range finder tilt/Pythagorean theorem

[Florida_Native]

So I'm in the market for a range finder. After doing research and over simplifying the math here are my current thoughts. Please tell me if  I am wrong!

When shooting at an angle your shot should be made at the horizontal distance or b in terms of the theorem. However, a range finder without the tilt/arc function would give you c.

Let say I am shooting at a distance of 50 yards my max with a bow and an elevation of 10 yards. My nontilt range finder will tell me to shoot at approx. 51 yards when I should be shooting at 50. Correct? So this is a difference of 1 yard or 3 feet.

Lets change the elevation to 50 yards just for giggles. the range finder will say to shoot at 70 yards and I should only shoot at 50.

So in scenario 1 the need for the tilt function is negligible an in scenario 2 necessary.

If I am correct in my math the decision to spend the extra money on the tilt function comes down to the probability I will shoot at above 10 yards. Any thoughts on this probability?

[Bob33]

Your math is correct. However, not all angle functioned rangefinders follow the Pythagorean theorem completely. For example, Leupold will tell you their calculation is proprietary.

[Magnum_Willys]

.. 6% difference at 20 degrees, 3.4% difference at 15 degrees  ( just type cos of angle in ur iphone )

[Magnum_Willys]

If I am correct in my math the decision to spend the extra money on the tilt function comes down to the probability I will shoot at above 10 yards. Any thoughts on this probability?

You mean "degrees" I think.  20 degrees is REALLY steep in the field.  You wouldn't think so but it is, unless maybe you are a sheep hunter.   Now if you are a bow hunter with a TALL tree stand maybe it makes a big difference. 

[Florida_Native]

I would imagine no range finder uses the Pythagorean theorem since it would have to know the elevation. I'm just pondering the necessity of the tilt function. I found a the Simmons LRF 600 for $80, but its about $70 more if you want the tilt. I don't imagine I will need the tilt that often since I am using my bow and rarely am at an elevation above my target over 10 yards. However, I likely won't be hunting in the same area for that much longer.

Based on my calculations it seems as though the function would rarely come in handy but I haven't hunted that many areas. Do you ever find that the tilt would be necessary? I don't want to get the cheaper one for now and end up needing the tilt later. 

[Florida_Native]

You mean "degrees" I think.  20 degrees is REALLY steep in the field.  You wouldn't think so but it is, unless maybe you are a sheep hunter.   Now if you are a bow hunter with a TALL tree stand maybe it makes a big difference.

No the formula I am using is based on height. The formula fro degrees was much longer and frankly hurt my head thinking about.

[Bob33]

I would imagine no range finder uses the Pythagorean theorem since it would have to know the elevation.

The Pythagorean theorem needs the actual distance, and angle. Elevation is irrelevant.

[Florida_Native]

Granted its wikipedia but check this out: https://en.wikipedia.org/wiki/Pythagorean_theorem. then look at other forms. The theorem assumes the largest angle, of the triangle, is 90 degrees.

I'm not using the right formula with angles. I believe its the riflemans formula or something. I was trying to oversimplify it.

[Magnum_Willys]

Assume you were 10 yards up in the tree....

Range finder says 20 yards its really 17.3
says 40 its really 38.7
says 60 really 59.2

square root of (range finder squared minus stand height squared) = true ballistic range

[Florida_Native]

Assume you were 10 yards up in the tree....

Range finder says 20 yards its really 17.3
says 40 its really 38.7
says 60 really 59.2

square root of (range finder squared minus stand height squared) = true ballistic range

Ok, I'm on the same page:) So at a longer distance the angle is less so it becomes closer to true distance per the rangefinder.

Next question. Would you shoot different at a 17 yard target than a 20? I'm not experienced enough with a bow to confidently answer?

Thanks for chatting this through with me BTW!

[JimmyHoffa]

Any angle not zero the distance will be less than the rangefinder.

[Magnum_Willys]

Next question. Would you shoot different at a 17 yard target than a 20? I'm not experienced enough with a bow to confidently answer?

Ballpark about an inch difference ,  4 inches if off by 10 yards

[RadSav]

Next question. Would you shoot different at a 17 yard target than a 20? I'm not experienced enough with a bow to confidently answer?

Depends on what target you are trying to shoot.  Are you wanting to shoot the head off a grouse or hit the lungs of an elk?

On my favorite bow my over/under on the X-Ring of a 20 yard NFAA field target is 20.7/19.1  Five ring on the same target is 21.4/18.3 and the 4 ring is 23.8/12.5   Extend the range and slow down the bow and the over/under gap gets larger to a fair degree.

IMO - The first time you miss a big buck at 50 yards downhill you will wish you spent the extra $70

[raydog]

Next question. Would you shoot different at a 17 yard target than a 20? I'm not experienced enough with a bow to confidently answer?

IMO - The first time you miss a big buck at 50 yards downhill you will wish you spent the extra $70

 

[flcracker]

Go Gators!!

[luvmystang67]

A rangefinder would not use Pythagorean as it would need actual height above your target, but its all trig.  It probably uses an internal level to gauge the downward or upward angle that you're using and then the distance along the hypotenuse and uses trig.

Someone on here has previously mentioned it, but if you take the cosign of the angle (angle above or below level) and multiply that by the range shown on the rangefinder, that'll give you the true level distance.

If you're looking down at 15 degrees and your old school rangefinder shows 200 yards, to figure out true distance:

1) Make sure you calculator is in degree mode (many default to radians, which for those of you who may not know, is just a different way to measure angle, instead of 360 degrees in a circle, there are 2xpi = ~6.28 radians in a circle).   If your calculator is in the wrong mode, when you type in 15, it may think you're talking 15 radians and not 15 degrees.

2) The equation is quite simple, plug in cos(15 degrees) * 200 yards = 0.9659 * 200 = 193 yards true aim.