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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."
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Ideas For Exploiting NASA's SRTM Data

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  • Games (Score:5, Interesting)

    by sopssa ( 1498795 ) * <> on Sunday January 03, 2010 @03:30PM (#30633568) Journal

    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.

    • Re: (Score:2, Insightful)

      by Anonymous Coward

      Especially to get realistic mountain range layouts. No longer do you have to sit there and tesselate or deal with fractals, you can just download mother nature's fractal mountain set and go to town.

      • by WED Fan ( 911325 )
        But, I want mountain ranges on Epsilon Baumfuhc 5. Can we get a radar mission so I can have realistic missions there?
      • Re: (Score:1, Insightful)

        by Anonymous Coward

        The fractals are easy to store, they can be define with just a few seed-like numbers for the random number generator. Storing shitloads of data acquired in the real world might not just be practical.

    • I was going to look at the data for the city were I was born but it's north of 60 degrees so I'm shit out of luck.
    • You mean like BattleCell []? Offensive/defensive military strength of each cell depends on troop counts as well as altitude differences between cells. (Yes, we used STRM data to acquire our altitudes.)
    • Re:Games (Score:4, Informative)

      by negRo_slim ( 636783 ) <> on Sunday January 03, 2010 @04:31PM (#30633924) Homepage

      It's just perfect use for games

      Probably if you could find the data being talked about. Hard to imagine what I'm going to do with it if I don't have it! []

    • Re: (Score:3, Funny)

      by melikamp ( 631205 )
      How much is "almost infinite"?
      • Re: (Score:3, Informative)

        At most, one less than infinity! Duh!
        • At most, one less than infinity!

          Sounds like a copyright term.

        • by mspohr ( 589790 )
          infinity minus one still equals infinity

          In fact, infinity minus any number equals infinity.

          • You win the award for completely missing the point, and doubling down on explaining basic math to an audience that mostly can be expected to know that. (I know, I'm being too generous.) Hey, did you ever notice that a set of things that don't contain themselves looks a little funny? Someone should write congress! Or maybe Glenn Beck.
            • by mspohr ( 589790 )
              Sorry that my being pedantic upset you.

              I did wish to point out one of the interesting things about the concept of infinity that some people may not understand... and from your reply it seems that you many not understand, either...

              Yes, a set of things that doesn't contain themselves does look a little funny but that is what makes the concept of infinity interesting... (to me, at least... apparently it's just irritating to you).

              BTW, found this fun story about infinity that you might enjoy.


              • by abulafia ( 7826 )

                Blah, sorry, I was being grumpy. Apologies.

                I'm unclear on what you think I don't get. I do understand infinite sets, and set theory in general is a bit of a hobby for me. I was referencing Russell's paradox, and perhaps should have punned something about Peano math lacking a couple of keys rather than reaching for a political reference.

      • Re: (Score:1, Insightful)

        by Anonymous Coward

        just over 9000!!

  • by cnettel ( 836611 ) on Sunday January 03, 2010 @03:39PM (#30633624)
    I live at 60 deg North, you insensitive clod! (Ok, right now it is 59 deg 51' 7"...) I don't want to learn that I'll fall off a cliff if I take a step in the wrong direction...
    • by Tablizer ( 95088 )

      You are probably related to the province that turned down Columbus.

    • "(Ok, right now it is 59 deg 51' 7"...) "

      Are you slowly moving south on the ice sheet/glacier?

      I only live at 46.3 degrees north, and it just now got up to 0F for the first time in 3 days.)

      • I only live at 46.3 degrees north, and it just now got up to 0F for the first time in 3 days.

        I live at 62.9 North, and it was a balmy -25C (-13F) over the weekend. The forecast for tomorrow is a more normal -29C (-20F). These polar weather conditions are obviously due to the SRTM-imposed flatness from here to the North Pole.

  • Raw data (Score:5, Informative)

    by cellarmation ( 1137865 ) on Sunday January 03, 2010 @03:46PM (#30633674)
    The raw data, as well as data from multiple other sources can be downloaded from NASA's Earth Explorer []. The article doesn't really address the fact that the Google data has been cleaned up a lot. SRTM has a lot of voids and areas of poor quality, especially over mountains. The resolution of the data is worse for anywhere outside of the USA.
    • Judging by your link the data is supplied through google maps I couldn't see a way to get at the raw data. As for what to do with it, I'd suggest providing it free in a commonly used format like SHP or BIL. Accurate terrain data is insanely expensive so any freely available data is good.

