[time-nuts] Ublox Neo-6M time error.
not.again at btinternet.com
Thu Jun 2 14:20:09 EDT 2016
I noticed that in 'Messages View' window in u-center, UBX-NAV-TIMEGPS
gives Time of week, but UBX-TIM-TP gives Time of next pulse, 1 second
later. The hex in the messages also differs by 1000ms.
Putting the correction data and the time of the next pulse together
like that would suggest that it is for the next pulse, but I've not
checked it with a counter.
On Thu, 2 Jun 2016 08:28:58 +0000, you wrote:
>The Ublox receivers do not have a message that outputs GPS time directly. It's easiest to take the UTC time message and subtract the leapsecond offset to get GPS time. The itow value in the NAV_TIMEGPS message is milliseconds past midnight of the start of the GPS week... probably not something you want to be doing calculations from. I use the TIMEUTC message. I only use the leapsecond offset from TIMEGPS.
>It looks like Ublox is sending the time message AFTER the 1PPS pulse ("at the beep, the time was...") , and just about everybody else sends it before the pulse ("at the beep, the time is ...") ... Bastards! I wonder about the thought (or lack of it) process that decided that was the way to do it. And don't get me started on the idiot receivers that send the sawtooth correction message after the fact...
>Despite re-checking I am still doubtful that my sums are right. Ill do a few more packets. Is this what you are seeing Mark?
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