Mercator.java :  » GPS » tripcomputer » pl » tripcomputer » map » Android Open Source

package pl.tripcomputer.map;

import pl.tripcomputer.map.GeoPoint;

import java.util.List;


//returns x/y position in meters
public class Mercator
{
  final private static double R_MAJOR = 6378137.0;
  final private static double R_MINOR = 6356752.3142;
  final private static double eccent_e = Math.sqrt(1.0 - Math.pow(R_MINOR / R_MAJOR, 2));
  final private static double eccent_e_half = 0.5 * eccent_e;
  final private static double PI_half = Math.PI * 0.5;

  public static void ConvertToFlat(final GeoPoint geoPoint)
  {
    geoPoint.mercX = GetX(geoPoint.wgsLon);
    geoPoint.mercY = GetY(geoPoint.wgsLat);
  }
  
  public static void ConvertToFlat(final List<GeoPoint> points)
  {
    for (int i = 0; i < points.size(); i++)
    {
      GeoPoint point = points.get(i);
      point.mercX = GetX(point.wgsLon);
      point.mercY = GetY(point.wgsLat);
    }
  }

  public static double GetX(double lon)
  {
    return R_MAJOR * Math.toRadians(lon);
  }

  public static double GetY(double lat)
  {
    if (lat > 89.5)
      lat = 89.5;

    if (lat < -89.5)
      lat = -89.5;
     
    double phi = Math.toRadians(lat);
    double con = eccent_e * Math.sin(phi);
    con = Math.pow(((1.0 - con) / (1.0 + con)), eccent_e_half);
    double ts = Math.tan(0.5 * (PI_half - phi)) / con;
    double y = 0 - R_MAJOR * Math.log(ts);
    return y;
  }

  //simple mercator for square area
  public static double GetSquareY(double lat)  
  {
    double latitude = Math.toRadians(lat);
    return R_MAJOR / 2.0 * Math.log( (1.0 + Math.sin(latitude)) / (1.0 - Math.sin(latitude)) );
  }
    
}