These errors probably don't make difference for typical boat navigation. Although, it is interesting to think about them as far as precision landing approach aids for aircraft.
The good thing is that the FAA is quite the stickler about making sure the probability of these types of errors affect the safe operation of a aircraft is very low.
I have heard that a two frequency version will be made available for commercial purposes just because the FAA is so concerned. (Currently, two frequency GPS is restricted to military use.)