Any GPS experts on the forum? I've been mulling over a few questions.
In Australia, AUSPOS provides accurate post processed GPS positions, it only processes observations from GPS satellites.
AUSPOS allows processing up to 7 full days of RINEX data.
Australia is one of the worlds fastest moving continents, moving approx. 7cm NE each year, 0.19mm / day or 1.35mm per week.
I have seen people process 24 hour data intervals over long periods and after converting to GDA2020 coordinates, average the result, which makes a lot of sense.
You have to wait a couple of weeks before processing, if you want the most accurate results.
The reality is, at this level of accuracy, the Australian plate is moving quickly, everything is changing, the ground might also be subsiding, uplifting, you get the picture, it's just a snapshot in time.
https://www.icsm.gov.au/publications/gda2020-technical-manual-v17
Now my antenna's don't have ground planes, usually it takes my antenna's about 7 days to produce the same level of confidence result as a geodetic antenna fitted with a ground plane can in 24 hours.
This does have me thinking about the improvements that modern Geodetic antenna's based on the choke ring design, however it's my understanding that choke ring antenna's may not capture as signals from satellites over the horizon so well.
To quote AUSPOS:
Question 3.1 - How does AUSPOS work?
All computations are undertaken using the Bernese Software System. Bernese is a high precision orbit and geodetic parameter determination software system. For more information see Bernese GNS Software.
The International GPS Service (IGS) product range is used in the computation process. Precise orbit parameters, Earth orientation parameters and coordinate solution IGS products are used.
NOTE: The IGS final orbit product is not available until approximately two weeks after the observation day. The rapid orbit product is available two days after observation. If both the final and rapid orbit products are unavailable, then the IGS ultra-rapid orbit product will be used.
Once a user has submitted a RINEX file, the nearest 15 IGS and APREF stations are used as the reference stations for the processing. That data is retrieved from Geoscience Australia's GNSS Data Archive. A precise solution using a 'double difference' technique is then computed using these stations. The coordinates of the IGS stations are constrained with uncertainties of 1mm for horizontal and 2mm for the vertical.
From AUSPOS reports:
