Hello Mariusz.

In the next link you have all information that you need:

https://www.novatel.com/assets/Documents/Bulletins/apn029.pdf

Best regards.

Dear Mr Emilio,

thank You very much for Your answer. Personally I also use the same position accuracy measures, which were published by NovaTel

Best regards.

In GNSS the accuracy measures are basic things :

1- the 2d/3d qualities, which are measures of the computions of position, but sometimes good 2d/3d qualities are obtained, while in reality the point is badly positioned.

2- the Dolution of Precision (DoP), ylthis is the geometric measure for the distribution of the satellites in the sky. good DoP values: in 3d Position PDoP

Concerning accuracy and precision, always I saw that that most of people make confusion. In the paper from Novatel, provided by Emilio Ramirez-Juidias also there is a misunderstanding. Accuracy, by definition is composed of bias and precision, ie, systematic and random errors. And always, if the precision is not good, the same will occur with accuracy. In the figure 1 provided in the paper, one of the example is not correct. The third one, where they say High accuracy, and low precision, should be Low accuracy as well. Like defined by Gauss, long time ago, one measure of accuracy may be given by sqrt(bias^2+precision^2). In a nutshell, the problem is to think that the bias is the accuracy.

GPS can provide very high precision (cm to mm) and if all systematic errors are very well modelled, can also provide high accuracy.

According to International Vocabulary of Metrology (https://www.bipm.org/en/publications/guides/vim.html), accuracy is a qualitative term(trueness + precision), which expresses the closeness of agreement between a measurement result and the value of the measurand. A quantitative estimate of the accuracy of a result is the measurement uncertainty (bias + e.g. standard deviation/repeatibility/reproducibility). If the bias are insignificant (close to zero), so the uncertainty is only composed of random effects.

The result of a measurement is said to be more accurate when it offers a smaller measurement error. From this definition, the term “accuracy” should be used just for general comparison (more accurate than). Furthermore, accurate is only an adjective used to indicate the quality of an unbiased and precise measurement result.

Dear Mariusz Specht,

I recommended to visit our project: https://www.researchgate.net/project/NEW-PROPOSALS-ON-GEODETIC-NETWORK-QUALITY-CONTROL-IN-A-CONTEXT-OF-MULTIPLE-OUTLIERS

Regards,

VFR.

This figure

images.jpeg

is the best one I saw to show the concept. Congratulation for sharing it.

Thank You very much for advanced answers. I have another question: what is the probability of occurrence of 2D and 3D position accuracy measures (expressed in %) and what does it depend on?

Dear Specht,

2D and 3D position accuracy are one of the most important factor of position analysis. 2D position accuracy are 2DRMS (Distance Root Means Square) and CEP (Circle of Error Probable) and 3D position accuracy are SEP (Spherical Error Probable) and MRSE (Mean Radial Spherical Error).

2DRMS (2-dimensional solution in Two horizontal plane) indicates the radius of a circle centering the average value, within which 95.8% – 98.2% of position solution points fit in.

CEP is the radius of circle centered at the true position, containing the position estimate with probability of 50%.

SEP represents the radius of a sphere centering the average value within which, 50% of all 3-dimensional positioning points (latitude, longitude and altitude) are confined.

MRSE represents the radius of a sphere centering the average value, the chance of all 3-dimensional positioning solutions to lie within this sphere is 61%.

For more information, Please read the attached article.

Hope the above information will help you.

With best regards,

Somnath Mahato

If I get stn, ste, stu through RTKLIB, how do I get 3DRMS?