GPS Precision without correction

Q&A forumCategory: QuestionsGPS Precision without correction
kirk asked 10 months ago
I’m new to this, thanks for your patience.
It’s my understanding that correction affects accuracy, but not necessarily precision. If that’s correct, how fast does precision drift over time. For example, I want to create a topo map of a small field (15 acres), absolute values aren’t necessary, I only care about the relative topography. Is there a time window in which I can expect uncorrect gps readings to have precision in the sub 3cm range? If so, is that window measured in minutes, hours, days? I have the simpleRTK2B – Basic Starter Kit.
replied 10 months ago

They are not corrections, that’s not how it works. It’s more of a geometry problem, where you’re holding tape measures, as long as you don’t drop them the ambiguity resolution persists.
The solution will remain reasonably good provided you don’t lose lock on the signals.
The receiver has a 120 seconds (2 minutes) timeout for RTCM3 data, its configurable.
Don’t enable SBAS, you will get abrupt discontinuities down to several metres.
The receiver will decay into FLOAT, and 3D overtime, and you can determine the receivers confidence via the accuracy estimates. You can get back into signal range, and if you’ve got a smart radio system you can move to a low bandwidth strategy.
If you lose satellite signal lock, you’ll be at a few metres, and need to reacquire an RTK solution using data.
Sub 3cm probably overly optimistic. Sub 20cm likely in FLOAT
Open fields, with high mounted telemetry antenna (say 2m above tripod), I’d expect my LoRa radios to get several KM.
Kit ones I don’t know/care, the GNSS and telemetry antennas can be independent, you can put high gain ones on the Rover, it only has to receive.

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