ArcGIS Coordinates and Projection

Use this skill for coordinate conversion, projection transformations, spatial reference handling, and displaying coordinates in various formats.

Important: The projection module (deprecated since 4.32) and geodesicUtils (deprecated since 4.33) were removed in v5.0. Use projectOperator and geodetic geometry operators instead.

Import Patterns

Direct ESM Imports

import projectOperator from "@arcgis/core/geometry/operators/projectOperator.js";
import SpatialReference from "@arcgis/core/geometry/SpatialReference.js";
import coordinateFormatter from "@arcgis/core/geometry/coordinateFormatter.js";
import webMercatorUtils from "@arcgis/core/geometry/support/webMercatorUtils.js";

Dynamic Imports (CDN)

const projectOperator = await $arcgis.import(
  "@arcgis/core/geometry/operators/projectOperator.js",
);
const coordinateFormatter = await $arcgis.import(
  "@arcgis/core/geometry/coordinateFormatter.js",
);
const [SpatialReference, webMercatorUtils] = await $arcgis.import([
  "@arcgis/core/geometry/SpatialReference.js",
  "@arcgis/core/geometry/support/webMercatorUtils.js",
]);

Coordinate Conversion Component

Basic Setup

<arcgis-map basemap="topo-vector" center="-117.049, 34.485" zoom="12">
  <arcgis-zoom slot="top-left"></arcgis-zoom>
  <arcgis-coordinate-conversion
    slot="bottom-left"
  ></arcgis-coordinate-conversion>
</arcgis-map>

Coordinate Conversion Widget (Core API)

import CoordinateConversion from "@arcgis/core/widgets/CoordinateConversion.js";

const ccWidget = new CoordinateConversion({ view });
view.ui.add(ccWidget, "bottom-left");

Custom Coordinate Formats

import CoordinateConversion from "@arcgis/core/widgets/CoordinateConversion.js";
import Format from "@arcgis/core/widgets/CoordinateConversion/support/Format.js";

const customFormat = new Format({
  name: "Custom XY",
  conversionInfo: {
    spatialReference: { wkid: 4326 },
    reverseConvert: (string) => {
      const parts = string.split(",");
      return [parseFloat(parts[0]), parseFloat(parts[1])];
    },
  },
  coordinateSegments: [
    { alias: "Lon", description: "Longitude", searchPattern: "X" },
    { alias: "Lat", description: "Latitude", searchPattern: "Y" },
  ],
  defaultPattern: "X°, Y°",
});

const ccWidget = new CoordinateConversion({
  view,
  formats: [customFormat],
});

Spatial Reference

Common Spatial References

Name	WKID	Type
WGS 84	4326	Geographic
Web Mercator	102100 or 3857	Projected
UTM Zone 11N	32611	Projected
State Plane (example)	2230	Projected

Create Spatial Reference

import SpatialReference from "@arcgis/core/geometry/SpatialReference.js";

// By WKID
const wgs84 = new SpatialReference({ wkid: 4326 });
const webMercator = new SpatialReference({ wkid: 102100 });

// By WKT (for custom projections)
const customSR = new SpatialReference({
  wkt: 'PROJCS["NAD_1983_StatePlane_California_VI_FIPS_0406_Feet"...',
});

// Shorthand (autocast)
const sr = { wkid: 4326 };

SpatialReference Properties

const sr = new SpatialReference({ wkid: 4326 });

console.log(sr.isGeographic); // true for lat/lon systems
console.log(sr.isWebMercator); // true for WKID 3857/102100
console.log(sr.isWGS84); // true for WKID 4326
console.log(sr.wkid); // 4326

Client-Side Projection (projectOperator)

The recommended way to project geometries client-side.

