Light at the end of the tunnel

在全球范围内，正在建造越来越多的隧道（以及更长的隧道）。目前，世界上最长的隧道是瑞士的57公里（35英里）长的Gotthard基座隧道，但这在数十年中可能会改变计划的123公里（76英里）的海底隧道达利安和扬泰的中国城市。每个隧道项目都是数百万美元的投资，隧道测量所需的准确度不断增加。当预计火车以高达300 kph（186 mph）的速度行驶时，必须以最高的精度维护计划的隧道轴。对于地下水中的隧道建设，例如汉堡的ELB隧道，巨型隧道钻孔机必须被驱车进入特殊的水域构造，并在完成后以厘米精度驱动。在研究这一规模的关键项目时，标题中最小的定向错误可能会导致大量的技术问题和财务风险。

隧道测量中起着至关重要的作用sure that the breakthrough of the tunnel occurs precisely at the specified target point. The challenge is to guide both sides of the tunnel in the right direction. The measurements for directional transmission occur using elongated traverse lines, which can only be connected to a control network of a known point at the tunnel's entrance. There is no way to check the directional accuracy of the advancing opposite end of the tunnel. As tunnel length increases, configuring both ends for the correctness of proper tunnel direction result in considerable risks and uncertainties.

Surveying under difficult conditions
Many tunnel tubes have entry starting shafts. From these starting shafts, fixed-point coordinates are transfered down to the tunnel's level so that the tunnel can be bored correctly and navigated toward its target, this being the other end of the advancing tunnel. This process, known as plumbing, always involves an element of risk, when transferring fixed reference points in such small and narrow shafts. If the measured data is so much as a millimetre inaccurate, this inaccuracy compounds itself and leads to considerable deviations in the lateral traversing line of the tunnel's many curves and its direction.

The measuring risks in the tunnel itself occur when the line of sight is diverted and subject to refractive influences such as temperature differences, humidity or dust. These make measuring angles and reliable measurements difficult and errors unavoidable. This applies even more due to the fact that in most tunnels the surveying points cannot be situated in the centre of the tunnel for logistical reasons and must therefore be located at the tunnel walls. Targeting close to the wall increases the risk of refraction even further. Tunnel courses with numerous (and tight) curves also require maximum accuracy.

随着隧道长度的增加，管道和折射的错误可能会加起来多达几米，从而使您在所需位置的突破不可能。在这种情况下，经常需要大量的额外工作。

解决方案是一个“玩具”
Previously, miners and tunnel builders solved this problem using compasses. In the modern tunnels of today, however, this is not possible due to the considerable amount of iron and steel used. Initial developments in solving this problem using gyroscopes came about in the early 1950s.

几乎每个人都熟悉童年时代的陀螺仪，在玩旋转上衣时。例如，我们在日常生活中不断地使用基本的进攻原则，例如，当我们在骑车时将手从自行车的车把上摘下，然后继续直奔魔术。

Precession is the directional change of the axis of a rotating body (a gyroscope) when external forces apply torque to it. If such a gyroscope is built into a measuring device which is positioned somewhere on the Earth for a certain period of time, the Earth's gravity will act on this gyroscope as the external force during this time. The gyroscope tries to counteract this external force and to remain in its original position. If it then manages to measure these values, such a gyroscope can be used to determine the direction to the Earth's axis (cartographic north).

Written by Norbert Benecke, Volker Schäpe and Volker Schultheiss