iOS bug report - positional ambiguity

[Ellie McNeill]

Hi, I've recently installed the aprs.fi app on iOS and I've noticed a bug.

I have positional ambiguity enabled. When beaconing my position via APRS-IS, if I look at the raw packets it does indeed reduce the number of digits included in the position report.

However, the app does this by replacing the digits with zeros. But the APRS protocol reference says that it should use spaces for positional ambiguity (APRS101).

The problem with using zeros is that other stations will have no way of knowing whether the positional ambiguity feature is being used or if it's just that the location happens to be at that precise spot. It's false precision, or to put it another way: It's ambiguous whether or not the positional ambiguity feature is being used hi hi.

For example, if my latitude is reported as "5558.00N", that would interpreted that I'm at that precise latitude (to the nearest 1/100th minute). But say I'm using positional ambiguity with 2 digits reduction then it should actually be sent as "5558.  ". Notice that the zeroes are replaced with spaces. This way it is clear that the precision has been reduced (either through uncertainty or by user choice).

Anyway, I hope this report is useful. APRS is an interesting mode that I'm enjoying learning about.

73,

Ellie

GM5ELE