comparability of dry firing on shorter distance than on original distance.

[Tarta86]

During the lockdown several athletes are dryfiring at home. but analyzing the traces of high level athletes I found really big differences if I compare the scatt traces of the issf-original-distance (IOD) compared to dry-firing-distance (DFD) of the same discipline. on scatt.com in the FAQ they claim "Working distances range from 2.5 up to 1000 meters". But an optical sensor is not able to estimate the distance of DFD (the scale of the sensor is to adjust the focus of the lense).
The following illustration is an explanation of the beforementioned problem. the aimingpoint trajectory on the target is a combination of angular and paralell movements of the rifle (or pistol): When shooters train on the IOD they learn the compensation mechanisms of angular and parallel movements for this same distance. In DFD the angular movements, required to move from one end of the target to the other, don't differ between DFD and IOD (black line). if we compare the demands on the parallel movements for the same range of motion on the target (from left to right) than the allowed range in DFD (red lines) differs from the IOD (green lines).
In other words, the parallel movements (mostly related to body sway) have a different influence on the aimingpoint trajectory compared between IOD and DFD.



Formulated provocatively: considering motor control theory it would be detrimental to train on DSD because shooters learn something that isn't related to IOD.
1. have other coaches or scientists thought on this problem as well? what are your thoughts?
2. Is there a solution to this problem?

 

[TimRB]

Very interesting observation--thanks for pointing that out. I think the effects of parallel motion vary greatly from one shooting discipline to another, since the distances to the targets (IOD) also vary greatly. For an air rifle shooter dry-firing at a target at 5m (half actual size) the parallel motion on the practice target gives rise to considerable error when projected onto the actual 10m target. On the other hand, a high power rifle shooter practicing at 5m has a dry-fire target that is tiny compared to the actual 200 yard target, so the error from parallel motion is negligible, probably not even measurable.

Tim

 

[Tarta86]

Very interesting observation--thanks for pointing that out. I think the effects of parallel motion vary greatly from one shooting discipline to another, since the distances to the targets (IOD) also vary greatly. For an air rifle shooter dry-firing at a target at 5m (half actual size) the parallel motion on the practice target gives rise to considerable error when projected onto the actual 10m target. On the other hand, a high power rifle shooter practicing at 5m has a dry-fire target that is tiny compared to the actual 200 yard target, so the error from parallel motion is negligible, probably not even measurable.

Tim

I must admit I don't know the specifics on 200 yard shooting, but I do know that the parallel movements vary for the positions in which we are shooting (standig > kneeling > prone). If I would apply my explanations of my illustration than I would completely contradict what you (Tim) are saying. I would rather say: the bigger the difference between IOD and DFD the bigger the error of compensation effects. the smaller the difference between the two distances the smaller the blue value becomes, the smaller the influence of these errors. 5m DFD to 10m IOD relates to 50% but 5m to 200yrds (182m) makes 2%. But again I do not know in which position you shoot on 200 yards. We should defenitively compare same positions when discussing that matter.

I mostly observed this differences in the olympic disciplines standing and kneeling, and heard some 300m 3-position-shooters complaining about the same issue when practicing on shorter distances.

 

[CharlesD]

If I would apply my explanations of my illustration than I would completely contradict what you (Tim) are saying.

