Draw arc in Geo map WGS84 coordinate system

Question

im trying to draw an arc in OpenLayers, in non Geo map it works well and here is my code:

function calculateArcPointsNonGeo(center, radius,startAngle,endAngle,segments)
 {
            var pointList =  [],
                Angle,
                x,
                y,
                point,
                i;

            var dAngle = segments + 1;
            for (i = 0; i < dAngle; i++) {
                Angle = startAngle - (startAngle - endAngle) * i / (dAngle - 1);
                 x = center.X + radius * Math.cos(Angle * Math.PI / 180);
                 y = center.Y + radius * Math.sin(Angle * Math.PI / 180);
                point = new MapPoint(x,y);
                pointList.push(point);
            }

            return pointList;
        }

in addition there is a great Example that demonstrates it , but when im trying to do this on Geo map (WGS84 coordinate system) its start to acting weird, i assume that i need to convert degrees to radinas or something like this. please help

Answer 1

solved It:

function calculateArcPointsGeo(center, radius, startAzimuth, endAzimuth, segments) {
        var pointList = [],
            point,
            i,
            d = radius / 1000, // d = distance in km
            R = 6371, // km, R = earth's radius (mean radius = 6,371km)
           lat1 = deg2Rad(center.Y),
           lon1 = deg2Rad(center.X),
           lat2,
           lon2,
           dAngle = segments + 1,
           azimuth;
        startAzimuth = deg2Rad(startAzimuth);
        endAzimuth = deg2Rad(endAzimuth);
        for (i = 0; i < dAngle; i++) {
            azimuth = startAzimuth - (startAzimuth - endAzimuth) * i / (dAngle - 1);
            lat2 = Math.asin(Math.sin(lat1) * Math.cos(d / R) +
                                  Math.cos(lat1) * Math.sin(d / R) * Math.cos(azimuth));

            lon2 = lon1 + Math.atan2(Math.sin(azimuth) * Math.sin(d / R) * Math.cos(lat1),
                                           Math.cos(d / R) - Math.sin(lat1) * Math.sin(lat2));
            lat2 = 180 * lat2 / Math.PI;
            lon2 = 180 * lon2 / Math.PI;

            point = new MapPoint(lon2, lat2);
            pointList.push(point);
        }

        return pointList;
    }