Look at the circles and reference from GPS Receiver to the Transducer...when you return to the waypoint from different direction the transducer can be anywhere on the outer ring of the circle and the GPS Location the same...farther apart the harder to return to the exact same spot if coming in from different direction. Comapre the Yellow Transom Circle to the Blue Circle...which do you prefer? This is why I recommend and prefer external receiver to reduce adding offset to waypoints and making it easier to return to the same spot.
My Transon Location for Console Unit
IF you mark a waypoint with the Console it will mark the data from the transom transducer and transom receiver. If you mark the waypoint from the bow it will mark the data from the trolling motor transducer and the bow mounted GPS Receiver. When returning depending on which unit you are using the location is the place you marked the waypoint. So trying to get back on a waypoint that was marked at the transom with trolling motor will be much easier and more accurate.
Tip: Bow Unit I do not see much added offset with External or Internal REceiver since the distance is not much greater.
FYI: With Networked units in the case of a GPS REceiver failure you can always switch to the other receiver in a couple button clicks and have GPS from the second receiver and get you back to navigating. Cheap Insurance in My Opinion.
Hope this helps.
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