What Is a Total Station?

Total station, also known as Electronic Total Station, is a high-tech measuring instrument that integrates light, machinery and electricity. ), Height difference measurement function in an integrated surveying and mapping instrument system. Compared with the optical theodolite, the electronic theodolite replaces the optical dial with a photoelectric scanning dial, and replaces the manual optical micrometer reading with automatic recording and display reading, which simplifies the angle measurement operation and avoids reading errors. Because it can complete all the surveying work at the station by setting up the instrument once, it is called a total station. Widely used in the field of large-scale buildings and underground tunnel construction, such as precision engineering measurement or deformation monitoring.

The total station is the abbreviation of the total station-type electronic speed measuring instrument, which is a combination of an electronic theodolite, a photoelectric range finder, and a microprocessor. At present, the world's total station brands are mainly Leica, Topcon, Nikon, South, Suojia and so on. ^[1]

The total station uses a photoelectric scanning angle measurement system, and its types mainly include: encoder disk angle measurement system, grating disk angle measurement system and dynamic (grating disk) angle measurement system.

Classified by its appearance structure

The total station can be divided into two categories according to its appearance and structure:

(1) Modular type (also known as modular type)

Most of the early total stations were block-type structures, that is, the electronic speed tester, the electronic theodolite, and the electronic recorder were all integrated. They can be used separately, or they can be combined through cables or interfaces to form a complete total station .

(2) Integral

With the further miniaturization of electronic rangefinders, most modern total stations have designed distance measurement, angle measurement, and recording units into an integral part in terms of optics, mechanics, etc., among which the transmitter axis and receiver axis of the rangefinder The collimation axis with the telescope is coaxial. This is very beneficial to ensure the accuracy of distance measurement under large vertical angle conditions.

Classification by measurement function

The total station is classified according to measurement function and can be divided into four categories:

The total station can be used in almost all measurement fields. The electronic total station is composed of a power supply part, an angle measurement system, a distance measurement system, a data processing part, a communication interface, and a display screen and a keyboard.

Compared with the electronic theodolite and optical theodolite, the total station adds many special components, so the total station has more functions than other angle and distance measuring instruments, and it is more convenient to use. These special components make the total station unique in terms of structure.

The vertical scale is composed of a main grating, an indicator grating, an indicator grating base, a shaft and a shaft sleeve. During the installation of the vertical scale, a vertical index difference and a horizontal axis tilt error will occur. The vertical index difference is caused by the improper installation of the fixed indicator grating, which means that when the collimation axis is horizontal, the vertical dial reading is not 90 degrees. After the vertical dial is installed, place the instrument on the pier of the instrument, aim the target at an infinite distance of the parallel light tube at the same height as the instrument, and observe the zenith distance of the target with the left and right sides. Then turn left: = 90 ° -L + I; turn right: = R-270 ° -I get I = 1/2 (L + R-360 °) If the index difference I exceeds the specified limit, then proceed There are two types of calibration: mechanical calibration and software calibration. Mechanical correction, loosen the 4 screws connecting the indicating grating base and the bracket, rotate and adjust the indicating grating base, and perform the left and right measurement again to calculate the index difference until it meets the requirements. Software calibration: Start the instrument's indicator difference correction program, and follow the prompts on the display. Collimate the parallel light tube with the left and right sides, extract the index difference and store it. After the above correction, the angle displayed by the instrument is Value, which is the value when the indicator is in the correct installation position. The tilt error of the horizontal axis is caused by the unequal height of the two brackets supporting the horizontal axis. When the horizontal axis is tilted, it will have a great impact on the measurement of the horizontal angle. under:

The center of the horizontal axis O is the circle center and the arbitrarily long is the radius. HH1 represents the horizontal position of the horizontal axis, and HH1 represents the position when the horizontal axis is inclined. When rotating, the inclination angle in each azimuth is constant. When the horizontal axis is horizontal, aim the target T, then the vertical collimation plane is OZTM . It reads M on the horizontal dial. If the horizontal axis is tilted by angle, when the collimation axis points to the zenith, collimate The axis will not be at the correct OZ position, but will move to the OZ position. When using this collimation axis to aim the target T, the collimation plane is the inclined plane OZTM, and the reading on the horizontal dial is M. The chord length MM = is the influence of the horizontal axis tilt error on the direction reading. As the OZM vertical plane, in the spherical triangle ZTM, ZT = Z, LZMT = , TM, LTZM = , then the formula of the spherical vertical angle is: sin = sin / sinz * sin because of and For a small angle, we can get = tg, which is the relationship between the horizontal axis tilt error and the horizontal angle. The horizontal axis tilt error is tested using the flat and low (high) point method: two points are selected indoors, one above the horizontal line of sight and one below the horizontal line of sight, and the vertical angle satisfies _high = - _low When observing high points: (LR) _high = 2L / cos _high + 2 * tg _high When observing low points: (LR) _low = 2L / cos _low + 2 * tg _low due to _high = _low ; Then = 1/2 (C _high- C _low ) cot When using flat and high reading, just set (LR) _flat = 2C and (LR) _low = 2L / cos _low + 2 * tg _low. Specific operation according to software prompt , Pan Pan pull and Pan right collimate the horizontal collimator, respectively, and solve the collimation axis error and indication difference _1. Then collimate the collimation point collimator with the collimation point, and solve the collimation axis error and index difference ₂ The horizontal axis tilt error can be obtained according to the above formula. When the tilt error of the horizontal axis is too large, it can be corrected by adjusting the relative position of the indicating grating base and the bracket on the vertical dial, or it can be compensated according to software.

The total station has angle measurement, distance (slope distance, horizontal distance, height difference) measurement, three-dimensional coordinate measurement,

During storage

1. The storage of the instrument is under the responsibility of a special person, and it will be taken back to the office every day after use on site; it should not be placed in the on-site tool box.

2. The instrument case should be kept dry, moisture-proof and waterproof, and the desiccant should be replaced in time. The instrument must be placed on a special rack or in a fixed position.

3. When the instrument is not in use for a long time, it should be taken out regularly for about one month to prevent mold and power to drive moisture to keep the instrument in good working condition.

4. The instrument should be placed neatly and not upside down. ^[2]

With the continuous development and application of computer technology, as well as the special requirements of users and the application of other industrial technologies, the total station has seen a new development period, and total stations with memory, waterproof type, explosion-proof type, computer type, etc. have appeared. instrument.

The world's most accurate total station: angle measurement accuracy (standard deviation of one measurement return direction) 0.5 seconds, distance measurement accuracy 0.5mm + 1ppm. With ATR (Auto Targets Recognition) function, both day and night (without lighting) can work. The total station has reached incredible angle and distance measurement accuracy, which can be operated manually or automatically, can be operated remotely or under the control of airborne applications, and can be used in precision engineering measurement, Deformation monitoring, mechanical guidance control with almost no tolerance, etc.

Total station, the most conventional measuring instrument, will increasingly meet the needs of various surveying and mapping tasks and play a greater role.

The angle measuring system of the total station is different from the traditional optical theodolite angle measuring system. Compared with the traditional optical theodolite angle measuring system, there are two main differences:

(1) The traditional optical dial is replaced by an absolute encoder dial or a photoelectric incremental encoder, and the traditional optical micrometer is replaced by an electronic subdivision system;

(2) Observation values are interpreted by traditional observers and manual recordings are changed into direct readings by observers and recorded automatically.

The distance measuring system of the total station is basically the same as that of a general distance measuring instrument, except that it is smaller in size and usually uses a semiconductor gallium arsenide light emitting diode as a light source. Different types and series of total stations produced by different manufacturers have large changes in their maximum range and distance measurement errors.

The recording system of the total station is also called electronic data logger. It is a hardware device with specific software that stores measurement data. There are many types of data loggers, but the basic functions are the same. They serve as a bridge between the total station and the electronic computer. It automates field recording, reduces errors in record calculation, and greatly improves the efficiency of field operations . There are three main types of total station recording system: interface type, magnetic card type and memory type.