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Rifle Scopes Inconceivable?

almsquattro

Private
Full Member
Minuteman
Apr 8, 2010
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The question was asked "what are the limitations of ranging with your reticle?"

Being a novice, but understanding the generally accepted ranging formula (target size in inches X 100/minutes of angle = distance in yards), I calculated a hypothetical math problem. Using an average height person 5 ft. 10 in. = 70 inches tall. So 70 X 100 = 7000. Now, I have a Nightforce NP-R1 reticle with 1 MOA hash marks. So, if the subject person is 1 MOA on my reticle (from top of head to toe), this calculates to 7000 yards. 7000 yards divided by 1760 yards per mile = <span style="font-weight: bold">3.97 miles</span>.

<span style="font-weight: bold">This means it is possible to range a person 4 miles away.</span> Even as I write it, it sounds ridiculous. What am I missing here? Can you really see a person 4 miles away or should I switch from tequila to vodka?
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: almsquattro</div><div class="ubbcode-body"><span style="font-weight: bold">This means it is possible to range a person 4 miles away.</span> Even as I write it, it sounds ridiculous. What am I missing here? Can you really see a person 4 miles away or should I switch from tequila to vodka?
</div></div>

A person at 4 miles viewed through a 15x optic would be equivalent to viewing the person at little more than a quarter mile away.
 
Re: Inconceivable?

So the calculation is not flawed, and it is possible to see and range a person 4 miles away (on my 22X scope). Thanks Drifter.
 
Re: Inconceivable?

It's not about the ability to see the target, it's the ability to accurately both measure it AND estimate the target size accurately. This is easy when you have a known size of target, and not so much when you don't. Top it off with mirage and the ability to perfectly define the target's edges and you have an even greater margin of error. Once you start trying this at longer distances, even a small error throws off your data to the point where you will miss.
 
Re: Inconceivable?

Of course....you are making the assumption that the atmospheric conditions allow resolving a target of this size....
 
Re: Inconceivable?

I believe it to be tMOA and I know the formula is slightly different. I understand the margin of error will be increase exponentially at greater distances but the calculation would be a bit better than a WAG (wild a__ guess). And reading the limitations of most laser range finders, at distance, even the best rangefinder would probably be useless.
 
Re: Inconceivable?

How many places do you have a clear LOS with no angle to skew the target when ranging a target vertically?

Let along mirage, position and other factors that would prevent an accurate mil at that distance.
 
Re: Inconceivable?

Okay guys, we are not talking about accuracy or ballistics here. I was just asked "what is the extreme limits of ranging with a ranging reticle". Based on the ranging calculations, in perfect conditions, if you see a 5'10" tall person and he is 1 MOA according to your reticle, then he must be 4 miles away (give or take a mile, haha).

4 miles. Possible or impossible?
 
Re: Inconceivable?

Give or take a mile! Big Miss

You need a Missal!
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: almsquattro</div><div class="ubbcode-body">Okay guys, we are not talking about accuracy or ballistics here. I was just asked "what is the extreme limits of ranging with a ranging reticle". Based on the ranging calculations, in perfect conditions, if you see a 5'10" tall person and he is 1 MOA according to your reticle, then he must be 4 miles away (give or take a mile, haha).

4 miles. Possible or impossible? </div></div>

Try this....

Lets say he is exactly 1 MOA, say you range him at 1.1 moa because of user error (which isnt much of an error).

How for is he now?

and that is only .1 or an MOA.
 
Re: Inconceivable?

Have another beer or go to bed it's late there
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: tipper</div><div class="ubbcode-body">Is it IPHY or Tmoa


TMOA=6,384.9yds = 3.6
</div></div>

Dam I had the right answer the whole time!
 
Re: Inconceivable?

Now I don't know about you but the ability to subtend moa further than 0.1 is pushing it, but the ability to EXACTLY do it in field conditions is pretty much impossible. The precision required to come up with a mil/moa measurement to that degree, even when forgiving mirage, angle to target and assuming you have the exact size of target.

Additional factors involved are being able to resolve a 1moa target image, that your glass was absolutely precisely produced and ground (they didn't even get the Hubble right the first time), that your reticle really is EXACT, that your SFP scope is dead on the required setting (if applicable), that you can hold your rifle absolutely perfectly still and that his hair isn't standing up or wearing a pair of boots giving him an extra couple inch height....

