How to ensure accuracy of RTK system?

Hello everyone,

For professional work I have to ensure the accuracy of the RTK system.

In the new version of ReachView, I see different values ​​below the values ​​of latitude, longitude and altitude of the rover.

How is this data calculated?
How can I retrieve this RTK data in my own application?

Thank you very much.

Commonly in the GNSS world, the word accuracy is used in place of the word precision. For example, commonly on device data sheets values such as 0.02m 2DRMS are reported as “accuracy”. This is actually a precision measurement.

Novatel a nice summary PDF that I refer back to frequently. It explains the difference between accuracy and precision and how to calculate it.

I believe the numbers under the Latitude and Longitude in ReachView are standard deviations of Lats and Longs separately for a certain number of points in history. RTKPLOT, a component of the underlying software does the same. This is not the same as a 2DRMS value, but is sort of similar as STD of lats and longs are used to calculate 2DRMS values.

To measure accuracy, you need to know the true coordinate, which you don’t know. And if you did you, would not need the GNSS device. In any case a good way to express the accuracy of a data sample would be the distance between the average point in the sample and the true location.

I believe we use precision measurements to discuss device accuracy because;

  1. we often can’t measure accuracy since we don’t know the true point.
  2. A device which does a good job mitigating enough errors in the system to produce highly precise data can be predicted to also produce highly accurate data.

Be careful of number 2 above, this prediction does not always true. I sometimes encounters occasions where a device shows centimeter level precision producing a very tight cluster of samples, but that cluster is 1-2 meters away from the actual location.

I don’t know how you would pipe the STD values for Lat and Long from ReachView to you own app. The NMEA standard has a GST sentence which contains precision data, but I don’t think ReachView/RTKLIB produces that sentence. If it did external apps could pick it up and show the errors to the user or save it as metadata to the collected point.

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