Ideas For Exploiting NASA's SRTM Data

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."

Raw data

[cellarmation]

The raw data, as well as data from multiple other sources can be downloaded from NASA's Earth Explorer http://edcsns17.cr.usgs.gov/EarthExplorer/ [usgs.gov]. 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.

30-meter data

[Anonymous Coward]

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.

Re:How different?

[toastar]

Actually it's lower resolution then many other maps, It does have very high coverage, The problem is trying to find a pass that doesn't have to much cloud cover. As someone who does GIS for a living, I can say we usually use this data til we can get a LIDAR Plane over the prospect.

Re:Raw data

[Anonymous Coward]

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. "
http://www.nasa.gov/topics/earth/features/aster-20090629.html

Re:Games

[negRo_slim]

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! [usgs.gov]

OpenStreetMap.org

[Baloo Uriza]

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:Best GIS software ?

[maeka]

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:Raw data

[cellarmation]

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:Games

[betterunixthanunix]

At most, one less than infinity! Duh!

Re:Best GIS software ?

[MaxTardiveau]

Take a look at Quantum GIS (http://www.qgis.org/), 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.

SRTM-DEM CSI-CGIAR v4 + ASTER-GDEM and more

[Lord Satri]

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 -

recreated ancient greece for pc rts

[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 [longbowgames.com].