With the new GPSMAP 65 and 66sr multi-GNSS, multiband receivers now available, many people are interested in what additional positional accuracy this technology actually brings.

I don’t know what statistical measure Garmin uses to determine the accuracy of the horizontal position fix as displayed on my 66st satellite screen and could not find the answer after lengthy googling, so I thought I would ask here.

The latest 2020 GPSMAP66st User Manual Appendix page 17 states: “Accuracy of GPS: The margin of error for your exact location. For example, your GPS location is accurate to within +/- 3.65 m (12 ft).

This statement is featured in most Garmin handheld device manuals. Does this mean that the number is the 50 % CEP (Circular Error Probable) as supported by this 2014 post on the GPSreview site:
[Only registered and activated users can see links. ] “The declaration of the accuracy by Garmin GPS receivers often leads to confusion. What does it mean if the receiver states an accuracy of 4 m? This readout refers to the so-called 50 % CEP (Circular Error Probable). This means that 50 % of all measurements are within a radius of 4 m. On the other hand, 50 % of all measured positions are outside of this radius. Furthermore, 95 % of all measured positions are within a circle of twice this radius (actually 2.08 times) and 98.9 % of all positions are within a circle of 2.55 the radius. In the given example, nearly all positions are within circle with a radius of 10 m. The determined position is in the worst case accurate to 10 m.”

Does anyone know if this is correct and Garmin are actually using the CEP statistic?