I've needed to range targets at those distances when calling in artillery and I did it with a map, not my reticle. That is your "better than a wild ass guess".
 
Re: Inconceivable?

inconceivable-indigo-princess-bride-demotivational-poster-1262620902.jpg
 
Re: Inconceivable?

On a cool morning coming down trail overlooking a valley, using an moa scope, I've ranged deer at just over two miles. Then verifed it with a USGS topo map, and then again with a GPS.

Later that afternoon, I could barely make a rack estimate of a deer standing about 700 yds. from me.

So, what I'm saying is on a perfect morning or evening, with enough light, without too much heat, but no frost, and a near perfect rest, and a comfortable position, and a really clear scope....you might get it done. One bad condition and it's like trying to clearly see a fish in the river. You see his shape. You might see his movement, but every boil of the water distorts the view of him. Air between you and the objective does the same thing. Any roughness or disturbance makes it impossible to clearly see.
 
Re: Inconceivable?

The limitations of ranging with a reticle happen when bullet drop can be significant enough to make small margins of error in ranging prevent a shot.

For example, 308 bullet drop difference between 900 yards and 1000 yards is roughly 90 inches (IIRC).

So, if you range a person using an assumed 2.1 yards tall and they measure 2.1 mils, they'd be 1000 yards away. But, if they were really 1.9 yards tall, they'd only be 904 yards away. There's no way you'd make that shot with 308.
 
Re: Inconceivable?

I have never ranged with my reticle but corrections are easier with my MP8 IOR reticle. First shot hits are great but not very often. Its the last 4 that count in a 5 shot group over 300 yards.

In the only comp I have shot at known distances the wind made the difference, and allowed me to shoot very well on my first outing.
 
Re: Inconceivable?

Sand Warrior.....conceivable? It sure sounds like it.

For those who disagree, please explain to me how (in perfect conditions) a man size (or even deer size) object just disappears if it is smaller than 1 (or even 2) MOA? And if the image of the man size object doesn't disappear, then you should be able to do a calculation and get an "idea" of how far the object is.

Let me spell it out again.....we are not talking about accuracy, precision, ballistics, or even if the lucky fella is touchable with a .22 lr or a 50 cal. projectile 3 miles away....I'm just saying that if you have a 5 ft. 10in. target that appears to be 1 MOA, can you really say that you have no clue how far the object is? If you can see the image and do 3rd grade math, well then "approximately" how far is the object? Again, I'm not asking you to hit it.
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: almsquattro</div><div class="ubbcode-body">Sand Warrior.....conceivable? It sure sounds like it.

For those who disagree, please explain to me how (in perfect conditions) a man size (or even deer size) object just disappears if it is smaller than 1 (or even 2) MOA? And if the image of the man size object doesn't disappear, then you should be able to do a calculation and get an "idea" of how far the object is.

Let me spell it out again.....we are not talking about accuracy, precision, ballistics, or even if the lucky fella is touchable with a .22 lr or a 50 cal. projectile 3 miles away....I'm just saying that if you have a 5 ft. 10in. target that appears to be 1 MOA, can you really say that you have no clue how far the object is? If you can see the image and do 3rd grade math, <span style="font-weight: bold">well then "approximately" how far is the object? Again, I'm not asking you to hit it.</span></div></div>

Best statement of the thread.
 
Re: Inconceivable?

Your hypothetical situations and scenarios are laughable. Can it get you within 1/2 mile, sure, and maybe even within 300yds sometimes, but your margin of error and potential accuracy is so limited that it's not worth it. There are far better methods to use.

You already proved in your OP that a lot use a less than accurate formula for moa ranging and the associated 3rd grade math. It's the simplified version that is used by shooters in the field to make faster calculations, and is in the same category as shooters using 1moa = 1"/100yds. You should multiply by 95.5, not 100. Getting out to the ranges you're talking about, the error really stacks up.

Look here for the details behind the math:
http://www.mil-dot.com/media/1027/the_derivation_of_the_range_estimation_equations.pdf

Or here for a nicely compiled listing of all the formulas compliments of Lindy:
http://www.arcanamavens.com/LBSFiles/Shooting/Downloads/Ranging/

But hey, I'll play your perfect atmospheric conditions and equipment game.

Lets bounce some figures around showing how little room for error there really is. For this I will use your example of a 70" target.

0.90 moa: 7428yds
0.95 moa: 7037yds
1.00 moa: 6685yds
1.05 moa: 6367yds
1.10 moa: 6077yds

In the span of 0.2 moa the range shifted over 1300yds and in 0.1 moa it shifted nearly 700yds. Hardly what I would consider accurate, but hey, if you're inside .05moa you're almost within 300yds.

Try this exercise out. Cut out a bunch of pieces of paper in random lengths, then tape them to your target board at 100yds. Make a map of them, measure them out with your reticle and note this on your map, then go back and measure them with your ruler converting them to moa. Any deviation greater than .05moa is unacceptable, and keep in mind that if you're more than 1/16" off you're wrong. You can put yourself exactly 95.5yds if you don't feel like converting.

Now lets play with a varying target size but measuring precisely 1 moa:

69.0": 6589yds
70.0": 6685yds
71.0": 6780yds

95yds variation per inch. That's easily within the pair of boots or having a bad hair day range of heights, and that's also assuming said target is standing full upright with princess perfect posture and you're viewing it at a direct square angle.

These are both commonly made errors that are good enough for us to shoot with inside 1000yds, but once you start playing with the distances you're talking about they compound to a level of inaccuracy that it isn't worth it. Coming back to reality and compounding these errors with atmospheric conditions, position stability, equipment accuracy and so on, you realize again why we break out the map or laser instead of using the reticle for these types of distances and still use a combination of range estimation methods.

It may be good enough for you to impress your friends that you can ballpark within 1/2 mile, but it's hardly what I would consider accurate and certainly less accurate than I can plot off a basic topo map. For you it may very well be good enough.
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">See what happens when you have no practical experience doing something... you end up playing with calculators and looking stupid on the internet.-Lowlight</div></div>
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HasgunWilltravel</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">See what happens when you have no practical experience doing something... you end up playing with calculators and looking stupid on the internet.-Lowlight</div></div></div></div>

That was funny!
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<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Redmanss</div><div class="ubbcode-body">Your hypothetical situations and scenarios are laughable. Can it get you within 1/2 mile, sure, and maybe even within 300yds sometimes, but your margin of error and potential accuracy is so limited that it's not worth it. There are far better methods to use.

You already proved in your OP that a lot use a less than accurate formula for moa ranging and the associated 3rd grade math. It's the simplified version that is used by shooters in the field to make faster calculations, and is in the same category as shooters using 1moa = 1"/100yds. You should multiply by 95.5, not 100. Getting out to the ranges you're talking about, the error really stacks up.

Look here for the details behind the math:
http://www.mil-dot.com/media/1027/the_derivation_of_the_range_estimation_equations.pdf

Or here for a nicely compiled listing of all the formulas compliments of Lindy:
http://www.arcanamavens.com/LBSFiles/Shooting/Downloads/Ranging/

But hey, I'll play your perfect atmospheric conditions and equipment game.

Lets bounce some figures around showing how little room for error there really is. For this I will use your example of a 70" target.

0.90 moa: 7428yds
0.95 moa: 7037yds
1.00 moa: 6685yds
1.05 moa: 6367yds
1.10 moa: 6077yds

In the span of 0.2 moa the range shifted over 1300yds and in 0.1 moa it shifted nearly 700yds. Hardly what I would consider accurate, but hey, if you're inside .05moa you're almost within 300yds.

Try this exercise out. Cut out a bunch of pieces of paper in random lengths, then tape them to your target board at 100yds. Make a map of them, measure them out with your reticle and note this on your map, then go back and measure them with your ruler converting them to moa. Any deviation greater than .05moa is unacceptable, and keep in mind that if you're more than 1/16" off you're wrong. You can put yourself exactly 104.7yds if you don't feel like converting.

