Measure

This example uses OpenLayers v4.0.1. The latest is v.

#### Measure

Measurement type
use geodesic measures

Example of using the ol.interaction.Draw interaction to create a simple measuring application.

NOTE: By default, length and area are calculated using the projected coordinates. This is not accurate for projections like Mercator where the projected meters do not correspond to meters on the ground. To get a standarized measurement across all projections, use the geodesic measures.

Related API documentation:

- ol.Map
,
- ol.Observable
,
- ol.Overlay
,
- ol.Sphere
,
- ol.View
,
- ol.geom.LineString
,
- ol.geom.Polygon
,
- ol.interaction.Draw
,
- ol.layer.Tile
,
- ol.layer.Vector
,
- ol.proj
,
- ol.source.OSM
,
- ol.source.Vector
,
- ol.style.Circle
,
- ol.style.Fill
,
- ol.style.Stroke
,
- ol.style.Style

Copy Edit
Measure Example of using the ol.interaction.Draw interaction to create a simple measuring application. var wgs84Sphere = new ol.Sphere(6378137); var raster = new ol.layer.Tile({ source: new ol.source.OSM() }); var source = new ol.source.Vector(); var vector = new ol.layer.Vector({ source: source, style: new ol.style.Style({ fill: new ol.style.Fill({ color: 'rgba(255, 255, 255, 0.2)' }), stroke: new ol.style.Stroke({ color: '#ffcc33', width: 2 }), image: new ol.style.Circle({ radius: 7, fill: new ol.style.Fill({ color: '#ffcc33' }) }) }) }); /** * Currently drawn feature. * @type {ol.Feature} */ var sketch; /** * The help tooltip element. * @type {Element} */ var helpTooltipElement; /** * Overlay to show the help messages. * @type {ol.Overlay} */ var helpTooltip; /** * The measure tooltip element. * @type {Element} */ var measureTooltipElement; /** * Overlay to show the measurement. * @type {ol.Overlay} */ var measureTooltip; /** * Message to show when the user is drawing a polygon. * @type {string} */ var continuePolygonMsg = 'Click to continue drawing the polygon'; /** * Message to show when the user is drawing a line. * @type {string} */ var continueLineMsg = 'Click to continue drawing the line'; /** * Handle pointer move. * @param {ol.MapBrowserEvent} evt The event. */ var pointerMoveHandler = function(evt) { if (evt.dragging) { return; } /** @type {string} */ var helpMsg = 'Click to start drawing'; if (sketch) { var geom = (sketch.getGeometry()); if (geom instanceof ol.geom.Polygon) { helpMsg = continuePolygonMsg; } else if (geom instanceof ol.geom.LineString) { helpMsg = continueLineMsg; } } helpTooltipElement.innerHTML = helpMsg; helpTooltip.setPosition(evt.coordinate); helpTooltipElement.classList.remove('hidden'); }; var map = new ol.Map({ layers: [raster, vector], target: 'map', view: new ol.View({ center: [-11000000, 4600000], zoom: 15 }) }); map.on('pointermove', pointerMoveHandler); map.getViewport().addEventListener('mouseout', function() { helpTooltipElement.classList.add('hidden'); }); var typeSelect = document.getElementById('type'); var geodesicCheckbox = document.getElementById('geodesic'); var draw; // global so we can remove it later /** * Format length output. * @param {ol.geom.LineString} line The line. * @return {string} The formatted length. */ var formatLength = function(line) { var length; if (geodesicCheckbox.checked) { var coordinates = line.getCoordinates(); length = 0; var sourceProj = map.getView().getProjection(); for (var i = 0, ii = coordinates.length - 1; i < ii; ++i) { var c1 = ol.proj.transform(coordinates[i], sourceProj, 'EPSG:4326'); var c2 = ol.proj.transform(coordinates[i + 1], sourceProj, 'EPSG:4326'); length += wgs84Sphere.haversineDistance(c1, c2); } } else { length = Math.round(line.getLength() * 100) / 100; } var output; if (length > 100) { output = (Math.round(length / 1000 * 100) / 100) + ' ' + 'km'; } else { output = (Math.round(length * 100) / 100) + ' ' + 'm'; } return output; }; /** * Format area output. * @param {ol.geom.Polygon} polygon The polygon. * @return {string} Formatted area. */ var formatArea = function(polygon) { var