[CA] [CA11] Heading indications in nav system and autopilot

[rieraney]

I have an E80 and an st7000 on my boat. If I set my autopilot to, say, 180, it will actually show up on the E80 screen as steering maybe 150. I will have the green sight line that shows my actual COG (about 150 in this example) and then the boat symbol on the screen will be canted off to where I set the autopilot, 180 in this example. I thought it was currents at first, or maybe wind setting me, but Day in, day out sailing down the CA coast from SF to LA I had this same discrepancy. What’s going on? Is it possible my flux gate compass is a problem? Or does the autopilot need adjustment?

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum rieraney,

Please click here to view a FAQ addressing this subject. When configured to Head Up chart orientation, the Chart will be aligned to COG and the vessel icon will be aligned to Heading. These values may differ based upon the accuracy of the heading data source (in this case, accuracy of the GPS data source (produces COG), and the influences of leeway. As you have suggested, troubleshooting should begin with the GPS data source and the autopilot. When the GPS status data dialog is displayed by the MFD, the reported HDOP should be examined. Typically, this value will be less than or equal to 1.0. A higher number indicated reduced GPS accuracy, which will also adversely affect the COG accuracy. Regarding heading, MFD should be configured to display the Heading data item. This value value reported by the MFD should be compared to that specified on the autopilot's control head when the autopilot is in standby mode. Should any significant difference be noted, then this difference may be resulting from incorrect application of local variation by the MFD. However, if the reported values are the same, then it would be recommended that the autopilot's fluxgate compass be tested and replaced it fails the points of testing. Afterwards and whether or not the fluxgate compass has been replaced, the autopilot's compass should be re-calibrated for deviation (verify that the reported value is less than 10 degrees ... if not, then it may indicate a problem with the fluxgate or the presence of strong magnetic fields in the location of the fluxgate compass) an the compass should be realigned. While not specified, the heading accuracy of these legacy autopilot would not have been much better than +/- 5 degrees.

[rieraney]

Fabulous, just what I was looking for.

[Chuck - Raymarine - Moderator]

You're welcome.