[time-nuts] high (spacial) precision GPS in Kickstarter

[Magnus Danielson]

On 25/01/14 11:42, Anders Wallin wrote:
> AFAIK 'normal' RTK does not provide a clock solution. There's something
> called 4D RTK which does:
> http://saegnss1.curtin.edu.au/Publications/2010/Feng2010Four.pdf
> apparently the results can be very good - but I think the errors quoted are
> for time-transfer between two RTK receivers (?).
>
> If there are papers comparing time-transfer with dual-frequency PPP to this
> 4D RTK I'd be interested..

I think you need to differentiate between common-view time-transfer and 
the precision you get from the system itself.

RTK uses the carrier phase corrections achieved from known position to 
kind of high-speed delta signals as received in it's neighbourhood. This 
affects both the position and time shifts of the receiver. If the RTK 
base also has a good timebase and is maintained in a good way time-wise, 
then both position and time gets good corrections.

It's about the same type of errors as you get in the difference between 
common-view time-transfer comparisons.

If you only do L1 C/A RTK, then naturally you will benefit from the RTK 
as you have no double frequency observations of your own. If you have 
double-frequency receiver, RTK assist to work on the tropospheric 
corrections and sat orbit and time errors for which a pure double 
frequency receiver isn't able to crack on it's own.

Cheers,
Magnus