Now lets play with a varying target size but measuring precisely 1 moa:

69.0": 6589yds
70.0": 6685yds
71.0": 6780yds

95yds variation per inch. That's easily within the pair of boots or having a bad hair day range of heights, and that's also assuming said target is standing full upright with princess perfect posture and you're viewing it at a direct square angle.

These are both commonly made errors that are good enough for us to shoot with inside 1000yds, but once you start playing with the distances you're talking about they compound to a level of inaccuracy that it isn't worth it. Coming back to reality and compounding these errors with atmospheric conditions, position stability, equipment accuracy and so on, you realize again why we break out the map or laser instead of using the reticle for these types of distances and still use a combination of range estimation methods.

It may be good enough for you to impress your friends that you can ballpark within 1/2 mile, but it's hardly what I would consider accurate and certainly less accurate than I can plot off a basic topo map. For you it may very well be good enough.</div></div>

My point about your numbers tirade is <span style="text-decoration: underline"><span style="font-weight: bold">IF</span></span> everything was <span style="text-decoration: underline">perfect</span>, the light, the mirage, the color of the target, your elevation in relation to the target, no wind, no frost, out West where it gets really clear, {cause I never saw that well when I was in Georgia}...

When does that ever happen? Often enough out West, but still not overly common.

Fast forward to the afternoon when mirage is boiling and running and trying to get an estimate of a deers antlers (yes, I trophy hunt) wasn't very easy. At far less than what would be considered a very doable distance.

All it takes is one pebble in the pool, and you can't see the bottom any more.

Yes, someone that height looks to be about <span style="text-decoration: line-through">1/2 of an</span> 1 moa, give or take a large margin of error. You're not going to see it every time by a longshot. On a lucky day you could...

And yes, for smart long range estimating, you'd use the tools you brought to range that far, topos and gps.
 
Re: Inconceivable?

sandwarrior, my post was not directed at you, it was at the OP who thinks that because you did it at 3400-ish yds that he can pull it off at double that distance with any reasonable degree of accuracy. Quite frankly his last post reminds me of this:

2f0ef064-30c9-4482-bd57-cb4de74cc9cb.jpg

<span style="font-style: italic">I know there's a typo in the pic phrase, I didn't make it.</span>

My whole post is to prove the point that the room for error is so minimal that one should be happy if they're within half a mile with that distance and target size. Accurately visually subtending a moa reticle that is in 1moa increments within 0.05moa accuracy on a target at that range really is <span style="font-style: italic">inconceivable</span>.

I remember some of those beautiful mornings in school at Stone Bay when we could actually see the full target image perfectly, and we were still happy to get within 0.1mil on the range est. exercises on a target we had the size of at distances <850yds. Taking that 8-fold further while requiring an even greater degree of accuracy is insane.

Seriously, can you or anyone else here mil/moa out a target at 100yds and never exceed 1/16" deviation all the time? Then apply that to a target over 6k away with the same degree of accuracy?

Maybe +/- 700yds is accurate for him. I'll stick to the map and lasers.
 
Re: Inconceivable?

Once I get past 600,700 yards range estimating gets really tricky. Some days it makes we wish I was shooting a laser!
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JFComfort</div><div class="ubbcode-body">Once I get past 600,700 yards range estimating gets really tricky. Some days it makes we wish I was shooting a laser! </div></div>

ssshhh.... That's the "top secret" weapon.

I read in a book somewhere, there are ways to light up the beam and give a direct pinpoint to your location. Not owning one, and still being alive...that obviously hasn't happened to me.
wink.gif
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Re: Inconceivable?

Redmanss, all due respect, but your ADHD is laughable. Or has it progressed to anterograde amnesia? (Go ahead. Look it up.) How many times do I have to keep reminding you that I'm not talking accuracy? I'm just asking if it is ever "possible" to see a person sized object that measures 1 MOA on a 22X scope. If not, explain. If yes, can you get an "approximation" of its distance. <span style="font-weight: bold">I AM NOT ASKING YOU TO HIT SOMETHING 4 OR EVEN 2 MILES AWAY. AND GUESS WHAT ADHD BOY, I AM NOT EVEN ASKING YOU TO SHOOT. CEASE FIRE AND JUST PUT THE RIFLE DOWN FOR A SECOND, READ THE QUESTION, AND CONCENTRATE!</span>

Anyways, I'm sure you have already forgotten, but you did unintentionally answer the question by indicating it is possible. Thanks for playing, Corky! Have a nice day.
wink.gif


Tipper, I appreciate the link to the article; however, my question was specifically about the possibility of ranging and independent of ballistics. Nonetheless, it is a very interesting article. Thanks.
 
