# How accurate would this measurement be? **URL:** \ **Category:** Factual Questions\ **Created:** [August 20, 2014, 7:53pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032 "2014-08-20T19:53:25Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 20, 2014, 7:53pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/1 "2014-08-20T19:53:25Z")
Looking for a primitive method of measuring arrow distances for flight shooting competitions. Best I can come up with is using the 100 yard tapes they sell and laying out a centerline 500 yards long, then build a t square I could set on the stretched out center line to site down with peep site type sights installed on it. Wondering how big the t square should be to attain accuracy of about 1 foot over a 50 yard distance. A target with a straight vertical line would be placed in the hole of the arrow being measured and held vertical while the measure was read, All measurement would be relative to the centerline regardless of how far off center they were. Or if you could suggest a better method. We are trying to encourage small flite shooting clubs to start up and will need an inexpensive starter kit for them to take measurement with. The official club uses a total station for dead on accuracy but this would not be practical for small informal groups. ---
**Author:** ![August\_West](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/august_west/32/18069_2.png) [@August\_West](https://boards.straightdope.com/u/August_West)\ **Post date:** [August 20, 2014, 8:03pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/2 "2014-08-20T20:03:00Z")
How about a [Laser Rangefinder](http://www.amazon.com/Simmons-801405-Rangefinder-4x20LRF-600/dp/B003X082A4/ref=sr_1_1?s=hunting-fishing&ie=UTF8&qid=1408564757&sr=1-1)? The one linked is about $100. Have someone stand at the arrow and raise a paper plate and shoot the distance. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 20, 2014, 8:16pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/3 "2014-08-20T20:16:53Z")
> [@August\_West](#): > > How about a [Laser Rangefinder](http://www.amazon.com/Simmons-801405-Rangefinder-4x20LRF-600/dp/B003X082A4/ref=sr_1_1?s=hunting-fishing&ie=UTF8&qid=1408564757&sr=1-1)? The one linked is about $100. Have someone stand at the arrow and raise a paper plate and shoot the distance. Thats what I use for personnal use but for some reason people seem to doubt the accuracy and consistency, I spent about $200.00 on mine and it seems to work great. Maybe if we verified the accuracy before each shoot using a 500 yard tape it would be acceptable, this is my preffered method. I use a 36" square piece of aluminum painted red for my target to site on. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [August 20, 2014, 9:54pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/4 "2014-08-20T21:54:31Z")
> [@HoneyBadgerDC](#): > > Thats what I use for personnal use but for some reason people seem to doubt the accuracy and consistency, I spent about $200.00 on mine and it seems to work great. Maybe if we verified the accuracy before each shoot using a 500 yard tape it would be acceptable, this is my preffered method. I use a 36" square piece of aluminum painted red for my target to site on. Even if it were inaccurate, what would be the downside? Farther shots would still be farther. Are you shooting for a specific distance? ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 20, 2014, 10:06pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/5 "2014-08-20T22:06:28Z")
> [@ZenBeam](#): > > Even if it were inaccurate, what would be the downside? Farther shots would still be farther. Are you shooting for a specific distance? ``` Creating a registry and going for distance records, accurate to 1 yard would be the lowest acceptable accuracy as the group would only be semi formal. So we wuld be keeping score but the events could be held anywhere as long as we are all using the same methods. ``` ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [August 20, 2014, 10:16pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/6 "2014-08-20T22:16:22Z")
Measure the circumference of a wheel of a bicycle and mark the tire, and walk it or ride slowly counting the rotations. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 20, 2014, 10:24pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/7 "2014-08-20T22:24:43Z")
If your colleagues won’t accept the accuracy of a laser rangefinder, then the real question of interest is what methods they will accept. This is not something we can answer on their behalf. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 20, 2014, 10:30pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/8 "2014-08-20T22:30:39Z")
> [@jtur88](#): > > Measure the circumference of a wheel of a bicycle and mark the tire, and walk it or ride slowly counting the rotations. We measure at a right angle to a center line comming off the shooting line. Actual distance shot is not measured, distance from the shooting line is measured and the shooting line theoreticaly goes into infinity. The total station we use at official events takes care of triangulation and does all the math. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [August 20, 2014, 10:45pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/9 "2014-08-20T22:45:37Z")
> [@jtur88](#): > > Measure the circumference of a wheel of a bicycle and mark the tire, and walk it or ride slowly counting the rotations. Or spend $20 and get a[professionally-made walking survey measuring wheel](http://www.amazon.com/1000FT-Walking-Counter-Survey-Measuring/dp/B004L181E6). ---
**Author:** ![chappachula](https://avatars.discourse-cdn.com/v4/letter/c/d2c977/32.png) [@chappachula](https://boards.straightdope.com/u/chappachula)\ **Post date:** [August 21, 2014, 8:22am UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/10 "2014-08-21T08:22:39Z")
> [@HoneyBadgerDC](#): > > We measure at a right angle to a center line comming off the shooting line.\*\* Actual distance shot is not measured\*\*, distance from the shooting line is measured and . The total station we use at official events does all the math. How far off of the centerline do the arrows usually fall? The actual distance shot should be pretty close to the distance which you want to measure along the centerline. Sure, a Total Station\* can “do all the math”, but it’s pretty simple math! The pythagorean theorem calculates the long side of a triangle: If you shoot 500 yards, the arrow can fall 35 yards off the centerline, and the actual distance shot is only 501 yards. If you shoot 300 yards, the arrow can fall 25 yards off the centerline, and the actual distance shot is only 301 yards If you shoot 100 yards, the arrow can fall 15 yards off the centerline, and the actual distance shot is only 101 yards. (\*for those who don’t know: a “Total Station” is an electronic instrument used by professional land surveyors) ---
