OpenLayers 3

Class: Projection

ol.proj.Projection

Projection definition class. One of these is created for each projection supported in the application and stored in the ol.proj namespace. You can use these in applications, but this is not required, as API params and options use ol.ProjectionLike which means the simple string code will suffice.

You can use ol.proj.get to retrieve the object for a particular projection.

The library includes definitions for EPSG:4326 and EPSG:3857, together with the following aliases:

  • EPSG:4326: CRS:84, urn:ogc:def:crs:EPSG:6.6:4326, urn:ogc:def:crs:OGC:1.3:CRS84, urn:ogc:def:crs:OGC:2:84, http://www.opengis.net/gml/srs/epsg.xml#4326, urn:x-ogc:def:crs:EPSG:4326
  • EPSG:3857: EPSG:102100, EPSG:102113, EPSG:900913, urn:ogc:def:crs:EPSG:6.18:3:3857, http://www.opengis.net/gml/srs/epsg.xml#3857

If you use proj4js, aliases can be added using proj4.defs(); see documentation. To set an alternative namespace for proj4, use ol.proj.setProj4.

new ol.proj.Projection(options)

src/ol/proj/projection.js, line 38
Name Type Description
options

Projection options.

Name Type Description
code string

The SRS identifier code, e.g. EPSG:4326. Required.
units ol.proj.Units | string | undefined

Units. Required unless a proj4 projection is defined for code.
extent ol.Extent | undefined

The validity extent for the SRS.
axisOrientation string | undefined

The axis orientation as specified in Proj4. The default is enu.
global boolean | undefined

Whether the projection is valid for the whole globe. Default is false.
metersPerUnit number | undefined experimental

The meters per unit for the SRS. If not provided, the units are used to get the meters per unit from the ol.proj.METERS_PER_UNIT lookup table.
worldExtent ol.Extent | undefined experimental

The world extent for the SRS.
getPointResolution function | undefined experimental

Function to determine resolution at a point. The function is called with a {number} view resolution and an {ol.Coordinate} as arguments, and returns the {number} resolution at the passed coordinate.

Methods

getCode(){string}

src/ol/proj/projection.js, line 139

Get the code for this projection, e.g. 'EPSG:4326'.

Returns:
Code.

getExtent(){ol.Extent}

src/ol/proj/projection.js, line 149

Get the validity extent for this projection.

Returns:
Extent.

getMetersPerUnit(){number|undefined}

src/ol/proj/projection.js, line 171

Get the amount of meters per unit of this projection. If the projection is not configured with metersPerUnit or a units identifier, the return is undefined.

Returns:
Meters.

getUnits(){ol.proj.Units}

src/ol/proj/projection.js, line 159

Get the units of this projection.

Returns:
Units.

getWorldExtent(){ol.Extent} experimental

src/ol/proj/projection.js, line 181

Get the world extent for this projection.

Returns:
Extent.

isGlobal(){boolean}

src/ol/proj/projection.js, line 206

Is this projection a global projection which spans the whole world?

Returns:
Whether the projection is global.

setExtent(extent)

src/ol/proj/projection.js, line 243

Set the validity extent for this projection.

Name Type Description
extent ol.Extent

Extent.

setGetPointResolution(func) experimental

src/ol/proj/projection.js, line 265

Set the getPointResolution function for this projection.

Name Type Description
func function

Function

setGlobal(global)

src/ol/proj/projection.js, line 216

Set if the projection is a global projection which spans the whole world

Name Type Description
global boolean

Whether the projection is global.

setWorldExtent(worldExtent) experimental

src/ol/proj/projection.js, line 255

Set the world extent for this projection.

Name Type Description
worldExtent ol.Extent

World extent [minlon, minlat, maxlon, maxlat].