MARPA on the Raymarine E Series setup requires a heading sensor. The fluxgate is that sensor. If you are using the X series autopilot
, the heading is stabilized by a laser gyro (inside the autopilot, not the fluxgate). I believe this also to be the case on the S3G systems. The more stable the heading source, the more accurate it can be. The narrower the radar
However, the results you will get from MARPA require that you understand some of its limitations. When we used to plot targets on the radar screen
with grease pencils, we used to put a cross over the target every three minutes. After six minutes we would draw a line joining the crosses and figure out if we were far enough at CPA. MARPA on this system tries to give you the answer much quicker. It takes into account every time the radar beam hits the target and the rate of change. This time is just simply too short, at least in the beginning, so you have to wait quite a bit to get a fairly decent vector. Feeding it anything else, like course, would be using incorrect information. I'm not sure you could anyway.
I hope I'm not preaching to the converted here....sorry if I do.