I have made a Openlayers integrated map that lets you draw a circle, On completion of the circle I have told the map to give me , Bounds, Center Long and Lats, and lastly the radius. My problem is that I can't understand in what decimal it gives the radius to me in. Below is a image that shows you I have drawn a very large circle and the alert for the radius. How many kilometers is this? (I made a google map with the same functionality and the radius works in meters with EPSG Projection.
Below is my code. I am using CRS:84 for my map projection.
Here is the initial bit of code I want working in Meters rather than the decimal structure of the above picture.
vectors.events.on({
featuremodified: onFeatureModified
});
function onFeatureModified(event) {
var bounds = event.feature.geometry.getBounds();
var answer = "bottom: " + bounds.bottom + "\n";
answer += "left: " + bounds.left + "\n";
answer += "right: " + bounds.right + "\n";
answer += "top: " + bounds.top + "\n";
alert(answer);
var area = event.feature.geometry.getArea();
var radius = 0.565352 * Math.sqrt(area);
alert(radius);
var lonlat = event.feature.geometry.getBounds().getCenterLonLat()
alert(lonlat);
Below this is my complete html document:
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<!--CSS for Map -->
<style type="text/css">
html, body, #map {
margin: 0;
width: 100%;
height: 100%;
}
</style>
<!-- END of CSS for Map -->
<!--CSS for Controls to draw circle and navigate -->
<style type="text/css">
#controls {
position: absolute;
bottom: 1em;
left: 100px;
width: 400px;
z-index: 20000;
padding: 0 0.5em 0.5em 0.5em;
}
#controlToggle {
padding-left: 1em;
}
#controlToggle li {
list-style: none;
}
#form {
position: absolute;
bottom: 1em;
left: 400px;
width: 200px;
z-index: 20000;
padding: 0 0.5em 0.5em 0.5em;
}
</style>
<!-- END CSS for Controls to draw circle -->
<link href="css/style.css" rel="stylesheet" type="text/css" />
<script src="js/firebug.js"></script>
<script src="js/OpenLayers.js"></script>
<script type="text/javascript">
var lon = 24.0000000000;
var lat = -29.000000000000;
var zoom = 4;
var map, layer, vectors, controls;
function init() {
// Because the Streetmaps system uses 300x300 tiles, we need to set up the scaling variables to work with these
var aRes = [90, 45, 22.500000, 11.250000, 5.625000, 2.812500, 1.406250, 0.703125, 0.351563, 0.175781, 0.087891, 0.043945, 0.021973, 0.010986, 0.005493, 0.002747, 0.001373, 0.000687, 0.000343];
for (var l = 0; l < aRes.length; l++) { aRes[l] = aRes[l] / 300; }
// Normal init, but we pass through the info about the zoom/scaling as options
map = new OpenLayers.Map('map', { tileSize: new OpenLayers.Size(300, 300), projection: 'CRS:84',units: "m", numZoomLevels: aRes.length, resolutions: aRes, maxResolution: 360 / 300 });
// At this point the control is used as per normal
layer1 = new OpenLayers.Layer.WMS(
'Streetmaps Streets',
'http://www.streetmaps.co.za/WMS/?',
{
key: 'HZPGNWPNDYPREPTIKSIHWKYKQYYOQVYX',
service: 'WMS',
request: 'GetMap',
version: '1.3.0',
layers: 'sm.maps.tiled',
format: 'image/png'
}
);
layer2 = new OpenLayers.Layer.WMS(
'Streetmaps Imagery',
'http://www.streetmaps.co.za/WMS/?',
{
key: 'HZPGNWPNDYPREPTIKSIHWKYKQYYOQVYX',
service: 'WMS',
request: 'GetMap',
version: '1.3.0',
layers: 'sm.imagery',
format: 'image/png'
}
);
// This loads the map
map.addLayer(layer1);
map.addLayer(layer2);
map.setCenter(new OpenLayers.LonLat(lon, lat), zoom);
map.addControl(new OpenLayers.Control.LayerSwitcher());
var vectors = new OpenLayers.Layer.Vector("vector", { isBaseLayer: true });
map.addLayers([vectors]);
// This loads the overlays
var wms = new OpenLayers.Layer.WMS("OpenLayers WMS",
"http://vmap0.tiles.osgeo.org/wms/vmap0?", { layers: 'basic' });
OpenLayers.Feature.Vector.style['default']['strokeWidth'] = '2';
// allow testing of specific renderers via "?renderer=Canvas", etc
var renderer = OpenLayers.Util.getParameters(window.location.href).renderer;
renderer = (renderer) ? [renderer] : OpenLayers.Layer.Vector.prototype.renderers;
vectors = new OpenLayers.Layer.Vector("Vector Layer", {
renderers: renderer
});
map.addLayers([wms, vectors]);
map.addControl(new OpenLayers.Control.LayerSwitcher());
