Pablo's Mission Planning Website

Home Links Tips Downloads MPSSF Tips

Greetings Mission Planners,

If you're interested in the data characteristics of the SRTM data then check out:

  http://www.usna.edu/Users/oceano/pguth/website/talks/asprs_may_2004_files/frame.htm 

Slides 13 and 14 do an especially good job of quantifying the shortfalls of the SRTM data - or rather of the SRTM instrument.  

On the links page I've added a link to Terraserver-USA, which provides quick access to view the USGS Digital Raster Graphics and Digital Ortho Quads.  You can search for a location with a street address, view the image date of the DOQ and format a page to send to the printer.  Here's a link to 1600 Pennsylvania Avenue.

Mission Planning Tip: High-Resolution Terrain Information (HRTI)

Although NGA has only published standards for Level 1 ( 3 arc second ~90 Meter) and Level 2 (1 arc second ~ 30 Meter) DTED, there's strong interest in higher resolution terrain data.  Although no standards exist, the defacto resolution for Level 3 DTED is a 1/3rd arc second (~10 Meter), Level 4 is 1/9th arc second (~3 Meter) and Level 5 DTED is 1/27th arc second (~1 Meter).  Because of the known limitations and problems with the existing DTED specification the higher resolution data is often called High-Resolution Terrain Information or HRTI ("Herty").  We use the acronym "DTED" generically to describe terrain data, but really DTED is one specification - and a pretty dated on at that.  

Who's interested in HRTI?  Folks who interact directly with the ground.  Those of us who fly above the earth don't need to know the details - just the big picture of where the rocks are.  People who have to jump out of the aircraft, land a helicopter, drive a vehicle or low crawl want much more detailed information.  They want to do threat masks, but instead of an SA-2  they're more concerned about masking the .50 cal in the bell tower.  

The following images show rendered images of the same area at resolutions ranging from 90 Meters (SRTM DTED, Level 1) down to 3 Meter (USGS National Elevation Database) and  give an idea as to what information the different terrain resolutions provide.

SRTM Level 1 DTED:

 

SRTM Level 2 DTED:

 

1/3" National Elevation Database (pseudo HRTI, Level 3):

 

1/9" National Elevation Database (pseudo HRTI Level 4):

 

Finally, an image of the same area:

For those of you who weren't lucky enough to attend, this is the University of Washington, with Husky Stadium (site of Washington State's defeat on 11/22/03) in the lower right and Drumheller Fountain in the upper left.

It's only been four years since the SRTM flew, but there's already a proposed mission that would collect worldwide HRTI Level 3 (10M) data.  Radarsat is preparing to launch Radarsat 2, a commercial all weather radar satellite with a 3 meter resolution. A proposed follow on mission would launch an identical satellite on a "tandem mission" into the same orbit, slightly behind Radarsat 2.  The two satellites would work together (just as the two SRTM antennas) to gather worldwide data.  Unlike the SRTM radar, these two satellites would remain in orbit for years and collect  HRTI amidst other Radarsat imaging. 

The good news is that's it for discussions of DTED!

Paul