Processing the SRTM data took two
years to complete.
Copying the SRTM data tapes
The first activity was the copying of
the flight data tapes. There are 208 C-radar data tapes containing over
seven terabytes of raw data. These invaluable tapes were held at the
Kennedy Space Center in climate-controlled safes. The copying was done at
KSC by a team of engineers from JPL. Two copies of the tapes were made at
KSC. The copies were transported to JPL, one batch at a time, for
processing. The X-SAR data are being processed in Munich byDLR, the
German space agency.
The SRTM processing software
The software for the Ground Data Processing System
(GDPS) was under development for some time by the Algorithm Development
and Verification (ADV) team. The system is broken into three parts:
interferometric processor, which converts the raw radar data into a height
map and radar image strips; mosaic processor, which takes the myriad of
strips from all over the world and compiles a mosaic of the height and
image data one continent at a time; and the verification system, which
tests the mosaics for quality, producing an accuracy map. The processors
operate on workstations at JPL; the next job was to install them on a set
of supercomputers for systematic processing of the full SRTM data set.
While this was going on, JPL released additional products to the public,
as we did during the flight.
Processing the SRTM data
After the GDPS was set up and tested, systematic
processing began in April 2002. The SRTM data were processed on
a continent-by-continent basis, with priorities given by NGA. As the continents
were finished, the data were sent to NGA for final data quality checking.
After that step, copies were sent to the U.S.
Geological Survey's EROS Data Center (EDC) for archive and distribution to the public.
NGA will reformat the data into their own DTED format and handle archive
and distribution to the Department of Defense.
Archiving the SRTM data
At the end of systematic processing, the full SRTM data set,
including ancillary data, will be archived at the EROS Data Center.
Formats and distribution of the SRTM data
Distriubtion of SRTM data is through the EROS Data
Center.
Data Similar to the SRTM DEMs
If you're interested in data similar to SRTM's DEMs, the USGS EROS
Data Center is the place to visit. The first two data sets listed
below are very similar to the resolution and quality of the
full-resolution SRTM DEMs.
National Elevation Dataset (NED)
- seamless, "best available" U.S. Geological Survey elevation data
- resolution: 1 arc second (approximately 30 meters); Alaska: 2 arc seconds
- coverage: United States (including Alaska and Hawaii)
- Web site: http://gisdata.usgs.gov/ned/
7.5-minute (1:24,000-scale) DEMs
- 7.5-minute tiles
- resolution: 30 meters; some at 10 meters
- coverage: conterminous United States, Hawaii, Puerto Rico
15-minute (1:63,360-scale) DEMs
- 15-minute tiles
- resolution: 2 by 3 arc seconds (approximately 60 meters)
- coverage: Alaska
- Web site: http://agdc.usgs.gov/data/usgs/geodata/dem/63K/dem63k.html
1-degree (1:250,000-scale) DEMs
- 1-degree tiles
- resolution: 3 arc seconds (approximately 90 meters)
- coverage: United States (including Alaska and Hawaii), Puerto Rico
- Web site: http://edc.usgs.gov/glis/hyper/guide/1_dgr_demfig/states.html
GTOPO30
- seamless, "best available" public domain elevation data
- resolution: 30 arc seconds (approximately 1 kilometer)
- coverage: global
- Web site: http://edcdaac.usgs.gov/gtopo30/gtopo30.html
