Testing E Target Accuracy

[243Mendoza]

repeatability of error is the error is always in a very similar place across the test or tests. AV or SD does not show or tell you where the error is only tells you have one. ...

I am beginning to think that your definition of 'repeatability error' is the difference between acoustic center and paper center which can be minimized by calibration.

AV and SD measure the accuracy your system to measure shot location and it will not be a simple number as 1mm or any near that number for AV.

 

[Bindi2]

The acoustic centre is not an X marks the spot. The repeatability over a test is the recorded plot shot error is the same or very close for each actual shot in still conditions. The acoustic centre can be 25/30 mm in size on a large target. Because my target is so small it is much smaller. The perfect target would place the plot on top of the shot. Because of the variables this does not happen but when the error is constant we are close.
Others with the same SMT target as mine were happy to be at half the bullet diameter repeatability @ 800m.

 

[243Mendoza]

The acoustic centre is not an X marks the spot. The repeatability over a test is the recorded plot shot error is the same or very close for each actual shot in still conditions. The acoustic centre can be 25/30 mm in size on a large target. Because my target is so small it is much smaller. The perfect target would place the plot on top of the shot. Because of the variables this does not happen but when the error is constant we are close.
Others with the same SMT target as mine were happy to be at half the bullet diameter repeatability @ 800m.

If your repeatability is constant then you can remove it by calibration
Since you are happy not knowing the extent of your random error, there is no point in further discussion.
And I think we talking in circles. It may be Aussie vs American English

 

[Bindi2]

The random error is environmental induced not the system error. I could not get to zero before the plot moved away from the actual. Nor could any body else.

 

[243Mendoza]

The random error is environmental induced not the system error. I could not get to zero before the plot moved away from the actual. Nor could any body else.

That may be because you do not know how to calibrate the SMT as evidence your using H&W to calibrate which is the incorrect procedure.

 

[Bindi2]

So you are saying external mike systems are not suitable for ranges with wind?

They are not of a competition grade.

 

[243Mendoza]

At least we have determined that the acoustic center is not x marks the spot. So we got that going for us.

On further thought the need to use algorithms that make several estimates on the location of a hit may mean the acoustic center is a area and not, as you said, 'x marks the spot'.

 

[Bindi2]

Yes, there is a specific option to calibrate the system:
1)click on the gear wheel icon shown on the upper left and enter the admin password
2)take a shot or more
3)measure the 'x,y' locations of the shot on paper
4)click on the shot data shown on the right side bar
5)click on the 'calibrate' button
6)enter the 'x,y' values for that shot
7)repeat for all shots used for calibration

Interesting as none of this is in the manual I have.

 

[6BRinNZ]

Interesting as none of this is in the manual I have.

Personally I think calibrate is the wrong word. The process allows the positioning of the acoustic center on the target face. It doesnt make the system any more precise in terms of random error.
With smts you have to setup new electronic frames if you "calibrate" each distance.
I'm dubious about the value as I have seen the acoustic center move from one day to the next. Certainly it's a lot fussier to manage on the day.

 

[6BRinNZ]

Tbh...I've seen the centre out by 90mm at 300 and none new the difference on the day.
The usuals smashed xs and took the win.
The big trick with Ets is figuring out what's important. A bit like reloading...
I shot an entire club season on ets and took my elevation zeros to nationals on manuals and smashed xs from the get go.

 

[6BRinNZ]

Nah it's out on the day not a gradual move.
Yes you do find the center as you are looking at the screen. I assume it can be out due to wind on the day and the angle that is being shot at. I.e sometimes a deliberate crossfire is used at the mound to keep the shot away from the flags.
Keep in mind I shoot at a notorious range so a range with more consistent or still conditions might not see the centre move from one day to the next and might require a higher level of precision.

 

[6BRinNZ]

Club wise they are an easy learning curve...
There some things to keep an eye on. More mechanical like nicked cables loose aerial connectors...charged batteries.
Keep firmware revisions up to date...don't update the day before a match.

 

[6BRinNZ]

I'm no technical expert. So this is just observations.
Some days that have been more consistent wind wise you can see where the acoustic centre is due to that area being shot out. It shows more so at 300. Past 300 the general groups start to spread and it's less obvious. This is just the wind affecting shooters.
I haven't noticed it moving in specific wind conditions if it changed during a relay for instance. Some one technical would need to advise what would technically be possible there. I suspect it is possible and if combined with a shooter not being square to the target I suspect mathematically there could be quite a shift in the centre. Tbh if it moved during a specific condition I have never been able to tell during my relay.

