GeoJS

transform

geo. transform

new transform(options) → {geo.transform}

Description:

This purpose of this class is to provide a generic interface for computing coordinate transformations. The interface is taken from proj4js, which also provides the geospatial projection implementation. The interface is intentionally simple to allow for custom, non-geospatial use cases. For further details, see http://proj4js.org/

The default transforms lat/long coordinates into web mercator for use with standard tile sets.

This class is intended to be extended in the future to support 2.5 and 3 dimensional transformations. The forward/inverse methods take optional z values that are ignored in current mapping context, but will in the future perform more general 3D transformations.

Source:

transform.js, line 47

Parameters:

Name Type Description

options

object

Constructor options

Properties

Name	Type	Description
`source`	string	A proj4 string for the source projection
`target`	string	A proj4 string for the target projection

Returns:

Type: geo.transform

Members

(static) defs

Description:

Contains a reference to proj4.defs. The functions serves two purposes.
1. It is a key value mapping of all loaded projection definitions
2. It is a function that will add additional definitions.
See: http://proj4js.org/

Source:

transform.js, line 286

Contains a reference to proj4.defs. The functions serves two purposes.

It is a key value mapping of all loaded projection definitions
It is a function that will add additional definitions.

See: http://proj4js.org/

Methods

(protected) forward(point) → {geo.geoPosition|Array.<geo.geoPosition>}

Description:

Perform a forward transformation (source -> target) in place.

Source:

transform.js, line 235

Parameters:

Name	Type	Description
`point`	geo.geoPosition \| Array.<geo.geoPosition>	The point coordinates or array of points in source coordinates.

Returns:

A point object or array in the target coordinates.

Type: geo.geoPosition | Array.<geo.geoPosition>

(protected) inverse(point) → {geo.geoPosition|Array.<geo.geoPosition>}

Description:

Perform an inverse transformation (target -> source) in place.

Source:

transform.js, line 251

Parameters:

Name	Type	Description
`point`	geo.geoPosition \| Array.<geo.geoPosition>	The point coordinates or array of points in target coordinates.

Returns:

A point object or array in the source coordinates.

Type: geo.geoPosition | Array.<geo.geoPosition>

source(argopt) → {string|this}

Description:

Get/Set the source projection.

Source:

transform.js, line 158

Parameters:

Name	Type	Attributes	Description
`arg`	string	<optional>	The new source projection. If `undefined`, return the current source projection.

Returns:

The current source projection if it was queried, otherwise the current transform object.

Type: string | this

target(argopt) → {string|this}

Description:

Get/Set the target projection.

Source:

transform.js, line 175

Parameters:

Name	Type	Attributes	Description
`arg`	string	<optional>	The new target projection. If `undefined`, return the current target projection.

Returns:

The current target projection if it was queried, otherwise the current transform object.

Type: string | this

(static) affineForward(def, coords) → {Array.<geo.geoPosition>}

Description:

Apply an affine transformation consisting of a translation then a scaling to the given coordinate array. Note, the transformation occurs in place so the input coordinate object are mutated.

Source:

transform.js, line 611

Parameters:

Name Type Description

def

object

Properties

Name	Type	Description
`origin`	geo.geoPosition	The transformed origin
`scale`	object	The transformed scale factor. This is an object with `x`, `y`, and `z` parameters.

coords

Array.<geo.geoPosition>

An array of coordinate objects.

Returns:

The transformed coordinates.

Type: Array.<geo.geoPosition>

(static) affineInverse(def, coords) → {Array.<geo.geoPosition>}

Description:

Apply an inverse affine transformation which is the inverse to geo.transform.affineForward. Note, the transformation occurs in place so the input coordinate object are mutated.

Source:

transform.js, line 634

Parameters:

Name Type Description

def

object

Properties

Name	Type	Description
`origin`	geo.geoPosition	The transformed origin
`scale`	object	The transformed scale factor. This is an object with `x`, `y`, and `z` parameters.

coords

Array.<geo.geoPosition>

An array of coordinate objects.

Returns:

The transformed coordinates.

Type: Array.<geo.geoPosition>

(static) lookup(projection) → {promise}

Description:

Look up a projection definition from epsg.io. For the moment, we only handle EPSG codes.

Source:

transform.js, line 295

Parameters:

Name	Type	Description
`projection`	string	A projection alias (e.g. EPSG:4326)

Returns:

Resolves with the proj4 definition

Type: promise

(static) onlyInvertedY(srcPrj, tgtPrj) → {boolean}

Description:

Return a boolean indicating if the projections only differ in their y coordinate.

Source:

transform.js, line 779

Parameters:

Name	Type	Description
`srcPrj`	string	The source projection.
`tgtPrj`	string	The destination projection.

Returns:

truthy if only the y coordinate is different between projections.

Type: boolean

(static) sphericalDistance(pt1, pt2, gcsopt, baseGcsopt, ellipsoidopt) → {number}

Description:

Compute the distance on the surface on a sphere. The sphere is the major radius of a specified ellipsoid. Altitude is ignored.

