Compass indicator from GPS(d) data?

Configuration
2

From here:

https://www.movable-type.co.uk/scripts/latlong.html

Formula: θ = atan2( sin Δλ ⋅ cos φ2 , cos φ1 ⋅ sin φ2 − sin φ1 ⋅ cos φ2 ⋅ cos Δλ )

You don’t say how you get the lat and long into your system. I’m going to assume you have a sensor.gpsd with a timestamp as the state, and lat/long as attributes.

Then we set up a trigger-based template sensor updated whenever that gpsd sensor changes (the from: null ensures it triggers only when the state changes):

template:
  - trigger:
      - trigger: state
        entity_id: sensor.gpsd
        from: null

    sensor:
      - name: Bearing
        unit_of_measurement: '°'
        state: >
          {% set lat1 = trigger.from_state.attributes.latitude * pi / 180 %}
          {% set long1 = trigger.from_state.attributes.longitude * pi / 180 %}
          {% set lat2 = trigger.to_state.attributes.latitude * pi / 180 %}
          {% set long2 = trigger.to_state.attributes.longitude * pi / 180 %}
          {% set y = sin(long2-long1) * cos(lat2) %}
          {% set x = cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(long2-long1) %}
          {% set r = atan2(y, x) %}
          {{ (r * 180 / pi + 360) % 360 }}

That gives the initial bearing between the two points, although if you’re updating with any reasonable frequency, that’s a distinction that doesn’t matter.

1 Like