Baseline surveying

Japanese: 基線測量 - きせんそくりょう（英語表記）base-line surveying

A distance measurement in which the length of the first side that serves as the reference for triangulation is precisely measured, this side being called the "baseline." Two points that are as close to horizontal as possible are selected and measured. Sometimes measurements are taken using a tape measure (baseline measure, 25m) made of invariant steel wire or tape, but nowadays, optical distance finders, radio distance finders, and especially laser distance finders, which use a helium-neon laser as a light source, are used to measure distances. There are 14 baselines set up throughout Japan, with the length of each side ranging from 3 to 10 km, and the measurement error being 0.1 to 1.8 mm.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

三角測量で基準となる最初の1辺の長さを精密にはかる距離測量で，その1辺を「基線」という。できるだけ水平に近い2点を選び，計測する。不変鋼製のワイヤまたはテープの巻尺 (基線尺。 25m) を用いてはかることもあるが，現在では光波測距儀や電波測距儀，特にレーザー測距儀というヘリウムネオンレーザーを光源とする精度の高い測距儀を用いている。日本には全国で 14ヵ所に基線が設けてあって，1辺の長さは3～10kmにとってあり，観測誤差は 0.1～1.8mmであった。

出典　ブリタニカ国際大百科事典小項目事典ブリタニカ国際大百科事典小項目事典について　情報

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