Source:

transform.js, line 661

Parameters:

Name	Type	Attributes	Default	Description
`pt1`	geo.geoPosition			The first point.
`pt2`	geo.geoPosition			The second point.
`gcs`	string \| geo.transform	<optional>		`undefined` to use the same gcs as the ellipsoid, otherwise the gcs of the points.
`baseGcs`	string \| geo.transform	<optional>	`'EPSG:4326'`	the gcs of the ellipsoid.
`ellipsoid`	object	<optional>	`proj4.WGS84`	An object with at least `a` and one of `b`, `f`, or `rf` (1 / `f`) -- this works with proj4 ellipsoid definitions.

Returns:

The distance in meters (or whatever units the ellipsoid was specified in.

Type: number

(static) transformCoordinates(srcPrj, tgtPrj, coordinates, numberOfComponentsopt) → {geo.geoPosition|Array.<geo.geoPosition>|Array.<number>}

Description:

Transform an array of coordinates from one projection into another. The transformation may occur in place (modifying the input coordinate array), depending on the input format. The coordinates can be an object with x, y, and (optionally z) or an array of 2 or 3 values, or an array of either of those, or a single flat array with 2 or 3 components per coordinate. Arrays are always modified in place. Individual point objects are not altered; new point objects are returned unless no transform is needed.

Source:

transform.js, line 340

Parameters:

Name	Type	Attributes	Description
`srcPrj`	string		The source projection.
`tgtPrj`	string		The destination projection.
`coordinates`	geo.geoPosition \| Array.<geo.geoPosition> \| Array.<number>		An array of coordinate objects. These may be in object or array form, or a flat array.
`numberOfComponents`	number	<optional>	For flat arrays, either 2 or 3.

Returns:

The transformed coordinates.

Type: geo.geoPosition | Array.<geo.geoPosition> | Array.<number>

(static) transformCoordinatesArray(trans, coordinates, numberOfComponents) → {Array.<geo.geoPosition>|Array.<number>}

Description:

Transform an array of coordinates from one projection into another. The transformation may occur in place (modifying the input coordinate array), depending on the input format. The coordinates can be an array of 2 or 3 values, or an array of either of those, or a single flat array with 2 or 3 components per coordinate. The array is modified in place.

Source:

transform.js, line 394

Parameters:

Name	Type	Description
`trans`	transform	The transformation object.
`coordinates`	Array.<geo.geoPosition> \| Array.<number>	An array of coordinate objects or a flat array.
`numberOfComponents`	number	For flat arrays, either 2 or 3.

Returns:

The transformed coordinates

Type: Array.<geo.geoPosition> | Array.<number>

(static) transformCoordinatesFlatArray3(srcPrj, tgtPrj, coordinates) → {Array.<number>}

Description:

Transform an array of coordinates from one projection into another. The transformation occurs in place, modifying the input coordinate array. The coordinates are an array of [x0, y0, z0, x1, y1, z1, ...].

Source:

transform.js, line 570

Parameters:

Name	Type	Description
`srcPrj`	string	The source projection.
`tgtPrj`	string	The destination projection. This must not be the same as the source projection.
`coordinates`	Array.<number>	A flat array of values.

Returns:

The transformed coordinates.

Type: Array.<number>

(static) vincentyDistance(pt1, pt2, gcsopt, baseGcsopt, ellipsoidopt, maxIterationsopt) → {object}

Description:

Compute the Vincenty distance on the surface on an ellipsoid. Altitude is ignored.

Source:

transform.js, line 705

Parameters:

Name	Type	Attributes	Default	Description
`pt1`	geo.geoPosition			The first point.
`pt2`	geo.geoPosition			The second point.
`gcs`	string \| geo.transform	<optional>		`undefined` to use the same gcs as the ellipsoid, otherwise the gcs of the points.
`baseGcs`	string \| geo.transform	<optional>	`'EPSG:4326'`	the gcs of the ellipsoid.
`ellipsoid`	object	<optional>	`proj4.WGS84`	An object with at least `a` and one of `b`, `f`, or `rf` (1 / `f`) -- this works with proj4 ellipsoid definitions.
`maxIterations`	number	<optional>	`100`	Maximum number of iterations to use to test convergence.

Returns:

An object with distance in meters (or whatever units the ellipsoid was specified in), alpha1 and alpha2, the azimuths at the two points in radians. The result may be undefined if the formula fails to converge, which can happen near antipodal points.

Type: object

(inner) parse_projection(value) → {object}

Description:

Parse a projection string. If the projection string includes any of +s[123][123]= or +[xyz]off=, those values are converted into a matrix and removed from the projection string. This allows applying affine transforms as specified in Proj 6.0.0 to be used (excluding toff and tscale). This could can be removed once proj4js supports the affine parameters.

Source:

transform.js, line 104

Parameters:

Name	Type	Description
`value`	string	A proj4 string possibly with affine parameters.

Returns:

An object with a string value 'proj' and optional array values 'matrix' and 'inverse' (either both or neither will be present). The returned matrices are always 16-value arrays if present. The proj value is the proj4 string with the affine parameters removed.

Type: object