What is a theodolite?

Theodolite, an instrument for measuring horizontal and vertical angles. It is designed according to the principle of angle measurement. At present, the most commonly used is optical theodolite.

structure

Mechanical parts of theodolite structure 1. Structure of theodolite (main commonly used components): theodolite

1 telescope brake screw 2 telescope 3 telescope inching screw 4 horizontal brake 5 horizontal inching screw 6 pin screw 9 optical sight 10 objective lens focusing 1 0 eyepiece focusing 12 degree dial reading microscope focusing 13 vertical dial indicator tube horizontal inching screw1 4 Optical Centering Device 65 438+05 Base Circular Horizontal 16 Instrument Base 17 Vertical Dial 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.

Theodolite can be divided into vernier theodolite, optical theodolite and electronic 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. Electronic theodolite Optical theodolite Optical theodolite The horizontal dial and vertical dial of optical latitude and longitude of electronic theodolite are made of glass, and the peripheral edge of the dial plane is engraved with sub-theodolite with equal spacing.

Scribbling, the central angle of the distance between two adjacent scribing lines is called the grid value of the dial, also called the minimum grid 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: DJ07, DJ 1, DJ2, DJ6, DJ30, etc. (d, j respectively. The whole instrument consists of instrument and tripod. Application list (coordinates of point A and point B are known, and coordinates of point C are obtained): set up the instrument at one of point A and point B with known coordinates (the instrument is set up at point A as a column), after completing the basic operation of placing and aligning, aim at another known point (point B), then configure and record a reading 1 according to your own needs, and aim at point C (unknown point) to read reading 2 again. The difference between reading 2 and reading 1 is the angle value of angle BAC, and then by accurately measuring the distance between AC and BC, the precise coordinates of point C can be calculated mathematically. In some construction sites, we often see some technicians taking measurements with an instrument, and the instrument they use is theodolite. The original invention of theodolite was closely related to navigation. 15, 16 th century, some developed countries, such as Britain and France, needed to draw various maps and charts because of navigation and war. Triangulation is the earliest method used to draw maps, which is to find out the position of the third point in the distance according to the observation results of two known points. However, due to the lack of suitable instruments, limited means of angle measurement and low accuracy, the topographic map drawn is not high either. The invention of theodolite improves the observation accuracy of angle, simplifies the process of measurement and calculation, and provides more accurate data for drawing maps. Later, theodolite was widely used in various engineering surveys. Theodolite includes three parts: base, scale (horizontal scale and vertical scale) and sighting part. The base is used to support the whole instrument. The horizontal dial is used to measure the horizontal angle. The sighting department includes a telescope, a leveling tube and a reader.

The purpose and working principle of editing this paragraph.

Theodolite is the main angle measuring instrument in measurement. It consists of a telescope, a horizontal dial, a vertical dial, a level and a base. When measuring, put the theodolite on a tripod, aim the center of the instrument at the ground measurement site with a vertical ball or an optical collimator, and use a horizontal theodolite.

Level the instrument, aim the telescope at the measurement target, and measure the horizontal and vertical angles with horizontal and vertical dials. 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. An instrument for measuring horizontal and vertical angles. It was first developed by British mechanic Xisong in about 1730, and was officially used in British geodesy after being improved and finalized. 1904, Germany began to produce glass dial theodolite. With the development of electronic technology, electronic theodolite appeared in 1960s. On this basis, an electronic rapid measuring instrument was manufactured in 1970s. 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. This kind of bracket has simple structure and low cost, and is mainly used with ground telescopes (geodesy, bird watching, etc.). ). If it is used to observe celestial bodies, it is necessary to rotate two axes at the same time and change the rotation speed with time to track the celestial bodies. However, other celestial bodies in the field of view rotate relative to the target celestial bodies, and unless a mechanism to counteract the rotation of the field of view is added, it is not suitable for long-exposure celestial photography.

