A method for back-calculating instrument height in precision trigonometric height measurement and its application

Abstract

The present invention belongs to the field of surveying and mapping technology applications, and particularly relates to a method and application for inverse calculation of instrument height in precision trigonometric height measurement. By finding a suitable reference point, the elevation difference between the leveling point to be measured and the reference point is measured respectively. Then, through the total station combined leveling method, the instrument height of the total station is calculated by the leveling height difference between the two points. This inverse calculation method is applied to the leveling work of large hydropower stations. In the precision second-class cross-river leveling, the instrument height can be controlled to an accuracy of 0.1mm. This overcomes the technical defects of the existing technology that cannot perform second-class cross-river leveling and that the workload is huge when implementing traditional cross-river leveling, and the difficulty in improving the working efficiency, and the reduced leveling accuracy due to the long leveling route.

Description

Technical Field

[0001] The present invention belongs to the field of surveying and mapping technology applications, and particularly relates to a method for back-calculating instrument height in precision trigonometric height measurement and its application. Background Art

[0002] In the construction of large hydropower stations, the elevation control network generally requires second-class leveling, and elevation control points must be arranged on both sides of large rivers. This requires us to conduct cross-river leveling. When conducting high-precision elevation control measurements, we often face the problem of not being able to conduct traditional cross-river leveling due to the wide river surface and the lack of bridges upstream and downstream of the survey area. Or, if there is a bridge, it is too far away from the survey area. When implementing traditional cross-river leveling, the workload is huge and the work efficiency is difficult to improve. In addition, the long leveling route leads to technical defects such as reduced leveling accuracy.

[0003] With the rapid development of surveying and mapping instruments and artificial intelligence, total stations have developed into measuring robots. High-precision, fully automatic measuring robots have been widely used in engineering control measurements and deformation measurements. Nowadays, in the measurement of elevation control networks, precision trigonometric height measurement can meet the accuracy requirements of second-class leveling. However, in the process of precision trigonometric height measurement, the measurement and setting of various parameters are extremely important, such as instrument height, prism height, air pressure and temperature. In the process of precision trigonometric height measurement, due to the influence of factors such as the structure and appearance of the total station (or measuring robot), such as Figure 1 The actual measured instrument height is the instrument inclined height i x , and the instrument high truth i h There is a certain error between △ , this error i △ It is often not a constant and cannot be corrected uniformly.

[0004] To address the problem of high-level elevation control measurements during large hydropower station construction, which cannot be performed using traditional river-crossing leveling, this paper conducts theoretical and practical research on photoelectric ranging precision trigonometric height measurement technology. This paper analyzes the factors influencing trigonometric height measurement errors in river-crossing areas and proposes targeted solutions based on the actual environment of large hydropower station survey areas. A method for inverse calculation of instrument height in precision trigonometric height measurement is also proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and application for back-calculating instrument height in precision trigonometric height measurement in response to the problems existing in the prior art.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for back-calculating instrument height in precision trigonometric height measurement comprises the following steps:

[0008] Step 1: Select the benchmark point A and the leveling point B to be measured;

[0009] Step 2: Set up a level between the reference point A and the leveling point B to be measured, and obtain the elevation H at point A. A and the elevation H at point B B , get the elevation difference H between points A and B AB ;

[0010] Step 3: Set up a total station at the reference point A, set up a prism at the leveling point B to be measured, and obtain the slope distance S between points A and B. AB ; The vertical angle between point A and point B is α AB , the height of the prism at point B is V B ;

[0011] Step 4: According to the elevation difference H AB And the trigonometric height triangle calculation formula: H AB =S AB sinα AB +i A -V B , get the height i of the total station at the reference point A A .

[0012] In order to minimize the error of trigonometric height measurement, the H AB =D tanα+iv; The inverse calculation method for obtaining the true height i of the total station is because, when the observation distance between two points is greater than 300m, the curvature of the earth and the refraction of atmospheric light have a greater impact on the height difference, increasing more measurement errors.

[0013] The errors in trigonometric height measurement mainly include errors in instrument height and target height, distance measurement error, angle measurement error, atmospheric refraction error, and errors caused by the curvature of the earth. During measurement, the errors in instrument height and target height include the accuracy error of the tape measure used to measure the instrument height and the reading error measured manually. The error in measuring the target height is easy to control during the measurement process. The target height at a fixed height can be used for measurement, thereby eliminating the influence of the target height measurement error on the height difference measurement during the measurement process. However, the error in measuring the instrument height is difficult to eliminate. In the prior art, a tape measure with a small fixed error is usually selected to measure the instrument height from three directions before and after the measurement to ensure the measurement accuracy of the instrument height. The height difference of the instrument in trigonometric height measurement has little effect on the accuracy of trigonometric height control measurement. The error in measuring the instrument height only needs to be considered in the process of precise trigonometric height measurement. The technical solution of the present invention adopts a combined leveling method to calculate the instrument height through the leveling height difference of two points. In the process of precise second-class cross-river leveling, the instrument height can be controlled to an accuracy of 0.1mm.

