[time-nuts] Need advice for multilateration setup

Attila Kinali attila at kinali.ch
Fri Mar 27 07:38:07 EDT 2015

On Thu, 26 Mar 2015 12:32:33 -0500
Robert Watzlavick <rocket at watzlavick.com> wrote:

> Thanks for the suggestion. Does the DSSS make it easier to correlate
> between ground stations?  I'm not sure how to handle the phase offset
> on the 10 MHz ref clocks. 

The DSSS allows you to make the integer ambiguity, you have with all
periodic signals low enough that you dont care anymore. Ie. if you
have a PRN that repeates every millisecond, then your you will have
an ambiguity of n*300km, which you can easily resolve. The other advantage
is that you have multiple edges (not just one, when you have a single pulse)
over which you can average, thus getting a better precision.
The downside of this is, that you have not only to solve for position and time,
but for position, velocity and time (or rather frequency of the oscillator).

The idea with the reference station on ground, to sync up all
other stations is quite good. Then you can use simple DVB-T dongles
(google RTL-SDR) as receivers, which you get almost for free on ebay.
But you pay for that in higher calculation complexity. On the other
hand, adding another measurment station is just another PC + USB dongle.

I think that most of the receiver work can be done with gnu radio
as basis. But i have never done any DSSS system in GR, so i cannot
say for sure.


			Attila Kinali

It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson

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