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Configurable hex grid on abstract surface

There is a newer version: 1.0.1

package com.gojuno.hexgridgeo;

import com.gojuno.hexgrid.Point;

public class ProjectionSM implements Projection {
    public static final Projection INSTANCE = new ProjectionSM();
    private static final double EARTH_CIRCUMFERENCE = 40075016.685578488;
    private static final double EARTH_METERS_PER_DEGREE = 111319.49079327358;

    private ProjectionSM() {
    }

    @Override
    public String getName() {
        return "sm";
    }

    @Override
    public Point geoToPoint(PointGeo geoPoint) {
        double latR = geoPoint.getLat() * (Math.PI / 180);
        double x = geoPoint.getLon() * EARTH_METERS_PER_DEGREE;
        double y = Math.log(Math.tan(latR) + (1 / Math.cos(latR)));
        y = (y / Math.PI) * (EARTH_CIRCUMFERENCE / 2);
        return new Point(x, y);
    }

    @Override
    public PointGeo pointToGeo(Point point) {
        double lon = point.getX() / EARTH_METERS_PER_DEGREE;
        double lat = Math.asin(Math.tanh((point.getY() / (EARTH_CIRCUMFERENCE / 2)) * Math.PI));
        lat = lat * (180 / Math.PI);
        return new PointGeo(lon, lat);
    }

    @Override
    public String toString() {
        return String.format("projection{name: %s}", getName());
    }
}