Free Satellite Data, Satellite Imagery, Digital Elevation Models (DEMs), Topographic Maps and free software links.

DEM Explorer

DEM download site for SRTM, GTOPO and more.

USGS Geographic Data Download

This is the original USGS data format. USGS ASCII DEM format is not particularly good as a data format because it is ASCII. This makes the file size several times larger than a well-constructed binary format, and makes the file more difficult to machine process. However, it is a fixed ASCII format, which makes it easier to handle from this aspect. More importantly, it was the original DEM format and had been around so long that many applications could (and still can) handle it. It is the de facto plain-vanilla standard for data transfer between different applications. However, at this point the USGS has converted most of its data to different formats (see below). Only the 1:250,000 scale DEMs are still offered by the USGS in this format, available at:

gisdatadepot.com

SDTS DEM data format was the USGS attempt at creating a new file format specification. SDTS format is an extremely versatile, self-describing structure capable of handling a wide variety of data types, produces a compact file size, and is theoretically is more machine readable than its predecessor. There was only one problem: it was utterly rejected by the user community as a standard because if its outstanding complication.

An SDTS DEM is comprised of 18 separate files, arranged in a most unfriendly structure from a processing standpoint. Almost half of the files have to be individually parsed in order to simply get at the elevation data. The rest of the files are chock-full of mostly useless information. Writing an SDTS file reader is a significant pain as a result. Writing an SDTS writer is virtually impossible and I do not know anyone who has done it. The failure was so total that the USGS did not even complete the conversion of its data to the new format before they gave up and adopted the new NED formats. However, there is nothing wrong with the data once you get at it. The entire 1:24000 (7.5') 15m and 30m United States DEM data set is available in this format. Many applications can read SDTS format, so using this data is generally no problem. From a technical standpoint, the NED is probably superior. This data is available from three commercial (but free) sources at:

USGS Seamless Data Distribution

The next attempt by the USGS took the existing SDTS data and reformatted it into a data structure that allowed the data to be selected by rubber-band box from a map GUI such that DEMs of any arbitrary size could be supplied to the user. The data is then offered to the user in four formats, ArcGrid, BIL, TIFF and Grid Float. This is OK, except the user interface is slow and awkward. The data format is OK if you use ESRI applications. The others are a little obscure but not impossible to handle. The data can be accessed at:

Geobase Canadian CDED DEM Data

DEM data for Canada is available in CDED format, which although it has its own specification is mostly identical to USGS ASCII format. Sometimes USGS DEM readers can read a CDED file, sometimes they get hung up on a single data field. MicroDem can usually handle CDED files. (If anyone is having trouble let me know as a couple of my conversion utilities can ingest CDED.) CDED DEM data at 1:50,000 and 1:250,000 resolution is available from:

Best source for ASTER GDEM V2 and SRTM data using the Seamless Server.

Coarse scale (1Km) DEM data

The NIMA Raster Roam site used to be an interesting and eclectic source of DEM and satellite image data. Its offerings were gradually curtailed over the year. After being completely taken down for years it is at least partially back. You can still get DTED and ONC and other data but the 10m satellite imagery is not available at the time of this writing.

EOS Data Gateway and also at
GLCF

ASTER DEM data provided the first high-resolution alternative to DTED0. Although this remarkable data set is extremely useful due to its relatively high resolution, it suffers from several drawbacks. The most significant is lack of coverage. Only a small fraction of the earth's landmass is covered by ASTER DEM. The second is data quality. Many ASTER DEMs have large areas of missing data. The user interface is not easy to navigate. And lastly is the file format. ASTER DEMs are available in HDF or Geotiff format. HDF is a self-describing format (like SDTS or shapefiles) that very few applications recognize. More can handle geotiff, but not the I16 or FP32 that ASTER DEMs are offered in. As a result, it takes more work than the casual user is willing to expend in order to use this data. Nevertheless, it is an extremely important data set and is expanding as more users request on-demand DEMs. See the article. This data is available at:

USGS Seamless Data Distribution or more conveniently at the FTP Site

SRTM stands for Shuttle Radar Tomagraphy Mission. STS99 extended a long boom and spent ten days mapping much of the earth's surface via overlapping radar imaging, producing the stereo pairs necessary for essentially worldwide DEM coverage. Much of this data was finally released to the public in 2003 and has rapidly moved to a position of prominence as a result of the extent of its coverage and superior resolution as compared to DTED0. When the African continent data is released hopefully later this year, most of the earth's landmass will be mapped.

SRTM DEM data is not offered to the general public at full resolution. Instead, the 30m data is averaged to 90m resolution. This is significantly less resolved then ASTER but ten times better than DTED0 or GTOPO30. The data is in flat binary format and is extremely easy to read and write. Many applications can process this data. At this point the data set is not completely processed and has null data areas, but not as many as ASTER.

Note: don't use this data for USA DEMs. Use the much higher quality NED or SDTS products instead.)

