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);
}
}
}
Projecting from WGS84 to SphericalMercator

2 gedachtes over “Projecting from WGS84 to SphericalMercator

  1. 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

    Like

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