> None, not even ZDA put out current time. They all put out time in the > past. It takes a long time for any of the messages to be composed in > the > receiver, to be queued, to be sent at 300-9000 bits per second, and to > be interpreted. >
It is easy to change most GPS receivers to send NMEA messages at a faster rate than 300-9000 bps. A rate of 57,600 works better and is easily achievable. For SiRF receivers there are two ways: 1. Search for SiRFDemo.exe. It will control most SiRF GPS receivers. The interface is intuitive, but as I recall, click on "Action/Switch Message Rate." 2. While most GPS boards have similar, you can search for 'SiRF NMEA Reference Manual.' This manual lists all the input/output NMEA messages that SiRF supports. Then write a small program to output the messages you need. It is trivial if you have a copy of Visual Studio (Express); just copy NTPD's GPS initialization code, but send out your own messages. I have this manual; if you can't find it on the Internet, send me an email and I will send you a copy. Please stop ragging us about carriage returns in email messages. Charles Elliott > -----Original Message----- > From: questions-bounces+elliott.ch=verizon....@lists.ntp.org > [mailto:questions-bounces+elliott.ch=verizon....@lists.ntp.org] On > Behalf Of unruh > Sent: Monday, February 11, 2013 6:57 PM > To: questions@lists.ntp.org > Subject: Re: [ntp:questions] NTP NMEA driver > > On 2013-02-11, Rob <nom...@example.com> wrote: > > unruh <un...@invalid.ca> wrote: > >> Please put carriage returns into your posts. These run on sentences > can > >> be very hard to read. > > > > Please get a decent newsreader instead of picking on posting format. > > I thought the OP was trying to communicate with us, not doing us a > favour > by writing down his least burps to send out into the world. If the > former is true, then it is up to him to try to make it as easy on the > listener/reader , not expect them to go out of their way to > conform to his peculiarities. > > Again, Please put carriage returns into posts. > > > > >> Secondly, many messages provide time informations. Why do you pick > out > >> one of the bunch? And No other messages do not provide the time of a > >> position fix, they mark the time of the nearest second that has > already > >> occured. None of the NMEA sentences mark the time of PPS pulse > because > >> they all occur long long after that pulse ( on the microsecond > scale). > > > > You are obviously wrong here. The messages that provide position > data > > do not include the current time, they include the "time of fix". > > None, not even ZDA put out current time. They all put out time in the > past. It takes a long time for any of the messages to be composed in > the > receiver, to be queued, to be sent at 300-9000 bits per second, and to > be intrpreted. > > > You are at the mercy of the receiver outputting the message shortly > > after the calculation of the fix. The OP was right. > > You are always at the mercy of the receiver. > And it is not the fix time. ZDA puts out only to the nearest 10 ms. the > others to the nearest second or 10ths of a second. Fix > times are in the nanosecond realm. They put out times which are the > time > label of the latest second (or they should if they are not > incompetently > designed as the Garmin 18x was.) > > > _______________________________________________ > questions mailing list > questions@lists.ntp.org > http://lists.ntp.org/listinfo/questions _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
