Raymarine RL70C Owner's Handbook Manual page 153

Chapter 7: Setting Up the System Defaults 139
CAUTION
Changing the chart datum does not cause any waypoint or routes stored in
the chartplotter to move. Waypoints and routes may therefore appear to
be at different positions when you change the datum.
When adding waypoints numerically to the waypoint list, or via SeaTalk,
NMEA or HSB, it is important that they are referenced to the same datum
that the chart is to be operated in.