Concept and principle of the hottest total station

Concept and principle of total station

total station, namely total station electronic total station. It is a high-tech measuring instrument integrating light, machine and electricity. It is a surveying and mapping instrument system integrating the functions of horizontal angle, vertical angle, distance (oblique distance, horizontal distance) and height difference measurement. It is called total station instrument because it can complete all the measurement work on the station at one time. It is widely used in precision engineering measurement or deformation monitoring fields such as large-scale buildings on the ground and underground tunnel construction

principle

total station is a new angle measuring instrument integrating light, machine and electricity. Compared with optical theodolite, electronic theodolite replaces optical dial with photoelectric scanning dial, and replaces artificial optical micrometer reading with automatic recording and display reading, which simplifies angle measuring operation and avoids reading error. The automatic recording, storage, calculation functions and data communication functions of the electronic theodolite further improve the automation of measurement operations

the difference between the total station and the optical theodolite lies in the dial reading and the upward movement system of the display strap open workbench. The horizontal dial and vertical dial of the electronic theodolite and their reading devices use two identical grating dial (or coding dial) and reading sensor for angle measurement respectively. According to the angle measurement accuracy, it can be divided into 0. 5 ″, 1 ″, 2 ″, 3 ″, 5 ″, 10 ″, etc.

brief history

total station is applied by people in the process of angle measurement automation, and all kinds of electronic theodolites play a great role in various surveying and mapping operations

the development of total station has experienced several stages, from the combination of photoelectric rangefinder and optical theodolite, or the combination of photoelectric rangefinder and electronic theodolite, to the integral total station, which combines the optical axis of the optical wave transmitting and receiving system of photoelectric rangefinder and the collimation axis of theodolite into coaxial

at first, the distance measurement of the tachymeter was realized by optical method. We call this tachymeter "optical tachymeter". In fact, "optical tachymeter" refers to a theodolite with sight distance wire. The plane position of the measured point is determined by direction measurement and optical sight distance, while the elevation is determined by triangulation

the optical tachymeter with "line of sight wire" has its advantages in short distance (within 100 meters) and low accuracy (1/200 (1/500) measurement, such as the measurement of broken points, and has been widely used because of its rapidity and simplicity

with the emergence of electronic ranging technology, the development of tachymeter has been greatly promoted. Using electromagnetic range finder instead of optical sight theodolite makes the measuring range larger, the measuring time shorter and the accuracy higher. People generally call the tachymeter whose distance is measured by electromagnetic wave rangefinder as "electronic tachymeter"

however, with the emergence of electronic angle measurement technology. The concept of "electronic tachymeter" has changed accordingly. According to different angle measurement methods, it is divided into half station electronic tachymeter and total station electronic tachymeter. Half station electronic tachymeter refers to the electronic tachymeter that uses optical method to measure angle, also known as "ranging theodolite". This kind of rapid measuring instrument appeared earlier and has been continuously improved. The optical angle reading can be input into the distance measuring instrument through the keyboard, and the oblique distance can be calculated. Finally, the horizontal distance, elevation difference, direction angle and coordinate difference can be obtained. These results can be automatically transmitted to the external memory. The total station electronic tachymeter is a three-dimensional coordinate measurement system composed of electronic angle measurement, electronic distance measurement, electronic calculation and data storage units. The measurement results can be automatically displayed, and can exchange information with peripheral devices. Because the total station electronic tachymeter perfectly realizes the electronization and integration of the measurement and processing process, it is usually called the total station electronic tachymeter or the total station for short

since the 1990s, it has basically developed into an integral total station

classification

the total station adopts the photoelectric scanning angle measurement system, which mainly includes three types: encoding disc angle measurement system, grating disc angle measurement system and dynamic (grating disc) angle measurement system

structure

total station can be used in almost all measurement fields. The electronic total station is composed of power supply, angle measurement system, distance measurement system, data processing part, communication interface, display screen, keyboard, etc. Compared with electronic theodolites and optical theodolites, the total station adds many special components, so it has more functions and is more convenient to use than other angle measuring and distance measuring instruments. These special components constitute the unique characteristics of the total station in terms of structure

1. coaxial telescope

the telescope of the total station realizes the coaxialization of the optical axis of the collimation axis and the transmission and reception of the ranging light wave. The basic principle of coaxialization is: a spectroscopic prism system is set between the telescopic objective and the focusing lens. Through this system, the multi-function of the telescope is realized, that is, the target can be aimed and imaged on the crosshair reticle for angle measurement. At the same time, the external light path system of the ranging part can make the modulated infrared light emitted by the photodiode of the ranging part shine on the reflective prism through the objective lens, reflect back through the same path, and then make the return light be received by the photodiode through the action of the light splitting prism; In order to measure the distance, another internal light path system needs to be set inside the instrument. The modulated infrared light emitted by the photodiode is also transmitted to the photodiode through the optical waveguide in the light splitting prism system, and the phase difference of the modulated light in the internal and external light paths indirectly calculates the propagation time of the light and the measured distance

coaxiality enables the telescope to measure all basic measurement elements such as horizontal angle, vertical angle and oblique distance at the same time. In addition, the powerful and convenient data processing function of the total station makes it extremely convenient to use

