There was a discussion about this at
viewtopic.php?f=5&t=3615&start=0.
There are three settings for chart orientation: North up, Heading up, or Course up.
From the Garmin manual regarding heading information source:
The source for the display of the heading line on the chartplotter is determined by the heading line source setting (
Auto or
GPS Hdg) and whether heading information is available from a heading sensor. (Autopilot CCU in our case).
If heading information is available from a heading sensor and the source heading is set to
Auto, both the heading line and the vehicle icon will be aligned to the heading from the sensor.
If heading information is available from a heading sensor and the source heading is set to
GPS Hdg, the heading line will be aligned to the GPS heading, but the vehicle icon will be aligned to the heading from the sensor.
If heading information is not available from a heading sensor, both the heading line and the vehicle icon will be aligned to the GPS heading.
To access these settings, while displaying the navigation chart, select Menu, Chart Appearance. Next select Orientation or Heading Line, Source.
Howard