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REST v2006 mapping projections

To get a projected map, you can use the output coordinate system (ocs) parameter in the REST URL for the most suitable map projection, for the default projection, or to specify a predefined map projection. You can also use EPSG ID or projection string in the ocs parameter to return a projected map.

For each projected map, you need to make two requests. The first request returns a projected map and turns projection on using the ocs parameter. The second request works in projection mode and requires two additional parameters: dc and cmr. The cmr value is derived from the results of the first projection request and contains all georeferencing information about the map.

Projections in REST URLs are done this way so all projection calculations are made on the server side. No parsing takes place and no calculations are performed on the client side. This ensures a swift response and makes it easy for developers to use.

See projection samples and the REST mapping live sample for URL sample requests you can use to help create your REST maps.

Parameters

The ocs parameter is required for all projection requests. The dc and cmr parameters are required with the ocs parameter for requests in projection mode. See projection samples for details.

Projection
Parameter	Description	Valid Values
ocs	The output coordinate system.	Valid values are 0–11. See OCS types for details. If you set ocs to 0 (Automatic), one of the 11 OCS types will be selected automatically based on current extent of the map. You can also use EPSG ID or projection string. See Projected coordinates listed by ID or Projected coordinates listed by name (string) for valid values. Default value is 4326 (EPSG ID for GCS_WGS_1984), which is an unprojected map.
dc (required if cmr is used)	The difference between the current center and the new center point in dx\|dy in pixels.	Two integers representing number of pixels separated by a pipeline (\|). For example, 50\|30 pans the map 50 pixels to the east and 30 pixels to the north. To pan the map in pixels, you must use this parameter with the cmr parameter.
cmr (required if dc is used)	Current map reference. This parameter contains all georeferencing information about the map in the following format: longitude\|latitude\|px\|py\|scale\|angle\|projection longitude: in decimal degrees; negative is west latitude: in decimal degrees; negative is wouth px: offset from center in pixels; negative is left py: offset from center in pixels; negative is up scale: gis scale, unitless, 1:N where scale is N angle: rotation in decimal degrees; negative is ccw (counter clockwise) projection: EPSG ID, projection number, projection string, or OCS type	For SVG format, the cmr value is contained in the first desc tag following the SVG tag of the projection request. For SWF format, the cmr value can be retrieved by the setCurrentMapReference(String) method call. The cmr value also is returned in the HTTP header for all formats. You must use this parameter with the dc parameter.

OCS types

The following OCS types are valid values for the ocs projection parameter. For details on these projections, see Understanding Map Projections.

Type	Preview	Name	Uses and applications
0	ALL	Automatic	Automatically selects an appropriate projection from the below OCS types 1–11 based on current extent of the map.
1		Albers Equal Area Conic	Used for small regions or countries but not for continents.
2		Cassini–Soldner	Normally used for large-scale maps of areas predominantly north–south in extent.
3		Transverse Mercator	State plane coordinate system, used for predominantly north–south state zones. United States Geological Survey (USGS) 7½-minute quad sheets. Most new USGS maps after 1957 use this projection.
4		Lambert Azimuthal Equal Area	Population density (area); political boundaries (area); Oceanic mapping for energy, minerals, geology, and tectonics (direction). This projection can handle large areas; thus, it is used for displaying entire continents and polar regions— equatorial aspect Africa, Southeast Asia, Australia, the Caribbean, and Central America; oblique aspect North America, Europe, and Asia.
5		Sinusoidal	Used for world maps illustrating area characteristics, especially if interrupted. Used for continental maps of South America, Africa.
6		Bonne	Used during the 19th and early 20th centuries for atlas maps of Asia, Australia, Europe, and North America.
7		Stereographic	The oblique aspect has been used to map circular regions on the moon, Mars, and Mercury.
8		Mercator	Standard sea navigation charts (direction). Other directional uses: air travel, wind direction, ocean currents.
9		Mollweide	Suitable for thematic or distribution mapping of the entire world.
10		Miller Cylindrical	Used for general-purpose world maps.
11		Gall's Stereographic	Used for world maps in British atlases. Used only for world maps.

REST v2006 mapping projections

Parameters

OCS types

See also