How to use theodolite

How to use theodolite and the significance of theodolite

Theodolite is a measuring instrument for measuring horizontal angle and vertical angle, which is designed according to the principle of angle measurement. It can be divided into optical theodolite and electronic theodolite, and electronic theodolite is the most commonly used one at present.

Theodolite is the mechanical part of the telescope, which enables the telescope to point in different directions. The theodolite has two perpendicular rotating shafts to adjust the azimuth and horizontal height of the telescope. Theodolite is an angle measuring instrument, which is equipped with telescope, horizontal dial and reading index, vertical dial and reading index.

Structure of theodolite

Structure of theodolite (main common parts):

1. Telescopic brake screw 2. Telescope 3. Telescopic inching screw 4. Horizontal brake 5. Horizontal inching screw 6. Anchor screw 9. Optical sight 10. Objective lens focusing 1 1. Eyepiece focusing 12. Dial reading microscope focusing 13. Vertical dial indicator tube +04. Optical aligner 15. Circular elevation of foundation 16. Instrument base 17. Vertical dial 18. Vertical dial illumination mirror 19. Collimator level 20. Horizontal dial position change handwheel.

The theodolite telescope is fixedly connected with the vertical disk and installed on the support of the instrument. This part is called the sighting part of the instrument and belongs to the upper part of the instrument. The telescope and the vertical disk can rotate around the horizontal axis in the vertical plane. The collimation axis of the telescope should be orthogonal to the horizontal axis, which should pass through the drawing center of the water tray. Several shafts of the sighting part (rotating shaft of sighting part) are inserted into the shaft sleeve of the instrument base, and the sighting part can rotate horizontally.

Classification of theodolite

Theodolite can be divided into electronic theodolite and optical theodolite according to the dial scale and reading mode. At present, optical theodolite and electronic theodolite are mainly used in China, and vernier theodolite has long been eliminated. Both the horizontal dial and the vertical dial of optical latitude and longitude are made of glass, and the peripheral edge of the dial plane is engraved with equally spaced dividing lines. The central angle of the distance between two adjacent dividing lines is called the lattice value of the dial, which is also called the minimum lattice value of the dial. The general accuracy is determined by the scale value, which is divided into: DJ6 scale value is 1 DJ2 scale value is 20'DJ 1(T3) scale value is 4'. According to the accuracy, it is divided into: DJ0.7, DJ 1, DJ2, DJ6, DJ30, etc. (d, j) The whole instrument consists of two parts: the instrument and the tripod.

Function of theodolite

When measuring, put the theodolite on a tripod, aim the center of the instrument at the ground station with a vertical ball or an optical collimator, level the instrument with a horizontal theodolite, aim the measuring target with a telescope, and measure the horizontal angle and vertical angle with a leveling disk and a verticality disk. According to the accuracy, it is divided into precision theodolite and ordinary theodolite; According to the reading equipment can be divided into optical theodolite and vernier theodolite; According to the shafting structure, it can be divided into retest theodolite and direction theodolite. In addition, there is a coded dial theodolite, which can automatically record dial readings according to coded perforations; An automatic tracking theodolite that can continuously and automatically aim at air targets; Gyro theodolite and laser theodolite that can determine the orientation of ground points quickly and independently by using gyro orientation principle; Universal theodolite for astronomical observation with three functions: theodolite, meridian instrument and zenith instrument; Phototheodolite, who combined the camera and theodolite for ground photogrammetry.

Placement method of theodolite

1) Adjust the tripod to make its length equal to the height of the operator, and fix the instrument on the tripod so that the bottom surface of the instrument is parallel to the top surface of the tripod.

2) Put the instrument on the measuring table, roughly center it, step on a tripod, adjust the eyepiece (see the crosshair clearly) and objective lens (see the measuring table clearly) of the optical centering device, lift a tripod with both hands and swing it back and forth, left and right, observe the centering device to make the crosshair intersection coincide with the measuring table, and step on the tripod firmly.

3) leveling round level for the leg length of telescopic tripod.

