Re: [Flightgear-devel] DAFIFT navids

[James Turner]

On Friday, February 21, 2003, at 02:27  pm, David Megginson wrote:

1. For VORs, we're interested in the slaved magnetic variation; you
   can always ignore the actual one, since we calculate that inside
   FlightGear anyway.

Already done

2. Entries for TACANs have only a channel, not a paired VHF
   frequency.  By trial and error, I've figured out how to get the VHF
   (I think):

<snipped scary conversion>

Err, I'm not sure this is correct. the VORTACs have an explicit frequency as well as a channel, and a straight TACAN isn't receivable using a VHF NAV radio, is it?

3. Entries for civilian DMEs also have only a channel.  You can use
   the same formula as you used for TACANs, but you have to add
   0.05MHz to every one (I don't know why, but that is the pattern I
   found on the charts).

I'm again not clear about this, I assumed these were 'DME only' military installations.

4. You have to split the NDB/DME entries into two to make them usable
   for FlightGear.  The DME channel will be provided, so handle it as
   above to get a paired VHF frequency (tuning the NDB will never
   automatically tune a DME).

I haven't done this, but right now I don't believe the radiostack logic works this way. I think it
simply looks for the 'isDME' flags on FGnav.

5. Non-U.S. VORs don't have a range provided, but they do have the
   usage code -- you can kludge a range from that (I used 200 nm for
   'H' or 'B', 20 nm for 'T', and 50 nm for anything else).

I was going to do this, but various people indicated these values were bogus and we'd be better using the 'practical approximation' you and Norman discussed a few weeks back.

I don't need any arm-twisting to dump Metakit -- these are tiny
databases for modern computers (that 20-second porn video clip your
roommate/son/neighbout just watched probably needed several times as
much memory as all our nav/arpt data put together).

Yes, please.  I'd also be interested in ILS.

Supporting new types is trivial. I would greatly prefer to switch the airport data over too, simply for consistency in the data set. Can anyone establish what (if anything we would lose by doing so?)

H&H
James


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