      You could then also import it into things like OpenLayers [] or things like Open Street View [].
      • the data is supplied through google maps I couldn't see a way to get at the raw data

        It's in the Digital Elevation category in step 1, the SRTM dataset. Enter your search string and go!

        • That's not what I thought of when I read downloading the data. I thought I'd be pointed to an FTP server of huge files or something similar. Instead I've found my way to a map where I can use various graphical means to select which subset of the data I want. There are many limitations with this interface.

          Why isn't this data posted to a large archive site where people can freely download more than that GUI allows (or get data in a differently controlled way that facilitates big downloads). Perhaps the In []

          • by Lakitu ( 136170 )

            One of the limitations of this interface is it doesn't allow random people to download 9 terabytes of mostly useless information. Each.

            Search for what you want, and then use it?

            • by jbn-o ( 555068 )

              It's not up to you to decide what is useless for anyone but yourself. People can determine for themselves what they want and what they don't want. The volume of data is no reason to restrict anyone from getting to that data.

          • Here is all the data from the radar mapping mission . . .
          • by pjt33 ( 739471 )

            If you don't mind processed data, []. There may also be a torrent somewhere - I know I've downloaded some NASA data with bittorrent, but I can't remember whether it was SRTM or Blue Marble.

            Warning: if you're thinking of using this data commercially, take note that if you dig around enough (why there isn't a README in that directory I don't know) you will find that at least one university claims copyright on some of the bathymetric data included in SRTM30+.

      • [] is a combination of open street map and that height data set.

    • Re:Raw data (Score:4, Informative)

      by Anonymous Coward on Sunday January 03, 2010 @04:23PM (#30633880)

      A lot of it has been suprseded by the meaurements by the Japanese Aster instrument:
      "Previously, the most complete topographic set of data publicly available was from NASA's Shuttle Radar Topography Mission. That mission mapped 80 percent of Earth's landmass, between 60 degrees north latitude and 57 degrees south. The new Aster data expand coverage to 99 percent, from 83 degrees north latitude and 83 degrees south. Each elevation measurement point in the new data is 30 meters (98 feet) apart. "

      • Re:Raw data (Score:5, Informative)

        by cellarmation ( 1137865 ) on Sunday January 03, 2010 @05:06PM (#30634210)
        The ASTER data is at a much higher resolution, but it is debatable if it is much better accuracy than SRTM. I think even the wikipedia page mentions this. I think the problem is the two data sources are developed using very different methods (InSAR vs photometric stereo). The error in SRTM is quite obvious, large voids and no signal areas. ASTER suffers from high frequency noise and poor feature matching in complex scenes, these types of errors are not so easy to detect and account for.
        • Re: (Score:1, Interesting)

          by Anonymous Coward

          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.

  • 30-meter data (Score:3, Informative)

    by Anonymous Coward on Sunday January 03, 2010 @03:47PM (#30633682)

    According to Wikipedia, the 30-meter data is only available for the United States. The rest of the world will have to do with 90-meter data.

  • by SmallFurryCreature ( 593017 ) on Sunday January 03, 2010 @04:08PM (#30633786) Journal

    1. mapped the entire world in eleven days.

    2. vast majority of solid Earth

    3. practically all land between 60 degrees North and 56 degrees South was included, with a resolution of 30 meters (90 feet).

    Mmm, within ONE paragraph the writer sure lowers his tune. ALL the earth vs a part of it and then that part of it that is land and not sea? Anyone remember why it is called the Blue Planet at times? Because the majority of the surface is water?

    Interesting news of course, but come on, can we at least on a tech site skip the hyperbole.

    • by shogun ( 657 ) on Sunday January 03, 2010 @04:23PM (#30633878)

      As much as it would be useful to scan all the sea for height data I suspect that the vast majority of the sea is at sea level.

      • by radtea ( 464814 ) on Sunday January 03, 2010 @05:01PM (#30634158)

        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.

    • by Alotau ( 714890 )

      Carnival Rube: Hey honey, let's see how good this guy is. What'd I win?

      Navin: Uh, anything in this general area right in here. Anything below the stereo and on this side of the bicentennial glasses. Anything between the ashtrays and the thimble. Anything in this three inches right in here in this area. That includes the Chiclets, but not the erasers.

    • Well, as other posters have pointed out, there is little value in mapping the surface of the oceans (at least with this technology).

