I tried mine without the remote module and it was pretty much useless. After adding the module it was within about 5-7 degrees without calibratation. After calibration it is great. Interesting note; when I did the calibration the unit told me to add 8 degrees average cal factor. When I did this it seemed to be about 4 degrees off on every heading. I changed the factor to 4 degrees and it's been near perfect ever since.
Just my mileage. Your's may vary.
Mel