225 lines
9.5 KiB
JavaScript
225 lines
9.5 KiB
JavaScript
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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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/* Geodesy representation conversion functions (c) Chris Veness 2002-2017 */
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/* MIT Licence */
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/* www.movable-type.co.uk/scripts/latlong.html */
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/* www.movable-type.co.uk/scripts/geodesy/docs/module-dms.html */
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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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'use strict';
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/* eslint no-irregular-whitespace: [2, { skipComments: true }] */
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/**
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* Latitude/longitude points may be represented as decimal degrees, or subdivided into sexagesimal
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* minutes and seconds.
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*
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* @module dms
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*/
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/**
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* Functions for parsing and representing degrees / minutes / seconds.
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* @class Dms
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*/
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var Dms = {};
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// note Unicode Degree = U+00B0. Prime = U+2032, Double prime = U+2033
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/**
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* Parses string representing degrees/minutes/seconds into numeric degrees.
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*
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* This is very flexible on formats, allowing signed decimal degrees, or deg-min-sec optionally
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* suffixed by compass direction (NSEW). A variety of separators are accepted (eg 3° 37′ 09″W).
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* Seconds and minutes may be omitted.
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*
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* @param {string|number} dmsStr - Degrees or deg/min/sec in variety of formats.
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* @returns {number} Degrees as decimal number.
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*
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* @example
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* var lat = Dms.parseDMS('51° 28′ 40.12″ N');
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* var lon = Dms.parseDMS('000° 00′ 05.31″ W');
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* var p1 = new LatLon(lat, lon); // 51.4778°N, 000.0015°W
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*/
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Dms.parseDMS = function(dmsStr) {
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// check for signed decimal degrees without NSEW, if so return it directly
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if (typeof dmsStr == 'number' && isFinite(dmsStr)) return Number(dmsStr);
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// strip off any sign or compass dir'n & split out separate d/m/s
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var dms = String(dmsStr).trim().replace(/^-/, '').replace(/[NSEW]$/i, '').split(/[^0-9.,]+/);
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if (dms[dms.length-1]=='') dms.splice(dms.length-1); // from trailing symbol
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if (dms == '') return NaN;
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// and convert to decimal degrees...
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var deg;
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switch (dms.length) {
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case 3: // interpret 3-part result as d/m/s
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deg = dms[0]/1 + dms[1]/60 + dms[2]/3600;
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break;
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case 2: // interpret 2-part result as d/m
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deg = dms[0]/1 + dms[1]/60;
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break;
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case 1: // just d (possibly decimal) or non-separated dddmmss
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deg = dms[0];
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// check for fixed-width unseparated format eg 0033709W
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//if (/[NS]/i.test(dmsStr)) deg = '0' + deg; // - normalise N/S to 3-digit degrees
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//if (/[0-9]{7}/.test(deg)) deg = deg.slice(0,3)/1 + deg.slice(3,5)/60 + deg.slice(5)/3600;
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break;
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default:
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return NaN;
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}
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if (/^-|[WS]$/i.test(dmsStr.trim())) deg = -deg; // take '-', west and south as -ve
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return Number(deg);
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};
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/**
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* Separator character to be used to separate degrees, minutes, seconds, and cardinal directions.
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*
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* Set to '\u202f' (narrow no-break space) for improved formatting.
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*
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* @example
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* var p = new LatLon(51.2, 0.33); // 51°12′00.0″N, 000°19′48.0″E
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* Dms.separator = '\u202f'; // narrow no-break space
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* var pʹ = new LatLon(51.2, 0.33); // 51° 12′ 00.0″ N, 000° 19′ 48.0″ E
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*/
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Dms.separator = '';
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/**
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* Converts decimal degrees to deg/min/sec format
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* - degree, prime, double-prime symbols are added, but sign is discarded, though no compass
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* direction is added.
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*
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* @private
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* @param {number} deg - Degrees to be formatted as specified.
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* @param {string} [format=dms] - Return value as 'd', 'dm', 'dms' for deg, deg+min, deg+min+sec.
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* @param {number} [dp=0|2|4] - Number of decimal places to use – default 0 for dms, 2 for dm, 4 for d.
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* @returns {string} Degrees formatted as deg/min/secs according to specified format.
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*/
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Dms.toDMS = function(deg, format, dp) {
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if (isNaN(deg)) return null; // give up here if we can't make a number from deg
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// default values
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if (format === undefined) format = 'dms';
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if (dp === undefined) {
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switch (format) {
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case 'd': case 'deg': dp = 4; break;
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case 'dm': case 'deg+min': dp = 2; break;
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case 'dms': case 'deg+min+sec': dp = 0; break;
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default: format = 'dms'; dp = 0; // be forgiving on invalid format
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}
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}
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deg = Math.abs(deg); // (unsigned result ready for appending compass dir'n)
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var dms, d, m, s;
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switch (format) {
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default: // invalid format spec!