Re: Inconceivable?

Hell No!

It is true that Harley showed quite correctly that the earth curves approximately 8 inches in one mile. The solution presented then goes on to find out over how many miles does the earth curve 72 inches or 6 feet. Then this distance is doubled which is required (and would be easy to forget), because each man looks this distance to his horizon, where the line of sight is tangent to the earth's surface midway between them. All of this reasoning is correct so far.

However, it turns out that while the earth does curve 8 inches in one mile, it does not take 9 miles to curve 72 inches. To show this, let us return to the Pythagorean Theorem method used by Harley, but using 6 feet for the curvature. Here is a copy of Harley's diagram with the 1 in the diagram replaced by x, since in this case the distance is unknown.

Again, using the theorem of Pythagoras

a2 = 39632 + x2 = 15705369 + x2

Solving for x,

x2 = a2 - 15705369

a must be 3963 miles + 6 feet (Let's say the men are actually 6'3", so their eyes are six feet above ground.). Thus
a = 3963.001136 miles

x2 = 15705378 - 15705369 = 9
x = 3 miles

Now, remember that each man looks 3 miles to the horizon, giving their distance from each other as 6 miles.

This shows that at eye level of 6 ft. the horizon is 3 miles (at sea or on a level plain).

A rule-of-thumb for line of sight problems such as this, where the distance is small in comparison to the size of the earth is

c = (2/3) times x2, where x is distance in miles and c is curvature in feet.

For the problem at hand, we then have x2 = (3/2)c

x2 = (3/2) 6 = 9
x = 3

This is the same result that the more lengthy solution yielded.

--Jerry

Thanks Jerry,

Penny
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: almsquattro</div><div class="ubbcode-body">Redmanss, all due respect, but your ADHD is laughable. Or has it progressed to anterograde amnesia? (Go ahead. Look it up.) How many times do I have to keep reminding you that I'm not talking accuracy? I'm just asking if it is ever "possible" to see a person sized object that measures 1 MOA on a 22X scope. If not, explain. If yes, can you get an "approximation" of its distance. <span style="font-weight: bold">I AM NOT ASKING YOU TO HIT SOMETHING 4 OR EVEN 2 MILES AWAY. AND GUESS WHAT ADHD BOY, I AM NOT EVEN ASKING YOU TO SHOOT. CEASE FIRE AND JUST PUT THE RIFLE DOWN FOR A SECOND, READ THE QUESTION, AND CONCENTRATE!</span>

Anyways, I'm sure you have already forgotten, but you did unintentionally answer the question by indicating it is possible. Thanks for playing, Corky! Have a nice day.
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Tipper, I appreciate the link to the article; however, my question was specifically about the possibility of ranging and independent of ballistics. Nonetheless, it is a very interesting article. Thanks. </div></div> Dude, please. You asked this:
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: almsquattro</div><div class="ubbcode-body">The question was asked "what are the limitations of ranging with your reticle?
</div></div>
And I told you that the limitations of ranging with your reticle is outside the possibilities of any realistic ranging accuracy. It doesn't matter if you can see the target, it matters if you can measure that target accurately. I wasn't talking about ballistics or shooting at all. I said if getting within 1/2 mile is what you consider accurate, then go on with your bad self.

Trust me, you're not going to hurt my feelings with your shit talking. I've done this for a long time as a professional and I've got the credentials to back it up. I might just know what I'm talking about because I've been using mil reticles on targets before we had the first GVS-5 issued to our platoon, and when you have a Bn of artillery running a mission for you it's a good thing to have an accurate O-T distance when running that polar mission on a target 7km away.

Hey self admitted novice, you know more than I do about the subject, don't you.... Why post up your insane hypothetical scenario if you already knew you answer anyhow and won't listen to countering facts from experienced persons?

Go back to playing with your calculator and using the wrong formulas. Have fun with that. My USMC Scout Sniper ass is out of this one and not attempting to teach this kid any more.
 
