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GeoscienceAustralia / ginan

The Australian Government, through Positioning Australia (part of Geoscience Australia), is funding the design, development and operational service of a Global Navigation Satellite System (GNSS) position correction system - the Ginan service and toolkit. The application of the Ginan correction service by a GNSS device has the potential to increase positioning accuracy from meters to centimetres across Australia. The suite of software systems in this repository (the Ginan toolkit) will be used to create the service. It is available now under an open source licence. Ginan will give individuals and organisations no-cost access to the Ginan software and service as a public good.
https://geoscienceaustralia.github.io/ginan/
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fit_sp3_pseudoobs #61

Closed mgrutten closed 6 months ago

mgrutten commented 9 months ago

Hi Team!

I'm using the release-v3.0-alpha branch, so I understand if it's a work in progress.

The reason I'm looking at that branch is the fit_sp3_pseudoobs.yaml example, which I think generates data very similar to what I'm after. I would like to take an existing (set of) sp3 files, fit orbits and precisely predict those orbits a day into the future.

I can run the example (using the docker image) and generate sp3 files, but I don't understand the output. The ephemeris that is generated (3 sp3 files) is over the same time-period as the input files and doesn't match the input at all? I've used the compare_orbits.yaml example to compare them and the distances are in the 1000s of km.

The only modification to the fit_sp3_pseudoobs.yaml file was to comment out the "mongo" section, as I'm not using the visualisation.

I'm sure it's a misunderstanding, since I'm very new to ginan. Could you please explain the output?

polytopes-design commented 9 months ago

Hello mgrutten. To address part of your query - to predict one day into the future the end_epoch configuration can be set to the end of the desired propagation. Use pea -Y 4 to see all yaml config parameters and their locations within the yaml file, but that parameter will be in the epoch_control section. You will likely also need to set require_obs to false, so that the prediction will progress despite the sp3 files having exhausted their data.

As for the bad fits - it appears that the fit_sp3_pseudoobs.yaml is set up to output_inertial values to the sp3, so the results are in a different reference frame - remove this config and the results will be in an ecef frame as per the input files.

Thanks for your feedback, our input helps us improve the software.

mgrutten commented 9 months ago

Hi @polytopes-design

Thanks for the very quick and very helpful reply! I've made both of the changes you suggested (epoch_control and output_inertial) and the output is exactly what I was hoping to see. Comparing the predictions against the FIN sp3 shows they align very closely (for my purposes).

It's very likely that I will have a few more questions. Is there a ginan forum, or is this the most appropriate place to ask?

Mark.