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Login Name Post: Counting Miles        (Topic#307414)
Loyalist Dave 
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Loyalist Dave
05-20-18 08:38 AM - Post#1685502    

    In response to tenngun

  • Quote:
It was just an avarage, if your ship was going five knots then in an hour you would run five nautical miles.



No, that means that a) five nautical miles of water had run beneath the ship, as it does not account for currents, nor deflection. In an oncoming current of five knots (for the sake of discussion) your log would show the ship "moving" at five knots, when in fact it was geographically stationary.

A current at an angle, such as when you try to go from the coast of Northern Spain to North America, and encounter what was later called The Gulf Stream, throws off your distance and location, which you can somewhat correct with the sextant. Not bad at first but each day, without correction of some type, the error increases. Navagation with a compass or sun and stars or all three merely keep your ship oriented in the right direction, but don't necessarily correct for the error as it grows.

LD

 
Loyalist Dave 
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Loyalist Dave
05-20-18 09:02 AM - Post#1685503    

    In response to juice jaws

I' ve done both land navagation on foot, as well as at sea in a powered rubber boat with only a compass (out of sight of land at night mind you) and there are a lot of variables.

On land, even with a topographic map and a well made compass, "dead reckoning" by paces and by magnetic direction even with correction for the magnetic pole location i.e. deflection, is tough to come within say 30 yards of your target. It's better to (in daylight) cross check your pace and direction with landmarks. My pace on level ground is five feet....I check it every now and then. Going down hill it's larger, going up hill it's shorter, going up a steep hill even less. The same was true even then.

So what you have are historic accounts of the locations of sites, or landmarks, which sometimes are very off. I'm looking for a private fort known as "Baker's Fort" that was a Ranger patrol boundary in the F&I in Maryland, supposed to be 12 miles from Fort Frederick, Maryland in a Northeast direction..., set on a creek. (All trace, at least so far, of that fort are gone) Well there is an old ford that is now a bridge on that creek, but it's closer to 8 miles from the fort though it's the right direction....going on the map to 12 miles you're not near anything that would suggest a fort or the direction is off if you coincide that with the creek..., but if you factor in the rolling terrain, you may account for folks thinking it was 12 miles, and you're at that ford, so that's where I'm looking for something in the fields etc that might suggest a missing structure....see?

The Romans had a wagon with wooden gears when they were marking off distances, BUT they had to keep the wagon as straight as possible and it's been found that the mile markers (which still exist where they lay in some places) are more accurate on a relatively level plain than in hilly terrain.

Still perhaps for folks on foot, if you were told it was 10 miles to point X, and it was over hilly terrain, if it was really 7 miles, but you were equal in fatigue to having walked 10 miles on smooth terrain, did it matter that much to those folks?

In conclusion they were probably gauging time and pace and using a SWAG to give how far they went OR.., went to a known landmark, and used the traditional distance, whether they remarked on the landmark or not....so you get a journal entry of "left the trading post and traveled 12 miles to Jacob's Ford, and camped," because everybody knew it was 12 miles to the ford from the trading post, or you get, "left the trading post heading East by North East, going about 12 miles..." [because they could see Jacob's Ford off to their East when they stopped and made note in the journal though omitted the name of the landmark, and thus knew the accepted distance the post was 12 miles]... or they simply, "Left at noon and went 20 miles by sundown" because they thought their horses had gone that far based on the speed they moved.


LD

 
tenngun 
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tenngun
05-20-18 12:51 PM - Post#1685525    

    In response to Cruzatte

  • Cruzatte Said:
Apropos of nothing, I once measured my customary walking step at 2ft. 9in. which coincidentally is exactly half my height. I calculated the distance while walking across a football practice field on the Wichita State University campus one afternoon.




That’s a step, a pace is each time your left foot comes down. For some reason the military starts out marching on the left foot. I don’t know if all military did this but the Romans and the navy did.

 
Spence10 
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Posts: 7001
05-20-18 04:22 PM - Post#1685541    

    In response to tenngun

  • tenngun Said:
That’s a step, a pace is each time your left foot comes down.


Oxford English Dictionary and 3-4 others I've checked define the pace as either one step or two, either the length between alternate feet hitting the ground, 28-30 inches, or the same foot hitting twice, 5 feet. Then you get the geometrical pace, military pace, Roman pace, Welch pace, Greek pace, etc., ad nauseum.

The most usual way it is used in the US is what you call a step. Take one pace forward means take one step, not two.

I can't find how they define it in Italy today.