Re: Inconceivable?

Is this a different case for the 'Picking on the Newbie' topic? Evidently this one isn't afraid...

In the end, on your perfect day, you can "see" the guy at 7200 yards (6' man 'milled' at 1MOA), but you can't find him unless he is: a) moving, b) wearing black out there on the desert floor, or c) he is silhouetting/back-lighting himself against a bright sky up on a ridge.

If he is holding still (not hiding - just standing) you won't find him if he is wearing anything colored like his surroundings.

You can play this game by having a buddy walk out and stand at 100 yards. You can see him no problem. Have him walk out and stand at 200 yards. You can see him no problem. Have him walk out at 300 yards. You can see him okay, and partly because you watched him walk out there. Now close your eyes (don't cheat) and have him walk out and stand at 360 yards (roughly equal to 7200 yards at 20x magnification - minus the mirage, etc.). When he's in place he can shout or radio you to open your eyes.

If he is in a wooded or grassy area, you'll spend a lot of time looking for him. If he's in some standard camo pattern, it'll take a long time to find him. If he's wearing full-value contrast to the surroundings (as noted above) you've got it easy, but otherwise you just won't find your guy.

It isn't what you asked, but that answer is already noted. You can do it - if things are just right AND your guy is cooperating with getting seen.
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: almsquattro</div><div class="ubbcode-body">The question was asked "what are the limitations of ranging with your reticle?"

Being a novice, but understanding the generally accepted ranging formula (target size in inches X 100/minutes of angle = distance in yards), I calculated a hypothetical math problem. Using an average height person 5 ft. 10 in. = 70 inches tall. So 70 X 100 = 7000. Now, I have a Nightforce NP-R1 reticle with 1 MOA hash marks. So, if the subject person is 1 MOA on my reticle (from top of head to toe), this calculates to 7000 yards. 7000 yards divided by 1760 yards per mile = <span style="font-weight: bold">3.97 miles</span>.

<span style="font-weight: bold">This means it is possible to range a person 4 miles away.</span> Even as I write it, it sounds ridiculous. What am I missing here? Can you really see a person 4 miles away or should I switch from tequila to vodka?
</div></div>
There is no limitation of the reticle, but the guy using it might have a few.

As far as what your missing, a lot, would be my answer.

Lets just say your target is wearing hide'y cloths, your not going to find him, but if you did and could define the toes an head, just a minor light change would put you out of the circular probability error range of a 155mm, let alone a shoulder weapon.

Now lets say your target is wearing red, yellow, gloss black, white or blaze orange, by the time you Factor in that correction,....

Take some 12X12 cardboard, paint it those colors. Set them out in different light, on a nice 2-4 ft above ground stand so you can define the edges, at least 400yds away, an report back.
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: tipper</div><div class="ubbcode-body">Hell No!

It is true that Harley showed quite correctly that the earth curves approximately 8 inches in one mile. The solution presented then goes on to find out over how many miles does the earth curve 72 inches or 6 feet. Then this distance is doubled which is required (and would be easy to forget), because each man looks this distance to his horizon, where the line of sight is tangent to the earth's surface midway between them. All of this reasoning is correct so far.

However, it turns out that while the earth does curve 8 inches in one mile, it does not take 9 miles to curve 72 inches. To show this, let us return to the Pythagorean Theorem method used by Harley, but using 6 feet for the curvature. Here is a copy of Harley's diagram with the 1 in the diagram replaced by x, since in this case the distance is unknown.

Again, using the theorem of Pythagoras

a2 = 39632 + x2 = 15705369 + x2

Solving for x,

x2 = a2 - 15705369

a must be 3963 miles + 6 feet (Let's say the men are actually 6'3", so their eyes are six feet above ground.). Thus
a = 3963.001136 miles

x2 = 15705378 - 15705369 = 9
x = 3 miles

Now, remember that each man looks 3 miles to the horizon, giving their distance from each other as 6 miles.

This shows that at eye level of 6 ft. the horizon is 3 miles (at sea or on a level plain).

A rule-of-thumb for line of sight problems such as this, where the distance is small in comparison to the size of the earth is

c = (2/3) times x2, where x is distance in miles and c is curvature in feet.

