I have completed construction of a Radio-Controlled Navy warship: USS Crockett (PG-88). Propulsion, rudder, radar antenna, and bilge pumps have passed bench tests and are ready for sea trials. Operation of these systems are under the control of a RadioMaster TX16S that transmits operational signals to a RadioMaster ER8 8-Channel ELRS PWM Receiver. By design, the purpose for the RadioMaster TX16S/ER8 is to control the speed and direction of the ship based on the same human actions that occur on the bridge of a Naval combatant. Simulating the Conning officer, a human will provide verbal commands for ship’s speed and direction. That is, I have no intention of installing an autopilot. I now have acquired components to install independent ships compass that will simulate the gyrocompass ships use for an accurate heading. Ships also have GPS, but GPS cannot determine the ship’s instantaneous orientation like the gyro, only its movement over the earth. So, I understand the USS Crockett must be in motion to obtain a ship’s heading and in the best case the accuracy will not be precisely due north, but that is OK. The architecture of the system I envision is as follows:
Holybro mini M9N (GPS + Compass)
Flight controller: Pixhawk 6C Mini
Power Supply sensor: PM06
Battery: Ovonic 11.1V LiPo power supply (sensor processor only)
MAVLink datatelemetry: SiK Telemetry Radio V3 100mW 433MH 915MHz
For simplicity, the sole purpose of thePixhawk 6C is to process data from the M9N mini for transmission from the ship to the laptop. The telemetry system is as follows: OEM Drone Accessories Fit For Holybro Fit For SIK Telemetry Radio V3 100mW 433MH 915MHz Open-Source SIK firmware -n-Play Fit For Pixhawk Standard Flight Controllers Replaceable (Color : 915MHz) Drone. So, to summarize, I am building a navigation instrument repeater. To complete this system, I am reaching out for those having experience with software. My research indicates that software I actually need includes:
(1) software compatible with Windows 11 to receive MAVLink telemetry,
(2) software to extract heading (yaw), and
(3) software to display a rotating compass card that is similar to a ship’s gyro repeater.
The research also indicate that programs “Python + pymavlink + a simple display library.” I am not a computer programmer, but willing to learn what I need. Are the softwares described suitable for this purpose and are the accompanying guidance sufficient for me to construct what I need?
For example “Mission Planner” is able to read MAVLink and shows the extracted heading in a more aircraft like HUD and also as values or Compass Instrument
Thank you for validating my approach. While I use Chat GPT, I typically reach out to human experts as a sanity check. I will now push forward with your suggestions 2 through 4 over the next month. Thanks again. Joe
FYI - Us who have built autonomous mowers use two GPS units: One for position and one for heading, moving or standstill. MP and Ardurover easily handle this configuration. Setup and details in the rover docs.
Beautiful build! Please keep us posted. Good luck!
An interesting point to consider. The constraint I face is both weight and space. It may be a two-phase approach. First phase - use the M9N-mini to obtain heading with options for course over ground and GPS status and evaluate if an upgrade is needed. Because of proximity to magnetic fields, I need to be mindful that there needs to be some distance between motors, ESCs and servos below the waterline. But for sure, something to keep in mind for a second phase. Thanks for the idea.
If you get it all set up with rover on the ship and mission planner on your laptop, you can then forward NMEA 0183 messages from the laptop to other software or even a real boat compass display (if it takes a serial input). Here is a screenshot of me playing back a log from my boat n3m0 on MP (left) and forwarding it to the OpenCPN chartplotter software (right). OpenCPN had 3 different compass display sources so I placed them all on top of the map. On the mission planner window you can see a little window with the settings I used to forward NMEA (from the advanced tab explained here), and I used similar settings on OpenCPN to get the chartplotter going.
Update for interested members of the group. With the support of ChatGPT, construction of a compass repeater is complete. Make no mistake, AI guided me through the process and the image shown is somewhat close to what I used at sea on a Naval combatant. During bench testing indoors, it struck me that change of direction reported on the compass repeater was close to the same change in direction observed with a ship’s gyrocompass. The next step is to perform bench trials to compare a Holybro M9N compass with a Holybro M9N mini when positioned inside of the replica ship. The tricky part is to locate the compass as far from magnetic fields as possible while installing as many components as possible below the waterline. My objective is to have the compass +/- 2 to 5 degrees.