1. Right ascension and declination In the vast sea, when a sailing ship is in danger, the first thing to do is to let the rescuer know where the ship is, that is to say, to inform the rescuer of the latitude and longitude of the ship. Latitude and longitude can not only indicate the position of a ship in the ocean. Its greatest advantage is that it can tell you the exact location of an object very concisely. Similarly, in the boundless night sky, once you find a new star, how do you make its correct position known to the world? Do you think there should be a similar latitude and longitude measurement system to calibrate the position of the planets and make star maps? The measurement systems used by astronomers are right ascension and declination. The unit of declination is degrees, and the unit of right ascension is hours and minutes. We may not be familiar with these, but it is not difficult to understand. Because the stars are too far away from us, we can't tell the difference between them with the naked eye, so these planets are all the same distance to us. Let's imagine that there is a suspended spherical shell covering the whole earth. This imaginary ball is called the celestial sphere. These stars are fixed inside the spherical shell, and we can only see half a sphere at a time. Due to the rotation of the earth, the celestial sphere seems to be constantly rotating around us from east to west. The north (south) pole of the celestial sphere is just above the north (south) pole of the earth's geography, and the equator of the celestial sphere is just above the equator of the earth, which is the center of the celestial pole. Like the earth, we marked the celestial sphere with latitude and longitude. In astronomy, this is equivalent to the latitude (longitude) of the earth and is called declination (right ascension). From the celestial pole to the celestial equator, declination is 90 degrees; Right ascension is divided into 24 hours and 60 minutes with 1, that is, 1h = 60m = 15, which is named after the hourly rotation of the earth or celestial sphere 15. This method of determining the position of celestial bodies looks quite complicated, but it has many advantages. For example, the celestial sphere is constantly rotating, so the apparent position of the stars is constantly changing, like crossing the night sky from east to west; At the same time, because of the revolution of the earth, although at the same time, after a few days, the stars are slightly west; Or if you walk from north to south, the relative position of the stars and the horizon is also changing. Because the apparent positions of stars are so changeable, it is quite difficult to explain their positions according to what they see. It can only be explained by right ascension and right latitude, because each planet corresponds to a set of right latitude and longitude. But also because the astrology changes rapidly, how should we measure right ascension and declination? Second, the production of theodolite theodolite is used to measure right ascension and declination. It is an observation device with many characteristics of astronomical telescope. Now, a simple theodolite measurement method is introduced. The required materials are listed in table 1. The size of each material is for reference only, and you can consider it yourself, but the relative position of each part must be clear. Look at the pictures 1, 2 and 3 before making. Method: 1. Saw off two disks with a (3/8) "thick splint, which is slightly smaller in diameter than the protractor (1/2)". Glue two protractors to each disk with super glue, and the midpoint of the bottom edge of the protractor must be glued to the center of the disk. (See Figure 2). 2. Fix the CD on D with two screws. The connecting line between the center of the disc and 90 must coincide with the center line of D. Nail a screw ring at each end of D (note that it is not nailed on the side with the disc, as shown in Figure 2). The line of sight can be observed through two small circles. 3. In the center of another disc, drill a hole (1/4) ",which should pass through both A and C (see Figure 3) and be fixed with a screw. Adjust the tightness to make C easy to rotate. 4. Dig a hole from the center of the protractor attached to D, and tighten D and C with a cork or screw. But d and c should be rotatable, not fixed. 5. Cut three triangles with iron sheet and fix them on C with screws or small nails. The tip of the triangle must be connected to the protractor. 