parse-coords/index.js

Parse string coordinates

const utm = require('utm')
const RegexBuilder = require('./RegexBuilder')

const parsers = [
  {
    regex: new RegexBuilder()
      .plusMinus().decimalNumber()
      .comma()
      .plusMinus().decimalNumber()
      .build(),
    parser: fromDecimalDegrees
  },
  {
    regex: new RegexBuilder()
      .plusMinus().integer().degreeOption().decimalNumber().minuteOption()
      .comma()
      .plusMinus().integer().degreeOption().decimalNumber().minuteOption()
      .build(),
    parser: fromDecimalMinutes
  },
  {
    regex: new RegexBuilder()
      .integer().degreeOption().integer().minuteOption().decimalNumber().secondOption().whiteSpace().with('[NS]')
      .whiteSpace()
      .integer().degreeOption().integer().minuteOption().decimalNumber().secondOption().whiteSpace().with('[EW]')
      .build(),
    parser: fromMinutesSeconds
  },
  {
    regex: new RegexBuilder()
      .integer(2).with('[C-X]')
      .whiteSpace()
      .decimalNumber()
      .whiteSpace()
      .decimalNumber()
      .build(),
    parser: fromUtm
  }
]

module.exports = function (input) {
  let { parser } = parsers.find(({ regex }) => input.match(regex)) || { parser: () => undefined }
  return parser(input)
}

function fromDecimalDegrees (input) {
  let coordinates = input.replace(',', ' ').replace(/\s+/g, ' ').split(' ')
  return {
    lat: parseFloat(coordinates[0]),
    lng: parseFloat(coordinates[1])
  }
}

function fromDecimalMinutes (input) {
  let coordinates = input.replace(',', ' ').replace(/°/g, ' ').replace(/\s+/g, ' ').split(' ')
  let lat = [coordinates[0], coordinates[1]]
  let lng = [coordinates[2], coordinates[3]]

  function getSign (input) {
    return parseFloat(input) > 0 ? 1 : -1
  }

  return {
    lat: parseFloat(lat[0]) + getSign(lat[0]) * parseFloat(lat[1]) / 60,
    lng: parseFloat(lng[0]) + getSign(lng[0]) * parseFloat(lng[1]) / 60
  }
}

function fromMinutesSeconds (input) {
  // remove spaces before NSEW
  let coordinates = input.replace(/\s(\D)/g, '$1').split(' ')
  let lat = coordinates[0].trim().match(/^(\d+)°(\d+)'(\d+(\.\d+))?"([NS])/)
  let lng = coordinates[1].trim().match(/^(\d+)°(\d+)'(\d+(\.\d+))?"([EW])/)

  let toDecimal = function (minutes, seconds) {
    let number = (parseFloat(minutes) * 60 + parseFloat(seconds)) / 3600
    // + to convert string to a number
    return +(number.toFixed(5))
  }

  let getSign = function (direction) {
    return direction === 'N' || direction === 'E' ? 1 : -1
  }

  return {
    lat: getSign(lat[5]) * (parseFloat(lat[1]) + toDecimal(lat[2], lat[3])),
    lng: getSign(lng[5]) * (parseFloat(lng[1]) + toDecimal(lng[2], lng[3]))
  }
}

function fromUtm (input) {
  let match = input.match(/^(\d{2})([C-X]) (\d+(\.\d+)?) (\d+(\.\d+)?)$/)
  let easting = parseFloat(match[3])
  let northing = parseFloat(match[5])
  let zoneNumber = parseInt(match[1])
  let zoneLetter = match[2]
  let coordinates = utm.toLatLon(easting, northing, zoneNumber, zoneLetter)
  return {
    lat: +(coordinates.latitude.toFixed(5)),
    lng: +(coordinates.longitude.toFixed(5))
  }
}