NavList:

The point is, I think, not how many decimal digits you get after the decimal point, but rather, what is the meaning of those digits after the decimal point.  When is the resolution empty or devoid of meaning?  

Example: One half second of arc is 1.3×10^(-4).  Determining that your particular version of calculator fails in the fifteenth or twentieth decimal digit isn't particularly relevant for calculations to the nearest "six seconds" of input.  If your calculation requires 1/2 arc second, perhaps you should rethink the equation.  Hence my 9°=9° remark.

Example: Giving your may day location to SAR in excess of 3 decimal digits.  Each arc second is ~100 feet.  0.001 degrees is roughly 365 feet.  SAR does not fly to the precise location and look down through an FOV limiting tube.  The purpose of your may day location is to "locate" you.  They use mark one eyeballs to "find" you when at or about location.  It does not matter if your EPIRB gives 15 decimal digits or 150, three is more than enough.