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case 'd': case 'deg':
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d = deg.toFixed(dp); // round/right-pad degrees
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if (d<100) d = '0' + d; // left-pad with leading zeros (note may include decimals)
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if (d<10) d = '0' + d;
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dms = d + '°';
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break;
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case 'dm': case 'deg+min':
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d = Math.floor(deg); // get component deg
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m = ((deg*60) % 60).toFixed(dp); // get component min & round/right-pad
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if (m == 60) { m = 0; d++; } // check for rounding up
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d = ('000'+d).slice(-3); // left-pad with leading zeros
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if (m<10) m = '0' + m; // left-pad with leading zeros (note may include decimals)
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dms = d + '°'+Dms.separator + m + '′';
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break;
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case 'dms': case 'deg+min+sec':
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d = Math.floor(deg); // get component deg
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m = Math.floor((deg*3600)/60) % 60; // get component min
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s = (deg*3600 % 60).toFixed(dp); // get component sec & round/right-pad
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if (s == 60) { s = (0).toFixed(dp); m++; } // check for rounding up
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if (m == 60) { m = 0; d++; } // check for rounding up
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d = ('000'+d).slice(-3); // left-pad with leading zeros
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m = ('00'+m).slice(-2); // left-pad with leading zeros
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if (s<10) s = '0' + s; // left-pad with leading zeros (note may include decimals)
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dms = d + '°'+Dms.separator + m + '′'+Dms.separator + s + '″';
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break;
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}
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return dms;
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};
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/**
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* Converts numeric degrees to deg/min/sec latitude (2-digit degrees, suffixed with N/S).
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*
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* @param {number} deg - Degrees to be formatted as specified.
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* @param {string} [format=dms] - Return value as 'd', 'dm', 'dms' for deg, deg+min, deg+min+sec.
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* @param {number} [dp=0|2|4] - Number of decimal places to use – default 0 for dms, 2 for dm, 4 for d.
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* @returns {string} Degrees formatted as deg/min/secs according to specified format.
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*/
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Dms.toLat = function(deg, format, dp) {
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var lat = Dms.toDMS(deg, format, dp);
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return lat===null ? '–' : lat.slice(1)+Dms.separator + (deg<0 ? 'S' : 'N'); // knock off initial '0' for lat!
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};
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/**
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* Convert numeric degrees to deg/min/sec longitude (3-digit degrees, suffixed with E/W)
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*
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* @param {number} deg - Degrees to be formatted as specified.
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* @param {string} [format=dms] - Return value as 'd', 'dm', 'dms' for deg, deg+min, deg+min+sec.
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* @param {number} [dp=0|2|4] - Number of decimal places to use – default 0 for dms, 2 for dm, 4 for d.
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* @returns {string} Degrees formatted as deg/min/secs according to specified format.
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*/
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Dms.toLon = function(deg, format, dp) {
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var lon = Dms.toDMS(deg, format, dp);
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return lon===null ? '–' : lon+Dms.separator + (deg<0 ? 'W' : 'E');
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};
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/**
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* Converts numeric degrees to deg/min/sec as a bearing (0°..360°)
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*
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* @param {number} deg - Degrees to be formatted as specified.
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* @param {string} [format=dms] - Return value as 'd', 'dm', 'dms' for deg, deg+min, deg+min+sec.
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* @param {number} [dp=0|2|4] - Number of decimal places to use – default 0 for dms, 2 for dm, 4 for d.
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* @returns {string} Degrees formatted as deg/min/secs according to specified format.
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*/
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Dms.toBrng = function(deg, format, dp) {
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deg = (Number(deg)+360) % 360; // normalise -ve values to 180°..360°
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var brng = Dms.toDMS(deg, format, dp);
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return brng===null ? '–' : brng.replace('360', '0'); // just in case rounding took us up to 360°!
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};
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/**
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* Returns compass point (to given precision) for supplied bearing.
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*
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* @param {number} bearing - Bearing in degrees from north.
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* @param {number} [precision=3] - Precision (1:cardinal / 2:intercardinal / 3:secondary-intercardinal).
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* @returns {string} Compass point for supplied bearing.
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*
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* @example
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* var point = Dms.compassPoint(24); // point = 'NNE'
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* var point = Dms.compassPoint(24, 1); // point = 'N'
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*/
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Dms.compassPoint = function(bearing, precision) {
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if (precision === undefined) precision = 3;
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// note precision could be extended to 4 for quarter-winds (eg NbNW), but I think they are little used
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bearing = ((bearing%360)+360)%360; // normalise to range 0..360°
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var cardinals = [
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'N', 'NNE', 'NE', 'ENE',
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'E', 'ESE', 'SE', 'SSE',
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'S', 'SSW', 'SW', 'WSW',
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'W', 'WNW', 'NW', 'NNW' ];
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var n = 4 * Math.pow(2, precision-1); // no of compass points at req’d precision (1=>4, 2=>8, 3=>16)
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var cardinal = cardinals[Math.round(bearing*n/360)%n * 16/n];
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return cardinal;
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};
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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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if (typeof module != 'undefined' && module.exports) module.exports = Dms; // ≡ export default Dms
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