Re: [Flightgear-devel] Typical NAV system errors

[David M. <dav...@gm...>]

I think we already model VOR twist; at least, we were doing so 10+ years
ago.

D

On Thu, 5 Jan 2017 at 09:40 John Denker <js...@av...> wrote:

> On 01/05/2017 05:39 AM, Thorsten Renk wrote:
>
> > * for TACAN, I found as figures of merit quoted 0.5 deg in azimuth, 0.2 %
> > in range with a minimum of 0.1 miles range error
>
> In practice, it's quite a bit worse than that, for a number of
> reasons.
>
> For starters, there is VOR twist:
>     https://www.av8n.com/how/htm/xc.html#sec-VOR-twist
>
> You could model this quantitatively, on a VOR-by-VOR basis, by
> looking at the VOR alignment in the A/FD and comparing it to
> up-to-date information about the magnetic declination.
>
> Also ... the VOR /receiver/ is part of the "system" and it could
> be off by 4 degrees, or maybe even 6 degrees.
>
> http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/0/92b0831bac15c193852566cf0061999e!OpenDocument
>
>
> The transmitter might be good to 0.5 degrees under absolutely
> ideal conditions, e.g. sited in the middle of an infinitely
> large flat uniform field.  However, under other conditions --
> with messy geography, geology, and hydrology -- it's going to
> be worse.
>
> If things get too messy, they will build a humongous ground
> plane under the transmitter
>    https://www.flickr.com/photos/toms_3d/4946837712
> but usually they don't bother.
>
> Also, if the A/FD says the VOR is unusable beyond XX miles
> in certain sectors, you'd better believe it.
>
>
>
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
> _______________________________________________
> Flightgear-devel mailing list
> Fli...@li...
> https://lists.sourceforge.net/lists/listinfo/flightgear-devel
>