maplair/dist/esm/geo/projection/Projection.Mercator.js

JavaScript library for mobile-friendly interactive maps

import { Point } from "../../geometry/Point.js";
import { Bounds } from "../../geometry/Bounds.js";
import { LatLng } from "../LatLng.js";
const Mercator = {
	R: 6378137,
	R_MINOR: 6356752.314245179,
	bounds: new Bounds([-20037508.34279, -15496570.73972], [20037508.34279, 18764656.23138]),
	project(latlng) {
		latlng = new LatLng(latlng);
		const d = Math.PI / 180, r = this.R, tmp = this.R_MINOR / r, e = Math.sqrt(1 - tmp * tmp);
		let y = latlng.lat * d;
		const con = e * Math.sin(y);
		const ts = Math.tan(Math.PI / 4 - y / 2) / ((1 - con) / (1 + con)) ** (e / 2);
		y = -r * Math.log(Math.max(ts, 1e-10));
		return new Point(latlng.lng * d * r, y);
	},
	unproject(point) {
		point = new Point(point);
		const d = 180 / Math.PI, r = this.R, tmp = this.R_MINOR / r, e = Math.sqrt(1 - tmp * tmp), ts = Math.exp(-point.y / r);
		let phi = Math.PI / 2 - 2 * Math.atan(ts);
		for (let i = 0, dphi = .1, con; i < 15 && Math.abs(dphi) > 1e-7; i++) {
			con = e * Math.sin(phi);
			con = ((1 - con) / (1 + con)) ** (e / 2);
			dphi = Math.PI / 2 - 2 * Math.atan(ts * con) - phi;
			phi += dphi;
		}
		return new LatLng(phi * d, point.x * d / r);
	}
};
//#endregion
export { Mercator };

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