89 lines
3.9 KiB
JavaScript
Executable File
89 lines
3.9 KiB
JavaScript
Executable File
"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
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// https://en.wikipedia.org/wiki/Rhumb_line
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var helpers_1 = require("@turf/helpers");
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var invariant_1 = require("@turf/invariant");
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/**
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* Returns the destination {@link Point} having travelled the given distance along a Rhumb line from the
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* origin Point with the (varant) given bearing.
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*
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* @name rhumbDestination
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* @param {Coord} origin starting point
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* @param {number} distance distance from the starting point
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* @param {number} bearing varant bearing angle ranging from -180 to 180 degrees from north
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* @param {Object} [options={}] Optional parameters
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* @param {string} [options.units='kilometers'] can be degrees, radians, miles, or kilometers
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* @param {Object} [options.properties={}] translate properties to destination point
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* @returns {Feature<Point>} Destination point.
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* @example
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* var pt = turf.point([-75.343, 39.984], {"marker-color": "F00"});
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* var distance = 50;
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* var bearing = 90;
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* var options = {units: 'miles'};
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*
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* var destination = turf.rhumbDestination(pt, distance, bearing, options);
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*
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* //addToMap
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* var addToMap = [pt, destination]
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* destination.properties['marker-color'] = '#00F';
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*/
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function rhumbDestination(origin, distance, bearing, options) {
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if (options === void 0) { options = {}; }
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var wasNegativeDistance = distance < 0;
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var distanceInMeters = helpers_1.convertLength(Math.abs(distance), options.units, "meters");
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if (wasNegativeDistance)
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distanceInMeters = -Math.abs(distanceInMeters);
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var coords = invariant_1.getCoord(origin);
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var destination = calculateRhumbDestination(coords, distanceInMeters, bearing);
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// compensate the crossing of the 180th meridian (https://macwright.org/2016/09/26/the-180th-meridian.html)
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// solution from https://github.com/mapbox/mapbox-gl-js/issues/3250#issuecomment-294887678
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destination[0] +=
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destination[0] - coords[0] > 180
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? -360
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: coords[0] - destination[0] > 180
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? 360
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: 0;
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return helpers_1.point(destination, options.properties);
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}
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/**
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* Returns the destination point having travelled along a rhumb line from origin point the given
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* distance on the given bearing.
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* Adapted from Geodesy: http://www.movable-type.co.uk/scripts/latlong.html#rhumblines
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*
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* @private
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* @param {Array<number>} origin - point
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* @param {number} distance - Distance travelled, in same units as earth radius (default: metres).
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* @param {number} bearing - Bearing in degrees from north.
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* @param {number} [radius=6371e3] - (Mean) radius of earth (defaults to radius in metres).
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* @returns {Array<number>} Destination point.
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*/
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function calculateRhumbDestination(origin, distance, bearing, radius) {
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// φ => phi
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// λ => lambda
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// ψ => psi
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// Δ => Delta
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// δ => delta
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// θ => theta
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radius = radius === undefined ? helpers_1.earthRadius : Number(radius);
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var delta = distance / radius; // angular distance in radians
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var lambda1 = (origin[0] * Math.PI) / 180; // to radians, but without normalize to 𝜋
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var phi1 = helpers_1.degreesToRadians(origin[1]);
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var theta = helpers_1.degreesToRadians(bearing);
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var DeltaPhi = delta * Math.cos(theta);
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var phi2 = phi1 + DeltaPhi;
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// check for some daft bugger going past the pole, normalise latitude if so
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if (Math.abs(phi2) > Math.PI / 2) {
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phi2 = phi2 > 0 ? Math.PI - phi2 : -Math.PI - phi2;
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}
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var DeltaPsi = Math.log(Math.tan(phi2 / 2 + Math.PI / 4) / Math.tan(phi1 / 2 + Math.PI / 4));
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// E-W course becomes ill-conditioned with 0/0
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var q = Math.abs(DeltaPsi) > 10e-12 ? DeltaPhi / DeltaPsi : Math.cos(phi1);
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var DeltaLambda = (delta * Math.sin(theta)) / q;
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var lambda2 = lambda1 + DeltaLambda;
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return [
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(((lambda2 * 180) / Math.PI + 540) % 360) - 180,
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(phi2 * 180) / Math.PI,
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]; // normalise to −180..+180°
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}
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exports.default = rhumbDestination;
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