Tachymeter (survey)

The tachymeter ( altgr. ταχύς tachýs ' fast ' and μέτρον métron, dimension ', ' scale ' ) is a device with which one horizontal directions, vertical angles and - unlike with a theodolite - the slope distance ( the diagonally measured distance ) to the target point can be determined. It is used for rapid set-up and calibration of points.

We distinguish between optical and electronic total station. In the latter, an automatic flow of data in the storage medium or the evaluation is realized except electronic measuring modules. Special tachymeter today have an automatic target recognition or even target tracking based on the miniaturization and acceleration of electronic components and CCD sensors.

Optical tachometer

Optical total stations are divided into non-reducing optical total stations and self-reducing optical total station:

Electronic total station ( total stations )

Operation

Electronic total station measuring the directions to the destination process automatically, the distances are calculated by electronic distance measurement. In this case, either the term or upon precise total station run time and phase shift of the transmitted and reflected light beam at the target point is measured. The light of the carrier wave in the infrared range or near infrared light spectrum. The reflection of the light beam at the target point takes place in a targeted, retroreflective triple prism (see triple mirror, depending on the size ranges of up to about 10 km) or on reflective films (reach a few hundred meters ).

Modern total stations are equipped with optional laser rangefinder that can measure on nearly any surface without reflectors. Range and accuracy of these so-called DR measurement (direct reflex ) but slightly lower than those of the above Infrared measurement to prismatic reflector, which is why both methods are used side by side. Crucial to reach and accuracy is mainly the nature of the targeted surface in terms of their reflection properties ( then light areas are far better than dark ). The various tachymeter series of various manufacturers offer depending on the device class ranges from 15 to just over 2000 m.

Data processing

The measured value determination ( direction and distance) is fully automatic electronically. For data storage peripheral computer are mostly connected. In modern total stations Processors and appropriate storage are often integrated. The data ( three-dimensional measuring points) can be two-dimensional (eg, architectural survey of facades / layouts ) or three-dimensionally mapped and exported as a dxf file immediately with appropriate computer programs. Usually, however, a 3D model is generated as a data reduction to two dimensions with any CAD program at a later date is also possible.

Motorized tachymeter

The latest generation of total stations has electrically driven lateral and vertical shoots. This will allow scientists to automatic sighting of the triple mirror and target tracking. In addition, a tachymeter to measure a predefined series of several points automatically. In this way, for example, the deformations of the arch dam of Lai be monitored because Nalps which may arise from the construction of the Gotthard Base Tunnel.

In the so-called " one-man", the user can be saved on the device and the operation is done only from the reflector. The engine plays a major role, as the unit must follow the reflector continuously. To initially must have a so-called " destination search " to facilitate the finding of the measuring prism, the total station. While the first generation single-operator stations had recorded throughout long search times, have modern devices via additional sensors that help in searching for a destination. Topcon developed an infrared -guided search that limits the measurement range and in addition allows the measurement on multiple channels. This has the consequence that, when working with multiple reflectors not always the next to the total station, is with the greatest signal strength, persecuted, but those with a certain frequency, thus carried the important unique assignment between total station and reflector. The manufacturer generates the unique target Trimble assignment means activated prism, in which a diode ring is detected by a quadrant sensor.

Imaging tachymeter

The total stations of the future rely on the use of image information during the measurement. The measured image is on the one hand used for documentation purposes, on the other hand it can be actively integrated into the measurement process. The aiming of the points must not take place on the eyepiece, but can be made directly on the image. Digital zoom or even optical magnification functions also allow the exact Detailanzielung. The measurement can be performed by the total station directly or via Wi-Fi from the field computer or PC. Measured objects and points that are displayed in the live image, which will help to preserve clarity. Built-in scanning features allow the areal sampling of test objects, thus helping in the creation of realistic 3D photo models.

In the one-man operation, in which the operator of the total station is carried by the reflector, the live image, which is taken from the total station is transmitted to the field computer via WiFi, which, for example, image-assisted stakeout is possible. Among the imaging total stations, the Leica TS15, Trimble VX and Topcon Imaging Station (IS) can be called with only the latter has an optical magnification and a coaxial camera.

Equipment manufacturers

• Breithaupt
• Geo -Fennel
• Hilti
• Leica Core 1992 Leica Geosystems
• Risen Wild 1990 Leica Geosystems

• Carl Zeiss ( historical ) went up in Trimble Navigation
• GDM (1997 to Spectra Precision, 2000 went up in Trimble Navigation )