Alaska Geospatial Data Clearinghouse

Hard-to-find Alaska DEM data!

Geographx

New Zealand DEM data.

CGIAR

CGIAR consurtium corrected SRTM data.

Viewfinder Panoramas

Corrected SRTM DEMs for mountainous areas in Central Asia, China, Europe, Caucasus, Northern Andes and Southern Andes from Jonathan de Ferranti's webpage

Equador DEM Data

Equador DEM data from Dr. Marc Souris' webpage.

Austrian DEM Data

Austrian DEM data from government webpage.

Danish DEM Data

Danish DEM data at Kort & Matrikelstyrelsen .

INEGI

Mexico DEM data from Instituto Nacional de Estadística, Geografía e Informática.

Australia Geoscience DEM Data

DEM data for Australia is available in ER-Mapper format, which BLACKART v3.92 and higher can read. This 9 arc-second (250m) DEM data is available from:

NOAA-NGDC Link Page
NOAA-NGDC Bathymetry Data
NOAA-NGDC Globe Data

The best source of global bathymetry data appears to be the ETPO2 data set available from the NGDC. The data is available on CD for USD $75 but an online map of tiles is offered that allows you to view the full resolution imagery for free. Since it is easy to screen capture the images, this may qualify as a free data source. Local bathymetry data is also available from widely disparate sources. Check the NOAA web site but there appear to be tons of disparate sources. The GLOBE data seems to be the best for integrating terrain data with bathymetry.

NOAA Office of Coast Survey

Great source for USA coastal maps.

Mars Express Imagery Page

ESA Mars Express Imagery

Mars Laser Altimetery Data

High Resolution Imaging Science Experiment (HIRISE)

High Resolution Imaging Science Experiment

Mars Orbiter Laser Altimetery (MOLA)

Mars USGS FTP Site

Mars Viking data may be obtained at (thanks to a pointer from Tony Standley):

USGS AstroGeology Site

Lots of great information

There are possibly a few other sources for free DEM data but I think I covered all the most useful types. I would certainly welcome any pointers to additional free sources and will post them if received.

World Wind Central

PANCROMA™ Free Satellite Data Listing

Most comprehensive listing of free satellite imagery around at the PANCROMA website.

USGS Global Visualization Viewer (GLOVIS)

USGS Earth Explorer

The gold standard for global data.

Free GIS Data

excellent compilation of sources posted by Robin Wilson

NASA EarthKam

This is the best site for beginners. Easy user interface, great true-color images in a friendly format (jpg). It will even provide the corresponding NIMA air navigation map and overlay your satellite image. Drawbacks: incomplete coverage, lots of clouds in many images, high camera obliquity for many images. Definitely worth checking out. (Absolutely great for school kids and in fact aimed at this audience.) See the article.

Global Land Cover Facility

The best source of free satellite imagery on the web, and one of the best websites anywhere specializing in near global Landsat TM, Landsat ETM, MODIS and other coverage. However, the Landsat 7, MODIS and other datasets can be daunting for the inexperienced, so beginners can expect to spend many many hours producing images from this data. Some of the issues to be dealt with: the data is presented in multiple bands spanning the ir, visible and uv electro magnetic spectra. Band data is contained in files each of which is tens of megabytes large. Creating true color RGB images takes a bit of work and a lot of computing power. However, this is one of the most important data sets for researchers and also for terrain modelers. See the article on this site.

GeoGratis

Source for Canadian Landsat 7 and many other types of GIS data. See the article.

NASA WIST

ASTER GDEM and free ASTER L1A/L1B data See the NASA WIST Website

ASTER Data Pool

Free ASTER L1A/L1B data, source of stereo pairs for ASTER DEMs and a rich multi spectral dataset. Unfortunately, USA only. See the article.

NASA ESAD

Global coverage; spectacular images composed of Landsat TM bands 7, 4 and 2. These are not true color images but you do not have to composite them yourself. Data is presented in MRSID format so you will need an application that reads this format, like ArcExplorer (free). This site periodically disappears from the internet. See the article.

Space Imaging Quicklook

This site is meant to be an index and teaser for the spectacular (and spectacularly expensive, for the amateur) Space Imaging full-resolution imagery. However, the b/w index images themselves are impressive and very well presented and seem to of about 16m resolution. See the article.

NGA Raster Roam

The same site that offers DTED0 1km DEM data used to offer some surprisingly high resolution but old satellite imagery. The NIMA DOI 10m data set is as its name implies 10m resolution b/w imagery for a limited part of the world, principally southern Europe and the Middle East. This site seems to be substantially broken.

NASA Gateway to Astronaut Photography of Earth

Over 500,000 images taken from the International Space Station, Space Shuttle, and other platforms. See the article.

NASA's World Wind

Integrated smart client application that can access Landsat, SRTM, USGS, MODIS and other remotely sensed data. Highly recommended.

JPL's OnEarth

Landsat, SRTM, MODIS and other data presented with a flat map Blue Marble user interface. Source for much of World Wind data. You will have to do some digging to get anything out of this one.

