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-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,7a2d45f282a1da1c X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-08-20 14:12:04 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!canoe.uoregon.edu!arclight.uoregon.edu!wn13feed!wn11feed!worldnet.att.net!204.127.198.203!attbi_feed3!attbi_feed4!attbi.com!rwcrnsc53.POSTED!not-for-mail Message-ID: <3F43E421.8000001@attbi.com> From: "Robert I. Eachus" User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.0.2) Gecko/20021120 Netscape/7.01 X-Accept-Language: en-us, en MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: float with 24-bit resolution References: <3F3CCB0F.543478AF@adrianhoe.nospam.com.my> <3f3cd7f4$1_2@news.tm.net.my> <3F3CE28D.B841A191@raytheon.com> <3F3D10B7.9080707@attbi.com> <3F3D2195.D984062E@raytheon.com> <3F3DA544.7080604@attbi.com> <3F40D70F.13CED347@raytheon.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit NNTP-Posting-Host: 24.34.139.183 X-Complaints-To: abuse@comcast.net X-Trace: rwcrnsc53 1061413922 24.34.139.183 (Wed, 20 Aug 2003 21:12:02 GMT) NNTP-Posting-Date: Wed, 20 Aug 2003 21:12:02 GMT Organization: Comcast Online Date: Wed, 20 Aug 2003 21:12:03 GMT Xref: archiver1.google.com comp.lang.ada:41746 Date: 2003-08-20T21:12:03+00:00 List-Id: Mark Johnson wrote: > I clearly understand the issue with truncation errors [hence the need > for better accuracy] but this appears to be getting well away from the > OP's problem area. Please also note that your solution assumes a > constant velocity vector (which is not the case in the example I > provided). > (I said:) >>(Of course, you are actually doing this for a set of tracks and looking >>for matches.) Mark again: > Only the first part is true, the last half does not apply. Actually, it is part of the magic. If you have two tracks at times t1 and t2, and they have different velocity vectors, they may be the same target. If when you project the first track ahead to t3, in between t1 and t2 and project track two back in time to t3, the tracks intersect, that is a pretty good guess. What really happens is that the aircraft may be constantly changing heading, but the interpolation is imprecise enough to allow the course to be represented by two line segments. So yes, my method does require an assumption of constant velocity vectors, but it is using that assumption to actually detect headings that are changing. But this (data fusion algoritms) is really getting off topic in this thread. ;-) -- "As far as I'm concerned, war always means failure." -- Jacques Chirac, President of France "As far as France is concerned, you're right." -- Rush Limbaugh