Theodolite is a device designed to work with both vertical and horizontal systems (angles). It is also used to obtain the values of the distances and calculate the reference present angles. If the device is equipped with circles (horizontal / vertical), the device refers to the optical structures.
Theodolite serves in topographic, geodesic surveys, in construction, to measure angles.
Theodolite device has its own classification by accuracy:
- "T1" - high accuracy;
- "T2", "T5" m - ordinary accuracy;
- "Т15", "Т30" - for technical use;
- "T60" - training.
The marking of the device, more precisely, its digital designation, indicates what the rms error will be when working with angle measurement.
The device device can be direct or inverse, have a cylindrical or compensatory level. This equipment allows you to automatically align the axis with the vertical position.
What does a theodolite consist of?
The design of such a device has its main elements, which, in turn, consist of additional details.
It consists of the following elements:
The optical axis is the line that runs exactly through the ocular and objective centers.
The sighting axis is the line that goes through the objective center and filament grid.
With the help of the observation tube, it is possible to approximate the measured object. The entire area that can be observed in the lens is called the field of view.
For the manufacture of this element using glass high strength. Its surface has a scale, where each division denotes a degree. The vertical axis is the line that goes through the center of the alidade or through the axis of rotation of the tool.
This item has:
The main axes of theodolite are:
Types of theodolites.
- vertical, it is also designated the axis of rotation;
- horizontal - the axis along which the observation tube rotates;
Compactness and ease of use helped theodolite to gain popularity in many areas: astronomy, construction, geodesy.
The main are four types, two of which are powered by electricity, one optical, and the other mechanical.
Electronic theodolite has a measuring laser.
Such a device is indispensable in the work on laying tunnels, bridges or mines. Immediately it should be noted that due to the presence of an auxiliary light source it becomes possible to use a theodolite in dimly lit rooms.
The great usability of the device is that even if there is a laser model, it is not afraid of low temperatures.Back to table of contents
Geometrical parameters of theodolites
Structural scheme of theodolite.
There are requirements for the geometrical conditions of the instrument, on which the accuracy of measurements will directly depend.
First, the central line of the cylindrical level with a gradient head of a horizontal circle must be strictly in perpendicular relation to the axis of rotation of the gradient head.
Secondly, the line of rotation of the gradshtok should have a strictly vertical arrangement.
Thirdly, the axis in the sighting tube should be strictly perpendicular to the line of rotation of the tube.
Fourthly, the axis of rotation of the pipe and the axis of rotation of the gradient stem should be perpendicular to each other.
Fifth, the mandatory location of the filament of the grid is a collimation plane.
In order to properly align the theodolite and configure it for computational work, it is necessary to calibrate the instrument.Back to table of contents
The principle of measurement by theodolite.
In any field, be it astronomy or construction, preference is always given to high-precision instruments. From this depends largely on how long the building will stay or how exactly the obtained figures will correspond to reality.
Therefore, while working with a theodolite, one should remember about the proper treatment with it. Firstly, it would not hurt to have an idea about the device itself and its design features. There are special training courses that affect these points. Why is this so important? In fact, theodolite is based on a fairly complex system that helps to obtain accurate calculations. Any mistake can be expensive, especially with regard to construction.
There are a number of positive points indicating the rationality of using such a device:
- Angular measurements are distinguished by high accuracy and reliability, regardless of physiographic or climatic conditions. Accuracy will be maintained in the presence of temperature fluctuations in the range from + 50 ° C to -20 ° C, which is very convenient for our latitudes.
- This device can be used even during expeditions, it easily withstands difficult working conditions.
- Despite the fact that the theodolite is quite compact and has a small weight, this does not affect its stability. He still easily adjusts his geometrical characteristics.
In order to maximize the capabilities of the device while being confident in the results obtained, the following conditions should be met:
In order to make the most of the theodolite's possibilities and to be sure of the correctness of the results obtained, all technical conditions should be followed when working with the tool.
- First of all, the instrument must be properly stored. For this purpose, it is best to have a case in which the device must be folded neatly after each use. If the instrument is new, before getting it, it is recommended to carefully inspect the original packaging. The whole procedure of seizure and laying of a theodolite should be carried out only by special handles or stands.
- Before packing the device, the fixing screws located on the alidade and the tube are pressed out, and then in the case they return to their place. If the lid of the suitcase does not close, then the theodolite is laid incorrectly.
- The tripod must be installed on “soft” legs, for which the screws are loosened. After its immersion in the ground and adjusting the height of the "sheep" are given in its original position.
- As soon as the theodolite is mounted on a tripod, it is immediately fixed with a dead-end screw.
- In no case should the lifting and guiding screws be fully screwed in or twisted.
- If it becomes necessary to move the device, it can be carried in a small case (long distances) or, without removing it from a tripod, on the shoulder (short distances).
- If the tool is in good working condition, the observing tube and alidade will rotate smoothly and without jamming after the clamping screws are in the “free” state.
- In order that nothing happened to the device even if it were accidentally dropped, it is necessary to use fixing clamps when placing it in the case.
Since high-frequency devices have electronic "insides", contact with moisture is absolutely contraindicated for them. It means not only rain, but also fog. If you leave the theodolite in this weather under the open sky, then it is required to protect it with a film. After the rain is over, the instrument is allowed to dry out and wiped with a dry cloth.
These requirements are absolutely simple, but fulfilling them will help the device last much longer and will save it from possible breakdowns that can seriously damage the computational work.