Despite a major rewrite of sensor fusion code to add many diagnostics, there were still issues during what was supposed to be our final installation trip to the site. As a result we added a simple magnetometer diagnostic check which appears on the visual display at start-up.

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Simple magnetometer diagnostic.

This allowed us to trace the problems to a magnetometer fault in one of the test units, and this was replaced. It was decided to make this diagnostic a permanent feature of the startup procedure to avoid issues like this happening again.