Hi @tony-white ,
regarding the altitude value, we had already discussed this in another thread:
https://discuss.bluerobotics.com/t/bin-logs-gps-raw-data-and-ekf3-outputs/22320
From the logs it seemed that AHR2.Alt follows the barometer, while GLOBAL_POSITION_INT.alt follows the GPS Z value.
If I understood correctly, does this mean that the EKF still uses the GPS altitude as the vertical reference?
I am currently running SonarView 1.14.39 and ArduPilot 4.6.3 (stable)
For the compass calibration I will try again as suggested. At the moment the payload cables are already routed under the batteries, away from the compass.
Regarding the misalignment between survey lines, you are correct: the effect increases with speed, although it is still visible even at lower speeds.
In that survey area the maximum depth was about 8.5 m, and the Surveyor ping rate was set to 20 Hz.
At the following link SwissTransfer - Send large files securely and free of charge you can find the original SonarView files . svlz and a CloudCompare .bin file, where I separated the point clouds by survey lines in the two navigation directions and generated the corresponding surface mesh
I also attchaed a cross-section where a structure on the seabed clearly shows the discrepancy:
(yellow and red represent the two opposite survey directions)
Thank you in advance for your help.