[time-nuts] Building a GPSDO & trouble using Jupiter-T

Tom Van Baak tvb at LeapSecond.com
Wed Feb 1 09:29:32 UTC 2012


Most of the high-end GPS receivers offer faster rates than 1 Hz.
This is required for RTK work, for example. It is not interpolation.

It is hard and accurate and wonderful and expensive. Remember
there is a lot of information in the phase and doppler of both the
code and the carrier (both L1 and L2), not to mention combined
data from both GPS and GLONASS so the update rate is limited
more by market forces and cpu power.

It is not hard to find receivers that output new calculated positions
every 5 or 10 or even 20 or 50 Hz, for a price. Google for words
like: GPS RTK L1 L2 update rate

See for example the receivers at javad.com (100 Hz solutions).


----- Original Message ----- 
From: "Chris Albertson" <albertson.chris at gmail.com>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Tuesday, January 31, 2012 4:29 PM
Subject: Re: [time-nuts] Building a GPSDO & trouble using Jupiter-T

> On Mon, Jan 30, 2012 at 6:17 PM, Didier Juges <shalimr9 at gmail.com> wrote:
>> You have to spend good money to get a GPS receiver capable of calculating
>> it's time and/or position more than once per second. I am not aware of that
>> being done for timing applications, but it is available for navigation GPS
>> receivers, such as those used to track race cars (for a race car, one
>> second is an eternity). I have seen navigation receivers capable of 10
>> fixes/second, I am sure there are better ones yet. They cost a lot of money.
> I'm pretty sure those GPS recievers that send out more frequent data,
> at say 2Hz or 5Hz are just interpolating.  It is not more accurate.
> The GPS sats only send a frame once over 6 seconds.
> They send at higher rate so that the system using the GPS does not
> need to know how to dead reckon and can have decent results for simply
> using last reported position
> Chris Albertson
> Redondo Beach, California

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