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Atlas of the Cryosphere

Atlas Info  •  Northern Hemisphere  •  Southern Hemisphere

Open Geospatial Consortium (OGC) Services

Interoperable and customizable data access to Atlas of the Cryosphere maps and source data are enabled via the following OGC specifications:

Web Map Service (WMS) 1.1.1 Provides map and legend images of selected data layers and basemaps.
Web Feature Service (WFS) 1.1.0 Provides vector source data (points, lines, and polygons) in Geography Markup Language (GML) format.
Web Coverage Service (WCS) 1.1.1 Provides raster source data (rectangular grids of data values) in GeoTIFF format.

Using these services, maps and source data can be accessed remotely for your spatial region and layers of interest either directly through a URL string (more on this below) or through the various OGC-compatible clients available for accessing these services, such as Gaia 3, MapServer, ArcGIS 9 Service Pack 2, ENVI Zoom 4.3.1, Google Earth 4, NASA World Wind, Quantum GIS (QGIS), GRASS, and uDig, to name just a few.

Table of Contents:

GetCapabilities Request

Remote access through an OGC-compatible client is normally obtained via an OGC GetCapabilities request as in the following examples for the Northern and Southern Hemispheres of the Atlas, where the service parameter can be either WMS, WFS, or WCS. Clicking on one of these requests will produce a document in Extensible Markup Language (XML) that lists and describes each of the available layers for its respective OGC service:

WMS:

WFS:

WCS:

Web Map Service (WMS)

Remote access to map and legend images can be obtained via OGC GetMap and GetLegendGraphic requests. These requests can include various parameters for customizing output, including those listed in the tables below. For complete documentation on creating GetMap requests, please see the WMS specification published through OGC (version 1.1.1). For complete documentation on creating GetLegendGraphic requests, please see the Styled Layer Descriptor (SLD) specification published through OGC.

GetMap:

The Parameters of a GetMap Request (optional parameters in italics)
Parameter Possible Values Description
service WMS Web Map Service
version 1.1.1 Request version, currently 1.1.1.
request GetMap Request name.
srs Northern Hemisphere: Spatial reference system. This must be specified as an EPSG code. These codes were developed and maintained by the European Petroleum Survey Group (EPSG) and are a shorthand way of specifying a map projection and other coordinate parameters. The web interface for the Atlas of the Cryosphere employs either the north or south NSIDC EASE-Grid EPSG Codes (EPSG:3408 and EPSG:3409, respectively).
EPSG:32661 WGS 84 / UPS North
EPSG:3413 WGS 84 / NSIDC Polar Stereographic North
EPSG:3411 Hughes / NSIDC Polar Stereographic North
EPSG:3408 NSIDC EASE-Grid North
EPSG:3571 WGS 84 / North Pole LAEA Bering Sea
EPSG:3572 WGS 84 / North Pole LAEA Alaska
EPSG:3573 WGS 84 / North Pole LAEA Canada
EPSG:3574 WGS 84 / North Pole LAEA Atlantic
EPSG:3575 WGS 84 / North Pole LAEA Europe
EPSG:3576 WGS 84 / North Pole LAEA Russia
EPSG:3973 WGS 84 / NSIDC EASE-Grid North
EPSG:32624 WGS 84 / UTM zone 24N (Greenland)
Southern Hemisphere:
EPSG:32761 WGS 84 / UPS South
EPSG:3031 WGS 84 / Antarctic Polar Stereographic
EPSG:3412 Hughes / NSIDC Polar Stereographic South
EPSG:3409 NSIDC EASE-Grid South
EPSG:3974 WGS 84 / NSIDC EASE-Grid South
EPSG:3976 WGS 84 / NSIDC Sea Ice Polar Stereographic South
Global:
EPSG:4326 WGS 84 / Latlong
EPSG:3410 NSIDC EASE-Grid Global
EPSG:3975 WGS 84 / NSIDC EASE-Grid Global
format image/gif Output format of requested map.
image/jpeg
image/png
width 500 Width and height of requested map, in pixels. Maximum allowable value is 2000 pixels. For a polar projection (EPSG:32661), you will likely want a square image and will set the width and height to the same value (e.g. 500). For a geographic projection (EPSG:4326) however, you will likely set the width to double the value of the height (e.g. 800 and 400) for a global map.
height 500
bbox -10700000,-10700000,14700000,14700000 Bounding box corners—lower left (min x, min y) and upper right (max x, max y)—in selected SRS units: degrees for EPSG:4326 or meters for all other EPSG codes. For full hemispheric coverage, view the projection information provided in the links above to each of the available EPSG codes.
-12500000,-12500000,12500000,12500000
-180,-90,180,90
layers sea_ice_extent_01,land,snow_extent_01,coastlines,north_pole_geographic Comma-separated list of one or more map layers as they are named in the WMS GetCapabilities request document. Note that the order in which the layers are listed matters: the second layer in the list will overlay the first layer in the list and so on.
transparent true Optional: Background transparency of the requested map (default = false). If transparency is not set to true, a background color defined by the web map server will be displayed in the requested map. In the case of the Atlas, this will be a dark blue that signifies open ocean.
false
bgcolor 0x000787 Optional: Hexadecimal red-green-blue color value for the background color (default=0xFFFFFF) of the requested map if the default is not desired.