Tarta86, Tim,
I think you are actually both saying the same thing! As a prone (only) shooter you raise an interesting observation about parallel motion (sway) that occurs in standing and kneeling positions but not in prone. I am not qualified to comment on the practical aspects of shooting standing or kneeling, but as an engineer I can see the issues associated with scaling at different distances, as between dry fire (DFD) and live fire (IOD).
Sway, due to the instability of the skeletal body structure (rather like a skyscraper), gives a lateral movement that is parallel to the line of sight. If this movement is, say, 2mm from side to side, it will move the aim point 2mm across the target face. At 300m (ISSF distance) the 10 ring is 100mm wide, so this 2mm movement is negligible compared with the bull (2%). If dry firing on a scale target at 5m, the 10 ring is now 1.67mm wide and the 2mm movement is 120% of the 10 ring dimension - much more significant (60 times as big)! At 300m, sway has such a small effect as to be negligible, but at shorter distances (50m for smallbore and 10m for air rifle), the effects of sway are much greater.
Presumably shooters at these shorter distances tend to adopt techniques to minimise the effects of sway. This may involve a slight twisting of the upper body (between the shoulder and the supporting hand) to counter the sway and keep the aim pointing in the middle of the target. Such twisting movements are purely angular, but would need to be larger at shorter distances to compensate for the same amount of parallel sway movement. The angular movement would need to be greatest at Scatt distances (~5m) - twice as big as at 10m, but 10x as big as at 50m and 60x as big as at 300m.
The effects of sway are likely to show up in the Elliptical Factor metrics on the Info tab. The x-axis (lateral) movements (Tracings) and shot placements (Group) are likely to be larger than the y-axis (vertical) movements, giving Elliptical Factors increasingly larger than 1 the closer the Scatt DFD is. If Scatt was used at 10m rather than 5m I would expect to see the Elliptical Factor drop significantly (if sway-induced parallel motion was the only factor, it would halve, but there are other factors involved!).
I imagine that sway may also introduce movements of the body backwards and forwards, as well as laterally. This, however, would show up as a vertical movement of the aiming point and would be a purely angular movement rather than a parallel movement, so the effects are similar at all distances.
I would be interested to hear if this theoretical supposition in any way ties up with shooters' experiences.

 

[TimRB]

Charles has described my thinking. I believe we are talking about error caused by moving the rifle back and forth due to sway, where the rifle's barrel stays perpendicular to the target face.

Edit: Just to clarify, using the axis system described by Charles in post number 7, what I mean is that the rifle stays perpendicular to the x-axis, and not, strictly speaking, the target face. (Since the rifle will be pointed slightly up to compensate for gravity.)

Tim

 

[Tarta86]

I think we should clear the directions first in my explanations the shooting direction is the x axis. perpendicular to it - the line with the different shooters in the range - is the y axis, and z axis would be up down...
do we agree on this??

 

[CharlesD]

I think we should clear the directions first in my explanations the shooting direction is the x axis. perpendicular to it - the line with the different shooters in the range - is the y axis, and z axis would be up down...
do we agree on this??

From a Scatt perspective (as reported in their graphs and data reports), the x-axis is the horizontal line through the centre of the target in the plane of the target face. The y-axis is the vertical line through the centre of the target in the plane of the target face. The z-axis would therefore be perpendicular to the target face (the line from the target to the shooter).
I assume your diagram above is looking down on the range from directly above. In this case the Scatt x-axis would be up and down the page, the y-axis would be out of the page towards the viewer and the z-axis is the line between the target and the shooter, i.e. horizontal across the page as drawn in your diagram. Sway is a lateral motion so primarily in the (Scatt) x-axis. Hope this clarifies.

 

[Tarta86]

I was applying the "right hand rule" of a 3D coordinate system... out of a shooters perspective. but I can adapt to target perspective . thanks @CharlesD

I agree that sway has mostly influence on x axis. but my diagram above could apply to the x-perspective or to the y-perspective.

in the y perspective (looking from above) you would see all the movements in the x-z-level and from the x perspective you could see all the movements in the y-z-level.

In the x perspective you can see the entering movement of the rifle-shooter-system into the target area. this movement is not just a rotation (angular movement) of the torso, but also a sinking (parallel movement) of the whole position, therefore a combination between angular and parallel movement occurs also in this perspective.

So I ask my questions again, don't you think it could be detrimental to practice on a DSD instead of a IOD concerning that motor control mechanisms differ between DSD and IOD?
To my knowledge scatt has no adaptation in their software for this problem, because the optical sensor doesn't measure the physical target distance (the older with the infrared sensor could do it)...

 

[CharlesD]

I was applying the "right hand rule" of a 3D coordinate system... View attachment 742 out of a shooters perspective. but I can adapt to target perspective . thanks @CharlesD

I agree that sway has mostly influence on x axis. but my diagram above could apply to the x-perspective or to the y-perspective.

in the y perspective (looking from above) you would see all the movements in the x-z-level and from the x perspective you could see all the movements in the y-z-level.