map.addControl(new OpenLayers.Control.MousePosition());
map.setCenter(new OpenLayers.LonLat(lon, lat), zoom);
// Now we call an alert to get the bounds or coordinates from a circle or vector we have drawn
vectors.events.on({
featuresadded: onFeaturesAdded
});
function onFeaturesAdded(event) {
var bounds = event.features[0].geometry.getBounds();
var answer = "bottom: " + bounds.bottom + "\n";
answer += "left: " + bounds.left + "\n";
answer += "right: " + bounds.right + "\n";
answer += "top: " + bounds.top + "\n";
alert(answer);
var area = event.features[0].geometry.getArea();
var radius = 0.565352 * Math.sqrt(area);
alert(radius);
var lonlat = event.features[0].geometry.getBounds().getCenterLonLat()
alert(lonlat);
// GET CENTER LAT + LON
// AUTOMATICALLY INITIATE: onFeatureModified (Incl. Click)
// DISABLE DRAW FEATURE
// ASSIGN VALUES TO HIDDEN FIELDS IN FORM:
//document.forms.item('hiddenfield').value = answer;
}
vectors.events.on({
featuremodified: onFeatureModified
});
function onFeatureModified(event) {
var bounds = event.feature.geometry.getBounds();
var answer = "bottom: " + bounds.bottom + "\n";
answer += "left: " + bounds.left + "\n";
answer += "right: " + bounds.right + "\n";
answer += "top: " + bounds.top + "\n";
alert(answer);
var area = event.feature.geometry.getArea();
var radius = 0.565352 * Math.sqrt(area);
alert(radius);
var lonlat = event.feature.geometry.getBounds().getCenterLonLat()
alert(lonlat);
// DISABLE DRAW FEATURE
// ASSIGN VALUES TO HIDDEN FIELDS IN FORM:
//document.forms.item('hiddenfield').value = answer;y
}
controls = {
regular: new OpenLayers.Control.DrawFeature(vectors,
OpenLayers.Handler.RegularPolygon,
{ handlerOptions: { sides: 40} }),
modify: new OpenLayers.Control.ModifyFeature(vectors)
};
for (var key in controls) {
map.addControl(controls[key]);
}
map.setCenter(new OpenLayers.LonLat(0, 0), 3);
document.getElementById('noneToggle').checked = true;
}
function update() {
// reset modification mode
//controls.modify.mode = OpenLayers.Control.ModifyFeature.RESHAPE;
controls["modify"].activate();
controls.modify.mode = OpenLayers.Control.ModifyFeature.ROTATE;
var resize = document.getElementById("resize").checked;
if (resize) {
controls.modify.mode |= OpenLayers.Control.ModifyFeature.RESIZE;
var keepAspectRatio = document.getElementById("keepAspectRatio").checked;
if (keepAspectRatio) {
controls.modify.mode &= ~OpenLayers.Control.ModifyFeature.RESHAPE;
}
}
var drag = document.getElementById("drag").checked;
if (drag) {
controls.modify.mode |= OpenLayers.Control.ModifyFeature.DRAG;
}
// if (rotate || drag) {
// controls.modify.mode &= ~OpenLayers.Control.ModifyFeature.RESHAPE;
// }
// var sides = parseInt(document.getElementById("sides").value);
// sides = Math.max(3, isNaN(sides) ? 0 : sides);
// controls.regular.handler.sides = sides;
// var irregular = document.getElementById("irregular").checked;
// controls.regular.handler.irregular = irregular;
}
function toggleControl(element) {
for (key in controls) {
var control = controls[key];
if (element.value == key && element.checked) {
control.activate();
} else {
control.deactivate();
}
}
}
</script>
</head>
<body onLoad="init()">
<div id="map" class="smallmap"></div>
<div id="controls">
<ul id="controlToggle">
<li>
<input type="radio" name="type" value="none" id="noneToggle"
onclick="toggleControl(this);" checked="checked" />
<label for="noneToggle">navigate</label>
</li>
<li>
<input type="radio" name="type" value="regular" id="regularToggle" onClick="toggleControl(this);" />
<label for="regularToggle">draw regular polygon</label>
</li>
<li>
<input type="radio" name="type" value="modify" id="modifyToggle"
onclick="update();" />
<label for="modifyToggle">modify feature</label>
<ul>
<li>
<input id="rotate" type="hidden"
name="rotate" onChange="update()" checked="checked"/>
</li>
<li>
<input id="resize" type="hidden"
name="resize" onChange="update()" checked="checked"/>
<input id="keepAspectRatio" type="hidden"
name="keepAspectRatio" onChange="update()" checked="checked" />
<label for="keepAspectRatio"></label>
</li>
<li>
<input id="drag" type="hidden"
name="drag" onChange="update()" checked="checked"/>
</li>
</ul>
</li>
</ul>
</div>
</body>
</html>
