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Tunnel of Eupalinos

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Re: Tunnel of Eupalinos

#4

Post by jareklupinski »

> tunnel of 1,036 m (3,399 ft) length... built in the 6th century BC... excavated from both ends... At the rendezvous, the closing error in altitude for the two tunnels was a few millimetres.

starting a hole from two ends a kilometer apart and meeting within a few millimeters in any axis is phenomenal, would love to learn more about what they used to ensure this kind of accuracy

Re: Tunnel of Eupalinos

#5

Post by prepend »

jareklupinski wrote: post #4

> tunnel of 1,036 m (3,399 ft) length... built in the 6th century BC... excavated from both ends... At the rendezvous, the closing error in altitude for the two tunnels was a few millimetres. starting a hole from two ends a kilometer apart and meeting within a few millimeters in any axis is phenomenal, would love to learn more about what they used to ensure this kind of accuracy

There’s a pretty significant section in the article called “Surveying techniques and construction” that answers your curiosity.

Re: Tunnel of Eupalinos

#6

Post by oh_sigh »

prepend wrote: post #5
jareklupinski wrote: post #4

> tunnel of 1,036 m (3,399 ft) length... built in the 6th century BC... excavated from both ends... At the rendezvous, the closing error in altitude for the two tunnels was a few millimetres. starting a hole from two ends a kilometer apart and meeting within a few millimeters in any axis is phenomenal, would love to learn more about what they used to ensure this kind of accuracy

There’s a pretty significant section in the article called “Surveying techniques and construction” that answers your curiosity.

It's actually not in there, but in one of the sources quoted.

> 4 Techniques for measuring altitude : Altitude measurements seem to have been made with a chorobates, a primitive leveller with a vessel for water, or forerunners of this instrument. Eupalinos probably measured the south and independently the north entrances more than to check once his between results and to obtain a higher level of accuracy. He would have chosen a flat path around the mountain following a contour line not necessarily on the same level as the entrances. When the two parts meet in the tunnel after three km, the closing error of the levelling is small, only a few decimetres and the accuracy is still better at the entrances. Eupalinos had probably arranged two stone blocks at each entrance, with flat and levelled top surfaces, aligned with the tunnels, from which the level of the floor of the tunnel could be guided. Possibly a movable wooden pole was used to level it with the surface of the two outer stone blocks. Further into the tunnels lines on the walls seem to have taken over the role of the outer stones. Eupalinos himself seems to have expected a somewhat less precise result as he raised the ceiling of the north tunnel by 2.5 m and lowered the floor of the south tunnel by 0.6 m, when approaching the meeting point.

Re: Tunnel of Eupalinos

#8

Post by colanderman »

oh_sigh wrote: post #6
prepend wrote: post #5

Earlier quoted context omitted.

There’s a pretty significant section in the article called “Surveying techniques and construction” that answers your curiosity.

It's actually not in there, but in one of the sources quoted. > 4 Techniques for measuring altitude : Altitude measurements seem to have been made with a chorobates, a primitive leveller with a vessel for water, or forerunners of this instrument. Eupalinos probably measured the south and independently the north entrances more than to check once his between results and to obtain a higher level of accuracy. He would ha…

> the closing error of the levelling is small, only a few decimetres

I guess "millimeters" in the article is in error. Decimeters is much more believable.

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