      If you think that land north of 60N and south of 56S represents a major portion of the earth, you need to stop using Mercator projection maps. and graduate to something like the Gall-Peters projection [].

      Having said that, it's absolutely true that the SRTM data set does not cover Iceland, most of Norway and Sweden, northern Russia, etc... It's not that NASA doesn't like Nordic

  • 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?

    • The Egyptians, Plato asserted, described Atlantis as an island comprising mostly mountains in the northern portions and along the shore, and encompassing a great plain of an oblong shape in the south "extending in one direction three thousand stadia [about 555 km; 345 mi], but across the center inland it was two thousand stadia [about 370 km; 230 mi]." Fifty stadia [9 km; 6 mi] from the coast was a mountain that was low on all sides...broke it off all round about[6]... the central island itself was five stades in diameter [about 0.92 km; 0.57 mi].[7] []

      I think Plato wasn't "BSing us", but just describing a vision of a perfect city.

  • by Angst Badger ( 8636 ) on Sunday January 03, 2010 @04:17PM (#30633834)

    I know Americans like to equate meters with yards, and when dealing with a small number, this is a close enough approximation for most purposes. However, 30 meters is 98.4 feet, so a better approximation for the purposes of this post would have been 100 feet.

    Didn't we learn our lesson regarding sloppy unit conversions during one of our recent multi-million dollar collisions with Mars? ;)

    • by mykdavies ( 1369 )
      I suspect that, given that this was a US mission, the resolution was originally stated by NASA as approximately 100 feet. This would later have been approximated to 30 metres for an international audience, and later still someone added the 90 feet approximation.
      • I suspect that, given this was a geographic mission, the resolution is specified in arc-seconds, which does not equate exactly to an integral number of yards or meters, and varies in size from the equator to the poles.

      • I suspect that, given that this was a US mission, the resolution was originally stated by NASA as approximately 100 feet. This would later have been approximated to 30 metres for an international audience, and later still someone added the 90 feet approximation.

        So really then, about 25 meters.

    • We're reading a summary not running around with a ruler taking measurements.

    • Good point. I have corrected the article to reflect this. Thanks for pointing it out. Unfortunately I can't correct the part of the article that is in Slashdot, but I think civilization will endure anyway.
    • by theCoder ( 23772 )

      30 meter resolution is itself an approximation. SRTM data is usually formatted in a geographic grid with a post spacing of 1 arc second. Because of the curvature of the Earth, the post spacing in meters varies from cell to cell (SRTM, like DTED, is usually distributed in files containing 1 degree by 1 degree of data). For example, the cell with Mt. Rainier in it (w122/n46) has a vertical (north-south) post spacing of 30.98 meters and a horizontal (east-west) post spacing of 21.52 meters. The horizontal

  • by Animats ( 122034 ) on Sunday January 03, 2010 @04:24PM (#30633890) Homepage

    The Canadian RADARSAT-I and RADARSAT-2 [] 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 []. Here's Paris. [] They did it first, too; here's RADARSAT-I's first image from 1995. [] 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 [] after processing.

    RADARSAT is a commercial service. You can order images. [] 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 []. 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.

    • by Volante3192 ( 953645 ) on Sunday January 03, 2010 @04:46PM (#30634038)

      RADARSAT is a commercial service.

      (SRTM) data is freely available to anyone.

      I know which set I'll be using if I want to play around with this data.

    • First, a quick reaction to your post. Radarsat-1 and 2 data, in regards to DEMs, is far from being comparable. The SRTM mission was dual-antenna interferometry, with Radarsat (or Envisat), you must use two images at different times. DEMs from Radarsat can be good and better than SRTM, but it's pretty expensive and there are alternatives (in Canada: CDED1 data is free and in many cases much more reliable than Radarsat data).

      If you ever want to use SRTM-DEM data, check the CSI-CGIAR version 4 version. It's the best out there, it's a *major* improvement over the original and previous versions. If you're in hydrography, look at HydroSHEDS SRTM-DEM data.

      This year, the advent of the ASTER-GDEM (global DEM) diminished the interest of SRTM-DEM. ASTER-GDEM is still "research-grade", but offers higher spatial resolution, and most important, cover much more land than SRTM (northerm Canada and URSS).