2. Double axis automatic compensation

the principle of double axis automatic compensation has been introduced in the inspection and correction of the instrument. If the longitudinal axis of the total station is tilted during operation, it will cause the error of angle observation, and the observation values on the left and right sides of the pan cannot be offset. The dual axis (or single axis) tilt automatic compensation system unique to the total station can monitor the tilt of the longitudinal axis and automatically correct the angle measurement error caused by the tilt of the longitudinal axis in the dial reading (the maximum tilt of the longitudinal axis of some total stations can be allowed to be ± 6 ')., The angle error caused by the vertical axis tilt can also be calculated automatically by the microprocessor according to the vertical axis tilt correction calculation formula, and added to the dial reading to correct it, so that the dial display reading is the correct value, that is, the so-called vertical axis tilt automatic compensation

3. Keyboard

keyboard is the hardware for total station to input operation instructions or data during measurement. The keyboard and display screen of total station instrument are double-sided, which is convenient for operation during forward and reverse mirror operation

4. Memory

the function of the total station memory is to store the measured data collected in real time, and then transmit it to other devices such as computers as needed for further processing or utilization. The total station memory has two kinds of memory: memory and memory card

the total station memory is equivalent to the computer memory (RAM), and the memory card is an external storage medium, also known as PC card, which is equivalent to the disk of the computer that is also related to the excessive capacity caused by the large expansion of production

5. Communication interface

the total station can input the data stored in the memory into the computer through the bs-232c communication interface and communication cable, or transmit the data and information in the computer to the total station through the communication cable to realize two-way information transmission

the use of

total station has many uses, such as angle measurement, distance (oblique distance, horizontal distance, height difference) measurement, three-dimensional coordinate measurement, traverse measurement, intersection point measurement and setting out measurement. After the built-in special software, the function can be further expanded

basic operation and use method of total station:

1) horizontal angle measurement

(1) press the angle measurement key to make the total station in the angle measurement mode and aim at the first target a

(268 silicon magnesium aerated concrete hollow lightweight partition board) set the horizontal dial reading in direction a as 0 ° 00 ′ 00 ″

(3) aim at the second target B, and the horizontal dial reading displayed at this time is the horizontal included angle between the two directions

2) distance measurement

(1) set the prism constant

before ranging, the prism constant must be input into the instrument, and the instrument will automatically correct the measured distance

(2) set the atmospheric correction value or air temperature and pressure value

the propagation speed of light in the atmosphere will change with the temperature and pressure of the atmosphere. 15 ℃ and 760mmhg are standard values set by the instrument, and the atmospheric correction at this time is 0ppm. During the actual measurement, the temperature and pressure values can be input, and the total station will automatically calculate the atmospheric correction value (or directly input the atmospheric correction value), and correct the ranging results

(3) measure the instrument height and prism height and input them into the total station

(4) distance measurement

aim at the center of the target prism, press the ranging key, the distance measurement starts, and the oblique distance, horizontal distance and elevation difference are displayed when the ranging is completed

the total station has three ranging modes: precision measurement mode, tracking mode and rough measurement mode. The precision measurement mode is the most commonly used ranging mode, with a measurement time of about 2.5s and a minimum display unit of 1mm; Tracking mode, commonly used for continuous ranging when tracking moving targets or setting out, the minimum display is generally 1cm, and each ranging time is about 0.3s; Rough measurement mode, the measurement time is about 0.7s, and the minimum display unit is 1cm or 1mm. During distance measurement or coordinate measurement, you can press the ranging mode key to select different ranging modes

it should be noted that some models of total station cannot set the instrument height and prism height during distance measurement, and the displayed height difference value is the height difference between the horizontal axis center of total station and the prism center

3) coordinate measurement

(1) set the three-dimensional coordinates of the survey site

(2) set the coordinates of the rear view point or set the horizontal dial reading of the rear view direction as its azimuth. When setting the coordinates of the backsight point, the total station will automatically calculate the azimuth of the backsight direction and set the reading of the horizontal dial of the backsight direction as its azimuth

(3) set the prism constant

(4) set atmospheric correction value or air temperature and pressure value

(5) measure the instrument height and prism height and input them into the total station

(6) aim at the target prism, press the coordinate measurement key, and the total station will start ranging and calculate the three-dimensional coordinates of the displayed measuring points

data communication of total station

data communication of total station refers to the two-way data exchange between total station and electronic computer. There are mainly two ways of data communication between the total station and the computer. One is to use the PCMCIA (personal computer memory card International Association, PC card for short, also known as memory card) card configured by the total station for digital communication, which is characterized by strong versatility and can be interchanged between various electronic products; The other is to use the communication interface of the total station to transmit data through cables

inspection

(1) the horizontal axis of the collimation part should be perpendicular to the vertical axis. During the inspection and correction, the instrument should be roughly leveled first, and the collimation part should be rotated to make it