# RTK uncertainty - for important control marks

I’ve attached a PDF of an excel doc I use to calculate Survey, Relative and Positional uncertainty for key marks.

This is based on the work of Matt Higgins (https://www.researchgate.net/profile/Matt-Higgins-4).
His slides are included which show the formulas etc.

Briefly, each point is measured for a minimum of 3 minutes (180 epochs). Then 20 minutes or more is allowed to pass so that there is a significant change in the satellite constellation geometry. Then a second 3 minute measurement takes place. Ideally, from a second known base.

These uncertainties are stated at the 95% confidence interval. The minimum we use for control points.
There is a little formula at the bottom that can be used to reduce the uncertainty if additional measurements to the mark are taken.

The Survey uncertainty is the uncertainty of the mark purely based off the survey itself and the receiver error etc.

The Relative uncertainty is the uncertainty between two marks (based on each of their survey uncertainties.

The Positional uncertainty is the absolute positional uncertainty, based of the positional uncertainty of the known mark (provided on a spec sheet of the publicly available mark…sometimes) and the survey uncertainty of the mark you just measured.

RTK Survey Uncertainty.pdf (2.0 MB)

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This is a great procedure to verify a point. Emlid should implement this or something like it. Realtime analysis of each epoch or a group of measurements. If solution exceeds 3cm or whatever accuracy the user has set, then dump that measurement and mean the rest for a solution. Obviously, this measurement should be at least 180 epochs. 3-5 minutes on station in a high multi-path area. Such a procedure would give the user some kind of faith on the “fixed” solution. Myself would have several solutions to verify the point. Also, RTK reset needs to be available to the user.

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@James

Happy too. However I couldn’t upload it into the forum. Did you want to message me your email?

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Not sure, but if you .zip it, maybe it will upload?

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See attached RTK Survey Uncertainty.xlsx.zip (2.0 MB)

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