Calculate geometries

Learn how to buffer, intersect, and union geometries.

A geometry calculation is an operation you can use to buffer, intersect, or union geometries to create a new geometry. The resulting geometry is commonly used to display a graphic on a map or as input for another analysis.

In this tutorial, you will use the geometry operators to buffer, intersect, and union geometries.

Prerequisites

Steps

Create a map with graphics

To get started, complete the Add a point, line, and polygon tutorial or .

Get an access token

You need an access token with the correct privileges to access the location services used in this tutorial.

Go to the Create an API key tutorial and create an API key with the following privilege(s):
- Privileges
  - Location services > Basemaps

In CodePen, set esriConfig.apiKey to your access token.

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  var esriConfig = {
    apiKey: "YOUR_ACCESS_TOKEN",
  };

To learn about other ways to get an access token, go to Types of authentication.

Add modules

Use $arcgis.import to add the required modules.

The ArcGIS Maps SDK for JavaScript is available via CDN and npm, but this tutorial is based on CDN. The $arcgis.import global function accepts a module path or array of module paths, and returns a promise that resolves with the requested modules. This function can only be used when working with the CDN; otherwise, use the standard import syntax. To learn more about the SDK's different modules, visit the References page.

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      const [
        Graphic,
        Map,
        geodesicBufferOperator,
        intersectionOperator,
        unionOperator,
        GraphicsLayer,
      ] = await $arcgis.import([
        "@arcgis/core/Graphic.js",
        "@arcgis/core/Map.js",
        "@arcgis/core/geometry/operators/geodesicBufferOperator.js",
        "@arcgis/core/geometry/operators/intersectionOperator.js",
        "@arcgis/core/geometry/operators/unionOperator.js",
        "@arcgis/core/layers/GraphicsLayer.js",
      ]);

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Add HTML elements

Add a simple user interface by placing actions in the arcgis-map that will either call a geometry operation or remove graphics from the arcgis-map.

Add a calcite-action-bar with calcite-actions to the top-right slot of the map to calculate the buffer, intersection, union, and to remove all resulting graphics with a reset action.

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    <arcgis-map center="-118.805, 34.020" zoom="13">
      <arcgis-zoom slot="top-left"></arcgis-zoom>

        <calcite-action-bar slot="top-right" expand-disabled expanded>
          <calcite-action id="buffer" text="Buffer" icon="circle-area"></calcite-action>
          <calcite-action id="intersect" disabled text="Intersect" icon="preserve"></calcite-action>
          <calcite-action
            id="union"
            disabled
            text="Union"
            icon="dissolve-features"></calcite-action>
          <calcite-action id="reset" disabled text="Reset" icon="reset"></calcite-action>
        </calcite-action-bar>

    </arcgis-map>
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In the script, create variables to store references to the newly added action elements.

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      const bufferAction = document.querySelector("#buffer");
      const intersectAction = document.querySelector("#intersect");
      const unionAction = document.querySelector("#union");
      const resetAction = document.querySelector("#reset");
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Run the app to verify that the action bar has been added to the arcgis-map.

Add new graphics layers

A graphics layer is a container for graphics. It is used with an arcgis-map component to display graphics on a map. You can add more than one graphics layer to a map. Graphics layers are displayed on top of all other layers.

Create an additional instance of a GraphicsLayer for the results of the geometry calculations and add both layers to the Map.

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      const graphicsLayer = new GraphicsLayer();

      const resultsLayer = new GraphicsLayer();

      viewElement.map = new Map({
        basemap: "arcgis/topographic",
        layers: [graphicsLayer, resultsLayer],
      });
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Create a buffer

A buffer is a polygon surrounding the input geometry at a specified distance. Use a buffer to help better visualize the geometries created from the intersectionOperator and unionOperator operations.

Create the global variable bufferGraphic and the createBuffer function. If there is a bufferGraphic, return.

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      let bufferGraphic;

      async function createBuffer() {
        if (bufferGraphic) {
          return;
        }

      }
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Create a 1 kilometer buffer around the Point graphic using the geodesicBufferOperator.

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      let bufferGraphic;

      async function createBuffer() {
        if (bufferGraphic) {
          return;
        }

        if (!geodesicBufferOperator.isLoaded()) {
          await geodesicBufferOperator.load();
        }
        const buffer = geodesicBufferOperator.execute(pointGraphic.geometry, 1, {
          unit: "kilometers",
        });

      }
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Create a Graphic to display the buffer geometry in your map. Set the geometry of the graphic to the buffer you just calculated, and set the symbol to a SimpleFillSymbol. Add the buffer graphic to the graphicsLayer. Enable the other actions and disable the Buffer action.

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      let bufferGraphic;

      async function createBuffer() {
        if (bufferGraphic) {
          return;
        }

        if (!geodesicBufferOperator.isLoaded()) {
          await geodesicBufferOperator.load();
        }
        const buffer = geodesicBufferOperator.execute(pointGraphic.geometry, 1, {
          unit: "kilometers",
        });

        bufferGraphic = new Graphic({
          geometry: buffer,
          symbol: {
            type: "simple-fill",
            color: [227, 139, 79, 0.5],
            outline: {
              color: [255, 255, 255, 255],
            },
          },
        });

        graphicsLayer.add(bufferGraphic);

        bufferAction.disabled = true;
        resetAction.disabled = false;
        intersectAction.disabled = false;
        unionAction.disabled = false;

      }
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Add an event listener to the buffer action that will call the createBuffer function when it is clicked.

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      const polygonGraphic = new Graphic({
        geometry: polygon,
        symbol: simpleFillSymbol,

        attributes: attributes,
        popupTemplate: popupTemplate,

      });
      graphicsLayer.add(polygonGraphic);

      bufferAction?.addEventListener("click", createBuffer);
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Run the app and click on the Buffer action to view the buffer graphic.