In the x perspective you can see the entering movement of the rifle-shooter-system into the target area. this movement is not just a rotation (angular movement) of the torso, but also a sinking (parallel movement) of the whole position, therefore a combination between angular and parallel movement occurs also in this perspective.
View attachment 743
So I ask my questions again, don't you think it could be detrimental to practice on a DSD instead of a IOD concerning that motor control mechanisms differ between DSD and IOD?
To my knowledge scatt has no adaptation in their software for this problem, because the optical sensor doesn't measure the physical target distance (the older with the infrared sensor could do it)...

I believe Scatt adopts a 2 dimensional frame of reference as it is merely interested in movement of the aiming point across the (2D) target face. It therefore follows the standard x/y coordinates of a graph (x-axis horizontal, y-axis vertical on the page), both in the plane of the target face.
As I mentioned, I don't shoot standing (nearly started over 40 years ago but then met the lady who became my wife!), so am not in a position to comment from personal experience. However, in all the videos of standing shooters that I have seen, the settling of the rifle as it approaches the Natural Point of Aim (NPA) appears to be rotational, pivoting about the butt in the shoulder with the movement coming from the settling of the forearm onto the pelvis. To settle as a parallel, sinking motion would require the shoulder to drop as well. I'm sure standing shooters will correct me!
I don't know for sure, but I suspect there is a tendency, conscious or sub-conscious, to compensate for lateral sway with a slight lateral rotation of the torso or front arm, to try to keep the foresight pointing at the middle of the target. As you rightly point out, for a given amount of sway (parallel motion), any such rotational correction will be larger the closer the target is (whether dry or live fire). However, it will also be larger the greater the sway motion is. I suspect that the effect of truly parallel sway motion on the aim is more noticeable at 10m than at 50m and much less noticeable at 300m. Someone who shoots at 300m may not even notice they are swaying, but shooting/dry firing at closer distances will probably show it up. From that perspective, dry firing with Scatt at ~5m is in fact probably a very good training technique, because you will see any sway far more clearly and develop your position to try to reduce it. Learning to reduce the sway will in turn reduce the need for any compensation in the aim, and will also reduce the differences between dry fire training on Scatt and live firing at longer distances. The fact that dry firing with Scatt magnifies the effect could well be an effective way of helping you to improve the stability of your position - use it to your advantage!

 

[Modena]

Interesting, but aren't you assuming in your first diagram that the sensor is rotating about a fixed point, whereas it is really moving in the X axis (mostly) ? i.e. just taking into consideration X sway, if you sway 3mm to the left, the sensor just moved in space 3mm to the left, it did not rotate about its axis. 3mm of movement to the left is 3mm of movement, and doesn't scatt calculate what this would do at 10M? (assuming a 10M air rifle target). The sensor looking at the target is just to give it a reference point and hence ability to "detect" the 3mm of actual movement in space (not 3mm of change of impact, but 3mm of sensor movement). The fact that the target is at 5m and larger, is irrelevant, because scatt takes the 3mm of movement (in our example) and calculates what that looks like at 10M and displays the result. That's how I understand it anyway.

 

[Davidf92]

Hi,

Tarta86 is making a very good point and I agree with his analysis 100%.
In order to test the point while dry-firing my pistol at home, I modified my target setup to bring the target much closer (3m compared to my usual 8m). Of course this included printing a 3m target with the Scatt print tool. It came out surprisingly small (black area <1" in diameter compared to the 6cm original).
The effect described by Tarta86 was immediately obvious. Letting my body sway forward (on my toes, therefore parallel to the aiming line) just a few centimeters, without rotating my upper body at all, was enough to move my aiming line far out of the black. Tarta86's drawing perfectly illustrates his point.
It is worth adding that this ill effect only concerns parallel moving or swaying but not body/arm rotating, which is also perfectly illustrated on the drawing: the line tangent to the close target area is also tangent to the far target area.

