[time-nuts] Re: GPSDO/GNSSDO project: STM32G4 + u-blox ZED-F9T + TDC7200

[John Ackermann N8UR]

I hesitate to post this because I haven't had time to go back and 
refresh thoroughly, but I'm not sure how you would apply RTK corrections 
to the F9T.

I believe that the "T" models can output RTCM data so can serve as an 
RTK base station, but only the "P" models have the built-engine to 
receive corrections via UART or USB and do RTK internally.  So without 
that, I don't see how you can get corrected time directly from the module.

(I'm assuming that SBAS doesn't count as "RTK" for this purpose.  I've 
never experimented with what that would do to the timing output.)

John
----
On 8/6/22 03:41, Carsten Andrich via time-nuts wrote:
> On 06.08.22 00:50, Hal Murray wrote:
>> All of the timing receivers that I'm familiar with assume a fixed 
>> location.
>>
>> Are you sure the F9T will work while moving?
>> If so, does it maintain the same accuracy?
> 
> The F9T datasheet [1] specifies the "operational limits" as ≤ 4 g 
> dynamics, 80 km altitude, and 500 m/s velocity. The time pulse accuracy 
> (5 ns absolute, 2.5 ns differential) is specified only for "fixed 
> position mode", so it may degrade when used on the move.
> 
> The F9P RTK positioning accuracy does not degrade substantially for 
> non-stationary use, as far as I can tell without a 20k€ INS groundtruth. 
> I hope the same applies to the F9T's timing performance. Verifying that 
> is one of the reasons behind building the prototype.
> 
> [1] 
> https://content.u-blox.com/sites/default/files/ZED-F9T-00B_DataSheet_UBX-18053713.pdf#page=4 
> 
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