Remove graphics from the result layer

Create a function that will reset and remove all graphics from the graphics layer.

Create the resetGraphics function. Remove the bufferGraphic from the graphicsLayer and removeAll graphics from the resultsLayer. Set the bufferGraphic to null. Disable all actions except the Buffer action.

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        bufferGraphic = new Graphic({
          geometry: buffer,
          symbol: {
            type: "simple-fill",
            color: [227, 139, 79, 0.5],
            outline: {
              color: [255, 255, 255, 255],
            },
          },
        });

        graphicsLayer.add(bufferGraphic);

        bufferAction.disabled = true;
        resetAction.disabled = false;
        intersectAction.disabled = false;
        unionAction.disabled = false;

      }

      function resetGraphics() {
        graphicsLayer.remove(bufferGraphic);
        resultsLayer.removeAll();
        bufferGraphic = null;
        bufferAction.disabled = false;
        resetAction.disabled = true;
        intersectAction.disabled = true;
        unionAction.disabled = true;
      }
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Add an event listener to the Reset action to call the resetGraphics function when the action is clicked.

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      bufferAction?.addEventListener("click", createBuffer);

      resetAction?.addEventListener("click", resetGraphics);
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Run the app. Switch between the Buffer and Reset actions to create a buffer and then remove it from the arcgis-map.

Intersect geometries

Two geometries intersect when they have a geometric area in common. When the Intersect action is clicked, call the findIntersect function and add the resulting graphic to the resultsLayer.

Define the findIntersect function.

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      function resetGraphics() {
        graphicsLayer.remove(bufferGraphic);
        resultsLayer.removeAll();
        bufferGraphic = null;
        bufferAction.disabled = false;
        resetAction.disabled = true;
        intersectAction.disabled = true;
        unionAction.disabled = true;
      }

      async function findIntersection() {

      }
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removeAll graphics from the resultsLayer. If there is not a bufferGraphic with which to execute the intersectionOperator, then return.

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      async function findIntersection() {

        resultsLayer.removeAll();
        if (!bufferGraphic) {
          return;
        }

      }
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Use the intersectionOperator to find the intersection between the two geometries.

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      async function findIntersection() {

        resultsLayer.removeAll();
        if (!bufferGraphic) {
          return;
        }

        const intersectGeom = intersectionOperator.execute(
          polygonGraphic.geometry,
          bufferGraphic.geometry,
        );

      }
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Create a graphic to display the intersecting geometry and add it to the resultsLayer.

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      async function findIntersection() {

        resultsLayer.removeAll();
        if (!bufferGraphic) {
          return;
        }

        const intersectGeom = intersectionOperator.execute(
          polygonGraphic.geometry,
          bufferGraphic.geometry,
        );

        const intersectionGraphic = new Graphic({
          geometry: intersectGeom,
          symbol: {
            type: "simple-fill",
            style: "cross",
            color: "green",
            outline: {
              color: "green",
            },
          },
        });
        resultsLayer.add(intersectionGraphic);

      }
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Add an event listener to the Intersect action to call the findIntersect function when the action is clicked.

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      resetAction?.addEventListener("click", resetGraphics);

      intersectAction?.addEventListener("click", findIntersection);
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Run the app. Click the Buffer action followed by the Intersect action to calculate and display the resulting geometry.

Union geometries

A union is the result of combining two or more input geometries. When the Union action is clicked, calculate the union between the buffer and polygonGraphic geometries and add the result to the resultsLayer.

Define the createUnion function.

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        const intersectGeom = intersectionOperator.execute(
          polygonGraphic.geometry,
          bufferGraphic.geometry,
        );

        const intersectionGraphic = new Graphic({
          geometry: intersectGeom,
          symbol: {
            type: "simple-fill",
            style: "cross",
            color: "green",
            outline: {
              color: "green",
            },
          },
        });
        resultsLayer.add(intersectionGraphic);

      }

      function createUnion() {

      }
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removeAll graphics from the resultsLayer. If there is not a bufferGraphic with which to execute the unionOperator operation, then return.

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      function createUnion() {

        resultsLayer.removeAll();
        if (!bufferGraphic) {
          return;
        }

      }
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Use the unionOperator to find the union between the two geometries.

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      function createUnion() {

        resultsLayer.removeAll();
        if (!bufferGraphic) {
          return;
        }

        const unionGeom = unionOperator.execute(polygonGraphic.geometry, bufferGraphic.geometry);

      }
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Create a graphic to display the resulting geometry and add it to the resultsLayer.

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      function createUnion() {

        resultsLayer.removeAll();
        if (!bufferGraphic) {
          return;
        }

        const unionGeom = unionOperator.execute(polygonGraphic.geometry, bufferGraphic.geometry);

        const unionGraphic = new Graphic({
          geometry: unionGeom,
          symbol: {
            type: "simple-fill",
            style: "cross",
            color: "green",
            outline: {
              color: "green",
            },
          },
        });
        resultsLayer.add(unionGraphic);

      }
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Add an event listener to the Union action to call the createUnion function when the action is clicked.

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      bufferAction?.addEventListener("click", createBuffer);

      resetAction?.addEventListener("click", resetGraphics);

      intersectAction?.addEventListener("click", findIntersection);

      unionAction?.addEventListener("click", createUnion);
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Run the application. Click the Buffer action followed by the Union or Intersect actions.

Run the app

In CodePen, run your code to display the map.

The map should load with a point, line and polygon displayed on the map. Click the Buffer action to add a buffer graphic around the point graphic. Then, when you click on the intersect or union actions, it should create a graphic for the results of those calculations.

What's next?

Learn how to use additional SDK features and ArcGIS services in these tutorials: