- What is a total station?
- History and principle of operation of the total station
- Types of electronic total stations
- Advantages of the total station
- Tacheometer manufacturers
- What is hidden behind the price of a total station?
- At the end
In this Article: Defining a Total Station history and working principle; types of electronic total stations; advantages over other geodetic instruments; the largest manufacturers of total stations.
When performing any construction or survey work, an accurate calculation of the differences in the landscape on a given site is required, and sometimes its area is thousands of square meters. Traditional geodetic instruments – theodolite, rangefinder, level and tape measure will not work here, otherwise measurements will take weeks, no less. And the timing has become an important point today – customers will give preference to those performers who complete the work as quickly as possible and the contractors have more and more reasons to equip their specialists with modern construction equipment … In our age of advanced computer technology, the need for physical calculations and drawings has disappeared – everything does computer with appropriate software. A universal geodetic device – an electronic total station will help to survey the site in the shortest possible time and with the most accurate results.
What is a total station?
A tacheometer is a geodetic device that allows you to quickly and with high accuracy get a survey of a given area “in plan” with a complete picture of the relief. The design of this device includes a light range finder, a theodolite, a computer and an electronic data logger – with its outwardly compact dimensions, the tacheometer combines the functions of several geodetic instruments at once. Measurements of vertical and horizontal distances, areas at a distance of 5000 m with an error of only 1 cm, angles with an accuracy of 2? up to 20? (depending on the type and class in accordance with GOST R 51774-2001), automatic storage of the received data for several thousand points on the measured area, reception and transmission of data via GPRS to a remote computer – this does not exhaust the capabilities of an electronic total station.
History and principle of operation of the total station
The first geodetic instruments, remotely similar to modern tacheometers, were created 50 years ago – in these semi-mechanical and semi-electronic devices, an optical range finder and a theodolite were independently installed. After some time, the theodolite and the range finder were combined in one housing, the resulting device was equipped with a special panel that allows you to enter the angle values. The first full-fledged total station was created in Sweden – in it the angle reading was changed from optical to electronic, which made it possible to automate geodetic work. Thus, electronic total stations appeared on the market about 25 years ago, they are produced by American, Japanese and Swiss companies..
The principle of operation of an electronic total station is based either on the phase method, or, in more modern models, on the impulse method. The first method is the phase difference between the projected and returned beams, the second is the time it takes for the laser beam to travel from the total station to the reflector and back. The distance at which the device is capable of operating in reflectorless mode depends on the color of the surface onto which the beam is projected – light and smooth surfaces increase the working distance of the total station several times compared to dark ones, but it will not exceed 1,000 – 1,200 m. Linear range measurements in reflective mode – not less than 5000 m.
Types of electronic total stations
All manufactured models are subdivided into several types according to their application:
- technical total stations. Electronic devices of this type are the cheapest, because are equipped only with a reflective rangefinder and require geodetic measurements by a team of two employees – an operator of a technical total station and a rack-and-pinion;
- construction tacheometers. Equipped with a reflectorless rangefinder, i.e. capable of both reflective and non-reflective shooting. There is no alidad in the construction of building total stations;
- engineering tacheometers. Designed to perform a wide range of tasks, these devices are equipped with a camera used to build three-dimensional terrain models, a color touch screen, a modern processor and convenient software, slots and ports for USB and flash cards. Modern models of engineering total stations support a number of communication channels – Wi-Fi, Bluetooth, etc..
In addition, tacheometers are subdivided into modular, consisting of separate (independent) elements, and integrated, in which the devices are combined under one housing into a single mechanism. The last types are motorized and automated total stations. The first of them are equipped with a servo drive that allows surveying multiple points simultaneously, the second with a servo drive and systems capable of recognizing, capturing and tracking targets, in fact, these are already robotic geodetic systems. Devices of this design are designed for measurements by one person, and robotic total stations allow remote shooting, while the accuracy of the results will be guaranteed high.
According to the characteristics of the survey, electronic total stations are divided into:
- circular, with a filament rangefinder and a cylindrical level on the vertical circle of the alidade;
- nomogram, calculation of exceedances and horizontal distances of distances according to the nomogram, distinguishable in the pipe of the device during observation, as well as along the vertical rail;
- autoreduction, overshoot and horizontal spacing of distances in which are determined by a horizontal rail with a dual image rangefinder;
- in-base, the base of which is at the tacheometer and is intended for direct calculation of the horizontal distance, and measurements of vertical angles allow you to calculate the elevations;
- electro-optical, equipped with an additional electronic device that allows automation of shooting.