Spence


 
tenngun 
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Posts: 8045
tenngun
05-20-18 04:55 PM - Post#1685549    

    In response to Spence10

That’s a trueism we use so many words so many different ways. I was useing it here in the Roman 1000 paces to the mile sense.
Spence, I think you enjoy making other have to think to much. You know all human suffering have been caused by people thinking too much don’t you

Edited by tenngun on 05-20-18 04:57 PM. Reason for edit: No reason given.

 
Spence10 
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Posts: 7001
05-20-18 06:16 PM - Post#1685554    

    In response to tenngun

  • tenngun Said:
Spence, I think you enjoy making other have to think to much. You know all human suffering have been caused by people thinking too much don’t you


I don't think we are in much danger from that in today's world, tenngun.

Spence


 
tenngun 
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tenngun
05-20-18 06:51 PM - Post#1685558    

    In response to Spence10



 
Canute 
40 Cal.
Posts: 218
05-24-18 02:12 PM - Post#1686231    

    In response to tenngun

Thanks, Tenngun. A double pace answers the mystery.

Similar but different, that song lyric we all learned in school: "I've got a mule and her name is Sal, fifteen miles on the Erie Canal..." Mules were worked in six hour shifts towing canal boats and walked a steady 2-1/2 miles per hour, hence fifteen miles.

 
nessmuk 
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Posts: 139
07-19-18 09:25 PM - Post#1694144    

    In response to Colorado Clyde

Double post, sorry about that.

Edited by nessmuk on 07-19-18 09:28 PM. Reason for edit: No reason given.

 
nessmuk 
40 Cal.
Posts: 139
07-19-18 09:26 PM - Post#1694145    

    In response to Colorado Clyde

  • Colorado Clyde Said:
Ships logs recorded miles traveled every day....Anybody want to take a stab at how they measured that?...



Sextant.

 
tenngun 
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Posts: 8045
tenngun
07-19-18 10:14 PM - Post#1694148    

    In response to nessmuk

A sextant will measure angles and so can give your place on the globe, but not miles. On the equator one second of one degree it is one nautical mile. Traditional of 6000 feet, 10 cables or 1000 fathoms. It’s actually a few feet longer. As you go north an east west degree gets shorter while a north south degree stays the same.
Bad weather and poor skies made dead rekeoning about the only way. Above it was noted that currents and drift had to be factored in. A ship doing five knots every half hour for a four hour watch went twenty miles, but a two knot current could mean really twelve miles or twenty eight. Since you tried to put the wind at about a 45 degree corse you could slip sideways too. Once the wind may not be going your way you might constantly have the wind pushing your head off corse.
The British lost most of a fleet coming up the Chanel thinking they were east of their true position.this was the 1740s I think.

 
Coot 
69 Cal.
Posts: 3143
07-19-18 10:26 PM - Post#1694149    

    In response to nessmuk

Speed x time = distance. A ships' log (weighted drag) was dropped over the side. It was attached to a light line that had knots tied at uniform intervals of 47' & 3". A 30 second sand glass was used while counting the number of knots that went over the side. If say six knots passed out in the 30 seconds, speed was 6 knots or six nautical miles an hour. Multiply speed by the number of hours since last checked & then total the measurements made during the past 24 hours for the distance traveled during the 24 hours. Easy to do, only simple math required - system used for hundreds of years.

 
Kansas Jake 
54 Cal.
Posts: 1530
07-22-18 01:15 PM - Post#1694472    

    In response to Coot

Years ago I read and I don’t remember the source that even on very cloudy days there is often a break in the clouds for a few moments at noon. Since that time I have often observed it happening.

 
Loyalist Dave 
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Posts: 6922
Loyalist Dave
07-23-18 07:02 AM - Post#1694536    

    In response to Coot

  • Quote:
A ships' log (weighted drag) was dropped over the side. It was attached to a light line that had knots tied at uniform intervals of 47' & 3". A 30 second sand glass was used while counting the number of knots that went over the side



Yes if you watch Master and Commander: The Far Side of The World with Russel Crow, you can see them doing this at the beginning of the movie.

LD

 
tenngun 
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Posts: 8045
tenngun
07-23-18 10:28 AM - Post#1694561    

    In response to Loyalist Dave

On war ships the log was cast every turn of the glass- every 30 min. So a ship had a better idea of its constant speed. I don’t know if merchant ships did so or not. Navel officers were pretty well educated where as a merchant captain often ‘came up through the hawes pipe’ meaning he started as a common seaman and learned all his craft at sea. He could be illiterate or just be able to read enough to mark his log.
Often a merchant ship would head in a direction until it hit land then turn north or south as needed to get to the desired port.

 
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