6. connect a and b with a hinge. (see figure 1) 7. G, h, cut a small hole from one end (3/4) ",and from the hole 1", cut a slit with the width of (3/ 16 "along the center line of each wooden frame until it is away from the other end 1". Fix G and H on both sides of A with bolts at the small holes, and then fix G and H on one side of B with bench drill through a narrow seam. Bench drill is used to adjust the angle X. When screwing screws or setting drills, nail them in a proper position, so that A and B can overlap when adjusting to the end of the slit. At this time, theodolite can be used. Third, the use of theodolite will be supported on a shelf, such as a chair or a camera tripod. The purpose is just to make the line of sight easy to observe through the screw ring of D, and place the theodolite facing south. First, don't lift the sight arm D (that is, the latitude table E points to zero). Adjust the inclination of the B board so that the line of sight can see the horizon along the viewing arm. Fix the B plate in this position, and then keep the B plate horizontal. Now rotate c and d to observe the celestial body, and then e represents the height of the celestial body. Now raise the theodolite to an angle x, where X = 90- (the latitude of the measuring place). For example, measured in Taipei, the latitude is about 25 3', and the angle X is equal to 64 57'; Another method is to aim the aiming arm at the north star, keep D in this direction, and move the A board to make the reading of latitude table E 90. At this time, board A and board B are at an angle of X. Of course, if you think about it a little, you can measure the latitude of your position in this way. Why is the angle between a and b x? (Note 1) When you look up at the celestial pole (the North Star), the elevation angle is your latitude. Therefore, when the reading of E is zero, the aiming arm points to the celestial equator after lifting the plate A by X angle. Why? (Note 2) The purpose of adjusting the X angle is to find the elevation angle of the star to the equatorial plane of the celestial sphere (that is, declination), regardless of the change of the apparent position of the star caused by the latitude of the observation point. At this time, the equatorial position of the celestial sphere is drawn by rotating the sight arm from west to east. In order to measure the right ascension, the longitude table F must be carved into the right ascension unit hour. When the interval of 15 is 1, it must be carved counterclockwise from zero. Now move the sight arm to see a known star in the southern sky, determine the right ascension and declination of this star from the star map, astronomical calendar or other reference star sources, and rotate the longitude table F to make the pointer of C point to the appropriate right ascension value. At this time, the latitude table should automatically indicate the correct declination value, otherwise the instrument will be biased. Fixed f, now rotate c and d, and point the aiming arm at another planet. At this point, we can read the declination and declination of the planet from E and F. The declination of the star north of the celestial equator is positive, and the declination of the star south of the celestial equator is negative, that is, the protractor at the opening on the E disk is positive and the other is negative. For example, you can see Kikuchi in the night sky in April, May and June. Its declination (R.A.)= 13h23m37s, declination (D.) =-119. Now rotate the observation arm D and look at Xuanyuan XIV. At this time, we can read 12 06' on E and 10h07m on F, so we know that R.A.= 10h07m, D. = 12 06 of Xuanyuan XIV. For another example, in the winter night sky, Sirius's R.A is about 6h44m, and D is about-16 40'. After adjusting F to 6h44m, raise the visual arm by about 25 declination, and then rotate it to the west by about 3h45m. At this time, you can see through the spiral ring on D, and in early autumn and winter nights, you can see a hazy bright belt near Pegasus Square. It is Andromeda, the only spiral nebula that can be clearly seen by the naked eye. Are you interested in finding its approximate location? It is about R.A.=0h40m, d. = 4 1. The advantage of finding right ascension and declination by this method is that there is no need to worry about the factors that cause the apparent position change of the planet because of the different observation time. Why? Because disk A is coincident with the equatorial plane of the celestial sphere after X-angle correction, the elevation angle of the star to disk A (that is, the equatorial plane of the celestial sphere) obtained by E is naturally declination. Although the celestial sphere is constantly rotating, all the stars are almost distant stars, and their relative positions remain unchanged. We know the declination of a star. Based on this, we can naturally calculate the declination of another star from the angle between this star and other stars, so no matter what latitude, season and time you observe, the declination number and declination number of the star you get will not be different. Table 2 lists some reference star sources. For many great experiments, the equipment it needs is often quite simple. Don't underestimate the theodolite. It is very likely that one day, you will use it to locate a planet that has never been