[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [gpsd-users] Position accuracy of AIS data in gpsd json?

From: Gary E. Miller
Subject: Re: [gpsd-users] Position accuracy of AIS data in gpsd json?
Date: Thu, 9 Aug 2018 10:41:22 -0700

Yo Sven!

I'll admit to being unfamiliar with the AIS code, few use it.

On Thu, 9 Aug 2018 17:33:37 +0200
Sven Geggus <address@hidden> wrote:

> looking at the code, I see, that lat/lon positions are truncated
> after the fourth decimal place (%.4f) when running in scaled mode.

Where exactly are you looking?  In the JSON, or in one of the

> Looking at the spec, the accuracy of the messages should be 0.0001’
> which would be 0.0000017°

Citation?  Which spec?  I'm guessing that would be 0.617 feet at the
equator.  Only survey grade GPS and RTK GPS are that accurate.

> So whats the rationale behind this behaviour?

Someone probably coded it to the same accuracy as the AIS they had.

> Would'nt %.6f be a more correct joice?

That would exceed the accuracy of any AIS I ever heard of.  Maybe 
%.5f would be best.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

            Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin

Attachment: pgpqW6s5keOTs.pgp
Description: OpenPGP digital signature

reply via email to

[Prev in Thread] Current Thread [Next in Thread]