[0014] Preferably, in step 1, the distance between the reference point A and the reference point B to be measured is in the range of 15m-25m. The distance between points A and B should be neither too short, which would make observation difficult and easily damage the stability of the reference point, nor too long, which would eliminate the influence of spherical aberration on trigonometric height measurement; it should be between 15-25 meters.

[0015] The spherical aberration in trigonometric height measurement is calculated according to the following formula: The spherical aberration in trigonometric height measurement is calculated according to the following formula: f = (1-k)D 2 / 2R;

[0016] Among them, f represents the spherical aberration, k represents the atmospheric refraction coefficient, D represents the observation side length, unit is km; R represents the radius of the earth, generally taken as 6378km.

[0017] The spherical aberration in trigonometric height measurement is related to the atmospheric refractive index and the observed side length. It is inversely proportional to the atmospheric refractive index and directly proportional to the square of the observed side length. Since the observed side length in trigonometric height measurement can be accurately determined to the millimeter, the effect of the observed side length can be precisely calculated. When D < 300m, the spherical aberration f can be ignored.

[0018] By analyzing the sources of error, it was found that when implementing trigonometric height control measurements, the control errors in target height error, instrument height error, distance measurement error, and angle measurement error are relatively easy to control. However, due to the large and irregular range of atmospheric refraction coefficient, the errors caused by the curvature of the earth and atmospheric refraction are difficult to control. In actual measurements, the error in trigonometric height measurement mainly comes from the influence of spherical aberration.

[0019] Preferably, in step 1, the height difference between the reference point A and the leveling point B to be measured is within the range of ±1° from the observation zenith.

[0020] Preferably, the reference point A and the leveling point B to be measured are in sight of each other. The two points A and B must be in sight of each other. That is, the elevation difference between points A and B must be such that it can be measured with a single leveling station. This is to reduce station setup errors and quickly measure the elevation difference between points A and B.

[0021] Preferably, during the elevation control in step 2, a total station is used to collect data.

[0022] Specifically, the model of the total station is Leica TS50 total station.

[0023] Preferably, the specific steps of level measurement are: set up the level between points A and B, set up level rods at points A and B respectively, and the level rod readings are H and A 、H B , calculate the height difference H between points A and B AB, that is, H AB =H B -H A .

[0024] Preferably, the level measurement is not lower than the second-class leveling measurement specification requirements (or the leveling point B to be measured is not less accurate than the measured reference point A), and the working environment and measuring instruments must meet the measurement accuracy requirements.

[0025] In step 2, the level measurement shall be carried out according to the requirements of the second-class leveling measurement specifications (or the accuracy of the leveling point B to be measured shall not be lower than that of the measuring reference point A), and the working environment and measuring instruments shall meet the measurement accuracy requirements.

[0026] Preferably, in step 3, the systematic error of setting up the prism at point B is no longer considered, and the measurement accuracy of the total station (or surveying robot) should be greater than the accuracy requirement of the control network to be measured.

[0027] During distance measurement, a highly accurate measuring robot is used. The distance measurement accuracy of the measuring robot reaches the millimeter level. If the distance accuracy reaches the millimeter level, by controlling the height difference between two points during trigonometric height measurement, the impact of distance measurement error on trigonometric height measurement can be calculated using a formula to be negligible at the micron level.

[0028] Preferably, in step 4, the height calculation formula of the precision trigonometric height measuring instrument should be selected from:

[0029] i A =H AB -S AB sinα AB +V B , it is not advisable to choose i A =H AB -D AB tanα AB +V B ,

[0030] Where S AB is the slope distance between points AB, D AB is the horizontal distance between two points AB.

[0031] The inverse calculation method for instrument height in precision trigonometric leveling is applied to large hydropower stations. This method is used for precision second-order river-crossing leveling. The inversely calculated total station height value, i, is incorporated into the trigonometric leveling formula to map the elevation difference across the river.

