What are the World Elevation services?

Note:

Access to the World Elevation services requires authentication using an ArcGIS Online subscription.

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 200 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 grayscale hillshade is generated from the DTM that defines the ground surface. Heights are orthometric and sea level is 0. There is also a color-tinted hillshade, created from the DTM and color rendering of Slope and Aspect.

DTM Hillshade

DTM Slope

DTM Aspect

Analysis

The World Elevation services also provide layers for analytical purposes and orthorectification. The services for analysis include the DTM, as well as Slope Degrees, Slope Percent, and Aspect.

Note:

When using these image services in geoprocessing tools, use the Make Image Server Layer tool to define some of the properties of the image service, such as the extent and band number. The size of the output layer is limited to 4,000 by 4,000 pixels. To learn more, see Using mosaic datasets and image services in geoprocessing tools.

Image services

These image services are available on ArcGIS Online. You access them by connecting to the Terrain 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	A digital terrain model (DTM) that defines the ground surface. Heights are orthometric and sea level is 0. This is the base service from which all of the other services are generated.	No	Yes
Grayscale Hillshade	A hillshade created from the DTM with a solar azimuth of 315 degrees and solar altitude of 45 degrees.	Yes	No
Tinted Hillshade	A colorized hillshade surface created from the DTM.	Yes	No
Aspect Map	Aspect generated from the DTM. The orientation of the downward-sloping terrain is indicated by green to blue to red to yellow (clockwise from north).	Yes	No
Aspect	Numeric values representing aspect. Values represent the orientation of the downward-sloping terrain as 0 to 360 degrees (clockwise, for example, due east = 90 degrees).	No	Yes
Slope Map	Visualization of slope. Rendered with color to represent flat to steep slope (gray to yellow to red-brown).	Yes	No
Slope Degrees	Values represent the angle of downward-sloping terrain from 0 to 90 degrees.	No	Yes
Slope Percent	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. The table below provides a list of sources contributing data to the World Elevation services.

Additional data will be incorporated in the future via a Community Maps model. If your organization has data to contribute, contact [e-mail].

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	93
www.usgs.gov	GMTED DEM 7, 5, 15, and 30 arc-second	232, 464, and 928

Data sources