NavList:

That is an interesting question.  Can a general purpose GPS receiver determine latitude to within 0.3 arcseconds?

Surely, the decimal readout of your gps shows many significant digits.  The question becomes, how meaningful are they.  From the internet, we have: "Most consumer GPS accuracy devices are around 5-10m. To achieve the sub-meter level accuracy, you have to use the professional GNSS receivers that connect to ground based or satellite based augmentation systems".   That is relative to some arbitrary axis of rotation.

But note very carefully.  10 meters is 32 feet or just over 0.3 arc seconds.  That's a very interesting coincidence.  It does answer your question directly.  It just happens to be at the Chandler wobble level.  But is it just a coincidence?

I think we need Dr. Langley to weigh in on this question, because I do not know the answer.  Does GPS account for the Chandler Wobble?

Brad

PS.  You pay your money and you get your choice.  My prognostication is that the GPS system will account for it, as the satellite data upon which the broadcast is made is uploaded regularly.  Once the true wobble component is determined (by reference to radio telescope and pulsars?) then the satellite data can be modified to account for it.  But that is 100% WAG.