discovered before and become famous in the world. ChallengegeGeoftheuriverse117 Page Project and Experiment 1962 was published by the National Association of Science Teachers. The original text only explains the production method and does not discuss the principle. The translator has made some simple explanations for this principle. Note 1: As shown in Figure 4, plate B points to the southern horizon, plate D points to the north pole of the celestial sphere, and plate A is perpendicular to it. ∠Y is the latitude of the observation site. Because Polaris is far away from the earth, it points to the north pole of the celestial sphere and is parallel to the straight line from the north pole to the center of the earth. We can easily prove that ∠Z=∠Y and ∠ X+. Note 2: When the reading of E is zero, D is parallel to A, as shown in Figure 4, A is at right angles to the celestial north pole, that is, it points to the celestial equator, so D also points to the celestial equator. Principle theodolite is designed according to the principle of angle measurement. In order to determine the horizontal angle, it is necessary to horizontally place an angular disk-a horizontal dial (Figure 2) on the vertical line passing through the intersection of two directions in space. In the figure, the intersection of the vertical plane of OAA 1 and the horizontal dial gets a reading ι, and the intersection of the vertical plane of OBB 1 gets a reading b on the dial, and B minus ι is the central angle β, which is the angle value β 65438 of the horizontal angle A 1O 1. In order to determine the vertical angle, a disk-a vertical dial must be placed vertically. Because one direction of the vertical angle is a specific direction (horizontal direction or zenith direction), the vertical angle value can be obtained only by reading the reading on the vertical dial when the line of sight points to the target. There are many types of theodolite, which can be divided into ordinary theodolite and precision theodolite according to accuracy, and there are certain series standards. The horizontal median error of the precision optical theodolite produced in China is not more than 0.7 ",the telescope magnification is 56 times, 45 times and 30 times, the horizontal dial diameter is 158 mm, the minimum reading is 0.2", the vertical dial diameter is 88 mm, and the minimum reading is 0.4 ". Theodolite is divided into vernier theodolite, optical theodolite and electronic theodolite according to reading equipment; According to the shafting, it can be divided into retest theodolite and direction theodolite. At present, the most commonly used is optical theodolite. In order to facilitate operation and improve efficiency, this instrument has been improved on the original basis. For example, using an upright telescope; Fast focusing and slow focusing mechanisms; Coaxial braking and micro-motion mechanism; Digitize the dial reading by using a reading microscope with reticle or an optical micrometer; The two dial images show different colors; It is equipped with a coarse and fine dial mechanism and an automatic zeroing device with a vertical dial indicator. There are also some theodolite with special functions, such as sight distance theodolite with optical ranging device; A compass theodolite that uses a magnetic needle to determine the northern position; Gyro theodolite (see mine survey), which can determine the true north direction by combining gyro and theodolite; A laser theodolite that uses laser to form a visible collimation axis and can conduct guidance, positioning and collimation measurement; Photographic theodolite for ground photography: film theodolite for automatic tracking and measurement; Automatic angle measurement and recording of electronic theodolite: and electronic fast measuring instrument integrating electronic theodolite, electromagnetic wave rangefinder, micro-information processor and recorder. Electronic velocimeter can not only quickly obtain data such as oblique distance, horizontal distance, height difference (or elevation), coordinate increment (or coordinates) in the field, but also automatically display, print and record holes, or store the data on magnetic tape, and also establish a digital terrain model, or connect with a computer through a special interface to automatically map. When working in dark environment, such as tunnel engineering, using LDT520 can effectively control and locate the visible laser beam emitted by the measuring point. In cloudy environment, the effective working radius of laser beam reaches 600m, which is even farther in dark environment. The spot diameter focuses the beam 2.1mm @ 20m/10.3mm @100m/15.5mm @150m.

Parallel beam 15. 1 mm @ 20m/15.3mm @100m/15.5mm @150m.

Telescope magnification

30X

Minimum display

1 inch/5 inch optional

Accuracy (ISO17123-3: 2001)

5"

Standard battery life

13.5 hours (1mw power output)

Weight (including battery)

5.7 kg