      On top of my mind, don't forget SRTM-DEM is available at a higher spatial resolution over the USA than elsewhere (1 arc-second vs 3). The 1-arc-second for the whole world is suppose to become available some time in the future, but that has not happened yet. Also, the X-band (the actual SRTM-DEM comes from the C-band data IIRC) is in the hands of the Germans, but to my knowledge, no public DEMs has come out of it yet (even after all those years). Still relying on my memory (I can be mistaken, see next paragraph), the TerraSAR-X in orbit should be able to give us an even better near global DEM than what's available at the moment.

      Sorry for the lack of links. I'm still in my holiday break and you can simply google your way in. Or search SRTM on the site in my sig! have fun -

      • ASTER-GDEM data is excellent, but unfortunately is not without restrictions []:

        "ASTER Global DEM (GDEM) data are subject to redistribution and citation policies. Before ordering ASTER GDEM data, users must agree to redistribute data products only to individuals within their organizations or projects of intended use, or in response to disasters in support of the GEO Disaster Theme."

        Part of what makes SRTM data so great is that anyone can use it for any purpose. That makes a huge difference. I wish government

        • The key word in your post is "trying". The bureaucrats are trying to control it, yes. However, it is still freely available from NASA to anyone who wants it. You have to jump through a couple hoops (another of which is their ridiculously clunky website) but essentially you are just agreeing to an EULA, and since you're on slashdot I'm sure you know how pointless that is :)

          You're correct, though, that I don't think they'll approve of commercial use of the data yet. However, consider the cost of commercially

    • by hyc ( 241590 )

      But it took NASA to develop SAR and refine its use. I worked on the control software for SIR-C [] back in 1991-1994; all of the software that I wrote for that got re-used by RADARSAT and SRTM and probably other missions as well. (Haven't really kept tabs after I left.)

    • You can get high resolution data for free through GeoBase in Canada. Your tax dollars at work.. []

  • Best GIS software ? (Score:2, Interesting)

    by parens ( 632808 )
    I've been trying to play with GIS data for a few months now, and always seem to get hung up on what to do with said data once I've downloaded it. I've attempted to find some open-source visualization software, and had some limited success with SAGA GIS ... but the interface is pretty clunky, and the documentation is either outdated or for previous versions. Anyone have any suggestions for visualization of terrain data ? Frankly, whatever was used in the article would be useful, but I didn't see the autho
    • Re: (Score:3, Informative)

      by maeka ( 518272 )

      and had some limited success with SAGA GIS ... but the interface is pretty clunky, and the documentation is either outdated or for previous versions

      A clunky UI and poor documentation appears to be an industry standard. You won't fix either of those problems going to a commercial package. ;)

    • Re: (Score:3, Informative)

      Take a look at Quantum GIS (, it's really good. It reads raw SRTM data directly, along with a huge list of other formats, raster and vector. It's free and it does a superb job. It's not ESRI, but it's excellent.
      • by parens ( 632808 )
        Many thanks, MaxTardiveau - I was able to import the SRTM data directly using QGIS. This is what I was looking for.
        • To answer your original question -- all the screenshots in the article are from our iPhone apps [], which cover about 20 U.S. states so far. They come with many layers, one of which is the SRTM data limited to (typically) 180-meter resolution, because you only have so much storage on a phone. The 30-meter resolution data is obviously even better than what I showed (nine times better, in fact :-)
          • by parens ( 632808 )
            That looks ideal for what i'm wanting to do (generally, geek out on maps while camping and such) ... any plans for an Android port ? I'd hate to have to buy an iPhone for this app, as ideal as it seems.
            • We're planning on an Android port this year. Blackberry is another possible platform, but we're very small and on a shoestring budget, so we have to stay focused.

              You can run the app on an iPod, in case that's relevant... No GPS, though.

    • check out virtual terrain project [] or for GIS alternatives to SAGA, OSGeo foundation: [] GRASS / QGIS worth checking out
    • Quantum GIS might be intereting to you: and so may gvSIG. If you need raw power, look at GRASS GIS (the interface isn't up to par if you ask me and you can access many GRASS features directly from QGIS). (if you need a spatial database, there's nothing better than PostGIS)

      The (the open source geospatial foundation) is a great resource in that regards. Depending on your needs (geospatial is vast, see my sig), you may "need" ArcGIS from ESRI - it's commercial, it's expensive and it crashes

