GPS nav is just the AP doing what it has to in order to stay on the current course being output from a GPS. In this case, the AP will overfly waypoints along the course because the GPS outputs course info from point to point. The AP will fly to the waypoint and then at the waypoint the GPS will switch to the next waypoint and then the AP will have to rejoin the course.
GPS steering is different in that the GPS outputs the roll and for some pitch commands as well to keep the AP on the desired course. The GPS anticipates the needed bank and or pitch in order to make smooth transitions along the route without overflying waypoints. Some can even fly Holding pattters, proceedure turns and DME arcs with near perfect precision.
The GPS steering is also needed for fully coupled GPS based precision approaches. GPS steering normally requires the ARINC 429 interfaces on the GPS and the AP. Typical handhelds do not have this interface. Lower end AP's also typically don't have this interface as well.
There is much more to it than this, but this is a high level overview of the difference.
I have been reading about your new AP.
What is the difference between GPS navigation and GPS Steering.
Thanks,
Joost
