90m-resolution, near-global SRTM elevation mosaic and hillshading maps
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More than 14000 SRTM 1 x 1 degree tiles (90m-resolution) publicly available at USGS are stitched together to make a seamless, near-global elevation mosaic, followed by elevation gaps filling and shaded-relief map production.
Shuttle Radar Topography Mission (SRTM), flew on the Space Shuttle Endeavour launched on 11 February 2000, had successfully collected 3-D measurements of the ~80% Earth's surface. The mission was a cooperative project between NASA, the National Geospatial-Intelligence Agency (NGA) of the U.S. Department of Defense, and the German and Italian space agencies, and was managed by NASA’s Jet Propulsion Laboratory (JPL) for NASA's Earth Science Enterprise, Washington, D.C.
USGS freely distributes the latest SRTM Version 2 (also known as the "finished" version) data set, which is the result of substantial editing effort by NGA. It features the following:
- Well-defined water bodies (e.g., lakes, reservoirs and major rivers) and coastlines;
- Absence of spikes and wells (single pixel errors); and
- A small percentage of elevation voids (gaps, holes or missing data) still present.
We advocate the significance and potential of this public-domain data set, and have undertaken significant post-processing to produce a seamless, near-global SRTM mosaic and a series of cartographically-designed, GIS-ready shaded-relief maps.
More than 14,000 separate SRTM tiles were first stitched together, and elevation gaps were filled with 1km-resolution data including SRTM30 and GTOPO30 (bi-linear resampling from 1km to 90m-resolution was used). Further improvements over gap-filling methods or by ancillary elevation sources are on-going.
The shaded-relief maps vividly illustrate both hillshading effects and topographic heights in colour gradients. Efforts have been made to highlight and better visualise geological and geomorphologic features such as seismic faults and coastal fluvial plains.
1. Overview
| Coverage | Longitude 180W-180E Latitude 60N-56S |
| Projection | Latitude/longitude Geographic, WGS84 |
| Resolution | 90m |
| Image size | 432,000 X 139,200 pixels |
| Format | JPEG2000, GeoTIFF, ENVI's IMG or any other format major GIS software packages support |
| File size | Single file for near-global SRTM elevation mosaic or hillshading map - 112GB for the SRTM elevation mosaic (by default, ENVI's IMG format) with gaps filled by coarse-resolution inputs - 3 to 20GB for each hillshading map (under JPEG2000 compression) |
| Additional file | SRTM mosaic mask showing pixels with elevation voids (gaps) in the raw SRTM tiles |
| Media | DVD, external hard drives with USB 2.0 compliant interfaces |
2. Spatial resolution comparison
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| Sample regions | 1km-resolution SRTM30 Size: 480 X 480 pixels |
90m-resolution SRTM Size: 4800 x 4800 pixels |
Tokyo
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Los Angeles
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| New Zealand |  |
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| ... |
3. 90m-resolution, near-global SRTM shaded-relief maps on offer
A series of shaded-relief maps are produced under various colour schemes and hillshading settings. Hillshading colour schemes are shown below: A1, A2, A3, B1, B2, ...
Hillshading settings:
- Light source altitudes: 60 (by default) or 45 degrees
- Light source azimuth: 45 (by default), 0 or 315 degrees
- Elevation vertical exaggeration: 0.8 (by default), 1.4 or 2.8
| A1 | |
| A2 |  |
| A3 |  |
| B1 |  |
| B2 |  |
C1
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... more to add |
4. 90m-resolution SRTM elevation mosaic available
This is a single file with the size of 112GB. All elevation gaps have been filled. A separate mask file indicating those gaps pixels in the raw SRTM tiles is also provided.
With this data set at hand, users can conveniently subset any small-sized region of interest and then perform dedicated 2D and 3D terrain modelling in GIS, for example:
| 3D: Shaded relief Region: Mt. Fuji, Japan |
3D: SRTM elevation | 3D: SRTM elevation + Earth Land Surface 2000 (version 1) satellite imagery |
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| 3D: SRTM elevation + Earth Land Surface 2000 (version 1) satellite imagery (more samples) |
| Mt. Rainier, Washington | Switzerland | North India - Pakistan |
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Are you interested in the above GIS-ready imagery data sets? Please consider the following:
- While many business applications (e.g., real eatate property searches) require very detailed images such as Street View and oblique aerial photos, for applications such as regional environmental studies and landscape simulations, medium-resolution data at 30m to 90m-resolution could be sufficient.
- Imagine you have infrastructure and platform to make another virtual world, but are seeking a low-cost solution for near-global imagery data ...
- Imagine you are interested in GIS desktop mapping and wish to own a copy of the imagery data locally and make underlying elevation and imagery layers fully dynamic and integrative.
- Are you thinking of boosting agency-wide mapping productivity using globally consistent data sets?
- Imagine you do not wish to have access to online imagery from virtual globes such as Google Maps or Microsoft Bing Maps, concern about licensing terms or unexpected network disconnections ...
5. Free download: 1km-resolution, global SRTM30_PLUS hillshading map
Scripps Institution of Oceanography, at University of California, San Diego, has recently created a popular 1km-resolution global elevation and bathymetry data set called SRTM30_PLUS. The data can be downloaded from its website freely for non-commercial uses. Users should read SRTM30_PLUS COPYRIGHT and README files for more information. We at GeoSage have also implemented a terrain analysis and created hillshading maps in JPEG2000 format for the SRTM30_PLUS (SRTM30_PLUS data courtesy of Joseph Becker). Interested users can download a copy of SRTM30_PLUS hillshading map below freely for non-commercial applications, with due acknowledgement.
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SRTM30_PLUS hillshading map in Google Earth |
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SRTM30_PLUS hillshading map A Download |
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SRTM30_PLUS hillshading map B Download Small sizes: |
Free, efficient tools for viewing large-sized JPEG2000 files:
Nowadays almost all popular GIS and remote sensing software can display JPEG2000 files easily. |