"Differential Data Lost" - raymarine RC425

[cmedsailor]

Does anybody know what this alarm message means on a Raymarine RC425? Is it the internal battery probably? Time to replace it?
Thanks

 

[lw395]

I would imagine it thinks it should be working as a differential GPS, but is getting no data.
Some sort of factory reset required?

 

[Strolls]

The manual explains how the differential GPS system works and how to disable it.

http://www.busse-yachtshop.de/pdf/raychart425.pdf

Not sure where you're located, but it looks like the the differential GPS might work only in some areas.