Range Report Labradar V0 Consistency

[chrisward3]

Afternoon All!

I have a question regarding readings I've been getting on my Labradar over several range trips and wondering if anyone is having similar experiences. The problem:

I'm recording velocities at V0, V10, V20, V30, V40 out of a CZ455 Lilja 22lr with Lapua CenterX ammo.

The ES at V0 is roughly around 35fps, whereas the other readings consistently group around 28fps for the remaining velocity bands.

I've also noticed this on my 260 load with a V0 ES of around 30fps, and V10-V40 averaging an ES of 23fps.

I know that the radar cone will pick up the round, and then reverse-engineer a V0 velocity, but given the numbers above, is it fair to assume that their calculation is a bit off?

 

[whatsupdoc]

Not sure why but I get the same.
---------V0-----V10-----V25-----V50
Max---2794---2770----2747----2710
Min---2726---2712----2690----2652

ES-----68------58------57--------58

 

[chrisward3]

glad to see im not the only one!

 

[sled_mack]

Are you getting those numbers from the labradar/app, or are you opening the files off the SD card to see them?

 

[Subwrx300]

I work with radar in a different field (tracking golf balls, if you can believe it) and this is likely due to a combination of noise and precision of t0 measurement. It's fairly easy to determine velocity as objects move downrange (radar signal shift and time for return signal) but objects oblique to radar are very difficult. If the T0 estimate is of by a fraction of a millisecond, the velocity will have some error. Couple that with signal noise as bullet leaves muzzle and you will have lower precision.

In our product, we have to scrub data prior to displaying solution to ensure it falls in 95%+ confidence or we don't display. The average of the data is likely correct, but I'd use the downrange ES as a better indicator of spread and SD.