    • by Huntr ( 951770 )
      If you're just wanting to play around with similar data, you might have luck with national elevation data (NED) in 10m or 30m grids. You can then display and explore these in ESRI's free ArcReader. It's limited though. Just useful for displaying and simple map making, basically.
    • by phyr ( 586855 )
      For visualizing terrain data the open source NEST ESA SAR Toolbox [] is great. It automatically downloads SRTM tiles as needed to orthorectify SAR images. When the interferometry modules are ready it will also be able to generate new DEMs from SAR images
  • Data is trash (Score:1, Interesting)

    by Anonymous Coward
    The 30m SRTM data is trash, the mission totally fucked up collecting the data. We've been trying to use it for years. It isn't still being 'refined', it's being gap filled with various interpolation algorithms and other data sets. The best NASA DEM is the one from the ASTER instruments []. Not only is it also 30m horizontal resolution, but it goes up to 82 degrees north and south.
  • I was an early user. (Score:3, Interesting)

    by RNLockwood ( 224353 ) on Sunday January 03, 2010 @04:33PM (#30633944) Homepage

    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.

    • by adosch ( 1397357 )
      My project I work on at the USGS used to host this data until we turned it over to the USGS long-term archive project in late 2009. And just clarify so it doesn't sound like as though you need a special NASA contact to go get this, go to the SRTM website [] and more importantly, go download it from here []
  • (Score:4, Informative)

    by Baloo Uriza ( 1582831 ) <> on Sunday January 03, 2010 @04:34PM (#30633962) Journal
    OpenStreetMap uses this data to give the elevation contour lines on the cycle map rendering. Eventually, it'll be used to guide cyclists on a flatter, faster (but possibly slightly longer) route to avoid the steep stuff.
    • Re: (Score:2, Interesting)

      by timothy ( 36799 ) * Works for Slashdot

      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 so

    • If it's accurate to 30 meters, that could easily result in very impossible to navigate slopes for bicycles. I know plenty of small roads around here, that have inclines of 25 meters in less than 100 meters, and that is pretty close to impossible to drive up (they're gravel roads, and I can make wheel spin, going backwards in a high gear).

  • NASA imaging (Score:5, Interesting)

    by digitalhermit ( 113459 ) on Sunday January 03, 2010 @04:46PM (#30634036) Homepage

    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. []

    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.

    • by pjt33 ( 739471 )

      I think it's intended to be built in an IDE. I don't have any problems importing it into Eclipse and building there.

  • We have no idea where many photographs were taken. Also, there are many old paintings with poor titles such as "Landscape at Dawn/Sunset".

    By scanning images with definable features (e.g. two hills, river in the foreground, somewhere in France), it shouldn't be that hard to exhaustively search the SRTM data for possible location matches- especially if individuals could enrich the scanned data by providing height or distance estimates?

    • Throughout most of art history, exacting realism in paintings is pretty much a small blip - an artist will alter the shape of anything, including landscape, to be more aesthetically pleasing. I am really dubious you could get anything out of trying matches with exacting terrain data...

      It would work better with photographs but then you also have to figure out a feature distance map from a flat image.

  • I used the SRTM data extensively last year developing a program to identify set gradients for intelligent transport.

    One liter of fuel passed through a small engine will provide enough energy to raise you to the height of Mount Everest.

    From the top of Mt Everest a consistent 0.7% gradient will travel for over 1,000 km

    Current technology, like an aero-dynamic coffin on rails, will roll down a 0.7% gradient at over 65 km/hr

    That's 1,000 km/litre, or over 2,500 mpg, and the efficiency we need to be aiming for w

  • Big thanks to NASA for this data, I've used it with the Splat! tool [] for radio path profiling to generate maps and estimate height above average terrain (HAAT). I've been using these maps to show what the approximate footprint is for amateur radio repeaters. See this example [] for a 90W 440Mhz repeater on top of the Empire State Building.


  • If you have access to MATLAB, give the following project a shot: []

    Unfortunately, it only supports the worldwide 90m dataset, not the 30m dataset exclusive to the USA.

    No idea if it works in Octave or not.

  • SRTM 3sec DEM is also available via anon FTP in GeoTIFF format from []
  • by Anonymous Coward

    As a small indie video game developer NASA's srtm data was an invaluable resource for assembling an accurate map of ancient greece for our upcoming rts Hegemony: Philip of Macedon [].

  • You can find the MOLA MEGDR DEM on FTP here [], or browse the datasets here [].

Research is what I'm doing when I don't know what I'm doing. -- Wernher von Braun