The GNGST sample in the screenshot above shows: dev-lat=0.330m dev-long=0.217m and dev-alt=0.558m
The position/horizontal accuracy (XY) is calculated by very simple mathematics.
It's the square root of the square sum of the deviation latitude error and deviation longitude error.
In this example: Accuracy.XY = sqrt(0.330^2 + 0.217^2) ~ 0,39m
If your external GNSS antenna doesn't send the GST string the GNSS-Commander app can't display the accuracy!
But on almost all external antennas (U-Blox, Prolific, etc.) the GST-string can be activated by device configuration.
If the internal GPS is selected as current data source we never receive the GST string.
There is no GST string send by the internal GPS, so the accuracy is requested right by the Google Location API.
see method https://developer.android.com/reference ... etAccuracy for further information
Google Developers API:
There is no vertical accuracy (Z) provided by the Location API.We define horizontal accuracy as the radius of 68% confidence. In other words, if you draw a circle centered at this location's latitude and longitude, and with a radius equal to the accuracy, then there is a 68% probability that the true location is inside the circle.
A pretty good estimated value for the vertical accuracy is 1.5 times the value of horizontal accuracy. (that's displayed by GNSS-Commander)