area; if (geodesicCheckbox.checked) { var sourceProj = map.getView().getProjection(); var geom = /** @type {ol.geom.Polygon} */(polygon.clone().transform( sourceProj, 'EPSG:4326')); var coordinates = geom.getLinearRing(0).getCoordinates(); area = Math.abs(wgs84Sphere.geodesicArea(coordinates)); } else { area = polygon.getArea(); } var output; if (area > 10000) { output = (Math.round(area / 1000000 * 100) / 100) + ' ' + 'km<sup>2</sup>'; } else { output = (Math.round(area * 100) / 100) + ' ' + 'm<sup>2</sup>'; } return output; }; function addInteraction() { var type = (typeSelect.value == 'area' ? 'Polygon' : 'LineString'); draw = new ol.interaction.Draw({ source: source, type: /** @type {ol.geom.GeometryType} */ (type), style: new ol.style.Style({ fill: new ol.style.Fill({ color: 'rgba(255, 255, 255, 0.2)' }), stroke: new ol.style.Stroke({ color: 'rgba(0, 0, 0, 0.5)', lineDash: [10, 10], width: 2 }), image: new ol.style.Circle({ radius: 5, stroke: new ol.style.Stroke({ color: 'rgba(0, 0, 0, 0.7)' }), fill: new ol.style.Fill({ color: 'rgba(255, 255, 255, 0.2)' }) }) }) }); map.addInteraction(draw); createMeasureTooltip(); createHelpTooltip(); var listener; draw.on('drawstart', function(evt) { // set sketch sketch = evt.feature; /** @type {ol.Coordinate|undefined} */ var tooltipCoord = evt.coordinate; listener = sketch.getGeometry().on('change', function(evt) { var geom = evt.target; var output; if (geom instanceof ol.geom.Polygon) { output = formatArea(geom); tooltipCoord = geom.getInteriorPoint().getCoordinates(); } else if (geom instanceof ol.geom.LineString) { output = formatLength(geom); tooltipCoord = geom.getLastCoordinate(); } measureTooltipElement.innerHTML = output; measureTooltip.setPosition(tooltipCoord); }); }, this); draw.on('drawend', function() { measureTooltipElement.className = 'tooltip tooltip-static'; measureTooltip.setOffset([0, -7]); // unset sketch sketch = null; // unset tooltip so that a new one can be created measureTooltipElement = null; createMeasureTooltip(); ol.Observable.unByKey(listener); }, this); } /** * Creates a new help tooltip */ function createHelpTooltip() { if (helpTooltipElement) { helpTooltipElement.parentNode.removeChild(helpTooltipElement); } helpTooltipElement = document.createElement('div'); helpTooltipElement.className = 'tooltip hidden'; helpTooltip = new ol.Overlay({ element: helpTooltipElement, offset: [15, 0], positioning: 'center-left' }); map.addOverlay(helpTooltip); } /** * Creates a new measure tooltip */ function createMeasureTooltip() { if (measureTooltipElement) { measureTooltipElement.parentNode.removeChild(measureTooltipElement); } measureTooltipElement = document.createElement('div'); measureTooltipElement.className = 'tooltip tooltip-measure'; measureTooltip = new ol.Overlay({ element: measureTooltipElement, offset: [0, -15], positioning: 'bottom-center' }); map.addOverlay(measureTooltip); } /** * Let user change the geometry type. */ typeSelect.onchange = function() { map.removeInteraction(draw); addInteraction(); }; addInteraction(); .tooltip { position: relative; background: rgba(0, 0, 0, 0.5); border-radius: 4px; color: white; padding: 4px 8px; opacity: 0.7; white-space: nowrap; } .tooltip-measure { opacity: 1; font-weight: bold; } .tooltip-static { background-color: #ffcc33; color: black; border: 1px solid white; } .tooltip-measure:before, .tooltip-static:before { border-top: 6px solid rgba(0, 0, 0, 0.5); border-right: 6px solid transparent; border-left: 6px solid transparent; content: ""; position: absolute; bottom: -6px; margin-left: -7px; left: 50%; } .tooltip-static:before { border-top-color: #ffcc33; } <div id="map" class="map"></div> <form class="form-inline"> <label>Measurement type &nbsp;</label> <select id="type"> <option value="length">Length (LineString)</option> <option value="area">Area (Polygon)</option> </select> <label class="checkbox"> <input type="checkbox" id="geodesic"> use geodesic measures </label> </form>