[0032] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0033] In the technical solution of the present invention, the difficult problem of high-precision measurement of instruments in the process of engineering surveying is successfully solved through inverse calculation, which can significantly improve the accuracy of precise trigonometric height measurement, and the continuity of the precise surveying process can be guaranteed to the greatest extent during the implementation of this method.

[0034] The inverse calculation method of the present invention has controllable accuracy during the process of precise second-class cross-river leveling, solves the technical problem that traditional leveling cannot be implemented in the construction of large hydropower stations, and facilitates the construction and maintenance of the elevation control network. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the height measurement of the total station (or surveying robot) of the present invention;

[0036] Figure 2 It is a schematic diagram of measuring with the level instrument of the present invention;

[0037] Figure 3 This is a schematic diagram of a total station (or surveying robot) of the present invention;

[0038] Figure 4 Survey plan for the cross-river control network of a hydropower station.

[0039] Reference numerals:

[0040] 1-Total station, 2-Level, 3-Level rod, 4-Prism. DETAILED DESCRIPTION

[0041] The present invention will be described in detail below with reference to the accompanying drawings.

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0043] Example 1

[0044] Figure 2 This is a schematic diagram of the level instrument of the present invention. Figure 3 This is a schematic diagram of the surveying of the total station (or surveying robot) of the present invention. Figure 4This survey plan outlined the river crossing control network for a hydropower station. The planned survey areas included the dam, ship locks, and the downstream construction area of ​​a bridge. The elevation control network was measured using second-class accuracy. During the actual survey, the power station was located on a wide river, exceeding 300 meters, making traditional cross-river leveling impractical. Approximately 2 kilometers downstream of the proposed power station dam, a bridge spans the river. As this bridge spans the river, traffic is heavy and traffic control is costly. Therefore, a second-class elevation control approach was proposed, using leveling combined with precision trigonometric height measurement.

[0045] The specific implementation method of precise trigonometric height measurement is as follows:

[0046] 1. Layout of elevation control network

[0047] To meet the needs of power station construction, control points were required on both sides of a river near the power station's dam. Two second-class elevation control points were set up on each side of the power station. The location of these control points significantly impacts the precision cross-river trigonometric elevation measurement. To ensure the accuracy of this precision cross-river trigonometric elevation measurement, the locations of these second-class elevation control points were selected to meet the following requirements: the second-class control points maintained line of sight with the two control points on the opposite bank of the river, and the elevation difference between the elevation control points was minimal, controlled within the observation zenith distance of ±1°. Through actual survey and point selection, two second-class elevation control points, BM01 and BM03, were set up on the left bank of the river, and two second-class elevation control points, BM02 and BM04, were set up on the right bank of the river.

[0048] 2. Selection of surveying and mapping instruments

[0049] The Leica TS50 total station was used for precision trigonometric height measurement, with a distance measurement accuracy of ±(0.6mm+1ppm*D) and an angle measurement accuracy of ±0.5″. The total station features automatic target search, automatic sighting, and automatic target observation, effectively reducing human error. The measuring prisms used were three Leica Jeoc ADS13 high-precision metal-cased prisms equipped with three fixed-height prism poles. Repeatability and interchangeability were checked before use, and the prism height was verified, eliminating target height measurement errors before measurement began. Thirty minutes before the measurement, the instrument was placed in an open-air environment to allow the Leica TS50 total station to approach the ambient temperature.

[0050] 3. The specific plan is as follows:

[0051] refer to Figure 4As shown: Before the survey, first select a location about 20 meters near BM01, BM02, BM03, and BM04 to bury four ordinary leveling marks A, B, C, and D, and ensure that the elevations of adjacent leveling points are basically equal. Use BM01, BM02, BM03, and BM04 as measuring stations, set up level 2, and measure the height difference H1 between BM01 and point A (A level rod 3 reading - BM01 level rod 3 reading), the height difference H2 between BM02 and point B (B level rod reading - BM02 level rod reading), the height difference H3 between BM03 and point C (C level rod reading - BM03 level rod reading), and the height difference H4 between BM04 and point D (D level rod reading - BM04 level rod reading) respectively; these are used to calculate the height of total station 1. The elevation control points on the same bank of a river were measured using the traditional second-class leveling method and connected to the national leveling points, of which 12(09) and 1(09) are national first-class leveling points. The elevation control points on different banks were measured using the precise trigonometric elevation method. During observation, a total station 1 was first set up on BM01, and prisms 4 were set up on A, BM02, and BM04. The total station 1 simultaneously observed prisms 4 on A, BM02, and BM04. Since the elevation difference between BM01 and point A has been measured using a digital level that meets the accuracy requirements, and the distance between BM01 and point A is only 20 meters, the spherical aberration can be ignored. Therefore, the height of the total station can be calculated based on the elevation difference between BM01 and point A measured by the total station. The instrument height calculated in this way can be accurate to 0.1mm. Then, the elevation difference between BM01 and BM02 and the elevation difference between BM01 and BM04 are calculated based on the instrument height. According to this method, the total station was set up on BM02, BM03, and BM04 for observation. To ensure the accuracy of precise trigonometric height measurement, each height control point is observed at 6 different time periods.

