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I am trying to create a GeodesicPolygon using using the code given in http://geographika.co.uk/samples/geodesic/GeodesicPolygon.js. But the circle is not visible, I guess its a projection problem but couldn't find where it is. Any help plz..........

My code goes like this:

<html>
<head>
<title>OpenLayers Example</title>
<script src='http://maps.google.com/maps?file=api&amp;v=2&amp;key=ABQIAAAAjpkAC9ePGem0lIq5XcMiuhR_wWLPFku8Ix9i2SXYRVK3e45q1BQUd_beF8dtzKET_EteAjPdGDwqpQ'></script>
<script src="http://openlayers.org/api/OpenLayers.js"></script>
<script type="text/javascript" src="./geodesicpolygon.js">
    </script>
</head>
<body>
  <div style="width:100%; height:100%" id="map"></div>
  <script defer='defer' type='text/javascript'>
 var options = {
            projection: new OpenLayers.Projection("EPSG:4326"),
            displayProjection: new OpenLayers.Projection("EPSG:900913"),
            units: "m",
            numZoomLevels: 18,
            maxResolution: 156543.0339,
            maxExtent: new OpenLayers.Bounds(-20037508, -20037508,
                                             20037508, 20037508.34)
        };
 var map = new OpenLayers.Map('map',options);

 <!--var layer = new OpenLayers.Layer.WMS( "World Map","http://labs.metacarta.com/wms-   c/Basic.py?", {layers: 'basic', format: 'image/png' } );-->
 var layer = new OpenLayers.Layer.Google("google maps",{sphericalMercator: true});
 var pois = new OpenLayers.Layer.Text( "My Points",
                { location:"./datanew.txt",
                  projection: map.projection
                });
 map.addLayers([layer,pois]);
 var projection1 = map.getProjectionObject();
 var origin_xy=new OpenLayers.Geometry.Point(78.5046,17.3157);
 <!--var circle = OpenLayers.Geometry.Polygon.createRegularPolygon(origin_xy, 5, 50);-->
 var circle=OpenLayers.Geometry.Polygon.createGeodesicPolygon(origin_xy,5, 50, 45,projection1);
 circle.transform(new OpenLayers.Projection("ESPG:4326"),new     OpenLayers.Projection("ESPN:900913"));
 var vlayer = new OpenLayers.Layer.Vector("Editable Vectors");
  map.addLayer(vlayer);
 vlayer.addFeatures(new OpenLayers.Feature.Vector(circle,null,null));
 map.zoomToMaxExtent();
  </script>
</body>
</html>
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Try zooming in - I think you are making the circle 50m across which is pretty small. – iant♦ Mar 13 '11 at 0:02
Even when I am giving 5000 , its not visible sir....... Are projections in my code correctly specified? – Vikash Talanki Mar 13 '11 at 5:00

2 Answers

up vote 2 down vote accepted

At a first glance OpenLayers.Projection("ESPN:900913") should be OpenLayers.Projection("EPSG:900913")

Also the addFeatures function takes an array, not a single feature, so it should be:

vlayer.addFeatures([new OpenLayers.Feature.Vector(circle)]);

The code below works. The createGeodesicPolygon actually transforms the feature back into the projection you pass into the function. The origin point is also assumed to be in the same projection you pass to createGeodesicPolygon. As you define yours in a different projection (4326) you should transform it beforehand (although strangely this does not seem to make a difference in this case - possibly as the point is left untransformed if invalid coords are returned). 

var options = {projection: new OpenLayers.Projection("EPSG:900913"),
            displayProjection: new OpenLayers.Projection("EPSG:900913"),
            units: "m",
            numZoomLevels: 18,
            maxResolution: 156543.0339,
            maxExtent: new OpenLayers.Bounds(-20037508, -20037508, 20037508, 20037508.34)};
var map = new OpenLayers.Map('map',options);
var layer = new OpenLayers.Layer.Google("google maps",{sphericalMercator: true});
map.addLayer(layer);
var origin_xy=new OpenLayers.Geometry.Point(78.5046,17.3157);
//following line not actually required
origin_xy.transform(new OpenLayers.Projection("ESPG:4326"),new OpenLayers.Projection("EPSG:900913"));
var circle=OpenLayers.Geometry.Polygon.createGeodesicPolygon(origin_xy, 500000, 50, 45, map.getProjectionObject());
var vlayer = new OpenLayers.Layer.Vector("Editable Vectors");
map.addLayer(vlayer);
vlayer.addFeatures([new OpenLayers.Feature.Vector(circle)]);
map.zoomToMaxExtent();
share|improve this answer
But even when I corrected it, the problem remains, the circle is not visble – Vikash Talanki Mar 12 '11 at 19:50
I have made the changes that you suggested, but even then the circle is not visible – Vikash Talanki Mar 12 '11 at 20:29
@user1795 - also ESPG:4326 should be EPSG:4326 - have you tried debugging the code? – geographika Mar 14 '11 at 12:06
Thanks alot and lot..... It worked perfectly... – Vikash Talanki Mar 14 '11 at 16:38
up vote 0 down vote

Sorry didn't feel like registering, but just wanted to add that I got hung up for a long time because the circle wasn't drawing for me either. Turns out my code was generally "right", but the demo page allows you to choose the radius in kilometers, but the function actually uses meters. So my circle was being drawn the whole time, but just really small :) I just had to multiple the radius by 1000.

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