@signalk/nmea0183-signalk/hooks/GLL.js

A node.js/javascript parser for NMEA0183 sentences. Sentences are parsed to Signal K format.

'use strict'

/**
 * Copyright 2016 Signal K and Fabian Tollenaar <fabian@signalk.org>.
 *
 * Licensed under the Apache License, Version 2.0 (the 'License');
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an 'AS IS' BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

const debug = require('debug')('signalk-parser-nmea0183/GLL')
const utils = require('@signalk/nmea0183-utilities')
const moment = require('moment-timezone')

/*
=== GLL - Geographic Position - Latitude/Longitude ===
------------------------------------------------------------------------------
        0       1 2        3 4         5 6
        |       | |        | |         | |
 $--GLL,llll.ll,a,yyyyy.yy,a,hhmmss.ss,a,m,*hh<CR><LF>
------------------------------------------------------------------------------
Field Number:
0. Latitude
1. N or S (North or South)
2. Longitude
3. E or W (East or West)
4. Universal Time Coordinated (UTC)
5. Status A - Data Valid, V - Data Invalid
6. FAA mode indicator (NMEA 2.3 and later)
*/

function isEmpty(mixed) {
  return (
    (typeof mixed !== 'string' && typeof mixed !== 'number') ||
    (typeof mixed === 'string' && mixed.trim() === '')
  )
}

module.exports = function (input) {
  const { id, sentence, parts, tags } = input

  let valid = parts.reduce((v, part) => {
    v = !isEmpty(part)
    return v
  }, true)

  if (typeof parts[5] === 'string' && parts[5].toLowerCase() === 'v') {
    valid = false
  }

  if (!valid) {
    return null
  }

  const time = parts[4].indexOf('.') === -1 ? parts[4] : parts[4].split('.')[0]
  const timestamp = utils.timestamp(time, moment.tz('UTC').format('DDMMYY'))

  const delta = {
    updates: [
      {
        source: tags.source,
        timestamp: timestamp,
        values: [
          {
            path: 'navigation.position',
            value: {
              longitude: utils.coordinate(parts[2], parts[3]),
              latitude: utils.coordinate(parts[0], parts[1]),
            },
          },
        ],
      },
    ],
  }

  return delta
}