[0052] With BM01, BM02, BM03, and BM04 as measuring stations, set up a total station (or measuring robot) and measure the slope distance S1 between BM01 and point A; the slope distance S2 between BM02 and point B when the vertical angle is α1 and the prism height is V1; the slope distance S3 between BM03 and point C when the vertical angle is α2 and the prism height is V2; the slope distance S4 between BM04 and point D when the vertical angle is α3 and the prism height is V3; and the slope distance S4 between BM04 and point D when the vertical angle is α4 and the prism height is V4.

[0053] Assume that the instrument heights of the total stations (or measuring robots) at BM01, BM02, BM03, and BM04 are i1, i2, i3, and i4 respectively. According to the calculation formula:

[0054] H AB =S AB sinα AB +i A -V B, respectively calculate the instrument height of the total station (or measuring robot) set up at each measuring station BM01, BM02, BM03, and BM04, namely:

[0055] The instrument height at point BM01 is i1 = H1 - S1 sin α1 + V1;

[0056] The instrument height at point BM02 is i2 = H2 - S2 sin α2 + V2;

[0057] The instrument height at point BM03 is i3 = H3 - S3 sin α3 + V3;

[0058] The instrument height at point BM04 is i4=H4-S4sinα4+V4.

[0059] In this embodiment, the national first-class leveling points 12 (09) and 1 (09) are known point data. This embodiment can constitute multiple leveling compliance routes (or closed routes) to perform accuracy verification on the instrument height data calculated by each measuring station BM01, BM02, BM03, and BM04.

[0060] The elevation control points on different banks were measured using a precise trigonometric method. A total station was first set up on BM01, and prisms were set up on points A, BM02, and BM04. The total station simultaneously observed the prisms on points A, BM02, and BM04. Since the elevation difference between BM01 and point A had been measured using a digital level that met the accuracy requirements, and the distance between BM01 and point A was only 20 meters, the spherical aberration was negligible. Therefore, the height of total station 1 could be calculated from the elevation difference between BM01 and point A measured by the total station. This instrument height was calculated to an accuracy of 0.1 mm. The elevation differences between BM01 and BM02, and between BM01 and BM04, were then calculated based on the instrument height. Following this method, total station 1 was set up on BM02, BM03, and BM04, respectively, for observation.

[0061] A total of four sections of second-class leveling routes were surveyed, with two round trips conducted on each section. The round trip data results are shown in Table 1:

[0062] Table 1 is the data of the second-class leveling survey results

[0063]

[0064] The precision trigonometric height measurement completed four sets of opposite-direction observations, each of which was conducted in six time periods. After completing all data collection, all measurement data were processed and analyzed using Leica total station measurement software, and can be considered as equal-precision observations. The data results statistics include the difference in height between the opposite-direction observations of the two stations in each time period and the height difference between the two points in each time period. The statistical results are shown in Tables 2 and 3:

[0065] Table 2 shows the difference in height between the two observation stations at different times.

[0066]

[0067] (Note: Period 1: 9:00-10:30; Period 2: 10:30-12:00; Period 3: 12:00-13:30; Period 4: 13:30-15:00; Period 5: 15:00-16:30; Period 6: 16:30-18:00)

[0068] Table 3 shows the height difference between two points in each period

[0069]

[0070] (Note: Period 1: 9:00-10:30; Period 2: 10:30-12:00; Period 3: 12:00-13:30; Period 4: 13:30-15:00; Period 5: 15:00-16:30; Period 6: 16:30-18:00)

[0071] The measurement results of the above six time periods clearly show that the observation results in the two observation periods from 12 noon to 15 o'clock have large errors. During the observation, the surveyors also found that air waves could be clearly seen in the total station during these two periods, and the prism could be seen jumping up and down in the air waves. This situation occurred because the observation season was summer, and the temperature was high from 12 noon to 15 o'clock, the sunlight was strong, and the air flow was violent. Based on the observation results of the four time periods of total station observation, excluding the two periods with large errors, and unified adjustment processing with the leveling route, this cross-river leveling formed a total of 5 closed loops and 4 attached routes. The accuracy of the 5 closed loops and 4 attached routes was statistically analyzed, and the results fully met the accuracy requirements of second-class leveling. The accuracy statistics are shown in Table 4.

