光在隧道的尽头

Across the globe, more and more tunnels (and longer tunnels) are being built. Currently, the longest tunnel in the world is the 57 km (35 mi) long Gotthard Base Tunnel in Switzerland, but this could change in the decades to come with the planned 123 km (76 mi) under-sea tunnel to be built between the Chinese cities of Dalian and Yantai. Every tunnel project is a multi-million dollar investment, and the level of accuracy required for tunnel measurement increases continually. When trains are expected to travel through at a speed of up to 300 kph (186 mph), the planned tunnel's axis has to be maintained with maximum precision. In the case of tunnel construction in ground water such as with the Elb Tunnel in Hamburg, the giant tunnel boring machine has to be driven into a special watersealed target construction with centimetre precision when finished. The smallest directional error in the heading can lead to considerable technical problems and financial risks when working on critical projects of this magnitude.

The tunnel surveyor plays a crucial role in making 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.

在困难条件下进行测量
许多隧道管都有入门轴。从这些起始轴上，固定点坐标被转移到隧道的水平上，以便可以正确地无聊并朝目标导航，这是前进隧道的另一端。当在如此狭窄和狭窄的轴中传输固定参考点时，这种称为管道的过程始终涉及风险元素。如果测得的数据像毫米不准确，那么这种不准确性就会使自己复杂化，并在隧道的许多曲线及其方向的横向横向线上造成相当大的偏差。

当视线被转移并受到折射影响（例如温度差异，湿度或灰尘）时，隧道本身的测量风险就会发生。这些使测量角度和可靠的测量变得难以置信，并且不可避免地会出现错误。由于后勤原因，在大多数隧道中，测量点不能位于隧道的中心，因此必须位于隧道壁上，因此这更适用于此。靶向靠近墙壁会增加折射的风险。具有众多（和紧）曲线的隧道课程也需要最大的精度。

As the tunnel length increases, errors from plumbing and refraction can add up to as much as several meters, making breakthrough at a desired position impossible. A considerable amount of additional work is then often required in such cases.

The solution is a “toy”
以前，矿工和隧道制造商使用指南针解决了这个问题。然而，在当今的现代隧道中，由于使用了大量的铁和钢，这是不可能的。在1950年代初期，使用陀螺仪解决此问题的初步发展。

Just about everyone is familiar with gyroscopes from childhood, when playing with a spinning top. We are constantly using the underlying physical principle of precession in our daily lives, for example, when we take our hands off a bicycle's handlebars while riding and continue going straight as if by magic.

旋进的定向改变轴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).

由诺伯特·贝克克（Norbert Benecke），沃尔克·施氏（VolkerSchäpe）和沃尔克·舒尔西斯（Volker Schultheiss）撰写