Before constructing any structure or object on the ground, it is necessary to carry out a shooting justification. The shooting justification includes determining the coordinates of terrain points, calculating elevations, and also setting the position in the local coordinate system. Such a justification can be based on the theodolite move.
Geodetic works
Geodetic works include many items, including the creation of a survey justification of the area. This work is preceded by the construction of the theodolite course with measurements of horizontal angles and lengths of the sides, as well as the calculation of the coordinates of the points.
Using the theodolite move, you can transfer the coordinates of the strong points to all other points. This is necessary for the subsequent construction of buildings at this place or the use of the territory for economic purposes.
What is theodolite move
Theodolite course is a broken line built on the ground with horizontal angles and side lengths measured with it. This data is later used to calculate coordinates and directional angles in the calculation sheet.
The construction of the theodolite course consists of two stages. It:
- Construction of a broken line on the ground and the implementation of field work;
- Mathematical equalization of the course and the implementation of cameral processing of the results.
Both stages are carried out strictly according to the established rules in compliance with the rules and regulations. The accuracy of the construction and processing of the results ensures the correct operation and subsequent safety of construction or the implementation of any other activity on the ground.
Types of theodolite moves
Theodolite move is an open or closed broken line. Depending on the form of construction, there are three types of moves:
- An open theodolite move, based on two points with known coordinates and two directional angles.
- An open theodolite move, based on one starting point and one directional angle - such a move is also called hanging.
- A closed theodolite passage in the form of a polygon, based on one point and one corner.
All three types have different accuracy of work. The most preferred construction option will be a polygon, for the control of measurements of which there is a separate method. The hanging accuracy is the least accurate, tied to only one point of the geodetic network.
The choice of the type of creation of the theodolite course depends on the terrain, the presence of a number of starting points and the type of further activities on the territory.
Preparation for work on the ground
Before performing field work, it is necessary to carry out a preliminary survey of the area using the available maps and topographic plans. It includes the study of natural conditions and topography, the search for available points of geodetic substantiation. It will also be useful to know when the last time geodetic works were carried out on a given territory and what results were obtained as a result of their implementation.
In addition, it is necessary to choose tools for subsequent work, as well as to verify them to ensure the necessary accuracy.
Before starting work on a large-scale plan, a possible arrangement of points of the theodolite course is being designed. The next step will be their removal in kind and checking for good visibility.
Paving
Theodolite move is laid on the ground with a prerequisite for ensuring good visibility between points. Otherwise, they find a different location for the items.
The first step is to link the theodolite course to the point of the geodetic network, carried out using a theodolite or a tacheometer with high accuracy. An anchor is the determination of the location of a polygon in the area. The correctness of its execution will have an effect on the determination of all coordinates of the theodolite course.
Depending on the subsequent destination, the points are fixed on the ground with temporary or permanent signs. The first include wooden stakes, clogged flush with the ground. In order to maintain the exact location of the point, the stakes indicate the center. Next to such a temporary sign, as a rule, an identification element is set - a gatehouse 15-20 centimeters high.
Permanent signs mark points whose location will be necessary for further work for a long time. In this case, more durable materials are used - monoliths or concrete poles.
For a better orientation, the course points are signed: the number is indicated, as well as the distance from the first point.
Field work
After the points of the course have been marked, produce field work. They include taking various measurements and collecting data to solve the theodolite calculation sheet.
Inside the theodolite stroke, side lengths and horizontal angles are measured. Work can be carried out using various tools, depending on their availability. At the same time, more modern devices will give more accurate results compared to obsolete ones.
All measurements are made two times: in the forward and reverse motion. The results of the two moves must coincide or differ by an amount equal to the permissible error. This process, adopted in surveying, provides high accuracy and reduces the influence of systematic and random errors.
Measuring angles and stroke lengths
Horizontal angles are measured at each vertex using an electronic total station or optical theodolite. The device is placed on one of the points of the course, and on two neighboring places are placed rails or milestones. In this case, it is necessary to ensure that only the right or left lying corners are measured. In order for this to be easy to control, the outline of the terrain situation is carried out in parallel in the schematic drawing. Abris is an approximate image of the results of the work needed for subsequent cameral calculations.
Angles are measured by the method of methods, which is a double control of the measurements. In this case, unacceptable errors are easily detected by special control formulas. The work is redone until the necessary accuracy is ensured.
The lengths of the sides of the landfill are measured using laser, light rangefinders or earth roulettes. The distance between each two points of the theodolite course is determined, simultaneously fixing them in a specially designated journal.
Office work
A theodolite passage is a polygon or line built to determine the coordinates of points located far from points in the original network. Thus, the field work is followed by processing the obtained results and obtaining the desired values.
Office work is an equally important type of geodetic work, as a result of which it is possible to identify errors made by workers during the construction of the theodolite course. In addition, at the stage of processing the results, the influence of systematic errors arising due to inaccurate operation of the device, the impact of weather conditions (wind, sun, precipitation, etc.) and incorrect reading of the performer by the performer is excluded.
According to the results of the work, the statement of calculation of the theodolite course is calculated.
Drawing up the list of theodolite course
Theodolite list is a table that contains data obtained as a result of measurements of field work and calculations of cameral processing. They enter numerical information about the directional angles, increments and coordinates of the starting point and points of travel. There is a separate column for each value.
The initial values are the coordinates and directional angles of the starting and ending points. All other data are calculated using measured horizontal lengths and angles.
At the beginning of the work, the sum of the measured angles is calculated and the theoretical amount is analytically determined. Their difference will be the residual of the theodolite, calculated by the formula:
fβ = Σβism - Σβtheor.
The resulting value must be less than or equal to the permissible residual. It is calculated by the formula:
{fβ} = 1 '√n.
If the condition is met, the calculated residual can be distributed evenly with the opposite sign between all angles. Then the angles can be considered equalized. Corrections are written over the available values and are used in subsequent calculations.
The next step in calculating the sheet of theodolite course is to find the directional angles of the parties. Left lying corners are taken away, while right ones are added. The control of the correctness of calculations is to obtain in the final result the first directional direction of the starting point.
Next, the increments along the X and Y axes in the rectangular coordinate system are calculated. This is necessary for the subsequent location of the points of the theodolite. The increments are calculated as the product of the horizontal laying and the sine or cosine of the corrected directional angle:
ΔX = d * cosA;
ΔY = d * sinA.
The next step is to calculate the residual of the increments in the same way as the angular one. If it does not exceed the permissible value, the obtained value is distributed equally with the opposite sign.
The last item is the calculation of the coordinates of the sheet of theodolite. They are obtained as the sum of the coordinates of the previous item and the calculated increment, taking into account the residuals. For the X and Y axes, the values are considered separately, writing to the corresponding columns. The final control is obtaining the coordinates of the starting point, that is, returning to the beginning.
Theodolite course in geodetic substantiation
The construction of the theodolite course is an important step in creating a filming justification. Surveying points, as a rule, are far from each other and cannot be a sufficient basis for the construction of facilities or other activities.