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Build tools and sources for developing OpenLayers based mapping applications

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/** * @license * Latitude/longitude spherical geodesy formulae taken from * http://www.movable-type.co.uk/scripts/latlong.html * Licensed under CC-BY-3.0. */ goog.provide('ol.Sphere'); goog.require('ol.math'); /** * @classdesc * Class to create objects that can be used with {@link * ol.geom.Polygon.circular}. * * For example to create a sphere whose radius is equal to the semi-major * axis of the WGS84 ellipsoid: * * ```js * var wgs84Sphere= new ol.Sphere(6378137); * ``` * * @constructor * @param {number} radius Radius. * @api */ ol.Sphere = function(radius) { /** * @type {number} */ this.radius = radius; }; /** * Returns the geodesic area for a list of coordinates. * * [Reference](http://trs-new.jpl.nasa.gov/dspace/handle/2014/40409) * Robert. G. Chamberlain and William H. Duquette, "Some Algorithms for * Polygons on a Sphere", JPL Publication 07-03, Jet Propulsion * Laboratory, Pasadena, CA, June 2007 * * @param {Array.<ol.Coordinate>} coordinates List of coordinates of a linear * ring. If the ring is oriented clockwise, the area will be positive, * otherwise it will be negative. * @return {number} Area. * @api */ ol.Sphere.prototype.geodesicArea = function(coordinates) { var area = 0, len = coordinates.length; var x1 = coordinates[len - 1][0]; var y1 = coordinates[len - 1][1]; for (var i = 0; i < len; i++) { var x2 = coordinates[i][0], y2 = coordinates[i][1]; area += ol.math.toRadians(x2 - x1) * (2 + Math.sin(ol.math.toRadians(y1)) + Math.sin(ol.math.toRadians(y2))); x1 = x2; y1 = y2; } return area * this.radius * this.radius / 2.0; }; /** * Returns the distance from c1 to c2 using the haversine formula. * * @param {ol.Coordinate} c1 Coordinate 1. * @param {ol.Coordinate} c2 Coordinate 2. * @return {number} Haversine distance. * @api */ ol.Sphere.prototype.haversineDistance = function(c1, c2) { var lat1 = ol.math.toRadians(c1[1]); var lat2 = ol.math.toRadians(c2[1]); var deltaLatBy2 = (lat2 - lat1) / 2; var deltaLonBy2 = ol.math.toRadians(c2[0] - c1[0]) / 2; var a = Math.sin(deltaLatBy2) * Math.sin(deltaLatBy2) + Math.sin(deltaLonBy2) * Math.sin(deltaLonBy2) * Math.cos(lat1) * Math.cos(lat2); return 2 * this.radius * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a)); }; /** * Returns the coordinate at the given distance and bearing from `c1`. * * @param {ol.Coordinate} c1 The origin point (`[lon, lat]` in degrees). * @param {number} distance The great-circle distance between the origin * point and the target point. * @param {number} bearing The bearing (in radians). * @return {ol.Coordinate} The target point. */ ol.Sphere.prototype.offset = function(c1, distance, bearing) { var lat1 = ol.math.toRadians(c1[1]); var lon1 = ol.math.toRadians(c1[0]); var dByR = distance / this.radius; var lat = Math.asin( Math.sin(lat1) * Math.cos(dByR) + Math.cos(lat1) * Math.sin(dByR) * Math.cos(bearing)); var lon = lon1 + Math.atan2( Math.sin(bearing) * Math.sin(dByR) * Math.cos(lat1), Math.cos(dByR) - Math.sin(lat1) * Math.sin(lat)); return [ol.math.toDegrees(lon), ol.math.toDegrees(lat)]; };