ol
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OpenLayers mapping library
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JavaScript
/**
* @module ol/proj/Projection
*/
import {METERS_PER_UNIT} from './Units.js';
/**
* The function is called with a `number` view resolution and a
* {@link module:ol/coordinate~Coordinate} as arguments, and returns the `number` resolution
* in projection units at the passed coordinate.
* @typedef {function(number, import("../coordinate.js").Coordinate):number} GetPointResolution
* @api
*/
/**
* @typedef {Object} Options
* @property {string} code The SRS identifier code, e.g. `EPSG:4326`.
* @property {import("./Units.js").Units} [units] Units. Required unless a
* proj4 projection is defined for `code`.
* @property {import("../extent.js").Extent} [extent] The validity extent for the SRS.
* @property {string} [axisOrientation='enu'] The axis orientation as specified in Proj4.
* @property {boolean} [global=false] Whether the projection is valid for the whole globe.
* @property {number} [metersPerUnit] The meters per unit for the SRS.
* If not provided, the `units` are used to get the meters per unit from the {@link METERS_PER_UNIT}
* lookup table.
* @property {import("../extent.js").Extent} [worldExtent] The world extent for the SRS.
* @property {GetPointResolution} [getPointResolution]
* Function to determine resolution at a point. The function is called with a
* `number` view resolution and a {@link module:ol/coordinate~Coordinate} as arguments, and returns
* the `number` resolution in projection units at the passed coordinate. If this is `undefined`,
* the default {@link module:ol/proj.getPointResolution} function will be used.
*/
/**
* @classdesc
* 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](https://github.com/proj4js/proj4js).
*
* For additional projection support, or to use higher accuracy transforms than the built-in ones, you can use
* the [proj4js](https://github.com/proj4js/proj4js) library. With `proj4js`, after adding any new projection
* definitions, call the {@link module:ol/proj/proj4.register} function.
*
* You can use the {@link module:ol/proj.get} function to retrieve a projection instance
* for one of the registered projections.
*
* @api
*/
class Projection {
/**
* @param {Options} options Projection options.
*/
constructor(options) {
/**
* @private
* @type {string}
*/
this.code_ = options.code;
/**
* Units of projected coordinates. When set to `TILE_PIXELS`, a
* `this.extent_` and `this.worldExtent_` must be configured properly for each
* tile.
* @private
* @type {import("./Units.js").Units}
*/
this.units_ = /** @type {import("./Units.js").Units} */ (options.units);
/**
* Validity extent of the projection in projected coordinates. For projections
* with `TILE_PIXELS` units, this is the extent of the tile in
* tile pixel space.
* @private
* @type {import("../extent.js").Extent}
*/
this.extent_ = options.extent !== undefined ? options.extent : null;
/**
* Extent of the world in EPSG:4326. For projections with
* `TILE_PIXELS` units, this is the extent of the tile in
* projected coordinate space.
* @private
* @type {import("../extent.js").Extent}
*/
this.worldExtent_ =
options.worldExtent !== undefined ? options.worldExtent : null;
/**
* @private
* @type {string}
*/
this.axisOrientation_ =
options.axisOrientation !== undefined ? options.axisOrientation : 'enu';
/**
* @private
* @type {boolean}
*/
this.global_ = options.global !== undefined ? options.global : false;
/**
* @private
* @type {boolean}
*/
this.canWrapX_ = !!(this.global_ && this.extent_);
/**
* @private
* @type {GetPointResolution|undefined}
*/
this.getPointResolutionFunc_ = options.getPointResolution;
/**
* @private
* @type {import("../tilegrid/TileGrid.js").default}
*/
this.defaultTileGrid_ = null;
/**
* @private
* @type {number|undefined}
*/
this.metersPerUnit_ = options.metersPerUnit;
}
/**
* @return {boolean} The projection is suitable for wrapping the x-axis
*/
canWrapX() {
return this.canWrapX_;
}
/**
* Get the code for this projection, e.g. 'EPSG:4326'.
* @return {string} Code.
* @api
*/
getCode() {
return this.code_;
}
/**
* Get the validity extent for this projection.
* @return {import("../extent.js").Extent} Extent.
* @api
*/
getExtent() {
return this.extent_;
}
/**
* Get the units of this projection.
* @return {import("./Units.js").Units} Units.
* @api
*/
getUnits() {
return this.units_;
}
/**
* 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`.
* @return {number|undefined} Meters.
* @api
*/
getMetersPerUnit() {
return this.metersPerUnit_ || METERS_PER_UNIT[this.units_];
}
/**
* Get the world extent for this projection.
* @return {import("../extent.js").Extent} Extent.
* @api
*/
getWorldExtent() {
return this.worldExtent_;
}
/**
* 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
* @return {string} Axis orientation.
* @api
*/
getAxisOrientation() {
return this.axisOrientation_;
}
/**
* Is this projection a global projection which spans the whole world?
* @return {boolean} Whether the projection is global.
* @api
*/
isGlobal() {
return this.global_;
}
/**
* Set if the projection is a global projection which spans the whole world
* @param {boolean} global Whether the projection is global.
* @api
*/
setGlobal(global) {
this.global_ = global;
this.canWrapX_ = !!(global && this.extent_);
}
/**
* @return {import("../tilegrid/TileGrid.js").default} The default tile grid.
*/
getDefaultTileGrid() {
return this.defaultTileGrid_;
}
/**
* @param {import("../tilegrid/TileGrid.js").default} tileGrid The default tile grid.
*/
setDefaultTileGrid(tileGrid) {
this.defaultTileGrid_ = tileGrid;
}
/**
* Set the validity extent for this projection.
* @param {import("../extent.js").Extent} extent Extent.
* @api
*/
setExtent(extent) {
this.extent_ = extent;
this.canWrapX_ = !!(this.global_ && extent);
}
/**
* Set the world extent for this projection.
* @param {import("../extent.js").Extent} worldExtent World extent
* [minlon, minlat, maxlon, maxlat].
* @api
*/
setWorldExtent(worldExtent) {
this.worldExtent_ = worldExtent;
}
/**
* Set the getPointResolution function (see {@link module:ol/proj.getPointResolution}
* for this projection.
* @param {function(number, import("../coordinate.js").Coordinate):number} func Function
* @api
*/
setGetPointResolution(func) {
this.getPointResolutionFunc_ = func;
}
/**
* Get the custom point resolution function for this projection (if set).
* @return {GetPointResolution|undefined} The custom point
* resolution function (if set).
*/
getPointResolutionFunc() {
return this.getPointResolutionFunc_;
}
}
export default Projection;