Service Name: Terrain
Description: This dynamic image service provides numeric values representing ground surface heights, based on a digital terrain model (DTM). The ground heights are based on multiple sources. Heights are orthometric (sea level = 0), and water bodies that are above sea level have approximated nominal water heights.
This layer is generally not optimal for direct visualization. By default, 32-bit floating point values are returned, resulting in higher bandwidth requirements. Therefore, usage should be limited to applications requiring elevation data values. Alternatively, client applications can select from numerous additional functions, applied on the server, that return rendered data. For visualizations such as hillshade, elevation tinted hillshade, and slope, consider using the appropriate server-side function defined on this service.
Server Functions: This layer has server functions defined for the following elevation derivatives:
Data Sources: The data for this layer comes from the multiple sources listed below, with original source data in its native coordinate system. Depending on the scale being viewed, data from one of these datasets will be returned:
|Source Data||Source Native Pixel Size||Approximate Pixel Size (m)||Primary Sources|
OS Terrain 50
FEMA LiDAR DTM
NED 1/9 arc second
NED 1/3 arc second
NED 1 arc second
NED 2 arc second
SRTM 1 arc second
SRTM 1 arc second DEM-S
GMTED2010 7.5 arc second
GMTED2010 15 arc second
GMTED2010 30 arc second
The coverage map below illustrates the coverage:
For more information, see Use the Terrain image service.
Mosaic Method: This image service uses a default mosaic method of By Attribute, using Field Best and target of 0. Each of the rasters has been attributed with Best field value that is generally a function of the pixel size such that higher-resolution datasets are displayed at higher priority. Other mosaic methods can be set, but care should be taken as the order of the rasters may change. Where required, queries can also be set to display only specific datasets such as only NED or the lock raster mosaic rule used to lock to a specific dataset.
Accuracy: The accuracy of these services will vary as a function of location and data source. Refer to the metadata available in the services, and follow the links to the original sources for further details. An estimate of CE90 and LE90 are included as attributes.
Attribution: Sources: USGS, NGA, NASA, CGIAR, N Robinson, NCEAS, NLS, OS, NMA, Geodatastyrelsen, GSA, and the GIS User Community