With all respect, above comments from you guys kind of puzzle me. I don't really understand why it should be necessary to clarify any coordinate system. To describe the move in a geometrically formal way you would say that the barrel centerline moves away from its original position while staying parallel to that original position. Whether the barrel slightly moves forward or backward on its centerline, i.e. whether the barrel movement is or is not perpendicular to its centerline, is irrelevant. What counts is only the distance between the original and the new barrel centerlines, and since these original and new centerlines remain parallel no coordinate system is necessary to better describe the move. Parallel means parallel, period.

Also, considerations about shooting position (I suppose they concern rifle shooting) don't really change the issue. Standing with the rifle poses the same swaying risk as with a pistol. Positions on the ground would probably reduce the risk of swaying. But the issus is about the effects of swaying, not about it's risk or likeliness.

Maybe an easier way to perceive the situation would be with an extreme case: Consider training 10m air pistol with a target as close as 1 meter. To have the same aspect ratio the target should be 1/10th the size. Hence the black area would be 6mm in diameter (real one is 6cm). You can easily imagine what would happen if you really had this miniature target just 1m in front of you: A 1cm perfectly parallel sway (which you would hardly feel in your body) would be enough to bring your aiming line out of the black, whereas with the real target at 10 meter that same sway only moves you 1 zone out (zone radius is 8mm).

Does this clarify the point?

PS. of course this is not an issue concerning the Scatt itself, no malfunction there. It is just a side-effect and limitation of simulation at a closer distance. Obviously training the 10m at 2m is close to impossible even if the Scatt is optically able to do it. Contrarily, training 300yd at 10m should not be too much affected since you are not likely to sway your body enough for the pb to arise.

 

[Davidf92]

From that perspective, dry firing with Scatt at ~5m is in fact probably a very good training technique, because you will see any sway far more clearly and develop your position to try to reduce it.

Good point!

 

[CharlesD]

I don't really understand why it should be necessary to clarify any coordinate system.
Also, considerations about shooting position (I suppose they concern rifle shooting) don't really change the issue. Standing with the rifle poses the same swaying risk as with a pistol. Positions on the ground would probably reduce the risk of swaying. But the issus is about the effects of swaying, not about it's risk or likeliness.

Davidf92,
I only raised the coordinate matter so that we are all talking a common (Scatt-based) frame of reference when taking about directions of movement, both parallel and rotational. Scatt uses x & y on the Distance trace and in other measures (e.g. elliptical factor).

From a Scatt perspective, x is left/right across the target face and y is up/down across the target face. Scatt doesn't know whether the movement is parallel or rotational, just where the sensor is pointing relative to the centre of the target.
Nevertheless, what you are describing in terms of the effects of parallel and rotational movement are the same asTarta86 and I described, other than I used a 2mm sway and you used a 1cm sway. The effect is the same - parallel is more significant at shorter distances, rotational is independent of distance.
Shooting position is significant, in that you get no sway at all when prone with a rifle. The prone position is all triangles in 3 dimensions, which any structural or mechanical engineer will tell you is a rigid structure (all bracing uses triangles, look at the Forth Rail Bridge as an example). Any other shape is a mechanism, which can move with applied forces (e.g. wind or muscle action). That is why skyscrapers sway in strong winds and earthquakes. Standing and, to a lesser extent, kneeling are less stable positions than prone as they are not all triangles. Feet to pelvis is a triangle, but is only stable in one plane (liable to rock/sway perpendicular to the line between the feet). Kneeling provides 3D stability to the pelvis level (tetrahedron shape). The body above the pelvis is like a pole and only held rigid by weight balanced down the spine combined with muscle action. Guess why I only shoot prone!! (I have the greatest respect for people who master being able to shoot standing.)

 

[Davidf92]

talking a common (Scatt-based) frame of reference when taking about directions of movement, both parallel and rotational

Hi CharlesD,
The sensors are purely optical. They don't use motion detection. They don't make any difference between translation and rotation, all they see is the target's image moving in their field-of-view. In addition, movement in direction of the target (perpendicular to its surface) is not related to Tarta86's parallel movement issue. This is why I thought going into 3D coordinate systems was kind of misleading, it is more important to differentiate translation from rotation.