Project Geometry

import projectOperator from "@arcgis/core/geometry/operators/projectOperator.js";

await projectOperator.load();

const projected = projectOperator.execute(geometry, { wkid: 4326 });

Project with Geographic Transformation

import projectOperator from "@arcgis/core/geometry/operators/projectOperator.js";

await projectOperator.load();

const projected = projectOperator.execute(
  geometry,
  { wkid: 4326 },
  {
    geographicTransformation: {
      steps: [{ wkid: 108190 }], // NAD_1983_To_WGS_1984_5
    },
  },
);

Shape-Preserving Projection

For projecting geometries while preserving geodesic shape (great circle arcs):

import shapePreservingProjectOperator from "@arcgis/core/geometry/operators/shapePreservingProjectOperator.js";

await shapePreservingProjectOperator.load();

const projected = shapePreservingProjectOperator.execute(geometry, {
  wkid: 3857,
});

Geographic Transformation Utilities

import geographicTransformationUtils from "@arcgis/core/geometry/operators/support/geographicTransformationUtils.js";

// Get available transformations between two spatial references
const transformations = geographicTransformationUtils.getTransformations(
  { wkid: 4269 }, // NAD83
  { wkid: 4326 }, // WGS84
);

transformations.forEach((t) => {
  console.log(t.wkid, t.wkt);
});

Server-Side Projection (Geometry Service)

For complex projections or when the client-side engine is insufficient:

import * as geometryService from "@arcgis/core/rest/geometryService.js";
import ProjectParameters from "@arcgis/core/rest/support/ProjectParameters.js";

const gsUrl =
  "https://utility.arcgisonline.com/ArcGIS/rest/services/Geometry/GeometryServer";

const params = new ProjectParameters({
  geometries: [geometry],
  outSpatialReference: { wkid: 4326 },
});

const results = await geometryService.project(gsUrl, params);
const projected = results[0];

Coordinate Conversion Utilities

Web Mercator to/from Geographic

import webMercatorUtils from "@arcgis/core/geometry/support/webMercatorUtils.js";

const geoPoint = webMercatorUtils.webMercatorToGeographic(webMercatorPoint);
const wmPoint = webMercatorUtils.geographicToWebMercator(geoPoint);
const canProject = webMercatorUtils.canProject(fromSR, toSR);

Coordinate Formatter

Convert coordinates to/from DMS, UTM, MGRS, USNG strings.

import coordinateFormatter from "@arcgis/core/geometry/coordinateFormatter.js";

await coordinateFormatter.load();

// To Degrees Minutes Seconds
const dms = coordinateFormatter.toLatitudeLongitude(point, "dms", 3);
// Output: "34°29'06.000\"N 117°02'56.400\"W"

// To MGRS
const mgrs = coordinateFormatter.toMgrs(point, "automatic", 5, false);
// Output: "11SNU1234567890"

// To UTM
const utm = coordinateFormatter.toUtm(point, "north-south-indicators", true);
// Output: "11S 500000 3800000"

// To USNG
const usng = coordinateFormatter.toUsng(point, 5, false);

// From string to point
const pointFromDMS = coordinateFormatter.fromLatitudeLongitude(
  "34°29'06\"N 117°02'56\"W",
);
const pointFromMGRS = coordinateFormatter.fromMgrs("11SNU1234567890");
const pointFromUTM = coordinateFormatter.fromUtm("11S 500000 3800000");
const pointFromUSNG = coordinateFormatter.fromUsng("11SNU1234567890");

coordinateFormatter Methods

Method	Description
toLatitudeLongitude(point, format, decimals)	Format: "dd", "dm", "dms"
toMgrs(point, mode, precision, spaces)	Military Grid Reference System
toUtm(point, mode, spaces)	Universal Transverse Mercator
toUsng(point, precision, spaces)	US National Grid
fromLatitudeLongitude(string)	Parse DMS/DD string to Point
fromMgrs(string)	Parse MGRS to Point
fromUtm(string)	Parse UTM to Point
fromUsng(string)	Parse USNG to Point

