The precision of actual GPS chip sets is better than 2.5m CEP(*) or better than 2m using SBAS - satellite
based differential corrections as WAAS in the US or EGNOS in Europe
. SBAS is standard in these chipsets, but has to be enabled by the system integrator.
Data for the u-blox LEA8 or the SIRF Star V 5e families of products.
(*) CEP= 90% of the time in a circle of that diameter.
we have normally near to ideal conditions for GPS reception
- clear sky, little or no obstruction, little multi path reception
. We can take this precisions as valid.
Implies that our measurement expressed with 3 digits of a minute (=1nm or 1852m) should oscillate by 1 at the least significant digit.
Reading "001E 57.345"
the real value will be something in between the range of .344
. Or .343
if we want to take precautions.
Not sufficient for automatic docking
(and has the dock
being surveyed correctly?) but pretty good for navigating