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

[Gary E. Miller]

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
clients?

> 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.

RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
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