[time-nuts] LTE Lite time error

Bill Beam wbeam at gci.net
Mon Jan 26 20:29:39 EST 2015


Be careful with 'eyeball data'.  GPS receiver does not generate NMEA time data and the leading edge of PPS at the same time.
Programs like Tac32 (totally accurate clock) and Lady Heather increment the time display at the leading edge of PPS with a
value 1 second greater than the previous NMEA data time.

I am able to run multiple GPS receivers into multiple computers running Tac32.  The LTE-lite displays one second earlier than
all the others.

Prior to the announcement of "Leap Second Pending" in the GPS data stream the LTE-lite agreed with all other units.  Now it does not.

On Mon, 26 Jan 2015 22:59:36 +0100, Mike Cook wrote:

>Yes there is certainly an error here:
>With my timing module I was just eyeballing the output on a windows platform , comparing GUI data.
>I have just linked the module up to a BeagleBone Black syncG€™d with NTP and this is the NMEA msg log:

>root at bb3:/home/mike/serial-ports# while read GGA; do echo `date` $GGA; done < /dev/ttyO4
>Mon Jan 26 21:51:07 UTC 2015 $GPGGA,215106.000,4847.3526,N,00216.3005,E,1,04,2.8,192.8,M,47.0,M,,0000*5C
>Mon Jan 26 21:51:07 UTC 2015 $GPGLL,4847.3526,N,00216.3005,E,215106.000,A,A*56
>Mon Jan 26 21:51:07 UTC 2015 $GPGSA,A,3,25,12,06,31,,,,,,,,,3.0,2.8,1.0*3A
>Mon Jan 26 21:51:07 UTC 2015 $GPRMC,215106.000,A,4847.3526,N,00216.3005,E,000.0,173.5,260115,,,A*60
>Mon Jan 26 21:51:07 UTC 2015 $GPVTG,173.5,T,,M,000.0,N,000.0,K,A*0D
>Mon Jan 26 21:51:07 UTC 2015 $GPZDA,215106.000,26,01,2015,00,00*54
>Mon Jan 26 21:51:07 UTC 2015 $PSTI,00,2,0,4.6,,*30

snip

>The time data is all a second late so they appear to have a serious issue.

>> Le 26 janv. 2015 +  02:47, Bill Beam <wbeam at gci.net> a +ªcrit :

snip

>> Odd indeed.  My LTE-lite is one second late, appears to have already added the pending leap second.
>> I can compare with four other GPS timeing receivers using time pulse on DCD line.  The NMEA data
>> reports in error.

snip



Bill Beam
NL7F





More information about the time-nuts mailing list