GPS time sync to iphone clock

[Krx2009]

I have been using HLTpro for a year or so, have to say you do a fantastic job Harry.
I am involved in car club events and looking for a super smart method of timing sequential, intermediates, finish , HLT has a lot of the tools to make my ideas work.
I have a technical question, can the internal gps time signal sync to the iphones clock for accurate synced timing between multiple iphones down to say ms level.
If not what about HLT with the external gps devices?

[Harry]

Hi, the relation between iPhone system time and GPS (UTC) is not documented. LapTimer stores whatever time stamps it receives as UTC time. In case of the internal sensor, it is timezone converted from whatever is delivered, for external and NMEA integrated external GPSes, this is the original GPS time stamp. So if you have recorded times using external GPSes, you will have comparable recordings already. Please note that the time displayed for the lap list is always local system time.

Harry

[Krx2009]

sorry Harry having trouble getting my head around your answer.
Does it mean default stopwatch time is internal, and we dont really know where it comes from.
If an external NMEA GPS, like the NMEA ones you list as suitable, is attached the time would be derived from that external GPS time standard?
You mention the laplist time is always system, does that mean that if you go into the laplist item the time may be different to that in the laplist menu when you have an external NMEA GPS attached?
(please don't interpret any of this as negative, I am very positive about your product)

Sorry for being a little thick.

[Harry]

There are two 'times' displayed in the lap list. The actual lap time is derived from NMEA UTC time stamps and highly accurate. The date / time pair in the lap list is local system time, not GPS.

Harry

[Krx2009]

THANKS Harry that is excellent.