Best practices when sending GPS location data [HowTo]

Application Development
14

…or to decode using TTN’s payload functions, to get an additional human readable fields in the MQTT payload:

See below for an improved version to support negative decimal coordinates.

// Version 2 (production) needs a function name; see post below for a fix
function (bytes) {
  // Does NOT handle negative values; see post below for a fix
  var lat = (bytes[0] + (bytes[1] << 8) + (bytes[2] << 16)) / 10000;
  var lng = (bytes[3] + (bytes[4] << 8) + (bytes[5] << 16)) / 10000;
  return {
    location: {
      lat: lat,
      lng: lng
    },
    love: "TTN payload functions"
  };
}

…to return something like the following in the MQTT message:

{
  "app_id": "my-app-id",
  "dev_id": "my-node",
  "hardware_serial": "42CF4601045CE277",
  "port": 1,
  "counter": 19,
  "payload_raw": "ANX6nBIX",
  "payload_fields": {
    "location": {
      "lat": -33.8688,
      "lng": 151.2092
    },
    "love": "TTN payload functions"
  },
  "metadata": {
    "time": "2017-01-16T22:59:20.373495512Z",
    "frequency": 868.1,
    "modulation": "LORA",
    "data_rate": "SF8BW125",
    "coding_rate": "4/5",
    "gateways": [
      {
        "gtw_id": "eui-5ccf7ff42f1970ec",
        "timestamp": 494534657,
        "time": "2017-01-16T22:59:20.296723Z",
        "channel": 0,
        "rssi": -46,
        "snr": 11,
        "latitude": 52.373141,
        "longitude": 4.892435,
        "altitude": 3
      }
    ]
  }
}
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