Here are some examples of how to construct a GetMap request using the above parameters. For other examples, see the list of data sources for the Northern and Southern Hemispheres:

GetLegendGraphic:

The Parameters of a GetLegendGraphic Request (all required)
Parameter Possible Values Description
service WMS Web Map Service
version 1.1.1 Request version, currently 1.1.1.
request GetLegendGraphic Request name.
format image/gif Output format of requested legend.
image/jpeg
image/png
layer permafrost_classification Layer for which to produce a map legend, as named in the WMS GetCapabilities request document.
sea_ice_concentration_01
snow_water_equivalent_01
etc.

Here is an example of how to construct a GetLegendGraphic request using the above parameters. For other examples, see the list of data sources for the Northern and Southern Hemispheres:

Web Feature Service (WFS)

Remote access to vector source data (points, lines, and polygons) can be obtained via an OGC GetFeature request. You can also obtain additional information about these sources via an OGC DescribeFeatureType request including the available field names and their data types. These request strings must include various parameters, as listed in the tables below. While the WMS GetMap request returns a map image, a WFS GetFeature request returns the actual feature data to the client encoded in Geography Markup Language (GML) format. As a result, this process is more labor-intensive than WMS and can take noticeably longer to run depending on the resulting file size. Unlike the GetMap request, you cannot specify an alternative spatial reference system (EPSG code) for the output. Northern Hemisphere data are provided in EPSG:32661, and Southern Hemisphere data are provided in EPSG:3031. For complete documentation on creating GetFeature requests, please see the WFS specification published through OGC (version 1.1.0).

GetFeature:

The Parameters of a GetFeature Request (all required)
Parameter Possible Values Description
service WFS Web Feature Service
version 1.1.0 Request version, currently 1.1.0.
request GetFeature Request name.
typename antarctica_elevation_contours Layer for which to request source data as named in the WFS GetCapabilities request document.
greenland_elevation_contours
treeline
etc.
maxfeatures 2 Optional: Number of features to include in the output. Useful if you want to inspect the output first before requesting an entire file.

Here are two examples of how to construct a GetFeature request using the above parameters. For other examples, see the list of data sources for the Northern and Southern Hemispheres:

DescribeFeatureType:

The Parameters of a DescribeFeatureType Request (optional parameters in italics)
Parameter Possible Values Description
service WFS Web Feature Service
version 1.1.0 Request version, currently 1.1.0.
request DescribeFeatureType Request name.
typename antarctica_elevation_contours Layer for which to request information as named in the WFS GetCapabilities request document. If you do not specify a layer, all available features will be described.
greenland_elevation_contours
treeline
etc.

Here is an example of how to construct a DescribeFeatureType request using the above parameters. As with the OGC GetCapabilities request, clicking on this request will produce a document in Extensible Markup Language (XML) that describes the selected feature. For other examples, see the list of data sources for the Northern and Southern Hemispheres:

Web Coverage Service (WCS)

Remote access to raster source data (rectangular grids of data values) can be obtained via an OGC GetCoverage request. You can also obtain additional information about these sources via an OGC DescribeCoverage request such as the spatial extent, spatial resolution, grid size, data format, available coordinate reference systems, and expected pixel values. These requests can include various parameters for customizing output including those listed in the tables below. While the WMS GetMap request returns a map image, a WCS GetCoverage request returns the actual raster data to the client in GeoTIFF format. As a result, this process is more labor-intensive than WMS and can take noticeably longer to run depending on the resulting file size. For complete documentation on creating GetCoverage and DescribeCoverage requests, please see the WCS specification published through OGC (version 1.1.1).

GetCoverage:

