gps precision/accuracy

[Jossep]

I have a question about the precision/accuracy of my GPS.
I use the adafruit ultimate gps breakout. Datasheet sais it has an 1.8m position accuracy.
gpsd-class uses some estimated errors.
For instance altitude estimated error seems usually to be about 15m.
I don't get it... What is now the accuracy? What is the difference between both?

[gordon77]

http://www.ordnancesurvey.co.uk/busines ... guide.html

Says...

Accuracies using a single GPS receiver

Positional accuracy with a single receiver, to civilian users approximately equals 5m to 10m, 95% of the time, and the height accuracy is generally 15m to 20m 95% of the time.

This site talks about 1m horizontally...http://www.gps.gov/systems/gps/performance/accuracy/

Take a look at page 22 of the PDF you can download for vertical and horizontal accuracies

[joan]

I have a question about the precision/accuracy of my GPS.
I use the adafruit ultimate gps breakout. Datasheet sais it has an 1.8m position accuracy.
gpsd-class uses some estimated errors.
For instance altitude estimated error seems usually to be about 15m.
I don't get it... What is now the accuracy? What is the difference between both?

I'm not sure. But I'll hazard a guess it's because the world is not a true sphere.