTM. It can be accessed (as "SRTM-4" within that issue) at: http://www.asprs.org/Photogrammetric-Engineering-and-Remote-Sensing/PE-RS-Journals.html
SRTM V2 Released
NASA has released version 2 of the Shuttle Radar Topography Mission digital topographic data (also known as the "finished" version). Version 2 is the result of a substantial editing effort by the National Geospatial Intelligence Agency and exhibits well-defined water bodies and coastlines and the absence of spikes and wells (single pixel errors), although some areas of missing data ('voids') are still present. The Version 2 directory also contains the vector coastline mask derived by NGA during the editing, called the SRTM Water Body Data (SWBD), in ESRI Shapefile format.
The data may be obtained through this URL: http://dds.cr.usgs.gov/srtm/ and go to the directory where both version 1 and version 2 directories may be found. Please read the appropriate documentation, also found in the directories.