There is yet an other way to describe the issue: when using the Scatt whatever the arm and distance we tend to assume that the trace describes the shooter's angular movements, i.e. rotation as opposed to translation. It is mostly true, as in most cases (only exception being 10m rifle) small lateral movements, with the barrel staying parallel, make a negligible difference. The point is that to use a Scatt with a short distance simulation you need an artificial smaller target, with which the barrel's lateral movements become quite significant and therefore do no longer simulate the real-distance shooting.

In other words the Scatt as it exists today does not allow a perfect simulation using an artificial short-distance target. I would clearly answer 'No' (as of today) to Tarta86's #2 question "Is there a solution to this problem".

 

[CharlesD]

Hi CharlesD,
The sensors are purely optical. They don't use motion detection. They don't make any difference between translation and rotation, all they see is the target's image moving in their field-of-view. In addition, movement in direction of the target (perpendicular to its surface) is not related to Tarta86's parallel movement issue. This is why I thought going into 3D coordinate systems was kind of misleading, it is more important to differentiate translation from rotation.

There is yet an other way to describe the issue: when using the Scatt whatever the arm and distance we tend to assume that the trace describes the shooter's angular movements, i.e. rotation as opposed to translation. It is mostly true, as in most cases (only exception being 10m rifle) small lateral movements, with the barrel staying parallel, make a negligible difference. The point is that to use a Scatt with a short distance simulation you need an artificial smaller target, with which the barrel's lateral movements become quite significant and therefore do no longer simulate the real-distance shooting.

In other words the Scatt as it exists today does not allow a perfect simulation using an artificial short-distance target. I would clearly answer 'No' (as of today) to Tarta86's #2 question "Is there a solution to this problem".

Davidf92,
I think we are in complete agreement: translational movements become more significant at shorter distances but Scatt does not (and cannot) differentiate between translational and rotational movements. It merely sees where the sensor is pointing relative to the middle of the (smaller than real) target. I think the moral is to place the target at the longest distance you can, if you are shooting standing or kneeling, to minimise the increased effect of translational movements. The idea posted on another thread of using a mirror to increase the distance is a great idea (though it only works for MX series Scatt with the optical camera sensor).
There is another issue with shooting at too close a distance - convergence. This is where the line of the sights is different to the line of the barrel due to the vertical separation between them. When shooting, the two lines converge at the target for a rifle that uses centre aim (if you ignore gravity drop of the bullet/pellet, which makes the barrel line need to be a bit higher). The angle between the two lines necessarily increases the closer the target is to the shooter. For pistol, where you aim below the aiming mark, the angle is even greater as the two lines necessarily cross short of the target. Depending on where you mount your Scatt sensor, there is also a convergence between the line of sight of the sensor and the barrel. If the Scatt sensor is vertically below the barrel, the angle between the sensor line of sight and the sights' line of sight is even greater, and becomes really quite significant if the target is close. Hence the suggestion on another thread to mount your sensor as close to the sights as you can (without interfering with the sight picture). Fortunately the Scatt calibration process sorts out the alignment, but it is important to maintain the same distance between the sensor and the target throughout the practice, when using Scatt at short distances, otherwise you will effectively change your zero. Once again, the further away you can position your Scatt target, the better, as it minimises any of these effects.

 

[Tarta86]

Hi CharlesD,
The sensors are purely optical. They don't use motion detection. They don't make any difference between translation and rotation, all they see is the target's image moving in their field-of-view.

Actually it is not. At least in the mx-02, there are also other sensors inside like for instance an IMU.
here is a comparison between scatt and an IMU for the same shot with an Air Pistol on 10m:

As you can see, the IMU has a higher measurement frequency (200Hz). in the left image there are just angular values rescaled to a target, in the right image these are the coordinates the scatt software draws on the virtual target.
My assumption is, that the optical sensor (camera) is "just" for the calibration/placement of the trajectorys on the virtual target relative to the previous shot. But I am no expert regarding IMUs.

 

[Tarta86]

It is mostly true, as in most cases (only exception being 10m rifle) small lateral movements, with the barrel staying parallel, make a negligible difference.

Here's a quote of a study conducted on international air rifle shooters by Simo Ihalainen of the University of Jyväskylä.