Display Coordinates

Show Mouse Coordinates

view.on("pointer-move", (event) => {
  const mapPoint = view.toMap({ x: event.x, y: event.y });
  if (mapPoint) {
    document.getElementById("coords").textContent =
      `Lat: ${mapPoint.latitude.toFixed(6)}, Lon: ${mapPoint.longitude.toFixed(6)}`;
  }
});

Multi-Format Coordinate Display

import coordinateFormatter from "@arcgis/core/geometry/coordinateFormatter.js";

await coordinateFormatter.load();

view.on("pointer-move", (event) => {
  const point = view.toMap({ x: event.x, y: event.y });
  if (point) {
    document.getElementById("latlon").textContent =
      `${point.latitude.toFixed(6)}, ${point.longitude.toFixed(6)}`;
    document.getElementById("utm").textContent = coordinateFormatter.toUtm(
      point,
      "north-south-indicators",
      true,
    );
    document.getElementById("mgrs").textContent = coordinateFormatter.toMgrs(
      point,
      "automatic",
      5,
      true,
    );
  }
});

Geodetic Geometry Operations

For geodesic calculations (distance, area, length on Earth's surface):

import geodeticDistanceOperator from "@arcgis/core/geometry/operators/geodeticDistanceOperator.js";
import geodeticAreaOperator from "@arcgis/core/geometry/operators/geodeticAreaOperator.js";
import geodeticLengthOperator from "@arcgis/core/geometry/operators/geodeticLengthOperator.js";

// Geodesic distance between two points
const distance = geodeticDistanceOperator.execute(point1, point2, {
  unit: "kilometers",
});

// Geodesic area of a polygon
const area = geodeticAreaOperator.execute(polygon, {
  unit: "square-kilometers",
});

// Geodesic length of a polyline
const length = geodeticLengthOperator.execute(polyline, { unit: "kilometers" });

For full operator documentation, see arcgis-geometry-operations.

Migration from Removed Modules

Removed Module (pre-5.0)	Replacement (5.0)
projection.project(geom, sr)	projectOperator.execute(geom, sr)
projection.load()	projectOperator.load()
geodesicUtils.geodesicDistance(p1, p2, unit)	geodeticDistanceOperator.execute(p1, p2, { unit })
geodesicUtils.geodesicArea(geom, unit)	geodeticAreaOperator.execute(geom, { unit })
geodesicUtils.geodesicLength(geom, unit)	geodeticLengthOperator.execute(geom, { unit })

Common Pitfalls

1. Forgetting to load the projection engine: projectOperator.load() and coordinateFormatter.load() must be called before use:

   // Anti-pattern: using before load
   const projected = projectOperator.execute(geom, { wkid: 4326 }); // Error
   
   // Correct: load first
   await projectOperator.load();
   const projected = projectOperator.execute(geom, { wkid: 4326 });
   

2. Coordinate order: Geographic coordinates are (longitude, latitude) in the SDK, not (latitude, longitude). Point properties use x = longitude, y = latitude.

3. WKID vs WKT: Use WKID when a well-known ID exists. Use WKT only for custom coordinate systems not in the WKID registry.

4. Datum transformations: When projecting between different datums (e.g., NAD83 to WGS84), provide a geographic transformation for accuracy. Without it, results may be off by meters.

5. Client vs server: Use client-side projection (projectOperator) for speed. Use server-side (geometryService.project()) only for complex transformations the client engine cannot handle.

6. Using removed modules: The projection and geodesicUtils modules were removed in 5.0. Use projectOperator and geodetic operators instead.

Reference Samples

• coordinate-conversion - Converting between coordinate formats
• coordinate-conversion-custom - Custom coordinate formats
• widgets-coordinateconversion - CoordinateConversion widget usage
• widgets-coordinateconversion-custom - Custom coordinate widget formats
• client-projection - Client-side projection of geometries
• layers-csv-projection - CSV layer with projection

Related Skills

• See arcgis-geometry-operations for geometry creation and spatial operators.
• See arcgis-rest-services for server-side geometry service (project, buffer, etc.).
• See arcgis-core-maps for map and view spatial reference configuration.