On Tue, Oct 23, 2012 at 01:30:51PM -0700, Hal Murray wrote: > > [email protected] said: > > Are there GPS receivers that allow for the correction of position due to > > antenna length? > > There are two types of GPS receivers: navigation and timing. > > If you are not moving and know your location, you can compute the time from > only one satellite and/or get a better solution with more satellites. It > takes different firmware. > > The timing receivers usually have a survey mode to determine the position. > It averages over a large number of good position samples.
My understanding is that with a long cable between the antenna and the gps receiver, you will see all satelites with a fixed delay. And you would need to know the length of the cable and dielectric constant to compensate for both the position and time error. A typical speed of the signal over a coax is 200 000 km/s (2/3*c), or a delay of about 5 ns per meter. I wouldn't worry about that for ntp. You'll have bigger errors because of things like interupt delay. Kurt _______________________________________________ pool mailing list [email protected] http://lists.ntp.org/listinfo/pool
