Ideas For Exploiting NASA's SRTM Data 124
MaxTardiveau writes with an excerpt from an article where the pictures are worth clicking through for: "Ten years ago, in February 2000, NASA mapped the entire world in eleven days. It's true: the mission was called the Shuttle Radar Topography Mission (SRTM), and over the course of eleven days, it used a big radar attached to the space shuttle to get elevation data from the vast majority of solid Earth; practically all land between 60 degrees North and 56 degrees South was included, with a resolution of 30 meters (90 feet). Over 9 terabytes of data were captured. It then took two years to process that data and make it usable (and it is still being refined to this day). This data is freely available to anyone, and the number of possible applications is almost infinite. It's been used in GIS, cartography, environmental planning, weather modeling (weather patterns are enormously influenced by the topography), flight simulators, Google Earth, and the list goes on. In this short article, I would like to give you a quick tour of the kinds of things this data can reveal. My hope is to get you thinking about what else could be done with this incredible resource."
Games (Score:5, Interesting)
It's just perfect use for games, from flight simulators to city building and civilization series. It's a lot more fun to play on real terrain.
Atlantis (Score:2, Interesting)
I want to know if Plato was just BSing us. Perhaps other lost civilizations could be found?
Perhaps 30 meters isn't enough?
Canada and USSR way ahead in this area. (Score:5, Interesting)
The Canadian RADARSAT-I and RADARSAT-2 [radarsat2.info] satellites have better data. Resolution goes down to 3 meters if desired, and is 25 meters normally. That's much better than what NASA has. Here's Ottawa seen by RADARSAT-II [radarsat2.info]. Here's Paris. [radarsat2.info] They did it first, too; here's RADARSAT-I's first image from 1995. [ceos.cnes.fr] RADARSAT-I was launched from the US on a Delta booster back in 1995, but RADARSAT-II was launched from Kazakhstan on a Soyuz booster
They collect amplitude, phase, and range data, so they can do processing to get false-color images which bring out terrain features. Here's Washington [radarsat2.info] after processing.
RADARSAT is a commercial service. You can order images. [mdacorporation.com] The base price for a custom image (taken at your request, not from the archive) is $5400CN. Wait time is a week or two. If you're in a real hurry, an additional $4,800CN rush charge gets your picture taken within about 12 hours. Archival data is much cheaper, and is available from MDA Corporation [mdacorporation.com]. MDA also has data from Ikonos, Quickbird, Landsat, etc. Much topo data comes from those archives already.
Unlike the NASA data, this data is good enough to easily tell land from water. Better radar systems return "first and last" returns, which, over wooded areas, return both ground height and tree height, so areas of vegetation can be detected. The Washington DC false-color image shows all this.
It doesn't take all the NASA overhead of putting people in space to do this. The private sector is doing it just fine.
Best GIS software ? (Score:2, Interesting)
Data is trash (Score:1, Interesting)
I was an early user. (Score:3, Interesting)
I got access to the data through my NASA contacts early on and download quite a bit for some western states. We used/and still use the GPS position and altitude of our aircraft to extract elevation from SRTM and then compute the height over ground for our remote sensing data to aid in geo-rectification of our images of wildfires.
NASA imaging (Score:5, Interesting)
Hopefully this will spur more interest in some of the many tools that NASA provides for free on its website. There are many free Java applications (standalone or jnlp) to view the data or embed it within your own application. Though the documentation is not always the greatest, with a little tinkering you can make interactive websites for anything from planning your camping trip to searching for ancient meteor craters.
http://worldwind.arc.nasa.gov/java/ [nasa.gov]
Though a lot of the sources are availble, many of the Linux distributions don't have an easy way of building them. It's a real pain to build, but the results are spectacular.
Re:OpenStreetMap.org (Score:2, Interesting)
Even for motorized vehicles, that sort of route calculation would be really useful! (I've been daydreaming of it for years.) I'm glad to have driven a moving truck only a few miles total in my life, but boy was that an experience on hills! (And that was in Seattle, where the city is much, much flatter than it used to be.) Also, driving through mountains with an overloaded / underpowered car has made me long for a nice flat stretch of desert, an 18-wheeler in front of me, and a magnetic harpoon ...
Perhaps some GPS units allow users to request "flattest route" or "avoid grades over X deg," but mine doesn't.
timothy
Re:Don't you love weasel language (Score:5, Interesting)
I suspect that the vast majority of the sea is at sea level.
The Earth's gravitational field is not purely radial, resulting in very significant deviations from mean sea level over much of the ocean's surface. I believe the deviations can be up to tens of metres--I may be recalling incorrectly but I think there's a big one in the South Pacific that is something like 60 m deep and is getting on for a thousand kilometres across.
Re:Raw data (Score:1, Interesting)
I used STRM on my site since you simply cannot get the whole ASTER DEM. Anyone know how to do that? The Japanese site has a 100 tile download limit and you need to do it by hand on both the NASA and Japanese sites. Not that accessible.
Perhaps we just need to wait 2-3 years until they process the ASTER into a refined form.
Re:Don't you love weasel language (Score:3, Interesting)
Road2 (Score:3, Interesting)
My company makes use of SRTM data in our Road2 [rechargeamerica.net]electric vehicle range calculator. To tell how far an EV will *actually* go, we need to do a full physics simulation, including driver modeling, real-time weather, real-time-traffic, and of course, terrain. We first rely on NED data and use SRTM as a fallback, since NED has both higher vertical and horizontal resolution. There's a new dataset out that goes above 60 latitude, so we may be replacing SRTM data with that soon, though.
For those curious with some real-world downsides you get using such data in applications like this:
* Bridges and tunnels don't show up, so we have to hack around them by recognizing such situations and accounting for them. ;)
* The altitude data doesn't precisely match up with the locations of the roads, and in rugged areas, it can make a big difference.
* Random noise can introduce relevant artifacts into your simulation, so you need some smoothing.
* Obviously, you have to interpolate between datapoints, although it's pretty trivial.
* There are a few major errors in the dataset, places where you get huge vertical spikes (positive or negative) for one or more datapoints, then everything returns to normal. We actually make use of them to help line up our roads with the known points of the errors.