在法國，米（Metre）是從北極到赤道的距離的千萬分之一！法國開始進行大規模的測量工作。他們用稱為重複圓圈的儀器以及三角測量來測量從敦克爾克到巴塞羅那的距離，這項工作耗時7年。度量衡的標準化：米
到了16世紀，歐洲有超過25萬種重量和度量衡單位。這影響了貿易、航行、建築計劃等方面。消防軟管無法從一個城鎮連接到另一個城鎮。法國選擇通過測量一些不可變的事物來創造一個標準。他們選擇了地球。在這種標準化之前，人體（土地的統治者）在掌握權力後會進行新的測量。
重複圓圈是一種測地儀器，擁有兩個望遠鏡，旨在通過對圓圈的各個部分進行重複觀測來減少誤差。這種形式由博達騎士開發，首次由埃蒂安·勒諾瓦在1789年左右的巴黎製造，並流行了大約50年。
重複圓圈的歷史
重複圓圈是從反射圓圈發展而來的，是一種測地測量儀器，由埃蒂安·勒諾瓦在1784年發明，當時他是讓-查爾斯·德·博達（Jean-Charles de Borda）的助手，後來博達對該儀器進行了改進。它與著名儀器製造商傑西·拉姆斯登（Jesse Ramsden）製造的大測角儀相當。它被用於由讓·巴蒂斯特·德朗布爾（Jean Baptiste Delambre）和皮埃爾·梅尚（Pierre Méchain）測量的從敦克爾克到巴塞羅那的子午線弧（參見：德朗布爾和梅尚的子午線弧）。來源：維基百科
12英寸重複圓圈
12英寸重複圓圈-1866
重複圓圈由兩個安裝在共享軸上的望遠鏡組成，並帶有測量兩者之間角度的刻度。該儀器結合了多次測量的結果，以提高準確性。重複圓圈的操作方式如下：
重複圓圈的操作程序：
（1）將儀器對齊，使其平面傾斜與相對於地平線的方向。
（2）使用望遠鏡觀察目標點，並記錄下角度的讀數。
（3）旋轉整個儀器，使第二個望遠鏡對準相同的目標點。
（4）再次觀察並記錄下角度的讀數。
（5）重複以上步驟，直到獲得足夠的觀測數據。
（6）將所有觀測數據進行統計分析，計算出平均值和標準差，以得出最終的測量結果。
重複圓圈的優點在於它可以通過多次觀測來避免單次觀測的誤差，從而提高測量的準確性。它在測地測量和地圖製作中得到了廣泛的應用，特別是在測量長距離的子午線弧時。
重複圓圈是天文學和測地學中一個重要的儀器，它在測量和研究地球形狀、地理位置和天體位置等方面發揮著重要作用。它的出現和使用，推動了度量衡的標準化和國際測量標準的建立，為科學研究和人類活動提供了準確的基礎。
折疊內容
A repeating circle is a geodetic instrument with two telescopes that is designed to reduce errors by repeated observations taken on all parts of the circumference of a circle. The form was developed by the Chevalier de Borda, first executed by Etienne Lenoir in Paris around 1789, and popular for about 50 years.Jun 27, 2022
Posted on June 27, 2022July 14, 2022 by 3 The Metre – the repeating circle & triangulation
The Metre (meaning measure) was one ten-millionth of the distance from the North Pole to the Equator! France embarked on a first large scale measurement. It took 7 years to measure the distance from Dunkirk to Barsalona. They used triangulation with an instrument called the Repeating Circle along with trigonometry.The standardization of measurement: the Metre
Creating the Metre – a universal standard
By the 16th century, there we over 250,000 weights and measures in Europe. This effected trade, navigation, building plans, etc. Fire hoses would not connect from town to town. France chose to create a standard by measuring something unchangeable. They chose the Earth. Before this standardization, the human body (the Ruler of the land) would make new measurements upon gaining power.
The Repeating Circle
Repeating Circle
DESCRIPTION
This is one of two double repeating circles that Ferdinand Rudolph Hassler, the first superintendent of the U. S. Coast Survey, ordered from Edward Troughton in London in 1812, and that was shipped in 1815. The large circle may be angled from vertical to horizontal to the opposite vertical position. It is graduated to 10 minutes, and read by four verniers and two magnifiers to single minutes.
A repeating circle is a geodetic instrument with two telescopes that is designed to reduce errors by repeated observations taken on all parts of the circumference of a circle. The form was developed by the Chevalier de Borda, first executed by Etienne Lenoir in Paris around 1789, and popular for about 50 years.
Ref: F. R. Hassler, “Papers on Various Subjects Connected with the Survey of the Coast of the United States,” Transactions of the American Philosophical Society 2 (1825): 232-420, on 315-320 and pl. VII. “The Repeating Circle Without Reflection, as made by Troughton,” in The Cyclopaedia: or, Universal Dictionary of Arts, Sciences, and Literature, edited by Abraham Rees (London, 1819), Vol. VII, Art “Circle.”
Image credit:
NAME: repeating circle MAKER: Troughton and Simms PLACE MADE: United Kingdom: England, London MEASUREMENTS: overall: 32 1/8 in x 26 3/4 in x 17 in; 81.6356 cm x 67.945 cm x 43.18 cm upper circle: 17 1/2 in; 44.45 cm circle at base: 13 1/2 in; 34.29 cm telescope: 24 in; 60.96 cm overall; base: 16 3/4 in x 15 1/4 in x 16 in; 42.545 cm x 38.735 cm x 40.64 cm overall; horizontal circle: 13 in x 23 in x 20 in; 33.02 cm x 58.42 cm x 50.8 cm ID NUMBER PH.314640 CATALOG NUMBER 314640 ACCESSION NUMBER 208213
The Repeating Circle History
Developed from the reflecting circle, the repeating circle is an instrument for geodetic surveying, invented by Etienne Lenoir in 1784, while an assistant of Jean-Charles de Borda, who later improved the instrument. It was notable as being the equal of the great theodolite created by the renowned instrument maker, Jesse Ramsden. It was used to measure the meridian arc from Dunkirk to Barcelona by Jean Baptiste Delambre and Pierre Méchain (see: meridian arc of Delambre and Méchain). Source Wikipedia
12” Repeating Circle
12 inch Repeating Circle – 1866
The repeating circle is made of two telescopes mounted on a shared axis with scales to measure the angle between the two. The instrument combines multiple measurements to increase accuracy with the following procedure:
Repeating Circle Mode of Operation:
Procedure for Repeating Circle
(1) The instrument is aligned so its plane incl
Read More: What is the repeating circle in astronomy?