I was pleasantly surprised to see Figure 8 calibration for the compass included in the menus for the 830, thinking that Garmin had finally included a fully functioning magnetic compass chip at least as good as the ones used in my old Magellan 505 Cyclo and most modern smartphones.
However after some calibration and testing, the compass doesn't seem to work as a true magnetic compass even though it does seem to respond when turning the device at rest. Map rotation is patchy and unreliable unless you have a bit of speed.
Since there are no specs on the compass chip (if any) used in the 830, is it safe to assume that there isn't a magnetic compass included and that the compass functionality relies on GPS triangulation during movement only? DC Rainmaker suggests the 830 only has a GPS compass. The Figure 8 calibration suggests something (hopefully) more.