Advantages of the total station
If we compare the work with the theodolite and the tacheometer, then in the first case it is necessary to keep records in the journal, in the second – only to keep an outline, and the device will record and save data on distances, angles and picket numbers in memory. When you change the location of this geodetic device, you just need to set a new station and the first station, then point to the reflector and get the measurements calculated by the total station by pressing only one button.
The electronic tacheometer calculates horizontal distances independently, in automatic mode. The device monitor displays either the slope distance, horizontal position and elevations, or the slope distance and angles (horizontal and vertical) – the display of one of the two data options is manually controlled by the operator.
The tacheometer is irreplaceable when carrying out stakeout – set it at a point whose coordinates are known, set the coordinates of the orientation point, or enter the directional angle for orientation. Then you set the point to be set out by entering its coordinates – the angle of rotation and the distance that you want to measure in this direction are displayed on the monitor of the device. Of course, using a total station, you can measure the distance between points and the height of the object, measurements with an offset – this device performs all the functions of a theodolite.
When performing geodetic work in a quarry, such a function will be convenient – obtaining your own coordinates by resection. At the first installation of the electronic total station, using reflective tape, the coordinates of several objects located at the edges of the quarry are calculated. At the end of the quarry work, the device is reinstalled and, using the resection, the coordinates of the installation point are calculated, and the quarry is surveyed. The corresponding software based on the calculations of the total station will help you quickly get a picture of the work performed in the quarry – diagrams in squares, with their general description.
By its design, the electronic total station is intended for field work. Dust or dirt, rain or snow, temperature changes – all this will not damage the device. Among the models of total stations, each manufacturer has devices designed to work in especially harsh conditions – their low-temperature regime is up to minus 30 ° С. However, it is worth choosing them only in cases where it is really supposed to work in the northern regions or in some specific conditions..
The most famous global manufacturers of electronic total stations on our market are the Japanese company Sokkia Topcon with the Sokkia and Topcon brands, the Swiss company Leica Geosystems AG with the Leica brand, the Swedish GeoMax (brand of the same name), the American Trimble Navigation with the Nikon and Trimble brands, and Spectra Precision (eponymous brand).
Company Sokkia Topconknown for its products in the field of construction and geodesy for over 100 years, the instruments produced at its enterprises have traditionally high accuracy and Japanese quality.
Leica Geosystems, formerly known for its Leica brand in photographic equipment (cameras under this brand are still produced), it was formed in 1990 by the merger of several companies and is focused on the production of only geodetic equipment. Equipment of this brand is widely used in geodesy – both in terrestrial and in satellite.
Swiss manufacturer of equipment in the field of geodesy and construction, company GeoMax, Since its inception in the 90s, it has successfully competed with the Leica brand on the European market. The product line of this company, which is geodetic equipment and its software, is distinguished by exceptional quality and accuracy of measurements..
Company Trimble Navigation, based in the USA, it began its existence in 1978 with the production of navigation technologies for maritime navigation. With the development of space positioning, 25 years ago, the company began to create GPS navigators, and since 2003 and after acquiring the Nikon brand, a wide range of geodetic equipment.
American manufacturer of surveying equipment Spectra Precisionappeared in 1997 and was formed as a result of the merger of several manufacturers of surveying instruments and technologies. Today it is the largest brand of surveying equipment, known for its innovative technologies..
Among the brands of electronic total stations of the listed manufacturers, there is plenty to choose from the necessary equipment, be it a technical or a robotic total station. It all depends on the needs of the customer, the working conditions in which the total station is supposed to be used.
What is hidden behind the price of a total station?
There is a huge distance between the lower and upper price segments of tacheometers, hundreds of thousands of rubles. Robotic surveying instruments are frightening in their complexity and cost, I am sure that every chief accountant or business executive with very little knowledge of geodesy will be hostile to a request to purchase, say, a Sokkia NET1200 total station (average price – 1,300,000 rubles). If you translate everything into money only, then the much cheaper Topcon GTS-105N will be much nicer for the accounting department (the average price is 170,000 rubles)! Does it make sense to spend millions on a robotic total station?
