From: Pascal Obry on
[Second attempt to post this message. Sorry if you reveived
this multiple time, it seems this message never reached
comp.lang.ada].


Just curious, does someone have information to share about this problem:

<<
While attempting its first overseas deployment to the Kadena Air Base in
Okinawa, Japan, on 11 February 2007, a group of six F-22 Raptors flying
from Hickam AFB, Hawaii, experienced multiple computer crashes
coincident with their crossing of the 180th meridian of longitude (the
International Date Line). The computer failures included at least
navigation (completely lost) and communication. The fighters were able
to return to Hawaii by following their tankers, something that might
have been problematic had the weather not been good. The error was fixed
within 48 hours, allowing a delayed deployment.[24]
>> >>
I know that the F-22 is 90% of Ada. Is there some public information
about this bug? Is that a design bug?

Thanks,
Pascal.

--

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--| Pascal Obry Team-Ada Member
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From: Hibou57 (Yannick Duchêne) on
On 5 fév, 07:42, Dennis Lee Bieber <wlfr...(a)ix.netcom.com> wrote:
>
>         So far as I recall -- from some years ago -- it was an algorithm
> problem handling position information wrap-around from crossing, as
> mentioned, the International Dateline... -180.0 to +180.0 deg longitude.
>
>         I didn't hear that they had to follow the tankers back -- was under
> the impression once they managed to cross back heading east a reboot of
> the navigation system started working again...
>
> --
>         Wulfraed         Dennis Lee Bieber               KD6MOG
>         wlfr...(a)ix.netcom.com HTTP://wlfraed.home.netcom.com/

Do you know what was the pattern of this conception error ?
You've said “ from some years ago ” : this was a known problem ?
Wasn't solved since so long ?
From: Martin on
On Feb 5, 6:42 am, Dennis Lee Bieber <wlfr...(a)ix.netcom.com> wrote:
> On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...(a)obry.net>
> declaimed the following in comp.lang.ada:
>
> > I know that the F-22 is 90% of Ada. Is there some public information
> > about this bug? Is that a design bug?
>
>         So far as I recall -- from some years ago -- it was an algorithm
> problem handling position information wrap-around from crossing, as
> mentioned, the International Dateline... -180.0 to +180.0 deg longitude.
>
>         I didn't hear that they had to follow the tankers back -- was under
> the impression once they managed to cross back heading east a reboot of
> the navigation system started working again...
>
> --
>         Wulfraed         Dennis Lee Bieber               KD6MOG
>         wlfr...(a)ix.netcom.com HTTP://wlfraed.home.netcom.com/

For some reason (that I don't get at all) lots of systems define long
as -180 <= x <= +180 degrees.

Having the potential to alias a position seems like a bad idea for a
start, so when I've been coding such systems up, I've always spent a
bit of time making it convert positions into the range -180 <= x <
+180 degrees and using a proper ADT.

I wonder if it was anything to do with that?...

Cheers
-- Martin
From: Ludovic Brenta on
Martin wrote on comp.lang.ada:
> On Feb 5, 6:42 am, Dennis Lee Bieber <wlfr...(a)ix.netcom.com> wrote:
> > On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...(a)obry.net>
> > declaimed the following in comp.lang.ada:
> > > I know that the F-22 is 90% of Ada. Is there some public information
> > > about this bug? Is that a design bug?
>
> >         So far as I recall -- from some years ago -- it was an algorithm
> > problem handling position information wrap-around from crossing, as
> > mentioned, the International Dateline... -180.0 to +180.0 deg longitude..
>
> >         I didn't hear that they had to follow the tankers back -- was under
> > the impression once they managed to cross back heading east a reboot of
> > the navigation system started working again...
>
> > --
> >         Wulfraed         Dennis Lee Bieber               KD6MOG
> >         wlfr...(a)ix.netcom.com HTTP://wlfraed.home.netcom.com/
>
> For some reason (that I don't get at all) lots of systems define long
> as -180 <= x <= +180 degrees.
>
> Having the potential to alias a position seems like a bad idea for a
> start, so when I've been coding such systems up, I've always spent a
> bit of time making it convert positions into the range -180 <= x <
> +180 degrees and using a proper ADT.
>
> I wonder if it was anything to do with that?...

I would have thought a longitude was really a mod 360, shifted by -180
for display purposes? For fractional degrees (i.e. minutes and
seconds), make that mod (360 * 60 * 60), shift by -180 * 60 * 60 and
split in degrees, minutes and seconds when displaying.

--
Ludovic Brenta.

From: Martin on
On Feb 5, 8:52 am, Ludovic Brenta <ludo...(a)ludovic-brenta.org> wrote:
> Martin wrote on comp.lang.ada:
>
>
>
> > On Feb 5, 6:42 am, Dennis Lee Bieber <wlfr...(a)ix.netcom.com> wrote:
> > > On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry <pas...(a)obry.net>
> > > declaimed the following in comp.lang.ada:
> > > > I know that the F-22 is 90% of Ada. Is there some public information
> > > > about this bug? Is that a design bug?
>
> > >         So far as I recall -- from some years ago -- it was an algorithm
> > > problem handling position information wrap-around from crossing, as
> > > mentioned, the International Dateline... -180.0 to +180.0 deg longitude.
>
> > >         I didn't hear that they had to follow the tankers back -- was under
> > > the impression once they managed to cross back heading east a reboot of
> > > the navigation system started working again...
>
> > > --
> > >         Wulfraed         Dennis Lee Bieber               KD6MOG
> > >         wlfr...(a)ix.netcom.com HTTP://wlfraed.home.netcom.com/
>
> > For some reason (that I don't get at all) lots of systems define long
> > as -180 <= x <= +180 degrees.
>
> > Having the potential to alias a position seems like a bad idea for a
> > start, so when I've been coding such systems up, I've always spent a
> > bit of time making it convert positions into the range -180 <= x <
> > +180 degrees and using a proper ADT.
>
> > I wonder if it was anything to do with that?...
>
> I would have thought a longitude was really a mod 360, shifted by -180
> for display purposes? For fractional degrees (i.e. minutes and
> seconds), make that mod (360 * 60 * 60), shift by -180 * 60 * 60 and
> split in degrees, minutes and seconds when displaying.
>
> --
> Ludovic Brenta.


No...it's -180 <= x <(=) +180...always - check any map / globe!!

Lat is always -90 <= x <= +90 deg - no doubt about that one :-)

Adding "shifts" would make understanding any problem very hard...

"So the position coming in is (+40, -100) but what's that inside the
code again????"

Cheers
-- Martin
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