[0072] Table 4 Closure difference between the corresponding route and the closed loop

[0073]

[0074] The principle of height control measurement using trigonometric height measurement is adopted, and the sources of errors and methods of controlling errors are studied. The above-mentioned power station is applied in the actual project of implementing second-class cross-river height control measurement using precision trigonometric height measurement. When the photoelectric ranging trigonometric height measurement method is used for height control, a high-precision intelligent measuring robot (distance measurement accuracy reaches ±(0.6mm+1ppm*D), angle measurement accuracy reaches ±0.5″) is used, equipped with a prism with a fixed prism height, and an appropriate observation time window is selected. Precision trigonometric height measurement replaces second-class leveling measurement in large hydropower stations. The closure error of the attached route (closed loop) of precision trigonometric height measurement can meet the specification limit requirements of second-class leveling. Practice has proved that the method of the present invention is completely feasible and has controllable accuracy. The method of the present invention can be used for the construction and maintenance of height control networks in engineering projects where traditional leveling cannot be implemented during the construction of large hydropower stations.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An application of a method for back-calculating instrument height in precision trigonometric height measurement, characterized in that: The inverse calculation method is applied to large hydropower stations to conduct precise second-class cross-river leveling. The total station height value i obtained by inverse calculation is substituted into the trigonometric height calculation formula to map the cross-river elevation difference. The back calculation method of instrument height in precision trigonometric height measurement includes the following steps: Step 1: Layout of elevation control network: To meet the construction requirements of the power station, control points need to be laid out on both sides of the dam river. Two second-class elevation control points are laid out on each of the left and right banks of the power station. BM01 and BM03 are laid out on the left bank, and BM02 and BM04 are laid out on the right bank. Step 2: Set up a total station with BM01, BM02, BM03, and BM04 as survey stations. Select a location 15m-25m near BM01, BM02, BM03, and BM04 to bury four leveling points (A, B, C, and D). Measure the height difference H1 between BM01 and point A, the height difference H2 between BM02 and point B, the height difference H3 between BM03 and point C, and the height difference H4 between BM04 and point D, and calculate the height i of the total station at each survey station. The instrument height of the total station at point BM01 is i1= H1-S1sinα1+V1; The instrument height of the total station at point BM02 is i2= H2-S2sinα2+V2; The instrument height of the total station at point BM03 is i3 = H3-S3sinα3+V3; The instrument height of the total station at point BM04 is i4 = H4-S4sinα4+V4; In step 2, the instrument height back calculation method specifically includes the following steps: Step 21: Select the leveling point A and the control point BM01; Step 22: Set up a level between the control point BM01 and the leveling point A, and obtain the elevation H at the control point BM01. A , the elevation H at the benchmark A B , get the elevation difference H1 between points BM01 and A; Step 23: Set up a total station at the control point BM01 and a prism at the leveling point A to obtain the slant distance S1 between points BM01 and A; the vertical angle of point A observed at point BM01 is α1, and the height of the prism at point A is V1; Step 24: Obtain the height i1 of the total station at the control point BM01 according to the elevation difference H1 and the trigonometric height triangle calculation formula: H1=S1sinα1+i1-V1; Step 25, repeat steps 21-24, and calculate the total station height i2 at the control point BM02, the total station height i3 at the control point BM03, and the total station height i4 at the control point BM04; Step 3: Construct multiple leveling lines and perform accuracy checks on the instrument height data calculated at the BM01, BM02, BM03, and BM04 stations.

2. The application of the method for back-calculating instrument height in precision trigonometric height measurement according to claim 1, characterized in that: In step 21, the height difference between the leveling point A and the control point BM01 is within the range of ±1° from the observation zenith.

3. The application of the method for back-calculating instrument height in precision trigonometric height measurement according to claim 2, characterized in that: The leveling point A and the control point BM01 can see each other.

4. The application of the method for back-calculating instrument height in precision trigonometric height measurement according to claim 1, characterized in that: The model of the total station is TS50 total station.

5. The application of the method for back-calculating instrument height in precision trigonometric height measurement according to claim 1, characterized in that: In step 22, the specific steps of leveling are: set up a level between the control point BM01 and the leveling point A, set up level rods at the control point BM01 and the leveling point A, and the level rod readings are H A 、H B , calculate the height difference H1 between BM01 and A, that is, H1=H B -H A .

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