"Postural balance in shooting direction (y-Axis) was more stable than the postural balance in cross shooting (x-Axis) direction during all analyzed time periods.
sdX7 0.83 ± 0.17 mm vs. sdY7 0.31 ± 0.06 mm, p < 0.001
sdX2 0.45 ± 0.08 mm vs. sdY2 0.28 ± 0.06 mm, p < 0.001
sdX1 0.29 ± 0.05 mm vs. sdY7 0.27 ± 0.06 mm, p < 0.01"

Assuming the center of pressure displacements are the same as the parallel movements of the Air Rifle, in my opinion a lateral sway of the range of 0.83mm in Air Rifle Shooting on 10m is not negligible when analyzing aiming point trajectories. Most certainly not when we start considering intermediate and beginners to use scatt who are known to have a lot larger sway-range than 0.83mm.

But eventough thanks for the answer I was looking for the whole time

In other words the Scatt as it exists today does not allow a perfect simulation using an artificial short-distance target. I would clearly answer 'No' (as of today) to Tarta86's #2 question "Is there a solution to this problem".

 

[Davidf92]

Actually it is not. At least in the mx-02, there are also other sensors inside like for instance an IMU.
here is a comparison between scatt and an IMU for the same shot with an Air Pistol on 10m:

Fortunately the Scatt system (sensor + software) produces similar results as an IMU-based system, but it doesn't prove (nor contradict) this sensor uses an IMU. Various technologies can be used for such kind of movement analysis and will give consistent results, although each with specific advantages or limitations. And by the way previous Scatt sensors (before the MX-02) were not all optical.

It would not be too difficult to experiment around this question. For instance you could firmly attach your rifle on a steady support and take dry-fire shots while moving the target from side to side. A strictly IMU-based sensor will reproduce the same shot result each time ignoring the target, while a purely optical sensor will exactly respond to the target displacements.

However I do agree with the MX-02 and MX-W2 sensors probably containing at least accelerometers used to detect the angle vs. horizontal. Indeed as you probably noticed the sensor 'activates' when it comes inside an angle of more or less 10 degrees from the horizontal, whether or not there is a target in view. This is quite obvious in the preview calibration mode. But as far as I could guess this is not used for aiming by these sensors.
Some people do know, of course

 

[Tarta86]

However I do agree with the MX-02 and MX-W2 sensors probably containing at least accelerometers used to detect the angle vs. horizontal. Indeed as you probably noticed the sensor 'activates' when it comes inside an angle of more or less 10 degrees from the horizontal, whether or not there is a target in view. This is quite obvious in the preview calibration mode. But as far as I could guess this is not used for aiming by these sensors.
Some people do know, of course

that's what I meant by saying there has to be an IMU inside. though what the picture can show, is that at least for this particular air pistol shot the reduction of the pistol movement from angular AND parallel to just agular there seems not to be that much loss of information compared to SCATT (angular and parallel)

Let's take another shot:

• on the left just angular movements (no parallel)
• on the right (we assume) angular AND parallel ==> the reason why the red line doesn't go out that far are compensation mechanisms between parallel and angular movements. SCATT seems to take compensation mechanisms in to account. So there is the clear benefit of SCATT to an IMU. But what for me still does not work is a proper simulation of the aiming point trajectories on shorter target distance than the original.

It would not be too difficult to experiment around this question. For instance you could firmly attach your rifle on a steady support and take dry-fire shots while moving the target from side to side. A strictly IMU-based sensor will reproduce the same shot result each time ignoring the target, while a purely optical sensor will exactly respond to the target displacements.

been there done that scatt still does what it's supposed to do. So we could say for aiming such sensors are not used.

 

[Davidf92]

@Tarta86 What is this other IMU system with which you are doing the comparison? Is it another shooting simulator, or are you playing with a piece of hardware?

Back to Scatt I think @Peter did confirm on the forum that parallel sensor movement are not detected or at least not computed. They may use a simple IMU which does not integrate horizontal accelerations into distance measurements, or not handle that in the software. They may also have decided to invest in a generation of purely optical sensors and decided to do without IMU data altogether. Hard to know, as in my understanding they don't share this level of information.