From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: a07f3367d7,16f1030bd366bf59 X-Google-Attributes: gida07f3367d7,public,usenet X-Google-NewGroupId: yes X-Google-Language: ENGLISH,ASCII Path: g2news1.google.com!postnews.google.com!g29g2000yqe.googlegroups.com!not-for-mail From: Phil Clayton Newsgroups: comp.lang.ada Subject: Re: About the F-22 software bug Date: Fri, 5 Feb 2010 15:39:30 -0800 (PST) Organization: http://groups.google.com Message-ID: <92a42999-0632-4bc6-8348-29140337c3c6@g29g2000yqe.googlegroups.com> References: <4b6b15d2$0$929$ba4acef3@news.orange.fr> <4YKdnVFQX_suIPbWnZ2dnUVZ_rednZ2d@earthlink.com> <3050ef55-5dde-40ed-8a8f-a2daf245bf86@k19g2000yqc.googlegroups.com> NNTP-Posting-Host: 91.110.254.41 Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: posting.google.com 1265413170 16839 127.0.0.1 (5 Feb 2010 23:39:30 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Fri, 5 Feb 2010 23:39:30 +0000 (UTC) Complaints-To: groups-abuse@google.com Injection-Info: g29g2000yqe.googlegroups.com; posting-host=91.110.254.41; posting-account=v7gx3AoAAABfjb9m5b7l_Lt2KVEgQBIe User-Agent: G2/1.0 X-HTTP-UserAgent: Mozilla/5.0 (X11; U; Linux i686; en-GB; rv:1.9.0.15) Gecko/2009102704 Fedora/3.0.15-1.fc10 Firefox/3.0.15,gzip(gfe),gzip(gfe) Xref: g2news1.google.com comp.lang.ada:8929 Date: 2010-02-05T15:39:30-08:00 List-Id: On Feb 5, 9:02=A0am, Martin wrote: > On Feb 5, 8:52=A0am, Ludovic Brenta wrote: > > > > > Martin wrote on comp.lang.ada: > > > > On Feb 5, 6:42=A0am, Dennis Lee Bieber wrote: > > > > On Thu, 04 Feb 2010 19:46:15 +0100, Pascal Obry > > > > declaimed the following in comp.lang.ada: > > > > > I know that the F-22 is 90% of Ada. Is there some public informat= ion > > > > > about this bug? Is that a design bug? > > > > > =A0 =A0 =A0 =A0 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 longi= tude. > > > > > =A0 =A0 =A0 =A0 I didn't hear that they had to follow the tankers b= ack -- was under > > > > the impression once they managed to cross back heading east a reboo= t of > > > > the navigation system started working again... > > > > > -- > > > > =A0 =A0 =A0 =A0 Wulfraed =A0 =A0 =A0 =A0 Dennis Lee Bieber =A0 =A0 = =A0 =A0 =A0 =A0 =A0 KD6MOG > > > > =A0 =A0 =A0 =A0 wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.co= m/ > > > > For some reason (that I don't get at all) lots of systems define long > > > as -180 <=3D x <=3D +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 <=3D 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 <=3D x <(=3D) +180...always - check any map / globe!! > > Lat is always -90 <=3D x <=3D +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????" Interesting to see that 'cyclic fixed point types' are under discussion: http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ai05s/ai05-0175-1.txt?rev=3D1.2 http://www.ada-auth.org/ai-files/minutes/min-0911.html#AI175 Phil