Wednesday, November 21, 2007 at 10:41:12

ASTER is an experimental sensor that sits onboard NASA’s Terra platform and is jointly run by NASA and Japan’s Ministry of Economy, Trade and Industry. Whilst it is an experimental instrument, it has provided remarkably good data (14 spectral bands ranging from 15-90m) and has been very reliable (since launch in 1999). In addition to these 14 bands it also has an aft looking sensor for the collection of stereo imagery and subsequent generation of 30m resolution DEMs. This was originally performed manually “as requested” but has now moved to an automated “on demand” service.

Because of the success of the mission, and near-global coverage of stereo data, funding has been found to compile a DEM of (nearly!) the entire globe at a spatial resolution of 30m and 7m vertical accuracy. The project, called ASTER G-DEM is currently in the preliminary preparation stages, with processing due to start in January 2008 and to take a year. The website is quite informative, showing the scope of G-DEM and how it compares to its rivals, in particular SRTM. In fact this page shows ASTER stereo coverage for the world and compares this to SRTM coverage (which is limited to 56S-60N). Also note that ASTER is photogrammetric, whilst SRTM is interferometric. One of the “problems” with the latter is that the sensor is side-looking and therefore you get data “holes” in steep terrain. This is not a particular problem for the vertical ASTER imagery. Some sample data is already available which people can have a look at. This will be distributed as 16-bit (which means integer values and therefore rounded to the nearest metre) TIFFs in 1 degree tiles.

Definitely a project to watch.

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