165 lines
7.1 KiB
JavaScript
165 lines
7.1 KiB
JavaScript
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/**
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* Cesium - https://github.com/AnalyticalGraphicsInc/cesium
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*
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* Copyright 2011-2017 Cesium Contributors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* Columbus View (Pat. Pend.)
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*
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* Portions licensed separately.
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* See https://github.com/AnalyticalGraphicsInc/cesium/blob/master/LICENSE.md for full licensing details.
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*/
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define(['exports', './when-8d13db60', './Check-70bec281', './Math-61ede240', './Cartographic-fe4be337', './Cartesian2-85064f09'], function (exports, when, Check, _Math, Cartographic, Cartesian2) { 'use strict';
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/**
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* The map projection used by Google Maps, Bing Maps, and most of ArcGIS Online, EPSG:3857. This
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* projection use longitude and latitude expressed with the WGS84 and transforms them to Mercator using
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* the spherical (rather than ellipsoidal) equations.
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*
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* @alias WebMercatorProjection
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* @constructor
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*
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* @param {Ellipsoid} [ellipsoid=Ellipsoid.WGS84] The ellipsoid.
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*
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* @see GeographicProjection
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*/
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function WebMercatorProjection(ellipsoid) {
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this._ellipsoid = when.defaultValue(ellipsoid, Cartesian2.Ellipsoid.WGS84);
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this._semimajorAxis = this._ellipsoid.maximumRadius;
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this._oneOverSemimajorAxis = 1.0 / this._semimajorAxis;
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}
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Object.defineProperties(WebMercatorProjection.prototype, {
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/**
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* Gets the {@link Ellipsoid}.
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*
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* @memberof WebMercatorProjection.prototype
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*
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* @type {Ellipsoid}
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* @readonly
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*/
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ellipsoid : {
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get : function() {
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return this._ellipsoid;
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}
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}
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});
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/**
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* Converts a Mercator angle, in the range -PI to PI, to a geodetic latitude
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* in the range -PI/2 to PI/2.
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*
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* @param {Number} mercatorAngle The angle to convert.
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* @returns {Number} The geodetic latitude in radians.
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*/
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WebMercatorProjection.mercatorAngleToGeodeticLatitude = function(mercatorAngle) {
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return _Math.CesiumMath.PI_OVER_TWO - (2.0 * Math.atan(Math.exp(-mercatorAngle)));
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};
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/**
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* Converts a geodetic latitude in radians, in the range -PI/2 to PI/2, to a Mercator
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* angle in the range -PI to PI.
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*
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* @param {Number} latitude The geodetic latitude in radians.
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* @returns {Number} The Mercator angle.
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*/
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WebMercatorProjection.geodeticLatitudeToMercatorAngle = function(latitude) {
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// Clamp the latitude coordinate to the valid Mercator bounds.
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if (latitude > WebMercatorProjection.MaximumLatitude) {
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latitude = WebMercatorProjection.MaximumLatitude;
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} else if (latitude < -WebMercatorProjection.MaximumLatitude) {
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latitude = -WebMercatorProjection.MaximumLatitude;
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}
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var sinLatitude = Math.sin(latitude);
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return 0.5 * Math.log((1.0 + sinLatitude) / (1.0 - sinLatitude));
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};
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/**
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* The maximum latitude (both North and South) supported by a Web Mercator
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* (EPSG:3857) projection. Technically, the Mercator projection is defined
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* for any latitude up to (but not including) 90 degrees, but it makes sense
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* to cut it off sooner because it grows exponentially with increasing latitude.
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* The logic behind this particular cutoff value, which is the one used by
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* Google Maps, Bing Maps, and Esri, is that it makes the projection
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* square. That is, the rectangle is equal in the X and Y directions.
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*
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* The constant value is computed by calling:
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* WebMercatorProjection.mercatorAngleToGeodeticLatitude(Math.PI)
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*
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* @type {Number}
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*/
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WebMercatorProjection.MaximumLatitude = WebMercatorProjection.mercatorAngleToGeodeticLatitude(Math.PI);
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/**
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* Converts geodetic ellipsoid coordinates, in radians, to the equivalent Web Mercator
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* X, Y, Z coordinates expressed in meters and returned in a {@link Cartesian3}. The height
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* is copied unmodified to the Z coordinate.
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*
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* @param {Cartographic} cartographic The cartographic coordinates in radians.
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* @param {Cartesian3} [result] The instance to which to copy the result, or undefined if a
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* new instance should be created.
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* @returns {Cartesian3} The equivalent web mercator X, Y, Z coordinates, in meters.
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*/
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WebMercatorProjection.prototype.project = function(cartographic, result) {
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var semimajorAxis = this._semimajorAxis;
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var x = cartographic.longitude * semimajorAxis;
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var y = WebMercatorProjection.geodeticLatitudeToMercatorAngle(cartographic.latitude) * semimajorAxis;
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var z = cartographic.height;
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if (!when.defined(result)) {
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return new Cartographic.Cartesian3(x, y, z);
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}
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result.x = x;
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result.y = y;
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result.z = z;
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return result;
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};
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/**
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* Converts Web Mercator X, Y coordinates, expressed in meters, to a {@link Cartographic}
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* containing geodetic ellipsoid coordinates. The Z coordinate is copied unmodified to the
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* height.
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*
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* @param {Cartesian3} cartesian The web mercator Cartesian position to unrproject with height (z) in meters.
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* @param {Cartographic} [result] The instance to which to copy the result, or undefined if a
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* new instance should be created.
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* @returns {Cartographic} The equivalent cartographic coordinates.
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*/
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WebMercatorProjection.prototype.unproject = function(cartesian, result) {
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//>>includeStart('debug', pragmas.debug);
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if (!when.defined(cartesian)) {
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throw new Check.DeveloperError('cartesian is required');
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}
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//>>includeEnd('debug');
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var oneOverEarthSemimajorAxis = this._oneOverSemimajorAxis;
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var longitude = cartesian.x * oneOverEarthSemimajorAxis;
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var latitude = WebMercatorProjection.mercatorAngleToGeodeticLatitude(cartesian.y * oneOverEarthSemimajorAxis);
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var height = cartesian.z;
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if (!when.defined(result)) {
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return new Cartographic.Cartographic(longitude, latitude, height);
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}
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result.longitude = longitude;
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result.latitude = latitude;
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result.height = height;
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return result;
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};
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exports.WebMercatorProjection = WebMercatorProjection;
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});
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