leaflet/src/geo/crs/CRS.Earth.js

JavaScript library for mobile-friendly interactive maps

/*
 * @namespace CRS
 * @crs L.CRS.Earth
 *
 * Serves as the base for CRS that are global such that they cover the earth.
 * Can only be used as the base for other CRS and cannot be used directly,
 * since it does not have a `code`, `projection` or `transformation`. `distance()` returns
 * meters.
 */

L.CRS.Earth = L.extend({}, L.CRS, {
	wrapLng: [-180, 180],

	// Mean Earth Radius, as recommended for use by
	// the International Union of Geodesy and Geophysics,
	// see http://rosettacode.org/wiki/Haversine_formula
	R: 6371000,

	// distance between two geographical points using spherical law of cosines approximation
	distance: function (latlng1, latlng2) {
		var rad = Math.PI / 180,
		    lat1 = latlng1.lat * rad,
		    lat2 = latlng2.lat * rad,
		    a = Math.sin(lat1) * Math.sin(lat2) +
		        Math.cos(lat1) * Math.cos(lat2) * Math.cos((latlng2.lng - latlng1.lng) * rad);

		return this.R * Math.acos(Math.min(a, 1));
	}
});