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An Inventory of SRTM-DEM Versions

posted by Satri on Tuesday July 24, @01:45PM   Printer-friendly   Email story  Permalink  Trackback URI  Slashdotthis  Diggthis  Del.icio.us
from the data-data-everywhere-and-the-albatros dept.
DEM Ask Slashgeo Data Sharing NASA Radar
I invite everyone to comment and improve this tentative to gather relevant information on SRTM-DEM data and versions. The objective is to build an inventory of the different SRTM-DEM versions. Versions considered are those which (1) do not degrade the spatial resolution of the original dataset and (2) which maintain the original near-global coverage. Read more below.
** Objective **
Build an inventory of the different SRTM-DEM versions. Versions considered are those which (1) do not degrade the spatial resolution of the original dataset and (2) which maintain the original near-global coverage.

 
** General information **
The SRTM-DEM is a near-global coverage topography dataset produced from radar interferometry using C-band radar data acquired by the American space shuttle Endeavour in February 2000. This elevation data covers the globe from latutide 56 °S to 60 °N and is freely available at the 1 arc-second (~30m) spatial resolution over United-States and 3 arc-second (~90m) spatial resolution elsewhere. It is the highest spatial resolution existing DEM data with near-global coverage.

 
** SRTM-DEM versions**
The original SRTM-DEM has 'holes' anywhere topography changes abruptly such as mountainerous areas, and is noisy over water bodies. The data has been edited and a 'finished version 2' has been released which "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 original SRTM data can be downloaded at ftp://e0srp01u.ecs.nasa.gov/srtm/ in the HGT format.

 
SRTM-DEM data can be downloaded from the GLCF website (http://glcf.umiacs.umd.edu/data/srtm/) on a tile-by-tile basis. Unfinished SRTM datasets have missing pixels which were set by the JPL at value -32768. Their technical guide. We learn from this other document that "[the SRTM-DEM] Version 2 is the results of a substantial editing effort by the NGA 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".

 
This CGIAR-CSI SRTM website host a whole copy of SRTM version 3 which is said to to be a significant improvement over the version 2. This site also provides precious information on data processing methodology for SRTM version 3. This seems to be the most up-to-date and best SRTM-DEM version.

 
Also of interest (?) are the manually updated SRTM-DEM tiles found here, but however does not include improvements over North America.

 
** Questions **
- Are there other sources of SRTM-DEM improved versions?
- Is the CGIAR-CSI version 3 really the best global version available?
- Will a near-global DEM be generated from the recently launched TerraSAR-X?

 
** Main sources **
Official NASA SRTM site - http://www2.jpl.nasa.gov/srtm/
Additional NASA information - ftp://e0srp01u.ecs.nasa.gov/srtm/version2/Document ation/SRTM_Topo.pdf
Wikipedia SRTM entry - http://en.wikipedia.org/wiki/SRTM
Global Land Cover Facility - http://glcf.umiacs.umd.edu/data/srtm/
USGS SRTM website - http://srtm.usgs.gov/
CGIAR-CSI website - http://srtm.csi.cgiar.org/

 
** TO-DO **
- Update the Wikipedia entry.

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