ASTER Mineral Mapsfor western Australia.

Processd ASTER multispectral data showing mineral distributions based on processed reflectance data.

Canadian National Topographical Map

New source for Canaidan topographical maps. Coverage is not yet complete but presumably this will be increasing as Natural Resources Canada completes the collection.

USGS National Map

Simply the best map source for the USA.

Perry Castaneda US Army Map Service Topos

From the 1940s but still useful.

USGS Map Store

Free USGS topo maps in .pdf format for all USA.

Digital Topographic Map Library

Russian topos of Nepal.

Madmappers.com

Russian topos of Northern Africa.

Madmappers.com

Russian topos of Southern Africa.

Poehali

Great source for Russian topos.

Libre Map Project

Great source for high quality USGS topo maps.

Natural Graphics Free GIS Data

Another source USGS topo maps.

Stanford University Libraries and Academic Resources

Great directory for USA mapping resources

University of Oregon Library System State Directory

This is not actually a source of topographic maps, but is instead one of the most comprehensive listing of USA state mapping and GIS agencies. These agencies are often the best source of not only free USGS topographic maps for their state, but often also for tons of other valuable data like DOQQs, tax plats, etc. The University of Oregon site is one of the best listings.

UC Berkeley Map Library

Free Russian topos! For all you non-USA cartographers looking for free topos, this site may help. Very incomplete world coverage and not all of the collection is available on line. However this is one of the only free sources of Russian topos on the internet, and certainly the largest. See the article

UNR Keck Map Library

USGS Topos for all of Nevada and California border.

Doc Savage Archeology Site

This guy is a real-life Indiana Jones who has spent a good chunk of his life conducting archeological studies in Israel and Jordan. Plenty of very interesting information on his site, including a fine collection of Middle East topographic maps that you can download. Very limited coverage, but excellent source of very unusual maps, including topos published by the Royal Jordanian Geographic Centre. The maps are offered in several formats, including with and without collars. See the 'Lavant Topos' link.

University of Arkansas CAST

The most comprehensive compilation of USA state GIS resources, including topographical map sources.

NGA Raster Roam

Air navigation charts for much of Asia. See the article.

Jim Henthorn's Project MapScan

Awesome, awesome, awesome collection of scanned topographical maps for all of Southeast Asia. Veteran Jim Henthorn has done an outstanding piece of work. Check this out, it is awesome.

Toporama

Free 1:1,000,000 topos maps for all of Canada.

Lemkos Poland

Topographical maps for southeastern Poland.

Expidice Hindukus

Some excellent mountaineering maps for Pamir and Hindu Kush ranges. Czech language.

Austrian Map Online

Austrian topographic maps. German language site.

Luxembourg

Is that how you spell it? They speak French.

Maps of Japan

How's your Japanese?

Old maps of Russian Asia

Great collection of scanned old maps, Cryllic letters. Markus Hauser is looking for a home for 30GB of scanned maps from the early 20th century. This seems like a good project for Perry Castaneda, Berkely or the like. If anyone can help, contact Markus at pamirmountains@yahoo.com.

Karta Ykpanhbi

Excellent source of Russian military topos for Ukraine. Hope you read Russian.

Institut Cartografic de Catalunya

Very detailed and modern topographic maps for all of Cataluna in Spain. Select "CFAF Red". Spanish.

360 Panoramas of Mountain Regions

In Italian but easy to navigate

Some good free applications that every terrain modeler should have in their toolkit:

Google Earth The reigning heavyweight champion of GIS applications. Makes all the rest virtually obsolete.
World Wind The former heavyweight champion of GIS applications.
3DEM The best application for producing overlays. Great 3D renderings.
MicroDem The best application for merging DEMs. Reads a fairly wide variety of formats. OK for 3D rendering and overlays.
Terragen The best application for photo realistic terrain renderings. Reads only its own .ter format. (Several converters offered on this site).
POV-Ray Freeware ray tracer. Create terrains using height field utility. Not for the faint of heart, renderings are created using a C-like programming language. A lot like programming in OpenGL but much easier and very powerful. Warning: addictive. (Several converters offered on this site).
GEOTIFF4 Convert ASTER DEM HDF and Geotiff format to USGS ASCII, Terragen, flat binaray, etc. Written by a great guy
BLACKART Useful for patching holes in your SRTM DEMs or ASTER DEMs. Also written by a great guy.
ArcExplorer Necessary for reading DOQQs in MRSID format.
Multispec Multispectral image analysis tool.
Geotrans NIMA Geotrans coordinate transformation tool.
FRHED The best free hex editor. Essential tool for troubleshooting your binary data problems

Note: there are a couple of other great low-cost applications that are very helpful (i.e. used every day) that I recommend but that are not free. Since this site is directed at free data and applications, I will not mention them here but contact me if you want my short list of low cost commercial applications that are great.

Geotiff