# Point on distance calculator



## longbowguy (Nov 14, 2004)

You don't need calculation, you need observation. Get some good observations and you have something to calculate with.

Get a tall backstop, a small target spot set low and a tape measure. Put your arrow tip on the spot, at maybe 20 yards, make a good shot and measure the variance in elevation. Write it down. Walk back 5 yards and repeat. Eventually you will find the distance at which there is little variance. That will be your first approximate point-on range. 

It will take many such tests over days, weeks, and months as your form and execution change. From your observation notes you can calculate the trajectory and holds over and under for the intermediate distances, and make a chart or graph. Then repeat with a different or trimmed arrow. There a multiple variables so you need to build a body of data to calculate and estimate from.

Observe first, calculate later. - lbg


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## Hank D Thoreau (Dec 9, 2008)

I wrote a program that does it but it depends on face geometry, form, as well as ballistics. I am not sure it would give the correct answer.


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## grantmac (May 31, 2007)

You would need to know at least two gaps, preferably three and they would need to be accurate.

Otherwise anchor height plays far too critical of a role.

Grant


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## Sauk Mountain (Aug 3, 2015)

Just go out and shoot till you find it.


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## reddogge (Jul 21, 2009)

Trial and error is the best method. Go out with a notepad, ruler and pencil and write your gaps down. I shot the same course Sunday as last week and the club had an elk at 45 yards. How did I know? They set it in front of a field butt with field markers on the ground. Sunday when I shot it I knew my point on was 35 yards so I held the point on the cross member above the elk and plomp....twice... in the vitals. I don't use formulas for anything, just trial and error.


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## Easykeeper (Jan 2, 2003)

I'm sure it's possible to write a script that would calculate it, but it wouldn't be easy. There's also lots of places that error could creep in. Some of the input variables you would have to account for would be an accurate initial arrow speed, launch angle, distance from the nock to your eye, exact arrow length including point, fletching style and size, an accurate drag coefficient for feathers (good luck), physical dimensions of your arrow (length and cross sectional area, look up drag coefficient), altitude (air density) and probably several I can't think of at the moment.

And the assumption is a good tune, otherwise you will be shedding a lot of arrow speed through a wobbly arrow.

It might be a fun exercise but ultimately it's going to be easier, faster, and probably more accurate to just shoot to find out.


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## rraming (Aug 5, 2006)

You need your shoe size in order to calculate it:embara:


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## Isaac1982 (May 28, 2014)

longbowguy said:


> You don't need calculation, you need observation. Get some good observations and you have something to calculate with.
> 
> Get a tall backstop, a small target spot set low and a tape measure. Put your arrow tip on the spot, at maybe 20 yards, make a good shot and measure the variance in elevation. Write it down. Walk back 5 yards and repeat. Eventually you will find the distance at which there is little variance. That will be your first approximate point-on range.
> 
> ...


This is not financially effective. I can't randomly throw arrows together looking for a 40 yard point on, or a 60 yard, etc. I'd run out of dollars trying to come up with arrows with a set point on distance.


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## Isaac1982 (May 28, 2014)

Easykeeper said:


> I'm sure it's possible to write a script that would calculate it, but it wouldn't be easy. There's also lots of places that error could creep in. Some of the input variables you would have to account for would be an accurate initial arrow speed, launch angle, distance from the nock to your eye, exact arrow length including point, fletching style and size, an accurate drag coefficient for feathers (good luck), physical dimensions of your arrow (length and cross sectional area, look up drag coefficient), altitude (air density) and probably several I can't think of at the moment.
> 
> And the assumption is a good tune, otherwise you will be shedding a lot of arrow speed through a wobbly arrow.
> 
> It might be a fun exercise but ultimately it's going to be easier, faster, and probably more accurate to just shoot to find out.


I'm looking at the cost factor because I am trying come up with arrow recipes with a set point on before building them. Shooting a bow is always fun!


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## centershot (Sep 13, 2002)

I think that there are so many variables from archer to archer that you could never get an accurate calculation. Add to that the fact that many archers have so many form inconsistencies that you could not even establish a quality base line - next to impossible. Luckily it is pretty easy to do in real life. A good size target and piece of string and an aiming dot at you can do it in 5 arrows. Jimmy Blackmon demonstrates it very well in some of his videos.


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## xringer-10 (Apr 15, 2007)

Have you considered adjusting the nock height on your string to change your PO? My indoor, target, 3D and hunting rigs all have different nock heights to accommodate my desired point on. I also use a fixed crawl (shorter PO, hunting) or lower anchor point (farther PO, 80yd field) in some instances to achieve the desired PO.


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## 5 Arrow (Nov 20, 2015)

Kinematics equations for motion in 2 dimensions and least squares will give you the coefficients for the resulting second degree polynomial. You can then use this equation to estimate the x distance for point on.
I use this method as an initial estimate for sight settings on my FITA rigs. Changing anything that effects the initial velocity of the arrow requires gathering a new set of data. I do these calculations before shooting long distances like 70m with expensive arrows. It gets me a close sight setting (arrow in target) from where I can fine tune.

At traditional distances you need to decide how your time is best spent. Gathering empirical data to use in tedious calculations (definitely set up so a PC does the calculations) or shooting arrows taking some simple measurements and recording the results. In my way of seeing things being outside shooting the bow, recording some measurements, and taking a break for a lemonade and calculation is a lot more enjoyable than sitting in front a PC and crunching numbers. 

Either way your initial results are going to be estimates. They need to be tested and verified. Change some significant variable and the old data becomes an estimate of current situation. Shooting a bow is a labor of love. Just about like anything else the easy way is usually not the best way.


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