Don't try telling that to the Gunny at Sniper School !! 73, Dick, W1KSZ
-----Original Message----- >From: Bob Camp <[email protected]> >Sent: Nov 1, 2010 7:08 PM >To: Discussion of precise time and frequency measurement <[email protected]> >Subject: Re: [time-nuts] A real world project need for timing accuracy... > >Hi > >Two gotchas, one minor, the other a bit bigger. > >At 800 yards, even a *very* good optical setup can't / won't see holes in a >target. The atmosphere is just to unstable. You would have to mount the camera >down range (minor issue). > >The larger one is that you really don't want to truck down a half mile of path >to put up a new piece of paper. After a while the "target" gets pretty ragged. >There's not much for the optics to pick up, especially if you have good >groups. > >Cool idea though .... > >Bob > > >On Nov 1, 2010, at 10:04 PM, Predrag Dukic wrote: > >> >> Why not using optical methods for shot grouping? >> >> A cheap web camera with equally cheap telescopic lense can resolve 1mm. >> Some image processing software can find shot positions within the 1kx1k >> pixel bitmap.... etc.. >> >> >> >> >> At 01:03 2.11.2010, you wrote: >>> Timenutters-- >>> I appreciate the feedback for implementing my >>> ballistic field measurement project but I think >>> there is some misunderstanding of what the goal is. >>> For instance, it is not practical to find 800 meters >>> of coax and trench it in out to the downrange target. >>> This system needs to be relatively portable so it >>> can be set up at any given shooting range. >>> I need to determine: A) down-range velocity of the >>> still super-sonic projectile, B) time of flight and >>> C) shot-group size. >>> Measuring down-range shot-group size with an array of >>> ultrasonic sensors is pretty straightforward. I can >>> do all the computation with a $6 microprocessor and >>> send the X/Y coordinates back to the laptop at the >>> shooting bench with a simple RF link. Down-range >>> velocity is easily determined with a set of sky-screens >>> and the results also sent back via an RF link. >>> Time-of-flight is much more problematic to determine >>> but the plan is to determine the elapsed time between >>> the moment the projectile passes over the muzzle skyscreen >>> and the moment of passing over the downrange skyscreen. >>> This means syncing the 10 MHz clocks at both ends together. >>> I guess the crux of my question to the time-nuts gang >>> is what is the easiest (cheapest!!) way to do this. >>> For a number of years I have been using an ultrasonic >>> shot-group size measurement system made by Oehler >>> Research. It can resolve individual shot placement >>> to within 1 cm. Some less expensive systems that >>> use fewer sensors can only resolve to +/- 2 cm. The >>> Oehler Research system also determines time of flight. >>> The problem is that these systems all use a cable >>> to connect back to the equipment at the shooting bench. >>> I am trying to find a way to synchronize/coordinate >>> a downrange 10 MHz clock to the "master" 10 MHz system >>> clock at the shooting bench without spending hundreds >>> of $$ doing it. It is not too big a problem to process >>> all of the signals from the downrange skyscreens and the >>> ultrasonic shot-group sensors and telemeter the results >>> back to the shooting bench. >>> However, time-of-flight info (via an RF link requires >>> that I sync the 10MHz clocks at both ends together. >>> Use of GPS receivers seems to be the most likely way >>> to do this but how do I keep the cost and complexity >>> down? >>> Thanks in advance for any feedback on the matter! >>> Mike Baker >>> --------------------- >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > >_______________________________________________ >time-nuts mailing list -- [email protected] >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
