projection | API Reference | ArcGIS Maps SDK for JavaScript 4.30

See also

Method Overview

Return Type	Summary	Object
GeographicTransformation	Returns the default geographic transformation used to convert the geometry from the input spatial reference to the output spatial reference.	projection
GeographicTransformation []	Returns a list of all geographic transformations suitable to convert geometries from the input spatial reference to the specified output spatial reference.	projection
Boolean	Indicates if all dependencies of this module have been loaded.	projection
Promise	Loads this module's dependencies.	projection
Geometry\|Geometry []	Projects a geometry or an array of geometries to the specified output spatial reference.	projection

Method Details

getTransformation Method getTransformation(inSpatialReference, outSpatialReference, extent){GeographicTransformation}

Returns the default geographic transformation used to convert the geometry from the input spatial reference to the output spatial reference. The default transformation is used when projecting geometries where the datum transformation is required but not specified in the geographicTransformation parameter.

Known Limitations

This method returns equation-based geographic transformations only.
Geographic transformations are returned with their maximum number of steps. Currently, number of steps is limited to 2.

Parameters

inSpatialReference SpatialReference autocast

Autocasts from Object

The input spatial reference from which to project geometries. This is the spatial reference of the input geometries.

outSpatialReference SpatialReference autocast

Autocasts from Object

The spatial reference to which you are converting the geometries.

extent Extent

optional

An extent used to determine the suitability of the returned transformation. The extent will be re-projected to the inSpatialReference if it has a different spatial reference.

Returns

Type	Description
GeographicTransformation	Returns the default geographic transformation for the given parameters. If no transformation is required or there are no suitable transformations, then `null` is returned.

getTransformations Method getTransformations(inSpatialReference, outSpatialReference, extent){GeographicTransformation[]}

Returns a list of all geographic transformations suitable to convert geometries from the input spatial reference to the specified output spatial reference. The list is ordered in descending order by suitability, with the most suitable being first in the list.

Known Limitations

This method returns all the suitable equation-based geographic transformations.
Geographic transformations are returned with their maximum number of steps. Currently, number of steps is limited to 2.

Parameters

inSpatialReference SpatialReference autocast

Autocasts from Object

The spatial reference that the geometries are currently using.

outSpatialReference SpatialReference autocast

Autocasts from Object

The spatial reference to which you are converting the geometries to.

extent Extent

optional

An extent used to determine the suitability of the returned transformations. The extent will be re-projected to the input spatial reference if necessary.

Returns

Type	Description
GeographicTransformation []	Returns an array containing the maximum number the suitable geographic transformations that can be used to convert geometries between input and output spatial references. The list will be empty if the provided extent lies out of the area of use for the input spatial reference.

Example

const cs1 = new SpatialReference({
  wkid: 4272 //PE_GCS_ED_1950
});

const cs2 = new SpatialReference({
  wkid: 4167
});

const extent = new Extent({
  xmin: -186.0,
  ymin: -42.0,
  xmax: -179.0,
  ymax: -38.0
});

const geogtrans = projection.getTransformations(cs1, cs2, extent);
geogtrans.forEach(function(geogtran, index) {
  geogtran.steps.forEach(function(step, index) {
    console.log("step wkid: ", step.wkid);
  });
});

isLoaded Method isLoaded(){Boolean}

Indicates if all dependencies of this module have been loaded.

Returns

Type	Description
Boolean	Returns `true` if this module's dependencies have been loaded.

load Method load(){Promise}

Loads this module's dependencies. This method must be called before projecting geometries.

Returns

Type	Description
Promise	Resolves when the dependencies have been loaded.

See also

isLoaded

Example

projection.load().then(function() {
  // the projection module is loaded. Geometries can be re-projected.

 // projects each polygon in the array
 // project() will use the spatial reference of the first geometry in the array
 // as an input spatial reference. It will use the default transformation
 // if one is required when converting from input spatial reference
 // to the output spatial reference
 let outSpatialReference = new SpatialReference({
   wkid: 53008 //Sphere_Sinusoidal projection
 });
 polygonGraphics.forEach(function(graphic) {
   graphic.geometry = projection.project(graphic.geometry, outSpatialReference);
 });
});

project Method project(geometry, outSpatialReference, geographicTransformation){Geometry |Geometry[]}

Projects a geometry or an array of geometries to the specified output spatial reference. A default geographic transformation is used if not explicitly provided, but required. Use the getTransformation() method to find out which transformation is used by default for the given input and output spatial references.

Note that you must load this module before attempting to project geometries.

Known Limitations

This method uses the spatial reference of the first geometry as an input spatial reference. Therefore all geometries in the array must have the same spatial reference.

Parameters

geometry Geometry|Geometry []

The geometry or geometries to project.

outSpatialReference SpatialReference autocast

Autocasts from Object

The spatial reference to which you are converting the geometries' coordinates.

geographicTransformation GeographicTransformation

optional

The geographic transformation used to transform the geometries. Specify this parameter to project a geometry when the default transformation is not appropriate for your requirements.

Returns

Type	Description
Geometry \| Geometry []	The result will be an array if an array of geometries is used as input. It will be a single geometry if a single geometry used as input.

Examples

// projects each polygon in the array
// project() will use the spatial reference of the first geometry in the array
// as an input spatial reference. It will use the default transformation
// if one is required when converting from input spatial reference
// to the output spatial reference
let outSpatialReference = new SpatialReference({
  wkid: 53008 //Sphere_Sinusoidal projection
});
polygonGraphics.forEach(function(graphic) {
  graphic.geometry = projection.project(graphic.geometry, outSpatialReference);
});

let outSpatialReference = {
  wkid: 54044
};
// projects an array of points
let projectedPoints = projection.project(wgsPoints, outSpatialReference);
projectedPoints.forEach(function(point) {
  console.log(point.x, point.y);
});