GPS accuracy

[swelef]

Hello,

We're working on an application that uses GPS and we're wondering about the meaning of the accuracy reported by a GPS module. I've collected some data from both the GPS and A-GPS modules on the Nokia 6210 Navigator and it seems that sometimes the reported position differs from the real position by much more than the HorizontalAccuracy(), say more than twice.

What is the actual meaning of TLocality::HorizontalAccuracy (and TLocality::VerticalAccuracy)?

Thanks,
Vladimir

[skumar_rao]

for accuracy calculation and meaning you can refer to http://www.romdas.com/technical/gps/gps-acc.htm

[swelef]

for accuracy calculation and meaning you can refer to http://www.romdas.com/technical/gps/gps-acc.htm

That article seems to be a bit old, it speaks of the SA as active while
http://en.wikipedia.org/wiki/Global_...e_availability
says it's been effectively turned of on 1 May 2004.

Nevertheless, it points out that the accuracy may express different measures of the likely error. Thus, my question holds. Is TLocation::HorizontalAccuracy() supposed to return the RMSE or 95th percentile or something else?

Regards,
Vladimir