Give the ScaleLine control a geodesic option. Setting this to true will provide an accurate scale bar in Spherical Mercator maps. r=bartvde (closes #1890)
git-svn-id: http://svn.openlayers.org/trunk/openlayers@10110 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
This commit is contained in:
ahocevar
@@ -61,6 +61,12 @@ OpenLayers.Control.ScaleLine = OpenLayers.Class(OpenLayers.Control, {
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* {DOMElement}
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* {DOMElement}
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*/
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*/
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eBottom:null,
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eBottom:null,
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/**
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* APIProperty: geodesic
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* {Boolean} Use geodesic measurement. Default is false.
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*/
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geodesic: false,
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/**
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/**
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* Constructor: OpenLayers.Control.ScaleLine
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* Constructor: OpenLayers.Control.ScaleLine
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@@ -156,7 +162,14 @@ OpenLayers.Control.ScaleLine = OpenLayers.Class(OpenLayers.Control, {
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var inches = OpenLayers.INCHES_PER_UNIT;
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var inches = OpenLayers.INCHES_PER_UNIT;
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// convert maxWidth to map units
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// convert maxWidth to map units
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var maxSizeData = this.maxWidth * res * inches[curMapUnits];
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var maxSizeData = this.maxWidth * res * inches[curMapUnits];
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var geodesicRatio = 1;
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if(this.geodesic === true) {
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var maxSizeGeodesic = this.getGeodesicLength(this.maxWidth);
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var maxSizeKilometers = maxSizeData / inches["km"];
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geodesicRatio = maxSizeGeodesic / maxSizeKilometers;
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maxSizeData *= geodesicRatio;
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}
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// decide whether to use large or small scale units
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// decide whether to use large or small scale units
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var topUnits;
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var topUnits;
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@@ -182,8 +195,8 @@ OpenLayers.Control.ScaleLine = OpenLayers.Class(OpenLayers.Control, {
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bottomMax = bottomRounded / inches[curMapUnits] * inches[bottomUnits];
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bottomMax = bottomRounded / inches[curMapUnits] * inches[bottomUnits];
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// and to pixel units
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// and to pixel units
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var topPx = topMax / res;
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var topPx = topMax / res / geodesicRatio;
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var bottomPx = bottomMax / res;
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var bottomPx = bottomMax / res / geodesicRatio;
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// now set the pixel widths
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// now set the pixel widths
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// and the values inside them
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// and the values inside them
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@@ -200,6 +213,26 @@ OpenLayers.Control.ScaleLine = OpenLayers.Class(OpenLayers.Control, {
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},
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},
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/**
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* Method: getGeodesicLength
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*
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* Parameters:
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* pixels - {Number} the pixels to get the geodesic length in meters for.
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*/
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getGeodesicLength: function(pixels) {
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var map = this.map;
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var centerPx = map.getPixelFromLonLat(map.getCenter());
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var bottom = map.getLonLatFromPixel(centerPx.add(0, -pixels / 2));
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var top = map.getLonLatFromPixel(centerPx.add(0, pixels / 2));
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var source = map.getProjectionObject();
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var dest = new OpenLayers.Projection("EPSG:4326");
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if(!source.equals(dest)) {
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bottom.transform(source, dest);
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top.transform(source, dest);
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}
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return OpenLayers.Util.distVincenty(bottom, top);
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},
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CLASS_NAME: "OpenLayers.Control.ScaleLine"
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CLASS_NAME: "OpenLayers.Control.ScaleLine"
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});
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});
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@@ -0,0 +1,160 @@
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<link rel="stylesheet" href="../../theme/default/style.css" type="text/css" />
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<style type="text/css">
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#controlToggle li {
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list-style: none;
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}
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#options {
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position: relative;
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width: 512px;
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}
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#output {
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float: right;
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}
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/* avoid pink tiles */
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.olImageLoadError {
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background-color: transparent !important;
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}
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</style>
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<script src="../../lib/OpenLayers.js"></script>
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<script type="text/javascript">
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var map, measureControls;
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function init(){
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map = new OpenLayers.Map('map');
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var wmsLayer = new OpenLayers.Layer.OSM();
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map.addLayers([wmsLayer]);
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map.setCenter(new OpenLayers.LonLat(0,0), 5);
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map.addControl(new OpenLayers.Control.LayerSwitcher());
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map.addControl(new OpenLayers.Control.MousePosition());
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map.addControl(new OpenLayers.Control.ScaleLine({geodesic: true}))
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// style the sketch fancy
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var sketchSymbolizers = {
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"Point": {
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pointRadius: 4,