For the problem at hand, we then have x2 = (3/2)c

x2 = (3/2) 6 = 9
x = 3

This is the same result that the more lengthy solution yielded.

--Jerry

Thanks Jerry,

Penny
</div></div>

The question assumes there is an elevation difference enough to give a clear view.

As I said before, if everything is perfect, like visibility of the target, you would get about 1 moa of the subject being ranged.

Also, note that with 1 moa hashmarks they will cover up some of the subject and that's where you will get a huge error in the reading. I did say 1/2 moa in my previous post. I did mean 1
moa.

YES it is possible. NO, it's not common.
 
Re: Inconceivable?

Short story:

Nobody can <span style="font-weight: bold">reliably</span> read with better than 0.1 mil accuracy in the real world. Sometimes, under ideal conditions, you can break down to 0.05 mil, but don't count on it.

Even if you knew that the target is exactly 1.8 m (you don't, they come in all sizes, and it is difficult to see all the target clearly), at 850 m this is only 2.11 mils. Combined with the +/- 0.1 mil this is almost a 5% ranging error, and with a 308 this is a miss.

And if you use a shorter baseline like the "normal" guesstimation of 1.0 m top of head-to-crotch value, the ranging error using the reticle is enough to miss at about 650 m.
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gugubica</div><div class="ubbcode-body">Who cares?

Are we really talking about accurately ranging a human at 4 miles...seriously.

Simple answer, no. </div></div>

Not accurate ranging, just would they show up as about 1 moa in your scope.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TiroFijo</div><div class="ubbcode-body">Short story:

Nobody can <span style="font-weight: bold">reliably</span> read with better than 0.1 mil accuracy in the real world. Sometimes, under ideal conditions, you can break down to 0.05 mil, but don't count on it.

Even if you knew that the target is exactly 1.8 m (you don't, they come in all sizes, and it is difficult to see all the target clearly), at 850 m this is only 2.11 mils. Combined with the +/- 0.1 mil this is almost a 5% ranging error, and with a 308 this is a miss.

And if you use a shorter baseline like the "normal" guesstimation of 1.0 m top of head-to-crotch value, the ranging error using the reticle is enough to miss at about 650 m.</div></div>

All he asked was, if you could see a human who is 5' 10" would they show up as <span style="text-decoration: underline">'about'</span> 1 moa. MOA not MIL. Yes or no.

All of us delved way too deep into this. We all put the variables in there that weren't asked.

So, yah...that's what it would look like, if it could be done.
 
Re: Inconceivable?

He asked: <span style="font-weight: bold">"what are the limitations of ranging with your reticle?"</span>

and after his calculations, said: <span style="font-weight: bold">"This means it is possible to range a person 4 miles away"</span>

I explained the reticle reading limitations, and why this range is not possible. Same limitations for MOA or mil reticles, meters or yards.

Sorry if you took it as unnecessary blah, blah...
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TiroFijo</div><div class="ubbcode-body">He asked: <span style="font-weight: bold">"what are the limitations of ranging with your reticle?"</span>

and after his calculations, said: <span style="font-weight: bold">"This means it is possible to range a person 4 miles away"</span>

I explained the reticle reading limitations, and why this range is not possible. Same limitations for MOA or mil reticles, meters or yards.

Sorry if you took it as unnecessary blah, blah... </div></div>

Actually TF, he said "if the subject person was 1 moa on my reticle (from top of head to toe)", not "about 1 moa", or "close to 1 moa", ..... and you gave him a real answer about his statement (not question) that he could therefore range a person 4 miles away. Answer = no.

It can be done at 4 miles, but it will require something like a Vector 21 to do it.
wink.gif


http://www.vectronix.us/html/us/products/handhelds/long_range/vector_21_nite_superior_range
 
Re: Inconceivable?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DWood</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TiroFijo</div><div class="ubbcode-body">He asked: <span style="font-weight: bold">"what are the limitations of ranging with your reticle?"</span>

and after his calculations, said: "This means it is possible to range a person 4 miles away"

<span style="font-style: italic">I explained the reticle reading limitations, and why this range <span style="font-weight: bold">is not possible</span>. Same limitations for MOA or mil reticles, meters or yards.</span>

Sorry if you took it as unnecessary blah, blah... </div></div>

Actually TF, he said "if the subject person was 1 moa on my reticle (from top of head to toe)", not "about 1 moa", or "close to 1 moa", ..... and you gave him a real answer about his statement (not question) that he could therefore range a person 4 miles away. Answer = no.

