Class: Projection

ol/proj/Projection~Projection 


import Projection from 'ol/proj/Projection.js';

In most cases, you should not need to create instances of this class. Instead, where projection information is required, you can use a string projection code or identifier (e.g. EPSG:4326) instead of a projection instance.

The library includes support for transforming coordinates between the following projections:

  • WGS 84 / Geographic - Using codes 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, or urn:x-ogc:def:crs:EPSG:4326
  • WGS 84 / Spherical Mercator - Using codes EPSG:3857, EPSG:102100, EPSG:102113, EPSG:900913, urn:ogc:def:crs:EPSG:6.18:3:3857, or http://www.opengis.net/gml/srs/epsg.xml#3857
  • WGS 84 / UTM zones - Using codes EPSG:32601 through EPSG:32660 for northern zones and EPSG:32701 through EPSG:32760 for southern zones. Note that the built-in UTM transforms are lower accuracy (with errors on the order of 0.1 m) than those that you might get in a library like proj4js.

For additional projection support, or to use higher accuracy transforms than the built-in ones, you can use the proj4js library. With proj4js, after adding any new projection definitions, call the register function.

You can use the get function to retrieve a projection instance for one of the registered projections.

new Projection(options)

proj/Projection.js, line 54
Name Type Description
code string

The SRS identifier code, e.g. EPSG:4326.
units Units | undefined

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

The validity extent for the SRS.
axisOrientation string (defaults to 'enu')

The axis orientation as specified in Proj4.
global boolean (defaults to false)

Whether the projection is valid for the whole globe.
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 METERS_PER_UNIT lookup table.
worldExtent 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 a Coordinate as arguments, and returns the number resolution in projection units at the passed coordinate. If this is undefined, the default getPointResolution function will be used.

Methods

getAxisOrientation(){string}

proj/Projection.js, line 196

Get the axis orientation of this projection. Example values are: enu - the default easting, northing, elevation. neu - northing, easting, up - useful for "lat/long" geographic coordinates, or south orientated transverse mercator. wnu - westing, northing, up - some planetary coordinate systems have "west positive" coordinate systems

Returns:
Axis orientation.

getCode(){string}

proj/Projection.js, line 143

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

Returns:
Code.

getExtent(){Extent}

proj/Projection.js, line 152

Get the validity extent for this projection.

Returns:
Extent.

getMetersPerUnit(){number | undefined}

proj/Projection.js, line 172

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(){Units}

proj/Projection.js, line 161

Get the units of this projection.

Returns:
Units.

getWorldExtent(){Extent}

proj/Projection.js, line 181

Get the world extent for this projection.

Returns:
Extent.

isGlobal(){boolean}

proj/Projection.js, line 205

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

Returns:
Whether the projection is global.

setExtent(extent)

proj/Projection.js, line 238

Set the validity extent for this projection.

Name Type Description
extent Extent

Extent.

setGetPointResolution(func)

proj/Projection.js, line 259

Set the getPointResolution function (see getPointResolution for this projection.

Name Type Description
func function

Function

setGlobal(global)

proj/Projection.js, line 214

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)

proj/Projection.js, line 249

Set the world extent for this projection.

Name Type Description
worldExtent Extent

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