Thread: Accuracy figure of horizontal position fix on GPSMAP 66 satellite screen?

Good find, yes in this case they are clearly quoting 3m at 95%.

And it does appears to be in reference to the dual frequency units as per your original question when taken in context with this statement where they grade dual frequency at +/-3m and older units at +/-5m: [Only registered and activated users can see links. ]

Bear in mind they have all the data every time, whatever they quote is simply where they decide calculate the circle in the plots.

It could be a shift to standardizing on 95% going forward with the improved products. They can’t continue to claim smaller circles due to the other errors now becoming relatively significant, but increased confidence percentages similar to professional gear is good marketing.

Edit:
Taking this a step further it may be that the published/marketing accuracy is 3.0m at 95%, and this in turn could be confirming the device itself is reporting 50%.

With all else being equal, a lower confidence level would normally accompany a smaller circle.

And the reviewer here reports the 66sr as having “a GPS accuracy that is almost always 1.8 m in the ideal case”, and that observation is supported by a number of screen shots.
[Only registered and activated users can see links. ]

I’ve just had a quick look at a data point post processed 0.3m at 95%, and at 68% the circle now becomes 0.2m. My software doesn’t have an option of 50% but you can see it would be slightly smaller again so the order of magnitude is in the ball park.