OpenLayers v4.0.1 API - Class: Projection

# Class: Projection

This documentation is for OpenLayers v4.0.1. The latest is v.

## 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 | 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 | The world extent for the SRS.
  `getPointResolution` | function | undefined | 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 135

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

  ##### Returns:

  Code.

#### getExtent(){ol.Extent}

src/ol/proj/projection.js, line 145

  Get the validity extent for this projection.

  ##### Returns:

  Extent.

#### getMetersPerUnit(){number|undefined}

src/ol/proj/projection.js, line 167

  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 155

  Get the units of this projection.

  ##### Returns:

  Units.

#### getWorldExtent(){ol.Extent}

src/ol/proj/projection.js, line 177

  Get the world extent for this projection.

  ##### Returns:

  Extent.

#### isGlobal(){boolean}

src/ol/proj/projection.js, line 202

  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 239

  Set the validity extent for this projection.

  Name | Type | Description
  --- | --- | ---
  `extent` | ol.Extent | Extent.

#### setGetPointResolution(func)

src/ol/proj/projection.js, line 261

  Set the getPointResolution function for this projection.

  Name | Type | Description
  --- | --- | ---
  `func` | function | Function

#### setGlobal(global)

src/ol/proj/projection.js, line 212

  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)

src/ol/proj/projection.js, line 251

  Set the world extent for this projection.

  Name | Type | Description
  --- | --- | ---
  `worldExtent` | ol.Extent | World extent [minlon, minlat, maxlon, maxlat].