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

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

/**
 * Copyright 2019 Signal K and Fabian Tollenaar <fabian@decipher.industries>.
 *
 * 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/BWC')
const utils = require('@signalk/nmea0183-utilities')

/**
 * $GPBWC,225444,4917.24,N,12309.57,W,051.9,T,031.6,M,001.3,N,004*29
 *
 * Bearing and distance to waypoint - great circle
 *
 * 0)     225444        UTC time of fix 22:54:44
 * 1,2)   4917.24,N     Latitude of waypoint
 * 3,4)   12309.57,W    Longitude of waypoint
 * 5,6)   051.9,T       Bearing to waypoint, degrees true
 * 7,8)   031.6,M       Bearing to waypoint, degrees magnetic
 * 9,10)  001.3,N       Distance to waypoint, Nautical miles
 * 11)    004           Waypoint ID
 **/

module.exports = function BWCHook(input) {
  const { id, sentence, parts, tags } = input
  const upper = (str) => str.trim().toUpperCase()

  debug(`[BWCHook] decoding sentence ${id} => ${sentence}`)

  const values = []
  const result = {
    updates: [
      {
        source: tags.source,
        values,
      },
    ],
  }

  if (parts[0] !== '') {
    result.updates[0].timestamp = utils.timestamp(parts[0])
  }

  if (
    parts[1] !== '' &&
    parts[2] !== '' &&
    parts[3] !== '' &&
    parts[4] !== ''
  ) {
    const latitude = utils.coordinate(parts[1], parts[2])
    const longitude = utils.coordinate(parts[3], parts[4])
    values.push({
      path: 'navigation.courseGreatCircle.nextPoint.position',
      value: {
        longitude,
        latitude,
      },
    })
  } else {
    values.push({
      path: 'navigation.courseGreatCircle.nextPoint.position',
      value: null,
    })
  }

  if (parts[9] !== '' && parts[10] !== '') {
    const distance = utils.transform(
      parts[9],
      upper(parts[10]) === 'N' ? 'nm' : 'km',
      'm'
    )
    values.push({
      path: 'navigation.courseGreatCircle.nextPoint.distance',
      value: distance,
    })
  }

  if (parts[6] === 'T' && parts[5] !== '') {
    values.push({
      path: 'navigation.courseGreatCircle.bearingTrackTrue',
      value: utils.transform(parts[5], 'deg', 'rad'),
    })
  }
  if (parts[8] === 'M' && parts[7] !== '') {
    values.push({
      path: 'navigation.courseGreatCircle.bearingTrackMagnetic',
      value: utils.transform(parts[7], 'deg', 'rad'),
    })
  }

  return values.length > 0 ? result : undefined
}