66 lines
2.1 KiB
JavaScript
66 lines
2.1 KiB
JavaScript
const proj4 = require('proj4')
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const epsg = require('epsg')
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const isObject = require('lodash.isobject')
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const isNumber = require('lodash.isnumber')
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const epsgFromZone = (zone) => 'EPSG:'+(31464+zone) // zone 2 = 31466, zone 5 = 31469
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const toWGS = (coordinates) => {
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if(!isObject(coordinates) || !isNumber(coordinates.x) || !isNumber(coordinates.y)){
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throw new Error('missing or invalid parameter `coordinates`')
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}
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if(coordinates.x < 0 || coordinates.x >= Math.pow(10, 7)){
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throw new Error('`coordinates.x` out of bounds')
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}
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if(coordinates.y < 0 || coordinates.y >= Math.pow(10, 7)){
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throw new Error('`coordinates.y` out of bounds')
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}
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const zone = +(coordinates.x+'')[0]
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const projected = proj4.default(epsg[epsgFromZone(zone)], 'WGS84', Object.assign({}, coordinates))
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return ({
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longitude: projected.x,
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latitude: projected.y
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})
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}
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const toGK = (coordinates, zone) => {
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if(!isObject(coordinates) || !isNumber(coordinates.longitude) || !isNumber(coordinates.latitude)){
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throw new Error('missing or invalid parameter `coordinates`')
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}
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if(coordinates.longitude < -180 || coordinates.longitude > 180){
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throw new Error('`coordinates.longitude` out of bounds')
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}
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if(coordinates.latitude < -360 || coordinates.latitude > 360){
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throw new Error('`coordinates.latitude` out of bounds')
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}
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if(zone){
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if(!isNumber(zone)){
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throw new Error('`zone` parameter must be a number')
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}
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if(![2,3,4,5].includes(zone)){
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throw new Error('if set, `zone` parameter must be one of 2, 3, 4, 5')
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}
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}
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else{
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zone = Math.floor((+coordinates.longitude + 1.5) / 3)
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if(![2,3,4,5].includes(zone)){
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throw new Error('could not detect valid zone (2, 3, 4, 5) from input coordinates')
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}
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}
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const proj4coordinates = {
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x: coordinates.longitude,
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y: coordinates.latitude
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}
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const projected = proj4('WGS84', epsg[epsgFromZone(zone)], proj4coordinates)
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return ({
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x: projected.x,
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y: projected.y
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})
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}
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module.exports = {toWGS, toGK} |