OpenCPN course over ground unsteady

[ColinTapp]

I'm using OpenCPN on a powered catamaran cruising about 10 knots running on a raspberry PI 4. I use a Richie fluxgate compass and the OpenCPN dashboard magnetic compass heading display looks steady. I take GPS from a module that uses an MT3333 chip and seems to give very good accuracy i.e. within the length of the boat. The connection between OpenCPN and the GPS is via gpsd. All looks good on the display when following a route except that at times the course over ground seems to change and at some points the image of my boat can be pointing backwards. All other parts of the display are good including the 'road' as part of the active route console window. I run in the 'course up' mode and the display is steady apart from the COG moving around. Its annoying but doesn't affect navigation. Any suggestions gratefully received. Thanks Colin

[rgleason]

Colin, It might help a lot if you provide a recorded VDR_pi file of the conditions you are experiencing along with a screenshot of your track.

Also you need to provide much greater detail about your navigation system, where the data is coming from and what you have set under Opencpn Communications.

[ColinTapp]

I will try and get a screenshot and voyage record tomorrow. GPS is from an addafruit ultimate GPS HAT directly connected to the raspberry pi 4. The interface between opencpn and the GPS is via GPSD. Compass is a Richie fluxgate compass connected via a RS232 level translator to UART 4 ( setting the correct dtoverlay ). Its an NMEA0183 data stream. This connects to OpenCPN via KPlex. Kplex takes a further input from my AIS transceiver. To simplify things I can turn off the AIS and this has no effect on the issue. I hope to have some more info tomorrow.