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134 lines
3.3 KiB
134 lines
3.3 KiB
/**
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* @module ol/proj/epsg3857
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*/
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import Projection from './Projection.js';
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/**
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* Radius of WGS84 sphere
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*
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* @const
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* @type {number}
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*/
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export const RADIUS = 6378137;
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/**
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* @const
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* @type {number}
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*/
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export const HALF_SIZE = Math.PI * RADIUS;
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/**
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* @const
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* @type {import("../extent.js").Extent}
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*/
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export const EXTENT = [-HALF_SIZE, -HALF_SIZE, HALF_SIZE, HALF_SIZE];
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/**
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* @const
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* @type {import("../extent.js").Extent}
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*/
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export const WORLD_EXTENT = [-180, -85, 180, 85];
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/**
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* Maximum safe value in y direction
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* @const
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* @type {number}
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*/
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export const MAX_SAFE_Y = RADIUS * Math.log(Math.tan(Math.PI / 2));
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/**
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* @classdesc
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* Projection object for web/spherical Mercator (EPSG:3857).
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*/
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class EPSG3857Projection extends Projection {
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/**
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* @param {string} code Code.
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*/
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constructor(code) {
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super({
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code: code,
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units: 'm',
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extent: EXTENT,
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global: true,
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worldExtent: WORLD_EXTENT,
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getPointResolution: function (resolution, point) {
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return resolution / Math.cosh(point[1] / RADIUS);
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},
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});
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}
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}
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/**
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* Projections equal to EPSG:3857.
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*
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* @const
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* @type {Array<import("./Projection.js").default>}
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*/
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export const PROJECTIONS = [
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new EPSG3857Projection('EPSG:3857'),
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new EPSG3857Projection('EPSG:102100'),
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new EPSG3857Projection('EPSG:102113'),
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new EPSG3857Projection('EPSG:900913'),
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new EPSG3857Projection('http://www.opengis.net/def/crs/EPSG/0/3857'),
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new EPSG3857Projection('http://www.opengis.net/gml/srs/epsg.xml#3857'),
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];
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/**
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* Transformation from EPSG:4326 to EPSG:3857.
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*
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* @param {Array<number>} input Input array of coordinate values.
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* @param {Array<number>} [output] Output array of coordinate values.
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* @param {number} [dimension] Dimension (default is `2`).
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* @return {Array<number>} Output array of coordinate values.
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*/
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export function fromEPSG4326(input, output, dimension) {
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const length = input.length;
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dimension = dimension > 1 ? dimension : 2;
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if (output === undefined) {
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if (dimension > 2) {
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// preserve values beyond second dimension
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output = input.slice();
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} else {
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output = new Array(length);
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}
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}
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for (let i = 0; i < length; i += dimension) {
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output[i] = (HALF_SIZE * input[i]) / 180;
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let y = RADIUS * Math.log(Math.tan((Math.PI * (+input[i + 1] + 90)) / 360));
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if (y > MAX_SAFE_Y) {
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y = MAX_SAFE_Y;
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} else if (y < -MAX_SAFE_Y) {
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y = -MAX_SAFE_Y;
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}
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output[i + 1] = y;
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}
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return output;
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}
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/**
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* Transformation from EPSG:3857 to EPSG:4326.
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*
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* @param {Array<number>} input Input array of coordinate values.
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* @param {Array<number>} [output] Output array of coordinate values.
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* @param {number} [dimension] Dimension (default is `2`).
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* @return {Array<number>} Output array of coordinate values.
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*/
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export function toEPSG4326(input, output, dimension) {
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const length = input.length;
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dimension = dimension > 1 ? dimension : 2;
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if (output === undefined) {
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if (dimension > 2) {
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// preserve values beyond second dimension
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output = input.slice();
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} else {
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output = new Array(length);
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}
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}
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for (let i = 0; i < length; i += dimension) {
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output[i] = (180 * input[i]) / HALF_SIZE;
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output[i + 1] =
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(360 * Math.atan(Math.exp(input[i + 1] / RADIUS))) / Math.PI - 90;
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}
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return output;
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}
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