[time-nuts] Relationship of relative stability between distantlocations using GPS and environmental factors

Tom Van Baak tvb at leapsecond.com
Fri Jun 30 11:13:01 EDT 2006


> Hi,
>
> A number of recent entries to this list have mentioned topics relating to
> GPS timing and environmental corrupting factors (e.g. Ionosphere, Temp.,
> Humidity, etc.). Personally, I am very interested in setting up a very
> precise relative time between locations (maybe 100s of meters to 10s of
> kilometres apart) on time scales of (maybe 100s of seconds to 10s of
> minutes). I noted some members referred to dual frequency receivers for
> overcoming these effects. Can anyone point me to some literature, articles
> or links to overcome these environmental factors?
>
> Regards,
>
> Stephan.

I'm guessing a dual-frequency receiver is not so
important in your case because your stations are
geographically close enough together that many
of the GPS systematic errors are common for the
two sites. And since you're only concerned with
relative time rather than absolute UTC this is all
to your great advantage.

First, please read this excellent paper:

Introduction to time and frequency metrology
http://www.tf.nist.gov/timefreq/general/pdf/1288.pdf

It sounds like GPS common view would work for
you. This has been used for a decade or two. In
fact most timing labs use this technique today.
So here's where to start with GPS time transfer:

http://www.tf.nist.gov/timefreq/time/gps.htm

Can you give us an idea of what level of accuracy
you need and over what time intervals? Something
like a few ns over a few hours or a day? What local
frequency standard do you plan to have at each
station?

Here are a few good GPS time transfer papers:

Time and Frequency Measurements using the Global Positioning System
http://www.tf.nist.gov/timefreq/general/pdf/1424.pdf

Time and Frequency Dissemination: Advances in GPS Transfer Techniques
http://www.tf.nist.gov/timefreq/general/pdf/1998.pdf

A Comparison of GPS Common-View Time Transfer to All-in-View
http://www.tf.nist.gov/timefreq/general/pdf/2091.pdf

Comparison of the One-Way and Common-View GPS Measurement
  Techniques using a Known Frequency Offset
http://www.tf.nist.gov/timefreq/general/pdf/1827.pdf

Time and frequency distribution using satellites
http://www.tf.nist.gov/timefreq/general/pdf/1602.pdf

/tvb






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