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graphicName: "square",
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fillColor: "white",
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fillOpacity: 1,
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strokeWidth: 1,
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strokeOpacity: 1,
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strokeColor: "#333333"
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},
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"Line": {
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strokeWidth: 3,
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strokeOpacity: 1,
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strokeColor: "#666666",
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strokeDashstyle: "dash"
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},
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"Polygon": {
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strokeWidth: 2,
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strokeOpacity: 1,
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strokeColor: "#666666",
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fillColor: "white",
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fillOpacity: 0.3
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}
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};
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var style = new OpenLayers.Style();
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style.addRules([
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new OpenLayers.Rule({symbolizer: sketchSymbolizers})
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]);
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var styleMap = new OpenLayers.StyleMap({"default": style});
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measureControls = {
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line: new OpenLayers.Control.Measure(
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OpenLayers.Handler.Path, {
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geodesic: true,
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persist: true,
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handlerOptions: {
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layerOptions: {styleMap: styleMap}
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}
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}
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),
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polygon: new OpenLayers.Control.Measure(
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OpenLayers.Handler.Polygon, {
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geodesic: true,
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persist: true,
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handlerOptions: {
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layerOptions: {styleMap: styleMap}
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}
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}
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)
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};
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var control;
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for(var key in measureControls) {
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control = measureControls[key];
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control.events.on({
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"measure": handleMeasurements,
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"measurepartial": handleMeasurements
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});
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map.addControl(control);
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}
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map.setCenter(new OpenLayers.LonLat(0, 0), 3);
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document.getElementById('noneToggle').checked = true;
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}
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function handleMeasurements(event) {
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var geometry = event.geometry;
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var units = event.units;
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var order = event.order;
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var measure = event.measure;
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var element = document.getElementById('output');
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var out = "";
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if(order == 1) {
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out += "measure: " + measure.toFixed(3) + " " + units;
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} else {
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out += "measure: " + measure.toFixed(3) + " " + units + "<sup>2</" + "sup>";
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}
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element.innerHTML = out;
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}
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function toggleControl(element) {
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for(key in measureControls) {
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var control = measureControls[key];
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if(element.value == key && element.checked) {
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control.activate();
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} else {
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control.deactivate();
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}
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}
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}
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</script>
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</head>
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<body onload="init()">
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<h1 id="title">OpenLayers Geodesic Measurement & ScaleLine</h1>
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<p id="shortdesc">
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Tests geodesic measurement of distances and areas against a geodesic ScaleLine.
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</p>
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<div id="map" style="width: 512px; height: 300px;"></div>
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<div id="options">
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<div id="output">
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</div>
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<ul id="controlToggle">
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<li>
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<input type="radio" name="type" value="none" id="noneToggle"
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onclick="toggleControl(this);" checked="checked" />
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<label for="noneToggle">navigate</label>
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</li>
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<li>
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<input type="radio" name="type" value="line" id="lineToggle" onclick="toggleControl(this);" />
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<label for="lineToggle">measure distance</label>
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</li>
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<li>
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<input type="radio" name="type" value="polygon" id="polygonToggle" onclick="toggleControl(this);" />
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<label for="polygonToggle">measure area</label>
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</li>
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</ul>
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</div>
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<p>Zoom in so the ScaleLine shows units in the range of 10-100 km. Measure
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the length of the ScaleLine. The result should be approximately the same
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as the distance printed on the ScaleLine.</p>
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<p>Zoom out so the ScaleLine shows units in the range of 100-500 km. Drag
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the map to the South or North and see how the ScaleLine length changes.</p>
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</body>
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</html>
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Reference in New Issue
Block a user