**Author:** ![chappachula](https://avatars.discourse-cdn.com/v4/letter/c/d2c977/32.png) [@chappachula](https://boards.straightdope.com/u/chappachula)\ **Post date:** [August 21, 2014, 9:32am UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/11 "2014-08-21T09:32:37Z")
Oops! I just re-read the OP and realized that he is talking about accuracy of one foot, not one yard, and over a distance of just 50 yards.\* So a re-do of the math shows that: If you shoot 50 yards (150 feet), and the arrow falls 20 feet off the centerline, the actual distance shot is only 151 feet. If you shoot 30 yards (90 feet) and the arrow falls 15 feet off the centerline, the actual distance is shot only 91 feet. - (aside: so why are your friends so suspicious of your laser rangefinder that you’d have to verify it with a 500 yard tape?) ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [August 21, 2014, 12:55pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/12 "2014-08-21T12:55:40Z")
If your plan already includes buying a 100 yard tape measure, how is it a problem to measure accurately at 50 yards? ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 21, 2014, 2:11pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/13 "2014-08-21T14:11:30Z")
> [@Ethilrist](#): > > If your plan already includes buying a 100 yard tape measure, how is it a problem to measure accurately at 50 yards? ``` I don't think one person has understould the post. ``` We are NOT measuring the distance an arrow travels. The center line is laid out with a tape measure for 500 yards at a right angle to the shooting line We are measuring where the arrow intersects with the centerline at a right angle. The measurent is laid out ahead of time. The challenge is to find a way to accurately sight off the center line at a right angle. An arrow might be to the left or the right of the centerline and it might be 12" from the line or 200 yards from the line I just need a simple and acurate way to measure a bunch of scattered arrows at a right angle to this line. ---
**Author:** ![August\_West](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/august_west/32/18069_2.png) [@August\_West](https://boards.straightdope.com/u/August_West)\ **Post date:** [August 21, 2014, 3:22pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/14 "2014-08-21T15:22:05Z")
I’m completely confused and think I need a diagram. ---
**Author:** ![BubbaDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bubbadog/32/333_2.png) [@BubbaDog](https://boards.straightdope.com/u/BubbaDog)\ **Post date:** [August 21, 2014, 3:33pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/15 "2014-08-21T15:33:21Z")
Buy 2 100 yard tapes. Measure out 500 yards for the center line by leapfrogging the two tapes. Mark that center line every 100 yards (actually you can mark it 25 or 50 too). After the shot, you need to just determine two marker spots on your 500yard line. One marker spot before the perpendicular point of the arrow and one marker spot after the perpendicular point of the arrow. From those two spots, measure the distance to the arrow and determine the angles from the two spots. Use tenth grade geometry. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [August 21, 2014, 3:48pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/16 "2014-08-21T15:48:54Z")
You’re trying to measure how far from the center line, left or right, people hit? So if somebody is 11 feet to the left, and somebody else is 12 feet to the right, you need to be able to tell accurately which one is closer to the center line from 50 yards away, without walking out there with the measuring tape? ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 21, 2014, 3:50pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/17 "2014-08-21T15:50:19Z")
> [@August\_West](#): > > I’m completely confused and think I need a diagram. Think of a football field with a grid, both shooters are behind the one yard line, one is on the far left of the field and one is on the far right of the field. When they loose their arrows they both travel to the opposing one yard line but they land side by side on the left side of the field. The shooter on the right had his arrow travel further because he shot across the width of the field as well as the length of the field but the would both score the same. The archer is penalized for not shooting at a right angle to the shooting line regardless of where he is positioned on the shooting line. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 21, 2014, 3:52pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/18 "2014-08-21T15:52:29Z")
> [@Ethilrist](#): > > You’re trying to measure how far from the center line, left or right, people hit? So if somebody is 11 feet to the left, and somebody else is 12 feet to the right, you need to be able to tell accurately which one is closer to the center line from 50 yards away, without walking out there with the measuring tape? No we are just trying to find where the arrow intersects the center line on a right angle, it makes no difference how far he is from the center line, the challenge is to simply find a quick easy way to establish a right angle we can sight down off the center line. We may have 50 arrows to measure so it needs to be quick and easy. The center line is layed out with tape measures and marked ahead of time. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [August 21, 2014, 4:22pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/19 "2014-08-21T16:22:31Z")
I just thought of what would work, two sets of sights, one set pointing back to the shooting line to square up my t square and one set pointing at the arrow where it landed. All readings are comming off a premeasured shooting line. Plant the square lined up paralell to the shooting line using the sights and slide the right angle bar until it lined up with the arrow. Should be pretty accurate. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [August 21, 2014, 4:23pm UTC](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032/20 "2014-08-21T16:23:15Z")
So it’s like football, where you don’t care how far left or right it is, you just want to know how many yards you made: you could run the entire _width_ of the field, but if you only move the ball forward one yard, that’s one yard. [Next page](https://boards.straightdope.com/t/how-accurate-would-this-measurement-be/696032.md?page=2)