M4 iPad Pro GPS vs external

GNSS/GPS signals are principally line-of-sight - and for best performance need a clear view of the sky to provide good geometry to at least four satellites for an accurate position fix (at a technical level, obstructions will result in poor performance due to increased DOP - Dilution of Precision).

When used in automotive and aviation applications, the iPad might not be best positioned within the cabin to best receive the GNSS signals from visible satellites.

As such, using an external GNSS Receiver allows the receiver to be placed in a more optimal location (such as the dashboard - with a clearer view of the sky) than would otherwise be the case for the iPad that will likely be positioned for optimum viewing of its screen.

You should note the the iPad will need to be kept shaded from direct sunlight for two principal reasons:

1) to see the screen

2) to prevent overheating

There are various third-party GPS receivers available, of which two are BadElf and Garmin GLO. The GNS 3000 might also be of particular interest - as this GPS receiver provides both a Bluetooth connection to your iPad and can maintain an independent tracklog.

You are very welcome. I hope the information provided proves to be helpful to you.