2022-09-20, 11:40 AM
Hello to all.
I have a problem with non-linear calibration of the the pypilot compass I have recently fitted to our sailing cat.
The setup I have used is OpenCPN, Pypilot plugin and Pypilot run as a service on a Raspberry Pi 4 using an Adafruit ICM-20948 imu. Data is NMEA 0183 from Seatalk instruments via a multiplexer, no SignalK or Openplotter.
Basically the problem is, if the boat is turned 90 degrees, the reading for the heading change is not the same. I have calibrated the compass, twice, with the report that the second time was the same as the first. Accelerometers have been marked as level but I have not been able to get data to calibrate them, a cat on the flat water we have had of late doesn't move too much.
I set the compass offset on our dock which is roughly 90 deg mag with the result I get a heading of 33 on a course that is 03 and 135 on a 180 degree course. Readings appear repeatable. The imu is not in an ideal position relative to moveable magnetic influence but nothing was moved during these tests. Magnetic deviation here is about 8 deg east, location is Australia east coast GMT+10 time zone.
I am at a loss as to where to look for a solution. Obviously the imu could be suspect but I am getting a repeatable reading. The ICM-20948 is detected as such in the RTIMU.ini file. Any ideas?
And thanks to Sean and the others who have contributed to the programming and development of Pypilot, and OpenCPN as well.
Regards, John
I have a problem with non-linear calibration of the the pypilot compass I have recently fitted to our sailing cat.
The setup I have used is OpenCPN, Pypilot plugin and Pypilot run as a service on a Raspberry Pi 4 using an Adafruit ICM-20948 imu. Data is NMEA 0183 from Seatalk instruments via a multiplexer, no SignalK or Openplotter.
Basically the problem is, if the boat is turned 90 degrees, the reading for the heading change is not the same. I have calibrated the compass, twice, with the report that the second time was the same as the first. Accelerometers have been marked as level but I have not been able to get data to calibrate them, a cat on the flat water we have had of late doesn't move too much.
I set the compass offset on our dock which is roughly 90 deg mag with the result I get a heading of 33 on a course that is 03 and 135 on a 180 degree course. Readings appear repeatable. The imu is not in an ideal position relative to moveable magnetic influence but nothing was moved during these tests. Magnetic deviation here is about 8 deg east, location is Australia east coast GMT+10 time zone.
I am at a loss as to where to look for a solution. Obviously the imu could be suspect but I am getting a repeatable reading. The ICM-20948 is detected as such in the RTIMU.ini file. Any ideas?
And thanks to Sean and the others who have contributed to the programming and development of Pypilot, and OpenCPN as well.
Regards, John