[OpenLayers-Users] distances in spherical mercator

[Alessio Di Lorenzo]

Hi all,

I'm using the measurement tool in an application that uses google maps as
base.
My problem is that the measurement tool calculate the planar distance
(instead geodesic)...

I tried to use the Util.distVincenty and it works (very good) only if my map
projection is 4326.

Snippet:

function calcVincenty(geometry) {
    var dist = 0;
    for (var i = 1; i < geometry.components.length; i++) {
        var first = geometry.components[i-1];
        var second = geometry.components[i];
        dist += OpenLayers.Util.distVincenty(
            {lon: first.x, lat: first.y},
            {lon: second.x, lat: second.y}
        );
    }
    return dist;
}     


function handleMeasurements(event) {
	
    var geometry = event.geometry;
    var units = event.units;
    var order = event.order;
    var measure = event.measure;
    var element = document.getElementById('output_misure');
    var out = "";
    if(order == 1) {
    	
    	if (map.getProjection()== "EPSG:4326") {
    		out += "Distanza: " + calcVincenty(geometry).toFixed(3)+ " " + units;
    		
    	} else {
    		out += "Distanza: " + measure.toFixed(3)+ " " + units;
    	}
    } else {
    	if (map.getProjection() == "EPSG:4326") {
    		out += "Area: " +
(OpenLayers.Util.approxPolyAreaOnSphere(geometry)/1000000.0).toFixed(3)+ " "
+ units + "q";
    	} else {
    		out += "Area: " + measure.toFixed(3) + " " + units + "q";
    	}
    }
		element.innerHTML = out;
}


If I apply the calcVincenty function to the 900913 projection I get enormous
distance errors...
Is there a way to measure geodesic distances (and areas) also for 900913
projected maps?

Thx in advance, alessio
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