If we conditionally divide all existing models of total stations of the upper price segment into devices equipped with servo motors, semi-automatic (equipped with a tracking system) and automatic (robots controlled remotely) and consider the efficiency of work from the point of view of a field surveyor, then their advantages over less expensive models are obvious.
During field geodetic work, a significant part of the time is spent on multiple pointing and focusing of the total station, which is not equipped with servomotors and an automatic tracking system. After several hours, and not in the best weather conditions, the operator’s concentration decreases, his eyes watery, his body aches from fatigue – as a result, the measurement accuracy decreases. A semi-automatic tacheometer, which independently tracks changes in the location of the reflector and can easily aim at it, will help to significantly facilitate the operator’s physical activity, regardless of the weather conditions on the ground..
Tacheometer Sokkia NET1200
No need for a companion to move the reflector – as a rule, during work the engineer-operator of a simple (adjustable and manually controlled) total station points to the pickets to an assistant with a staff. The accuracy of measurements during geodetic work with a partner-railroad is far from ideal, because an experienced surveyor cannot assess the situation at the picket point, and the assistant does not have sufficient knowledge for this. Semi-automatic devices allow you to change the nature of geodetic work – the device has a less experienced operator who does not perform settings and only presses the buttons on the total station at the command of an engineer with a reflector, who accurately determines the position of the picket. When dealing with a robotic total station, all measurements are made only by an engineer with a staff who controls the geodetic device remotely – from a picket.
Robotic total stations do not get tired and do not make mistakes, because are not capable of this – for each picket they will spend no more than 4 seconds, regardless of the number of working hours. The most expensive models of tacheometers are designed for accurate engineering measurements with minimal errors, performing independent calculations in the shortest possible time. An example of such a robotic total station is the Leica TS30 with an angular accuracy of 0.5 ?, the ability to perform 5,000 measurements and make a 180 ° turn of the telescope and alidade in just one second, the average cost of which is 2,600,000 rubles.
High-precision electronic total station Leica TS30
Relatively inexpensive electronic total stations have a set of functions sufficient for use on construction sites, they will not be enough for engineering purposes. Characteristics of a simple electronic building total station, for example, Nikon DTM-322 (angular accuracy 5?): High-quality optics, low weight, single-axis compensator, instead of batteries, you can use ordinary 1.5 V batteries, the largest measurement range in prism mode is 2 300 m, average price – 160,000 rubles. More accurate building tacheometer Trimble M3 DR, with an angular accuracy of 5?, Two-axis compensator, range to the reflector rail 3,000 m, battery for continuous operation for 8 hours, the presence of bluetooth and an average price of 340,000 rubles.
Trimble M3 DR TA Total Station
Engineering total stations, for example, Sokkia SET1X: 1? angular accuracy, high-bit color touchscreen display, measurement range to the reflector 5,000 m, two-axis compensator, two lithium batteries for 14 hours of continuous operation, bluetooth, USB port, card reader, Windows CE OS – average price 690,000 rubles.
Motorized engineering total stations worth about 850,000 rubles. have a lower angular accuracy (of the order of 5?), but significantly facilitate the tasks of a surveyor. Using the Leica TS15 M R400 as an example – measuring range to a reflector up to 10,000 m, four-axis compensator, fast battery charging for 7 working hours, OS Windows CE 5.0 Core, rotation speed 45 ° per second, bluetooth, USB port, card reader, color touch screen.
The higher the characteristics of the models of engineering total stations in terms of accuracy, speed of measurements and data processing, the higher their cost. It should be noted that modern electronic engineering instruments for geodetic measurements are not threatened with rapid obsolescence – models that will enter the market of the future will be built on their basis and have a similar set of functions..
At the end
When choosing one or another model of an electronic total station, or, more correctly, choosing one or another manufacturer, since the characteristics of total stations in their price segment are generally similar, it will be important to deal with an experienced and professional supplier. Its specialists will select the model that best meets the needs of the customer, including the modern software, the work with which must be trained to the customer’s employees.
Modern total stations are complex in design and by no means cheap – careful selection of a device with an optimal set of functions is extremely important.