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Is the metric system based off a circle?

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Old December 30th, 2016, 02:57 PM   #16
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Now that it is all perfectly clear allow me to say Welcome to the forum. Enjoy!

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Old December 30th, 2016, 04:13 PM   #17
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I appreciate the response. Upon rereading my post I must note that my comment "I do not understand why schmidt and bender would have 1click=.1 MRAD on some turrets and 1click=0.1MRAD on others?" was meant to compare the 1click=1cm to 1click=.1mrad, not .1 mrad to .1mrad.... As far as I can tell by the answers, it is the same thing as far as 1cm=.1mrad at 100 meters

Thanks to all for your help and Happy New Year!!!!!

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Old December 30th, 2016, 04:15 PM   #18
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Originally Posted by nobelnatas View Post
I was looking at buying a scope which led me to looking at schmidt and bender. As I have yet to figure out how to grow and harvest money and have to work for it but still believe in quality over quantity and at least trying to be frugal I decided the 10x42 pmII would do just fine. After looking at it I saw that it is 1click=1cm. I do understand the basics of MOA and MRAD. I understand that MOA at 100yds is 1 inch though this is a nominal value as it is 1.047 to be exact and that is about 3.6" MRAD along with that, Is 1cm at 100 meters exactly .1 MRAD? I do not understand why schmidt and bender would have 1click=.1 MRAD on some turrets and 1click=0.1MRAD on others? If it is not exact for 1cm/.1MRAD at 100 meters then it would not exactly match a milldot reticle and if it does I find it not only interesting but that the metric system must be based on a circle...

Please help if you can as I am tired of reading about math
nobelnatas,

I put a SWFA 10X SS on my rifle in MILRAD. I tend to shoot at 100 meter ranges I set up. I use 3/8" of an inch per click as my base line to zero @ 100 meters... I am not a math person at all! But the mil come ups do seem to work for the longer ranges if you get your MV right.
I downloaded the G7 program

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Old December 30th, 2016, 04:21 PM   #19
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As mentioned by Lysander, the use of mils started in France, most likely by their artillery in WWI. It became the standard for NATO forces artillery in the 1950's. It's use in tactical riflescopes, however, is a relatively new concept. I'm going to guess that the earliest military use was just about 2-3 decades ago.

Hunting riflescopes, on the other hand, have used turret adjustments that are 1/4 inch/100 yds clicks on US scopes and 1 cm/100m clicks on European scopes. These were chosen simply because they are easy for your average hunter to understand. The scope was zeroed and holdover was used for longer ranges.

Now we have a situation where scope manufactures are trying to combine the long range accuracy of millradians with the simplicity of the traditional hunting adjustments. It doesn't surprise me that turrets will have either tactical or hunting adjustments, or both.

This is a pretty good article: http://www.outdoorhub.com/how-to/201...stable-scopes/

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Old December 30th, 2016, 04:27 PM   #20
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Originally Posted by lysander View Post
This is incorrect.

The distance perpendicular to your LOS at 100 meters subtended by .1 mrad is 1.0000000833 cm.

I forgot to take into account that R cos θ does not equal R . . .
I believe this is my answer... Thank you to all

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Old December 30th, 2016, 05:00 PM   #21
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I run my scopes in MOA. But I am on the metric calendar. 10 days a week. 10 months in a year.

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Old December 30th, 2016, 05:12 PM   #22
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nobelnatas,

I put a SWFA 10X SS on my rifle in MILRAD. I tend to shoot at 100 meter ranges I set up. I use 3/8" of an inch per click as my base line to zero @ 100 meters... I am not a math person at all! But the mil come ups do seem to work for the longer ranges if you get your MV right.
I downloaded the G7 program
I was thinking of just going with this scope

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Old December 30th, 2016, 05:14 PM   #23
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Here's a link that has a reasonable explanation for your question.

http://www.scout.com/military/sniper...-right-for-you
This is very helpful and an excellent resource for all, Thank you

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Old December 30th, 2016, 05:27 PM   #24
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Measuring the earth to make maps for navigation was done for a long time using surveying instruments (and still is at a local level), measuring angles with a level, or a theodolite, or a transit, and measuring distances using chains.

Even long distances could be measured this way, as long as the surveyors were careful and took lots of small measurements that could add up to thousands of miles.

However this method did not work across water. Figuring out how far it was from London to Paris with accuracy was impossible. You could set a clock to noon in Paris, when the sun was directly overhead, then travel to London with the clock, and measure when the sun passed overhead there, and calculate the distance based on the differences between observed noon at the two locations, however clocks were not accurate enough, especially considering the jostling to transport and the fact that the trip might take a week.

The solution did not come until people started to lay underwater telegraph lines, because they could communicate relatively instantly, so you could compare what time it was in Paris when the sun passed overhead in London. Indeed, telegraph lines were the thing by which the entire world could synchronize clocks, so that trains ran on time (and more importantly, did not collide, because the northbound train had set it's clocks by a different time standard than the southbound train).

So when the world started to synchronize clocks, they would use one observatory that would accurately measure the Sun's transit, and that noontime indicator would be telegraphed out such that, after the various transmission delays were accounted for, everyone would have a common and accurate time stamp by which they could synchronize.

When it came time to pick the prime meridian, it was a toss up between a French observatory in Paris, which was the most widely used, because they were in continental Europe, and Greenwich in England (perhaps also the US Naval Observatory). Because Greenwich was more isolated from the world, they had been working for years to link themselves telegraphically, and were actually connected to the trans-atlantic cable to the US. So the number to telegraph junctions in Greenwich was greater than anywhere else, and was the deciding factor in making them the Prime Meridian, and in a very basic sense, the origin of the internet.