    <!DOCTYPE html>
    <html>
      <head>
        <title>Measure</title>
        <link rel="stylesheet" href="https://openlayers.org/en/v4.0.1/css/ol.css" type="text/css">
        <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
        <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>
        <script src="https://openlayers.org/en/v4.0.1/build/ol.js"></script>
        <style>
          .tooltip {
            position: relative;
            background: rgba(0, 0, 0, 0.5);
            border-radius: 4px;
            color: white;
            padding: 4px 8px;
            opacity: 0.7;
            white-space: nowrap;
          }
          .tooltip-measure {
            opacity: 1;
            font-weight: bold;
          }
          .tooltip-static {
            background-color: #ffcc33;
            color: black;
            border: 1px solid white;
          }
          .tooltip-measure:before,
          .tooltip-static:before {
            border-top: 6px solid rgba(0, 0, 0, 0.5);
            border-right: 6px solid transparent;
            border-left: 6px solid transparent;
            content: "";
            position: absolute;
            bottom: -6px;
            margin-left: -7px;
            left: 50%;
          }
          .tooltip-static:before {
            border-top-color: #ffcc33;
          }    </style>
      </head>
      <body>
        <div id="map" class="map"></div>
        <form class="form-inline">
          <label>Measurement type &nbsp;</label>
            <select id="type">
              <option value="length">Length (LineString)</option>
              <option value="area">Area (Polygon)</option>
            </select>
            <label class="checkbox">
              <input type="checkbox" id="geodesic">
              use geodesic measures
            </label>
        </form>
        <script>
          var wgs84Sphere = new ol.Sphere(6378137);

          var raster = new ol.layer.Tile({
            source: new ol.source.OSM()
          });

          var source = new ol.source.Vector();

          var vector = new ol.layer.Vector({
            source: source,
            style: new ol.style.Style({
              fill: new ol.style.Fill({
                color: 'rgba(255, 255, 255, 0.2)'
              }),
              stroke: new ol.style.Stroke({
                color: '#ffcc33',
                width: 2
              }),
              image: new ol.style.Circle({
                radius: 7,
                fill: new ol.style.Fill({
                  color: '#ffcc33'
                })
              })
            })
          });

          /**
           * Currently drawn feature.
           * @type {ol.Feature}
           */
          var sketch;

          /**
           * The help tooltip element.
           * @type {Element}
           */
          var helpTooltipElement;

          /**
           * Overlay to show the help messages.
           * @type {ol.Overlay}
           */
          var helpTooltip;

          /**
           * The measure tooltip element.
           * @type {Element}
           */
          var measureTooltipElement;

          /**
           * Overlay to show the measurement.
           * @type {ol.Overlay}
           */
          var measureTooltip;

          /**
           * Message to show when the user is drawing a polygon.
           * @type {string}
           */
          var continuePolygonMsg = 'Click to continue drawing the polygon';

          /**
           * Message to show when the user is drawing a line.
           * @type {string}
           */
          var continueLineMsg = 'Click to continue drawing the line';

          /**
           * Handle pointer move.
           * @param {ol.MapBrowserEvent} evt The event.
           */
          var pointerMoveHandler = function(evt) {
            if (evt.dragging) {
              return;
            }
            /** @type {string} */
            var helpMsg = 'Click to start drawing';

            if (sketch) {
              var geom = (sketch.getGeometry());
              if (geom instanceof ol.geom.Polygon) {
                helpMsg = continuePolygonMsg;
              } else if (geom instanceof ol.geom.LineString) {
                helpMsg = continueLineMsg;
              }
            }

            helpTooltipElement.innerHTML = helpMsg;
            helpTooltip.setPosition(evt.coordinate);

            helpTooltipElement.classList.remove('hidden');
          };

          var map = new ol.Map({
            layers: [raster, vector],
            target: 'map',
            view: new ol.View({
              center: [-11000000, 4600000],
              zoom: 15
            })
          });

          map.on('pointermove', pointerMoveHandler);

          map.getViewport().addEventListener('mouseout', function() {
            helpTooltipElement.classList.add('hidden');
          });

          var typeSelect = document.getElementById('type');
          var geodesicCheckbox = document.getElementById('geodesic');

          var draw; // global so we can remove it later

          /**
           * Format length output.
           * @param {ol.geom.LineString} line The line.
           * @return {string} The formatted length.
           */
          var formatLength = function(line) {
            var length;
            if (geodesicCheckbox.checked) {
              var coordinates = line.getCoordinates();
              length = 0;
              var sourceProj = map.getView().getProjection();
              for (var i = 0, ii = coordinates.length - 1; i < ii; ++i) {
                var c1 = ol.proj.transform(coordinates[i], sourceProj, 'EPSG:4326');
                var c2 = ol.proj.transform(coordinates[i + 1], sourceProj, 'EPSG:4326');
                length += wgs84Sphere.haversineDistance(c1, c2);
              }
            } else {
              length = Math.round(line.getLength() * 100) / 100;
            }
            var output;
            if (length > 100) {
              output = (Math.round(length / 1000 * 100) / 100) +
                  ' ' + 'km';
            } else {
              output = (Math.round(length * 100) / 100) +
                  ' ' + 'm';
            }
            return output;
          };

