jander14indoor wrote:windu34 wrote:Jeff I was hoping you could provide some unofficial insight into how supervisors determine whether or not a penny is "in" a circle or not - especially the ones that are very borderline. Do you have a specific system or method?
UNOFFICIAL insight only! And "sight" is a key issue here.
Rule 7.a states: "Any pennies in multiple zones and/or touching the line separating two zones as determined by the ES..."
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As a reference, one source I looked up said a good eye can resolve details as small as 26 Microns, practical is closer to 40 microns. Without magnification.
I did some additional figuring, the smallest circle that fits 12 pennies is 7.915 cm. So there is 0.85mm of 'extra' space. The visual error is on the order of .04 mm or 1/20th of the available space. So the visual error here doesn't eat much of the admittedly SMALL tolerance for coin placement.
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Jeff Anderson
Livonia, MI
Nothing like quoting myself!! I'm not backing off the discussion of visual acuity, in fact what I discovered makes it an even SMALLER part of the error budget.
I do, however, hate when you guys figure out something we may have not thought through. Though we actually discussed scoring to higher or lower ring for touching the line. BUT I have an out. As long as my targets are consistent, it really doesn't change the nature of the challenge and easily hits the equally unfair to all standard.
Let me quote one more line from the rules. Para 5 Competition area.
"A standard 40 cm archery target following FITA standards (or a printout of it) is taped down on all sides or marked onto the Competition Area."
The FITA standards got me thinking on how this affects the questions, well I did a little digging on the FITA website in the rules. They pretty carefully define how the target is drawn.
- Turns out the line between colors (and it isn't always present!) is on the INSIDE of the dimension for that ring! So defining the penny as in the lower ring (opposite of archery and shooting practice, touch the line there and you get the higher score) when you touch the line by definition reduces the ring.
- And they are smart, they put a tolerance on the rings, +/- 1 mm on the inner rings, +/- 2 mm on the outer, that's on the diameter. So if you use a printed target for you board, another source of variability, but at least a known and defined one.
- I couldn't find anything on the width of the lines, not critical if you score by archery practices, but critical for SO as the rules are written. As a practical matter on the actual FITA targets they are pretty small. Followup assignment to me to measure how small.
So, what does that mean. For the center ring the OUTER edge of the line could go as large as 8.1 cm and as small as 7.9 cm.
- Max size case, 8.1 cm diameter circle, infinitely small line, 12 penny's will fit with about 2 mm clearance.
- Min size case, 7.9 cm diameter circle, let's assume a 0.5mm wide line reducing that to 7.8 cm, 11 penny's will fit with about 1.8mm clearance.
- That variation in actual ring (2000 microns) size is far larger than the visual accuity error of 40 microns.
- This is all allowed in the SO rules as we explicitly accepted the FITA tolerances!
The only thing that really changes is how many penny's fit. The accuracy with which you have to place the pennies doesn't change much. In either case you are placing each penny to a tolerance of a few tenths of a millimeter to maximize your score on the inner ring. The next ring is EASY by comparison.
So, as long as you are in a competition with one play field, no issue. Equal for all. If more than one, well, make sure the ES is consistent. But you wanted that anyway.
Oh, and of course max score depends on that size variation, but it doesn't affect the competition as it is again, the SAME for all competitors.
Another "Oh, by the way." If we'd made the rule that touching the line got the higher score, the issues wouldn't change! Same geometry calculations for circles in a circle, same visual acuity, only thing that would have dropped out is the possible variability of the lines themselves. Yes different max score, but NO difference on how accurate YOU have to be to achieve it!
Jeff Anderson
Livonia, MI
Hmm, do I have to much time on my hands today...
...mmm...
...could be, enjoy your weekend, and for those competing, good luck!
