[SOLVED] Converting coordinates from EPSG 3857 to 4326

Converting coordinates from EPSG 3857 to 4326

I have in my DB a list of coordinates in EPSG 3857 format. I need to convert them in EPSG 4326 I'm trying to use DotSpatial but my code always retun a double array of Infinity.

public double[] ConvertCoodinates()
    {
        double[] xy = new double[2];
        xy[0] = 5085240.8300000000;
        xy[1] = 1530088.9600000000;
    //An array for the z coordinate
        double[] z = new double[1];
        z[0] = 0;
        ProjectionInfo pStart = KnownCoordinateSystems.Geographic.World.WGS1984;
        pStart.AuthorityCode = 3857;
        ProjectionInfo pEnd = KnownCoordinateSystems.Geographic.World.WGS1984;
        pEnd.AuthorityCode = 4326;
        Reproject.ReprojectPoints(xy, z, pStart, pEnd, 0, 1);
        return xy;
    }

The xy array always cointain infinity; Can someone help me?

Solution

In the end I found a math formula to convert the coordinates.

I implemented it in a stored procedure because I have a list of point and this stored procedure calculates the distance.

DECLARE @e FLOAT=2.7182818284
DECLARE @X DECIMAL(18,2) =20037508.34

SET @StartLat3857 =(SELECT TOP 1 Latitude FROM Coordinates WHERE IdCoord=@IdCoord ORDER By IdTDFPath ASC)
SET @StartLng3857=(SELECT TOP 1 Longitude FROM Coordinates WHERE IdCoord=@IdCoord ORDER By IdTDFPath ASC)

--converting the logitute from epsg 3857 to 4326
            SET @StartLng=(@StartLng3857*180)/@X

--converting the latitude from epsg 3857 to 4326
            SET @StartLat = @StartLat3857/(@X/180)
            SET @StartLat = ((ATAN(POWER(@e,((PI()/180)*@StartLat))))/(PI()/360))-90

In the end is just a math formula that can be used in every language. for example is Javascript it will be

const e = 2.7182818284
const X = 20037508.34

const lat3857 = 1743704.947843 
const long3857 = 16978473.105100

//converting the logitute from epsg 3857 to 4326
const long4326 = (lat3857*180)/X

//converting the latitude from epsg 3857 to 4326 split in multiple lines for readability

let lat4326 = lat3857/(X / 180)
const exponent = (Math.PI / 180) * lat4326

lat4326 = Math.atan(e ** exponent)
lat4326 = lat4326 / (Math.PI / 360)
lat4326 = lat4326 - 90