          /**
           * Format area output.
           * @param {ol.geom.Polygon} polygon The polygon.
           * @return {string} Formatted area.
           */
          var formatArea = function(polygon) {
            var area;
            if (geodesicCheckbox.checked) {
              var sourceProj = map.getView().getProjection();
              var geom = /** @type {ol.geom.Polygon} */(polygon.clone().transform(
                  sourceProj, 'EPSG:4326'));
              var coordinates = geom.getLinearRing(0).getCoordinates();
              area = Math.abs(wgs84Sphere.geodesicArea(coordinates));
            } else {
              area = polygon.getArea();
            }
            var output;
            if (area > 10000) {
              output = (Math.round(area / 1000000 * 100) / 100) +
                  ' ' + 'km<sup>2</sup>';
            } else {
              output = (Math.round(area * 100) / 100) +
                  ' ' + 'm<sup>2</sup>';
            }
            return output;
          };

          function addInteraction() {
            var type = (typeSelect.value == 'area' ? 'Polygon' : 'LineString');
            draw = new ol.interaction.Draw({
              source: source,
              type: /** @type {ol.geom.GeometryType} */ (type),
              style: new ol.style.Style({
                fill: new ol.style.Fill({
                  color: 'rgba(255, 255, 255, 0.2)'
                }),
                stroke: new ol.style.Stroke({
                  color: 'rgba(0, 0, 0, 0.5)',
                  lineDash: [10, 10],
                  width: 2
                }),
                image: new ol.style.Circle({
                  radius: 5,
                  stroke: new ol.style.Stroke({
                    color: 'rgba(0, 0, 0, 0.7)'
                  }),
                  fill: new ol.style.Fill({
                    color: 'rgba(255, 255, 255, 0.2)'
                  })
                })
              })
            });
            map.addInteraction(draw);

            createMeasureTooltip();
            createHelpTooltip();

            var listener;
            draw.on('drawstart',
                function(evt) {
                  // set sketch
                  sketch = evt.feature;

                  /** @type {ol.Coordinate|undefined} */
                  var tooltipCoord = evt.coordinate;

                  listener = sketch.getGeometry().on('change', function(evt) {
                    var geom = evt.target;
                    var output;
                    if (geom instanceof ol.geom.Polygon) {
                      output = formatArea(geom);
                      tooltipCoord = geom.getInteriorPoint().getCoordinates();
                    } else if (geom instanceof ol.geom.LineString) {
                      output = formatLength(geom);
                      tooltipCoord = geom.getLastCoordinate();
                    }
                    measureTooltipElement.innerHTML = output;
                    measureTooltip.setPosition(tooltipCoord);
                  });
                }, this);

            draw.on('drawend',
                function() {
                  measureTooltipElement.className = 'tooltip tooltip-static';
                  measureTooltip.setOffset([0, -7]);
                  // unset sketch
                  sketch = null;
                  // unset tooltip so that a new one can be created
                  measureTooltipElement = null;
                  createMeasureTooltip();
                  ol.Observable.unByKey(listener);
                }, this);
          }

          /**
           * Creates a new help tooltip
           */
          function createHelpTooltip() {
            if (helpTooltipElement) {
              helpTooltipElement.parentNode.removeChild(helpTooltipElement);
            }
            helpTooltipElement = document.createElement('div');
            helpTooltipElement.className = 'tooltip hidden';
            helpTooltip = new ol.Overlay({
              element: helpTooltipElement,
              offset: [15, 0],
              positioning: 'center-left'
            });
            map.addOverlay(helpTooltip);
          }

          /**
           * Creates a new measure tooltip
           */
          function createMeasureTooltip() {
            if (measureTooltipElement) {
              measureTooltipElement.parentNode.removeChild(measureTooltipElement);
            }
            measureTooltipElement = document.createElement('div');
            measureTooltipElement.className = 'tooltip tooltip-measure';
            measureTooltip = new ol.Overlay({
              element: measureTooltipElement,
              offset: [0, -15],
              positioning: 'bottom-center'
            });
            map.addOverlay(measureTooltip);
          }

          /**
           * Let user change the geometry type.
           */
          typeSelect.onchange = function() {
            map.removeInteraction(draw);
            addInteraction();
          };

          addInteraction();
        </script>
      </body>
    </html>