It can be done at 4 miles, but it will require something like a Vector 21 to do it.
wink.gif
</div></div>

No, he said it can't be done. "Is not possible" means no can do. Can't see it. Tiro firo's statement clearly say's it can't be done.

I'm glad I don't believe him. He's called BS on a number of things that HAVE proven out. Events that have even been duplicated right here on the hide by some astounding members.

By his calculations perfect conditions will never exist like that. I can tell you a couple weeks ago when I was out in Nevada shooting to one mile that at that range, when the light was right you could easily see the target with the naked eye. Turn to our rear and you could see vehicles large and small moving up and down a highway, five miles away, with the naked eye.

So, I'm just saying, never say never because someone can and will prove you wrong.
 
Re: Inconceivable?

Perhaps you missed this key word...
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"Nobody can <span style="font-weight: bold">RELIABLY</span> read with better than 0.1 mil accuracy in the real world. Sometimes, under ideal conditions, you can break down to 0.05 mil, but don't count on it."

Of course Lady Luck can smile on you sometimes, but I guess this is not what we strive for here.
 
Re: Inconceivable?

Just for clarification, I'm going to quote myself;
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: almsquattro</div><div class="ubbcode-body">
Being a novice, but understanding the generally accepted ranging formula (target size in inches X 100/minutes of angle = distance in yards), I calculated a hypothetical math problem. Using an average height person 5 ft. 10 in. = 70 inches tall. So 70 X 100 = 7000. Now, I have a Nightforce NP-R1 reticle with 1 MOA hash marks. So, if the subject person is 1 MOA on my reticle (from top of head to toe), this calculates to 7000 yards. 7000 yards divided by 1760 yards per mile = <span style="font-weight: bold">3.97 miles</span>.

<span style="font-weight: bold">This means it is possible to range a person 4 miles away.</span> Even as I write it, it sounds ridiculous. What am I missing here? Can you really see a person 4 miles away or should I switch from tequila to vodka?
</div></div>

The bold-type sentence was more of a seemingly ridiculous "finding" (from the calculation) that led to my subsequent questions. I probably should have ended that sentence with a question mark. It was not intended to appear like a defensible claim. I was leaving it up to you guys to explain the flaws in the calculation or the limitations of the ranging reticle with the only assumption to include is that environmental conditions were perfect.

Well, I appreciate everyone's input. There are some great minds (except for ADHD Boy) with a lot of field experience in this forum. I understand the argument for both sides. After all, isn't the science behind the math just a guessing game anyways? As I understand it, unless you get a tape measure out there, you are not going to get a truly "accurate" distance. Even the high-end laser range finders decrease in accuracy the greater the distance (especially beyond 1600 yards). And with GPSs, although they are extremely useful tools, get you within something like 3-10 yards of a location? So if you are plotting two locations, you would double the possible error.

Anyhow, I may be putting the ranging question to the test this weekend. We have an open shooting location (BLM) that may have up to a 3-mile view from atop a ridge. I'll let you guys know what I can see or can't see.

And no, I'm not going to shoot 3-miles...I'm just going to see what I can see.

Cheers!
 
Re: Inconceivable?

Ahh, name calling..... Takes me back to my grade school days.

Good luck with your test run and we all expect a full report when you're done. Don't forget to multiply by 100.
 
Re: Inconceivable?

You see this a lot, theory vs reality.

Could you in theory see a human 4 miles away with enough resolution and clarity to mil them...sure.

But, the reality is that 4 miles is a looong way for light to travel and not be effected by atmospheric conditions...not go a happen. Then, even if you get a perfectly resolved image, you still have to absolutely NAIL your mailing, at that distance, it has to be perfect...zero room for any error.

I can't do it, I know that for a fact.
 
Re: Inconceivable?

Whatwver do you mean? I shoot 7,134.325 yds routinely with my .308. -I load my own!!