Solved: MQTT help needed for json

Configuration
,
1

I’ve been trying for hours now to get the GPS coordinates from Mosquitto into HA.

It’s broadcasted, and I can see the following in the MQTT explorer:

{
  "Base": {
    "time": 1764073526,
    "local_time": "25/11/2025 13:25:26",
    "time_iso_8601": "2025-11-25T13:25:26+0100",
    "fw": "RUTX_R_00.07.18.3\n",
    "name": "AllInOne",
    "id": "28"
  },
  "GPS": {
    "latitude": xxx,
    "longitude": xxx,
    "altitude": xxx,
    "angle": 0,
    "speed": 0,
    "accuracy": 0.7,
    "satellites": 10,
    "fix_status": 0,
    "timestamp": 1764077126,
    "date": "25/11/2025 14:25:26",
    "date_iso_8601": "2025-11-25T14:25:36+0100"
...

I try to get the latitude value with value_template: '{{ value_json.latitude }}'
but the sensor is shown as “unknown”. It doesn’t cause any error messages.

From the same MQTT broker, I successfully receive the data of opendtu to HA, which has HA_autodiscovery enabled. This is not available with the device I want to add now. It’s a Teltonika RUTX09.

As said, I receive messages with MQTT Explorer on a PC in the same network as my HAOS server.

Can anyone help me with the syntax to extract the JSON value correctly?

2

I figured it out by trial and error, my working solution:

value_template: '{{ value_json.GPS.latitude }}'