 

[Bindi2]

On further thought the need to use algorithms that make several estimates on the location of a hit may mean the acoustic center is a area and not, as you said, 'x marks the spot'.

Exactly as I implied acoustic centre is not X marks the spot. Which is probably why the error can be constant but not exact. Which then shows conditional effects added to that as what has been referred to as the random error.

 

[Bindi2]

The acoustic centre does not just get up and move unless a mic has shifted. It dosent move far and it is very slow, which indicates to me it is more to do with frame warp. 300m/y targets can look pretty awful for a number of reasons the most common is the aim mark is not in a true central position or has been placed a little to one side so the central aim point is not destroyed.

 

[Bindi2]

Afraid I'm not following you here. What is the purpose of the crossfire?

E targets are a hard subject to discuss on a forum. It's too hard to convey details.

It doesn't help when people are talking about different types of targets, closed versus open, for instance.

When the flags encroach into a line of fire the shooter closet to the flags shoots on the next target out from the flag. The other shooter shoots onto the encroached target because he has a clear shot from his position.

 

[Crow]

It will be interesting to see if any of the moving center issue and other problems discussed here get flushed out in the US as they start getting used at more places. We have already shot 2 Nationals on them without any criteria for testing them. Cat is kind of out of the proverbial bag now.

The NRA still doesn't have any test criteria for them, and I don't look for them to have any this year. I don't really look for them to have any meaningful test criteria at all. Maybe they will surprise me.

I have no doubt the NRA is going to have to rely on help from the folks developing this technology in order to come up with anything meaningful as far as test criteria goes. Judging from the current version of ShotMarker, I'd have to say it sure looks like it was thoroughly evaluated for accuracy of the results, and I wouldn't be surprised if Adam had some thoughts on the subject... same with the Hexta and Silver Mountain guys.

The back and forth discussion on 'acoustic center' and 'calibration' may have left some confused and questioning the suitability of e-targets in competition settings, so I thought an e-target screenshot along with a photo of the actual target might be useful for understanding why having an acoustic center that corresponds exactly with the center of the target isn't essential for accurate scoring.

First, the ShotMarker screenshot...


...and the paper target that provided the aiming point.


Notice the correspondence is very close, but not exact, and indicates the acoustic center of the ShotMarker is ever so slightly high and maybe a hair left (S2 and 3, illustrate this well). But even if acoustic center had been off by a larger margin, the same score would've been registered, assuming the shooter compensated accordingly (i.e. "My shots are landing high, thus I need to aim lower.").

 

[Bindi2]

I'm no technical expert. So this is just observations.
Some days that have been more consistent wind wise you can see where the acoustic centre is due to that area being shot out. It shows more so at 300. Past 300 the general groups start to spread and it's less obvious. This is just the wind affecting shooters.
I haven't noticed it moving in specific wind conditions if it changed during a relay for instance. Some one technical would need to advise what would technically be possible there. I suspect it is possible and if combined with a shooter not being square to the target I suspect mathematically there could be quite a shift in the centre. Tbh if it moved during a specific condition I have never been able to tell during my relay.

The testing done in Queensland showed the square issues.

 

[Crow]

Help me out here because I have struggled with this idea. I have a shot marker, but just got it set up and haven't shot on it, so I may figure this out on my own later.

What if the acoustic center had been off left or right and there was a complete wind reversal. Wouldn't the wind call for the reversal be affected? I can see where acoustic center on the vertical axis wouldn't be a big deal unless it moved during a match.

Doppler Effect aside, the acoustic center should stay in the same place it started, just like the X in the middle of the paper. I've only had my ShotMarker out a half dozen times, and haven't had to shoot through any significant wind, but have yet to see the acoustic center move.

After reading up on the Doppler Effect though, I'm hoping for a windy day tomorrow, just to see if I can spot it.

I think you're really going to like your ShotMarker.

 

[Bindi2]

I have not seen a 90mm shift. 30mm is the most I have seen and it was slow indicating a frame issue without looking for other factors. This was on a 6x8 frame The plot sheet did not show any thing out of what was the targets normal recording accuracy just a shift of acoustic centre. This is why we use quadrant lines
The acoustic centre is only used in conjunction with the actual target to check accuracy. The acoustic centre is the centre of the virtual target. The normal wind patterns affecting the bullet will show on the actuals the recorded X Y hits will show in a different place because of the interference from the conditions. Learn the differences they can be subtle to out there. Find yourself a copy of the clock showing where winds from hit and then relate to it. You will need a base no wind plot to actual to start with so you can look at that as well as the wind driven plot to actual.