mode-s-decoder

A library to decode a binary Mode S message to an easy to use JavaScript object.

Mode S is an aviation transponder interrogation mode used by Secondary Surveillance Radar (SSR) and Automatic Dependent Surveillance-Broadcast (ADS-B) systems.

For an example of this module in use, see AirplaneJS.

Installation

npm install mode-s-decoder --save

Usage

const Decoder = require('mode-s-decoder')
const decoder = new Decoder()

const data = new Uint8Array([0x8f, 0x46, 0x1f, 0x36, 0x60, 0x4d, 0x74, 0x82, 0xe4, 0x4d, 0x97, 0xbc, 0xd6, 0x4e])
const message = decoder.parse(data)

console.log(message)

API

Decoder.UNIT_FEET

A constant indicating that the unit used is feet. Used to check the unit of the message using the message.unit property.

Decoder.UNIT_METERS

A constant indicating that the unit used is meters. Used to check the unit of the message using the message.unit property.

decoder = new Decoder([options])

Initialize a new decoder object.

Arguments:

• options - An optional options object

The available options are:

• fixErrors - Set to false to disable automatic error correction (default: true)
• aggressive - Set to true to enable aggressive error correction algorithm. Only used if fixErrors is true (default: false)

message = decoder.parse(data[, crcOnly])

Parse a binary Mode S message into an easy to use JavaScript object.

Arguments:

• data - A binary Mode S message (e.g. a Buffer or Uint8Array object)
• crcOnly - Optional boolean indicating if the decoder should only validate the checksum. If true, the returned message object will only contain the properties msg, msgtype, msgbits, crc, and crcOk (default: false)

Returns a message object containing the decoded message.

It's recommended to use this module together with the mode-s-aircraft-store module. This allows you easy access to the decoded latitude and longitude as this information cannot be read from a single Mode S message, but needs multiple concurrent messages in order to be properly decoded:

const message = decoder.parse(data)

// store is an instance of AircraftStore from the mode-s-aircraft-store module
store.addMessage(message)

// ...

// later after storing multiple messages, output list of aircrafts:
store.getAircrafts().forEach(function (aircraft) {
  const unit = aircraft.unit === Decoder.UNIT_FEET ? 'feet' : 'meters'
  console.log('Aircraft:\n' +
    `  ID: ${aircraft.icao}\n` +
    `  Altitude: ${aircraft.altitude} ${unit}\n` +
    `  Speed: ${aircraft.speed}\n` +
    `  Heading: ${aircraft.heading}\n` +
    `  Latitude: ${aircraft.lat}\n` +
    `  Longitude: ${aircraft.lng}\n`)
})

License

MIT