The World Elevation services provide online access to global collections of multiresolution, multisource elevation data, or digital terrain models (DTM). This collection includes data with resolutions ranging from over 1,000 meters to approximately 3 meters in some limited areas. The services provide a single source for desktop and web applications to access elevation values and derived products.
You can use it in your desktop and web applications in the following ways:
- For visualization or analysis
- As information layers, such as a hillshade or aspect
- To orthorectify imagery
- As a data source in your analysis models or other geoprocessing tasks
- To obtain data locally
Visualization
The World Elevation services provide several products derived from the DTM that you can use in ArcMap to provide context to other layers. There are hillshades, tinted hillshades, slope maps, and aspect maps. Because they are already optimized for viewing on the web, they are ideal for any web application; however, since these are RGB renderings of the DTM (not actual elevation values), they are unsuitable for analysis.
One of the advantages of these products over the source DTM is that they are lower in data volume, enabling them to display faster. For example, the hillshade image service has a smaller bit depth (8 bit) than the DTM (32 bit) and can also be compressed using JPEG. Therefore, if you want to use the image service in a visual capacity and not for processing, it's faster to transmit the smaller bit-depth data. Also, if you transmit the source elevation data, your application still needs to process it to create the hillshade layer, which increases the time it takes to display.
The world elevation services provide access to visualizations such as hillshade, multidirectional hillshade, elevation-tinted hillshade, and slope to provide context to your work.
Analysis
The World Elevation services also provide layers for analytical purposes and orthorectification. The layers for analysis include the DTM as well as Slope Degrees, Slope Percent, and Aspect.
Image services
These image services are available on ArcGIS Online. You access them by connecting to the Terrain or TopoBathy service and selecting one of the server raster functions to output the other elevation-based products. These products generate on the fly, so you’ll see the outputs immediately. For more information, see the ArcGIS Online Elevation Layers Group
.
| Name | Description | For visualization | For analysis |
|---|---|---|---|
| Terrain | Displays ground surface heights, based on a digital terrain model from multiple sources. The sea level is set to 0 and water bodies that are above sea level have approximated nominal water heights. | No | Yes |
| TopoBathy | Combines topography and bathymetry (water depths) to show both elevation and the ocean floor. Heights are based on multiple sources | No | Yes |
| Hillshade | Displays a hypothetical illumination of the terrain where the sun is shining from the northwest (azimuth of 315 degrees) at an altitude of 45 degrees. | Yes | No |
| Elevation Tinted Hillshade | Displays a map where elevation is fused with hillshade and transitions smoothly from green (low elevations) to brown (low medium to higher elevations) to white (peaks). | Yes | No |
| Multi-Directional Hillshade | Displays a hypothetical illumination of the terrain by computing hillshade from six different directions. This hillshade offers a higher degree of detail than the traditional hillshade which uses only one illumination source. | Yes | No |
| Ellipsoidal Height | Applies a geoid model (EGM2008) to orthometric heights from the Terrain layer. This can be used for orthorectification. | No | Yes |
| Aspect Map | Applies a colormap to the Aspect layer. | Yes | No |
| Aspect | Displays the orientation of downward sloping terrain in degrees (0 to 359.9), clockwise from north. Cells in the input raster that are flat with zero slope are assigned an aspect of -1. | No | Yes |
| Slope Map | Applies a colormap to the Slope layer. | Yes | No |
| Slope Degrees | Calculates the steepness of changes in elevation from the Terrain layer. The values are integer and represent the angle of the downward sloping terrain (0 to 90 degrees). | No | Yes |
| Slope Percent | Calculates the steepness of changes in elevation from the Terrain layer. The values represent the angle of downward-sloping terrain, measured from 0 to 1,000 percent. | No | Yes |
Sources
The source elevation data is composed of the best publicly available elevation data. For more information about the coverage of the World Elevation services,check our Elevation coverage map. This shows the extent and source of the various datasets that make up the World Elevation services.
Organizations can contribute their authoritative high-resolution elevation data through Esri Community Maps for Elevation and become part of the ever growing Living Atlas of the World.
| Sources | Data | Approximate cell size (m) |
|---|---|---|
| www.usgs.gov | NED 2, 1, 1/3, and 1/9 arc-second DEM | 62 - 3.1 |
| www.usgs.gov www.cgiar-csi.org www.nasa.gov | SRTM DEM | 31 - 93 |
| www.usgs.gov | GMTED DEM 7, 5, 15, and 30 arc-second | 232, 464, and 928 |
| http://www.ahn.nl/ | Netherlands | 3 |
| http://www.geoland.at/ | Austria | 10 |
| http://www.maanmittauslaitos.fi/en/file_download_service | Denmark | 3.2 - 10 |
| http://data.kartverket.no/download/content/velkommen | Finland | 3 - 10 |
| http://www.ordnancesurvey.co.uk/business-and-government/products/terrain-50.html | Norway | 10 |
| http://www.ordnancesurvey.co.uk/business-and-government/products/terrain-50.html | OS Terrain | 50 |
| http://www.fema.gov/ | FEMA LiDAR DTM | 3 |
| http://www.earthenv.org/DEM.html | EarthEnv-DEM90 | 93 |