# Projecting from WGS84 to SphericalMercator

Projecting from one coordinate system to another is a big topic in the geo bizz. Most apps use comprehensive libraries to deal with all possible projections. These days 90% of the projections that I see are from WGS84 to SphericalMercator. Mostly this is GPS coordinates projected to a Google, Bing or OpenStreetMap tile background. If you would like to keep it simple the code below would suffice (Thanks to Steven Fruijtier for sharing the code).

`using System;using SharpMap.Geometries;namespace Projection{    public static class SphericalMercator    {        private readonly static double radius = 6378137;        private static double D2R = Math.PI / 180;        private static double HALF_PI = Math.PI / 2;        public static Point FromLonLat(double lon, double lat)        {            double lonRadians = (D2R * lon);            double latRadians = (D2R * lat);            double x = radius * lonRadians;            double y = radius * Math.Log(Math.Tan(Math.PI * 0.25 + latRadians * 0.5));            return new Point((float)x, (float)y);        }        public static Point ToLonLat(double x, double y)        {            double ts;            ts = Math.Exp(-y / (radius));            double latRadians = HALF_PI - 2 * Math.Atan(ts);            double lonRadians = x / (radius);            double lon = (lonRadians / D2R);            double lat = (latRadians / D2R);            return new Point((float)lon, (float)lat);        }    }}`

## 2 gedachtes over “Projecting from WGS84 to SphericalMercator”

1. Ray H zegt:

What are the limitations to this algorithm?

I'm trying to compare the displacement compared to Google Maps near Vancouver, BC and the distances are really off.

Thanks

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2. Sandy zegt:

Hi Paul,

Could you please post any leads to the derivation of forward Mercator transformation ?

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