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Old December 30th, 2016, 05:29 PM   #25
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I always thought the metric system was brain child of a drunk french man. Nicolas de Condorcet. Just what I was taught.
When I was a child in Sioux City back in 1970, the school officials announced that all 1st graders were only going to be taught using only the metric system going forward. All of the parents protested, (I mean 100's showed up at the PTA meetings) and then voted the school board members that proposed this out, and the various school principles that supported this idea got fired too.

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Old December 30th, 2016, 05:53 PM   #26
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Originally Posted by youngk5 View Post
I run my scopes in MOA. But I am on the metric calendar. 10 days a week. 10 months in a year.
French, by chance?

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Old December 30th, 2016, 09:07 PM   #27
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Originally Posted by lysander View Post
This is incorrect.

The distance perpendicular to your LOS at 100 meters subtended by .1 mrad is 1.0000000833 cm.

I forgot to take into account that R cos θ does not equal R . . .
Show off!

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Old December 30th, 2016, 09:23 PM   #28
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Originally Posted by ShootingSight View Post
Measuring the earth to make maps for navigation was done for a long time using surveying instruments (and still is at a local level), measuring angles with a level, or a theodolite, or a transit, and measuring distances using chains.

Even long distances could be measured this way, as long as the surveyors were careful and took lots of small measurements that could add up to thousands of miles.

However this method did not work across water. Figuring out how far it was from London to Paris with accuracy was impossible. You could set a clock to noon in Paris, when the sun was directly overhead, then travel to London with the clock, and measure when the sun passed overhead there, and calculate the distance based on the differences between observed noon at the two locations, however clocks were not accurate enough, especially considering the jostling to transport and the fact that the trip might take a week.

The solution did not come until people started to lay underwater telegraph lines, because they could communicate relatively instantly, so you could compare what time it was in Paris when the sun passed overhead in London. Indeed, telegraph lines were the thing by which the entire world could synchronize clocks, so that trains ran on time (and more importantly, did not collide, because the northbound train had set it's clocks by a different time standard than the southbound train).

So when the world started to synchronize clocks, they would use one observatory that would accurately measure the Sun's transit, and that noontime indicator would be telegraphed out such that, after the various transmission delays were accounted for, everyone would have a common and accurate time stamp by which they could synchronize.

When it came time to pick the prime meridian, it was a toss up between a French observatory in Paris, which was the most widely used, because they were in continental Europe, and Greenwich in England (perhaps also the US Naval Observatory). Because Greenwich was more isolated from the world, they had been working for years to link themselves telegraphically, and were actually connected to the trans-atlantic cable to the US. So the number to telegraph junctions in Greenwich was greater than anywhere else, and was the deciding factor in making them the Prime Meridian, and in a very basic sense, the origin of the internet.
Actually, there is a very accurate clock, available to all, always in perfect order and never jostled into inaccuracy by transport. The ancient Greeks knew of it, as did the Persians and Babylonians (but lacked accurate instruments to make use of it).

The stars.

Given a accurate quadrant or sextant, you can measure the angular distance from various stars to the moon and provided you have charts that has these distances from a known position on the Earth and from a known time, you can figure out how far you are displaced from from that known point (say the Naval Observatory in Washington).

This method of navigation is known as 'lunar distance'. Tables for charting lunar distance were first compiled by Nevil Maskelyne in 1763. Lunar distance was the primary time keeping method at sea from the time of its publishing to around the 1850's when naval chronometers were reliable enough not to require periodic checking.

As to trains running on timing to prevent collisions, that is largely a story made up by a prominent U.S. watch manufacturer, Webb C. Ball. Train traffic was controlled by a station in charge of a section of track between it and the next station down the line. Trains were logged into the controlled section of track, and a telegraph signal was sent to all stations further down the line. The far stations would display a signal that told inbound traffic the line was in use, and depending on how far away the train was, they would display a stop, or a proceed slowly and prepare for shunting. Whether you were shunted or the inbound train was shunted depended on who had the priority cargo. If the line was clear, the "all clear" signal was displayed.

The original signals were a large red ball on a string on a "flagpole" next to the track. If the ball was in the lowest position, the train was to stop and be shunted. If the ball was in the middle position, the train was to proceed as reduced speed, for possible shunting at the next station. If the ball was in the highest position, the track for at least the next two stations was clear, and you continue at speed, hence the term "high balling".

If telegraphs were not operational or not available, a brass ring was used. A brass ring was given to the train conductor and at the next station the ring was turned over to the station master, whereupon the ring was returned to the original station by the next train going in the opposite direction. No train could proceed on the line without the ring. The ring was used as these could be on-loaded and off-loaded in the same manner as mail bags, via a hook next to the track, or tossed back-and forth between the conductor and the station master while moving like a frisbee. (Some train lines in India still use this method of train control, they have better safety records than some "modern" rail lines.)

EDIT: Not having a common time is not a deal breaker. You can schedule traffic between Columbus GA (eastern time) and Phenix City AL (Central Time), easily, because the time offset is fixed. Essentially, each city or station was its own time zone with a fixed time offset from the previous station, and as soon as you passed a station you entered a new time zone. Common time just make life easier.


Last edited by lysander; December 30th, 2016 at 09:42 PM.
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Old December 30th, 2016, 09:26 PM   #29
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To simplify this, no not a circle. Multiples of 10!

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Old December 30th, 2016, 10:05 PM   #30
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To simplify this, no not a circle. Multiples of 10!
Thank you for simplifying this.

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