The Parameters of a GetCoverage Request (all required)
Parameter Possible Values Description
service WCS Web Coverage Service
version 1.1.1 Request version, currently 1.1.1.
request GetCoverage Request name.
crs Northern Hemisphere: Coordinate reference system. This must be specified as an EPSG code. These codes were developed and maintained by the European Petroleum Survey Group (EPSG) and are a shorthand way of specifying a map projection and other coordinate parameters. The web interface for the Atlas of the Cryosphere employs either the north or south NSIDC EASE-Grid EPSG Codes (EPSG:3408 and EPSG:3409, respectively).
EPSG:32661 WGS 84 / UPS North
EPSG:3413 WGS 84 / NSIDC Polar Stereographic North
EPSG:3411 Hughes / NSIDC Polar Stereographic North
EPSG:3408 NSIDC EASE-Grid North
EPSG:3571 WGS 84 / North Pole LAEA Bering Sea
EPSG:3572 WGS 84 / North Pole LAEA Alaska
EPSG:3573 WGS 84 / North Pole LAEA Canada
EPSG:3574 WGS 84 / North Pole LAEA Atlantic
EPSG:3575 WGS 84 / North Pole LAEA Europe
EPSG:3576 WGS 84 / North Pole LAEA Russia
EPSG:3973 WGS 84 / NSIDC EASE-Grid North
EPSG:32624 WGS 84 / UTM zone 24N (Greenland)
Southern Hemisphere:
EPSG:32761 WGS 84 / UPS South
EPSG:3031 WGS 84 / Antarctic Polar Stereographic
EPSG:3412 Hughes / NSIDC Polar Stereographic South
EPSG:3409 NSIDC EASE-Grid South
EPSG:3974 WGS 84 / NSIDC EASE-Grid South
EPSG:3976 WGS 84 / NSIDC Sea Ice Polar Stereographic South
Global:
EPSG:4326 WGS 84 / Latlong
EPSG:3410 NSIDC EASE-Grid Global
EPSG:3975 WGS 84 / NSIDC EASE-Grid Global
format GeoTIFF Output format of requested coverage (case-insensitive). There are three varieties of GeoTIFF available: one for 8-bit (byte) data values (GeoTIFF), one for 16-bit (integer) data values (GeoTIFFInt16), and one for 32-bit (floating-point) data values (GeoTIFFFloat32). The proper format to select depends on the particular coverage you are requesting and can be determined from a DescribeCoverage request for that coverage.
GeoTIFFInt16
GeoTIFFFloat32
width 500 Width and height of requested GeoTIFF in pixels. For a polar projection (EPSG:32661), you will likely want a square image and will set the width and height to the same value (e.g. 500). For a geographic projection (EPSG:4326) however, you will likely set the width to double the value of the height (e.g. 800 and 400) for a global map. The data will be resampled to the appropriate resolution to satisfy the requested width and height. To request a different resolution, use resx and resy instead of width and height.
height 500
resx 25000 You must either specify a width and height for the requested GeoTIFF or a resolution in the x and y dimensions as demonstrated here—you cannot specify all four. To find out what the native resolution of the source data is, see the <gml:offsetVector> flag in the DescribeCoverage request for that coverage.
resy 25000
bbox -10700000,-10700000,14700000,14700000 Bounding box corners—lower left (min x, min y) and upper right (max x, max y)—in selected CRS units: degrees for EPSG:4326 or meters for all other EPSG codes. For full hemispheric coverage, view the projection information provided in the links above to each of the available EPSG codes.
-12500000,-12500000,12500000,12500000
-180,-90,180,90
coverage greenland_accumulation Layer for which to request source data as named in the WCS GetCapabilities request document. You cannot select multiple layers in a single request.
sea_ice_concentration_01
snow_water_equivalent_01
etc.

Here are some examples of how to construct a GetCoverage request using the above parameters. For other examples, see the list of data sources for the Northern and Southern Hemispheres:

DescribeCoverage:

The Parameters of a DescribeCoverage Request (optional parameters in italics)
Parameter Possible Values Description
service WCS Web Coverage Service
version 1.1.1 Request version, currently 1.1.1.
request DescribeCoverage Request name.
coverage greenland_accumulation Layer for which to request information, as named in the WCS GetCapabilities request document. If you do not specify a layer, all available features will be described.
sea_ice_concentration_01
snow_water_equivalent_01
etc.

Here is an example of how to construct a DescribeCoverage request using the above parameters. As with the OGC GetCapabilities request, clicking on this request will produce a document in Extensible Markup Language (XML) that describes the selected coverage. For other examples, see the list of data sources for the Northern and Southern Hemispheres:

The Results of a DescribeCoverage Request
XML Tag Possible Values Description
<format> GeoTIFF Expected output format of requested coverage. There are three varieties of GeoTIFF available: one for 8-bit (byte) data values (GeoTIFF); one for 16-bit (integer) data values (GeoTIFFInt16), and one for 32-bit (floating-point) data values (GeoTIFFFloat32).
GeoTIFFInt16
GeoTIFFFloat32
<requestResponseCRSs> EPSG:32661 EPSG:4326 EPSG:3408 EPSG:3410 EPSG:3411 EPSG:3413 EPSG:3571 EPSG:3572 EPSG:3573 EPSG:3574 EPSG:3575 EPSG:3576 EPSG:3973 EPSG:3975 EPSG:32624 Available coordinate reference systems for requesting this coverage.
EPSG:3031 EPSG:4326 EPSG:3409 EPSG:3410 EPSG:3412 EPSG:3974 ESPG:3975 EPSG:3976 EPSG:32761
<gml:Envelope> -179.12303011456 63.0415709487752
179.982766500967 82.4151433839318
The spatial extent of the coverage in both latitude/longitude (decimal degrees) and x/y (meters). These are expressed as bounding box corners—lower left (min x, min y) and upper right (max x, max y).
-825267.555 -1151631.237
2173789.735 2041572.863
<gml:GridEnvelope> 599 columns, 638 rows The grid size of the full coverage in number of pixels.
<gml:offsetVector> 5000 m The pixel size or resolution of the coverage.
<description> > 0 = Greenland surface elevation (m); -0.1 or 0 = no data (outside of Greenland) A description of the coverage. In the case of the Atlas, this usually describes what the different pixel values represent.