4) Leveling the leveling pipe in parallel with two leveling screws to level the leveling pipe.

5) Turn the sighting part by 90 degrees and level the leveling tube with the third screw.

6) Check the optical alignment. If there is a small deviation, open the translation base of the connecting screw to align it accurately, tighten the connecting screw, and then check the alignment of the standard bubble.

Dial reading method

The reading system of optical theodolite includes horizontal and vertical disks, micrometer and reading microscope. Generally speaking, the minimum grid value of horizontal dial and vertical dial is 1 or 30'. When reading an angle value less than a grid value, a micrometer device must be used. DJ6 optical theodolite has two reading micrometer devices: micrometer and parallel glass micrometer.

(1) micrometer reading device

At present, the newly produced DJ6 optical theodolite adopts this device.

A reticle with a reticle is arranged in the field of view of the reading microscope, and the reticle on the reticle is imaged on the reticle after being amplified by the microscope. The imaging width of the minimum grid value (60') of the reticle is exactly equal to the length between the grid lines of 1 on the reticle. The reticle is divided into 60 units, and the labeling direction is opposite to that of the reticle. Use these 60 cells to measure the grid value of less than one cell on the crosshair. When measuring, the zero line is used as the indicator line.

(2) Single parallel glass plate micrometer reading device

The main components of the single parallel glass plate micrometer are: single parallel glass plate, sector ruler and micrometer wheel. The scale value of this instrument is 30', there are 90 small squares on the sector scale, and the scale value is 30'/90 = 20 ".

When measuring the angle, after aiming at the target, turn the micrometer wheel, clamp the dial with double indicators, mark the image and read it. According to the clamped dial, the integral degree is read with the dividing line, and the part less than the integral degree is read from the differential ruler.

(3) Reading microscope

The function of optical theodolite reading microscope is to image and amplify the reading, which is convenient for reading dial.

(4) liquid level gauge

There are 2 ~ 3 levels on the optical theodolite, whose function is to make the vertical axis of the theodolite vertical and the horizontal dial horizontal. There are two kinds of level: level and round level.

Pipeline liquid level

The pipeline level is installed on the sighting part, and its function is to level the instrument accurately.

Circular level

A circular level is used to roughly level the instrument. Its sensitivity is low, and its lattice value is 8″/ 2mm.

Principle of theodolite angle measurement

Measurement principle of 1. horizontal angle

The horizontal angle refers to the dihedral angle between vertical planes formed by two intersecting direction lines passing through space, and the angle value is 0 ~ 360. Two straight lines OA and OB intersect at point O, and points A, O and B are projected on the horizontal plane in the vertical direction, so that the included angle β between the corresponding projected points A', O' and B' and the horizontal lines O'A' and O'B' is the included angle between the vertical planes formed by the intersection of two straight lines, that is, the horizontal angle.

The horizontal angle has nothing to do with the elevation of the ground point.

The instrument for measuring angle must meet two basic conditions when measuring horizontal angle:

(1) can give a dial-water, which is placed horizontally, and its center can be conveniently placed on the same vertical line with the intersection point of the direction line.

Flat plate;

(2) There should be a telescope that can aim at distant targets, and it should be able to make a full rotation in the horizontal and vertical planes so as to pass through the telescope.

Aim at targets a and b at different heights. In the figure, the horizontal angle β is the difference between readings in directions A and B: β = B-A..

2. Measurement principle of vertical angle

The vertical angle refers to the included angle α between the line of sight in a certain target direction and the horizontal line in the same vertical plane, also called vertical angle or height angle; The angle value of the vertical angle is 0 ~ 90.

The angle between the line of sight and the vertical line is called zenith distance, and the angle value of zenith distance z ranges from 0 ~ 180.

When the line of sight is above the horizontal line, the vertical angle is called elevation angle, and the angle value is positive; When the line of sight is lower than the horizontal line, the depression angle is negative, as shown in the figure.

It can be seen that the theodolite of the angle measuring instrument must also be equipped with a vertical dial-vertical dial, or vertical dial.