Projection issue with ESRI JSAPI and ArcGIS map service

Question

I was trying to obtain a gpx file with some coordinates by drawing on an Openlayers map with an ArcGIS baseMap.

When I draw the polyline and create the gpx, if I open it on Google Earth, what I see is not what I drawed before, the line is totally different from the original and not positioned where I drawed it. I know it's a projection problem, I've tried trasforming the geometry object from Mercator to Geographic, also getting directly the geographic coordinates from the map coordinates, but nothing. I tried to set "spatialReference" to 4362 and then to 3857, but nothing changes.

I'm going to use that .gpx on a gps device (the next week I'll go to the Svalbard islands and I need some gps tracks to go around Longyearbyen by snowmobile, there there aren't any sign of life out the town, so I must be prepared to it), when I'll be there I'll adjust the output right for the device they will rent to me, but now I need to save on the .gpx file almost the right coordinates.

I'm getting from the map those coordinates: lat: 61.22582068741976 lon: 4.684820015391338 when I'm expecting instead something around 78. lat and 15. lon.

This is some of the code I use to create the map (I'm not pasting the code I know it's not responsible of my problems):

    var initialExtent = new esri.geometry.Extent({"xmin":505615.5801124362,"ymin":8678955.717187276,"xmax":525935.6207525175,"ymax":8689168.654279819,"spatialReference":{"wkid":32633,"latestWkid":32633}});

    map = map = new esri.Map("map", {extent: initialExtent, logo : false});
    basemapURL = "http://geodata.npolar.no/ArcGIS/rest/services/inspire1/NP_TopoSvalbard_U33_CHL/MapServer/";
    map.addLayer(new esri.layers.ArcGISTiledMapServiceLayer(basemapURL));

Here I'm using wkid 32633 that is the default for that map, tried to change with known ones, but nothing happened.

And now the code I use to get the coordinates:

        dojo.connect(tb, "onDrawEnd", getCoords);
        function getCoords(geo) {
            var r=confirm("Salvare tracciato?");
            if (r==true) {
                geo = esri.geometry.webMercatorToGeographic(geo);   
                for ( var path = 0; path < geo.paths.length; path ++ ) {                   
                    for ( var pt = 0; pt < geo.paths[path].length; pt++ ) {
                        tra += '<wpt lat="'+geo.paths[path][pt][1]+'" lon="'+geo.paths[path][pt][0]+'"></wpt>';
                    }   
                }
            }
        }

"tra" is a variable that stores all the code I'll insert into the gpx file with an other function. The "webMercatorToGeographic" function transform the map coordinates to geographic ones.

Answer 1

Thanks to Devdatta Tengshe on GIS.stackexchange I got what I need:

Use the proj4js library in your application. To do this, follow these steps:

Download the latest library from https://github.com/proj4js/proj4js/releases In your HTML file use You'll need to define the projections before you can use it. You can do this by using the following lines of code: var UTM33N= "+proj=utm +zone=33 +ellps=WGS84 +datum=WGS84 +units=m +no_defs"; var GCS84="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs";

When you need to transform, you can use the following line: var transformed=proj4(UTM33N,GCS84,[x,y]); where x & y are the coordinates in your given projection. As output you'll get an array with two elements, the longitude, & the Latitude

That worked fine.