what is the reference point of the BlueBoat (0,0,0 in the ardupilot parameters) ?
Is there an external point to reference to ?
I’m in the process of integrating a GNSS with RTK & a singlebeam (not the ping), and I need to know the reference point so i can change the GPS position in the parameters.
Hi @Morgoth, welcome to the forum 
The autopilot’s local positioning is based off an origin that gets set as part of initialisation, once per boot cycle. If you have a GNSS integrated then that origin gets set as the current location either when it first establishes a position lock, or when the vehicle is first armed.
When it gets set, the origin gets reported via the GPS_GLOBAL_ORIGIN MAVLink message, which you can also request manually.
I’m not sure what you mean by this. There are some ORIGIN parameters, but they’re not used if a GPS system is connected.
Hi @Morgoth -
I think you’re referring to offsets for the position of the GPS, IMU, and sonar relative to each other? These are already contained within the default BlueBoat parameters. You can find them in the Autopilot Parameters editor under INS_POS, GPS_POS, etc.
The “origin” of the vehicle is the very center of it, in x,y, and z - a point between the hulls. The INS Offsets give the position of the Navigator, and the GPS offset the gps receiver above it. You’d need to determine the offset of a mounted sonar yourself, the 3D cad model of the BlueBoat on the product page can help with this!