See the attached Quectel extensions (SDK) commands, the PQEPE can output the estimated position error (meters). Applies to Quectel L70, L80, L76, L76-L, L86 and L26 modules.
Also generally the HDOP (in the standard $GPGSA, $GPGGA and other messages) can also provide an estimate of the position error probability (accuracy).
The PQEPE is already an estimation of the precision in meters, we do not know the probability of it. It’s probably 95%. If you use PQEPE in combination with DOP, you’ll get a good impression of your positioning accuracy.
$PQEPE,5.3050,3.2000*53 //Output Horizontal and Vertical (The HACC value is .3050). HACC is in m
Horizontal: 5.3050 means 5 meter, 30 cm, 5 mm
You could filter the PQEPE results in your host. For example, you could set the horizontal limit to 10 m.
PQEPE versus HDOP VDOP
The DOP is a relative value, the EPE is in meters. The DOP values can be read from the NMEA GSA string. Example:
$GPGSA,<Mode>,<Fix status>,<PRN1>,<PRN2>,…<PRN12>,<PDOP>,<HDOP>,<VDOP>,<GNSS sys id>
|<1||Ideal||Highest possible confidence level, the highest possible precision at all times.|
|1-2||Excellent||Positional measurements are considered accurate enough to meet all but the most sensitive applications.|
|2-5||Good||Represents a level that marks the minimum appropriate for making business decisions. Positional measurements could be used to make reliable in-route navigation suggestions to the user.|
|5-10||Moderate||Positional measurements could be used for calculations, but the fix quality could still be improved. A more open view of the sky is recommended.|
|10-20||Fair||Represents a low confidence level. Positional measurements should be discarded or used only to indicate a very rough estimate of the current location.|
|>20||Poor||At this level, measurements are inaccurate by as much as 300 meters with a 6-meter accurate device (50 DOP × 6 meters) and should be discarded.|
Read about DOP: