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1CS 07.040
National Standard of the People's Republic of China
GB/T 20256—2006
Specifications for the gravimetry control
Specifications for the gravimetry control2006-05-24Promulgated
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of ChinaAdministrative Committee of Standardization of the People's Republic of China
2006-10-01Implementation
1Scope
2Normative references
3Terms and definitions
General principles·
Purpose of national gravity control measurement·
Grades of national gravity control measurement
National gravity control measurement Accuracy of excavation survey
Layout principles and technical requirements of national gravity control network Coordinate system and elevation system of gravity control points 4.5
Establishment of national gravity control points*
Establishment of benchmark points·
Establishment of basic points, first-class points and guide points
Establishment of short baselines·
Contents of data submitted for selection and burial
Absolute gravity measurement
Selection and requirements of absolute gravimeter:
Absolute gravity Requirements for the use of gravimeters
Adjustment and inspection of absolute gravimeters:
Observation outline
Observation value processing and accuracy assessment-
Determination of vertical gravity gradient·
Results collation and technical summary
Submitted results and materials,
Relative gravity measurement
Instrument selection and requirements
Instrument inspection and adjustment
Instrument performance test
Gravimeter scale factor Calibration
Observation outline,
Observation record·
Survey line calculation +
Accuracy assessment and supplementary survey requirements
Submission of results data 1
8Plane coordinates, business process determination
9Surveying results and submission of data·
Data collation-
9.2 Submission of data-
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GB/T20256—2006
GB/T 20256—2006
10 Data processing
10.1 Collection and arrangement of field data·
10.2 Data preprocessing
10,3 Mathematical model of adjustment·
10.4 Submission of adjustment results·
11 Inspection and acceptance of results
Appendix A (Normative Appendix)
Appendix B (Normative Appendix)
Appendix C (Normative Appendix)
Appendix 13 (Normative Appendix)
Appendix E (Normative Appendix) Appendix F (Normative Appendix)
Appendix G (Normative Appendix)
Appendix H (Normative Appendix)
Appendix I (Normative Appendix)
Appendix (Normative Appendix)
Appendix K (Normative Appendix)
Appendix 1 (Normative Appendix)www.bzxz.net
Appendix M (Normative Appendix)
Specifications of pressure point markers and signs of national gravity control network Records of national gravity control points
Mathematical model of gravity measurement and screening, FG5 absolute Gravity measurement observation record table
Absolute gravity measurement results table
Measurement and adjustment of optical displacement sensitivity
Inspection and adjustment of correct reading line
Inspection and adjustment of horizontal level
Inspection and adjustment of electronic reading zero and current meter zero position Measurement and adjustment of electronic sensitivity
Inspection of optical displacement linearity
Inspection of electronic reading linearity
LCR gravimeter observation record format example
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This standard is based on the CH/T2003—1999% National Gravity Measurement Specification (ZBA76001—1987), the 2000 National Gravity Basic Network Joint Measurement Technical Regulations and the Interim Technical Regulations "Absolute Gravity Measurement Technical Regulations" formulated by the State Administration of Surveying, Mapping and Geoinformation in 2000, and the practical experience of projects such as the National Gravity Basic Network, the First-Class Gravity Network and the China Crustal Movement Observation Network, combined with the latest scientific research and production results, and in accordance with the requirements of national gravity control measurement. Appendix A, Appendix B, Appendix C, Appendix D, Appendix E, Appendix F, Appendix G, Appendix H, Appendix I, Appendix J, Appendix K, Appendix L, and Appendix M of this standard are normative appendices. This standard is proposed by the State Administration of Surveying, Mapping and Geoinformation.
This standard is approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China. This standard is under the jurisdiction of the Jinguo Geographic Information Standardization Technical Committee. The main drafting units of this standard are: Surveying and Mapping Standardization Institute of the State Administration of Surveying and Mapping, Geodetic Data Processing Center of the State Administration of Surveying and Mapping, First Geodetic Survey Team of the State Administration of Surveying and Mapping, China Academy of Surveying and Mapping, Wuhan University. The main drafters of this standard are: Guo Chunxi, Xiao Xuenian, Qiu Qixian, Wang Huimin, Qichao, Li Tingcheng, Zhu Bin. http://www.nl.gov.cn/english/1.010 ... For any dated referenced document, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties reaching an agreement based on this standard are encouraged to study and apply the latest versions of these documents. For any undated referenced document, the latest version shall apply to this standard. GB 12898—1991 National third and fourth grade leveling specification GB/T18314—2001 Global Positioning System (GPS) measurement specification GJB2228—1994 Global Positioning System (GPS) geodetic survey rules CH1002 Inspection and acceptance regulations for surveying and mapping products
CH1003 Quality assessment standards for surveying and mapping products
3 Terms and definitions
The following terms and definitions apply to this standard. 3.1
Gravimetric datum point
The point whose gravity value is measured by a high-precision absolute gravimeter and used as the starting datum of the national gravity control network is referred to as the datum point. 3.2
Vertical datum gmyitydatum
The datum points in the national gravity control network constitute the national gravity datum. 3.3
Basic gravity point The gravity control point determined by relative gravity joint survey and overall adjustment with the gravity value of the datum point in the national gravity control network as the starting value, referred to as the basic point.
Convenient for use Gravity point connected for use from the basic point and the first-class point in the form of a branch line with the same joint survey accuracy. 3.5
Segment difference segmentdifference
The gravity difference between two adjacent points in gravity survey. 3. 6
gravimetrieline
In relative gravity measurement, the gravity measurement starting from a starting gravity point, measuring one or several gravity points, and returning to the starting point is called a closed survey line, and the gravity measurement starting from a known gravity control point, measuring one or several gravity points, and adjoining to another known gravity control point is called an attached survey line.
GB/T 20256—2006
4 General
4.1 Purpose of national gravity control measurement
The purpose of national gravity control measurement is to establish a national gravity base and load control network to provide a unified gravity starting value for various gravity measurements.
The establishment of the national gravity control network should meet the needs of space technology, national defense construction, resource exploration, earthquake monitoring, refinement of the earth's gravity field, determination of the earth's shape and other geoscience research. 4.2 Levels of national gravity control surveys
4.2.1 The national gravity control network consists of the national gravity basic network, first-class network and second-class points. The national gravity basic network consists of benchmark points and basic points; the national gravity-class network consists of first-class points. 4.2.2 The national gravity control survey report includes the determination of the gravity values of the benchmark points, basic points, first-class points and corresponding graded guide points and second-class points. 4.2.3 The national gravimeter calibration baseline is a component of the national gravity control measurement, which is divided into two types: long baseline and short baseline, for calibrating the gravimeter.
4.2.4 According to the needs, the reference point can be set up in the city where the basic point and the first-class point are located. 4.3 Accuracy of national gravity control measurement
4.3.1 The mean error of the determination of the absolute value of the reference point should not exceed 5×10-°ms-. 4.3.2 The requirements for the mean error of the segment difference joint measurement of the relative gravity measurement of each level of gravity control point are shown in Table 1. Table 1 Accuracy requirements for gravity control points of all levels
Mean error
Basic points (including lead points)
First-class points (including lead points)
Unit is 10-ms2
Second-class points
The average mean error of gravity values of gravity points after adjustment of the national gravity basic network should not exceed 10×10-\mIs2. 4.3.3
4.3.4The average mean error of the residual segment difference of the short baseline should not exceed 5×10-Ⅲs-*. 4.4 Layout principles and technical requirements of the national gravity control network 4.4.1 The national gravity basic network consists of a certain number of reasonably distributed benchmark points, which constitute the benchmark framework for controlling national gravity measurement. The layout density and design principles of the national gravity basic points should effectively cover the national territory to meet the accuracy requirements of the relative joint measurement of the first-class gravity points and the needs of national economy and national defense construction. -, the layout of the third-class gravity points should meet the needs of the city government for regional gravity measurement. 4.4.2 The national gravity control network is laid out according to the level control principle, and the basic network and the first-class network should be laid out in a closed loop. High-precision absolute gravimeters are used on the benchmark points to measure the gravity value, and high-precision relative gravimeters are used between the basic points and the benchmark points to establish the basic network. The first-class network uses the national gravity benchmark points and basic points as the control points, and the second-class points use high-grade gravity control points as the control points. 4.4.3 The national gravity control network is established under the auspices of the national surveying and mapping administrative department, completed within the prescribed survey period, and announced for use after data processing.
4.4.4 The long baseline should basically control the gravity difference within the whole country. It should be laid out in the north-south direction. The difference in gravity value between the two end points should be greater than 2000×10-°ms-, and each baseline point should be a benchmark point; the short baseline should be laid out according to the region, and the difference in gravity value between the two end points should be greater than 150×10-5ms-2. The relative error of the segment difference should be less than 5×103. At least one end point of the short baseline should be measured in conjunction with the national gravity control point. 4.4.5 The national gravity basic network should be updated every 10 years, and each update should not exceed two years. 4.5 Coordinate system and elevation system of gravity control points Coordinate system: The coordinates of the gravity points adopt the national geodetic coordinate system, and the elevation system: The elevation of the gravity points adopts the national geodetic datum. 5 Establishment of national gravity control points
5.1 Establishment of benchmark points
5.1.1 Requirements for the location of benchmark points
The location of benchmark points should meet the following requirements
a) Located on stable non-weathered bedrock.
GB/T 20256—2006
b) Away from various sources such as factories, mines, construction sites, railways and busy roads; avoid strong magnetic and electric fields such as high-voltage lines and substation equipment.
The nearby areas will not produce large mass migration, and it is not advisable to build points near large rivers, high tides and reservoirs, and in areas where the ground is subsiding, glaciers and groundwater levels change dramatically.
5.1,2 Benchmark observation room requirements
A special observation room should be built for the benchmark point, and the requirements are as follows: a) The observation area should generally be no less than 3m×5m, and the ceiling should be higher than 2 mb from the pier surface; the observation room should have a stable power supply and be kept dry. 5.1.3 Specifications and burial requirements for benchmark stones
The specifications and burial of benchmark stones should meet the following requirements: a) The size of the benchmark stone of the benchmark observation pier is 1200 mm×1200 mm×1000 mm, see A.1 for specifications; b) A seismic isolation groove with a width of 0.1 m should be left around the benchmark stone and the ground, filled with foam plastic; c) The vertical wall of the benchmark stone shall not be less than 0.5 m, and the distance between two observation towers shall be greater than 0.8 m. 5.1.4 Contents of filling in point records and collecting data When filling in point records and collecting point data, the following should be included: 1) Fill in point records, the format and content are shown in Appendix B 2) Collect relevant data related to the point, including: 1) Environmental conditions: industrial noise interference, climate and rainfall, groundwater level near the point 2) Building conditions: year of construction, structure, appearance photos, changes in the building after the point was built, and a brief diagram of the configuration of adjacent buildings. 3) Observation room conditions: power supply, air temperature, humidity, observation room floor plan, sign photos, etc. 5.2 Establishment of basic points, first-class points and guide points 5.2.1 Point location requirements
The selection of points should meet the following requirements:
a) Basic points and first-class points are generally selected near the airport (outside the airport's safety isolation zone); b) Points should be selected at locations with solid and stable foundations, safe and quiet places that can be preserved for a long time, and must not be selected at locations with unstable geological structures:
c) Points should be away from runways and busy traffic arteries, and avoid artificial lightning sources, high-voltage lines and strong magnetic equipment; d) Points should be convenient for gravity joint measurement and determination of point coordinates and elevation. 5.2.2 Requirements for buried stones
The selected buried stones shall meet the following requirements: a) The size of the stone shall be 1000 mm×1 000 mm×1 000 mm (see A.2); b) The stone shall be cast on-site with concrete;
) The stone shall indicate the north direction;
d) The stone surface shall be flat and smooth, and the mark shall be inlaid in the center of the stone surface. 5.2.3 Point record drawing
The point record shall be filled in and drawn after the selection work is completed (see Appendix B). When marking the ground of a permanent building, the name of the unit to which the building belongs must be filled in the remarks column. 5.3 Establishment of short baseline
The establishment of short baseline shall meet the following requirements:)
It shall consist of at least 3 points;
Points shall avoid being selected on steep cliffs
GB/T 20256—2006
c) The requirements for the burial of points are the same as those for basic points. 5.4 Contents of submitted burial materials
The submitted burial materials shall include the following contents: a) Point records:
b) Point photos,
Collected data;
Book of entrusted custody;
e) Technical summary.
6 Absolute gravity measurement
6.1 Selection and requirements of absolute gravimeter
Absolute gravimeter with a nominal accuracy better than 2×10-ms-2 shall be used for absolute gravity measurement. 6.2 Requirements for the use of absolute gravimeter
6.2.1 Before using the instrument, you should carefully read the instrument manual or user manual and be familiar with the operating steps. 6.2.2 Strictly operate the absolute gravimeter in accordance with the operating procedures in the instructions. 6.2.3 The operation of the absolute gravimeter must be performed by a dedicated person. 6.3 Adjustment and inspection of absolute gravimeter
The adjustment and inspection of the absolute gravimeter should include the following: a) Check and adjust the laser frequency converter, laser interferometer and time measurement system; b) Adjust the verticality of the measuring optical path;
) Adjust the parameters of the extra-long spring;
d) Confirm that the absolute gravimeter is in normal operation. 6.4 Observation outline
6,4. 1. Quantity requirements of benchmark points
The measurement matrix of benchmark points shall meet the following requirements: a) Each measuring point shall not have less than 48 groups of qualified data b) The number of drops in each group shall not be less than 100 times, and the number of qualified drops shall not be less than 80 times. The start time of each group of observations is set at the hour or 30 minutes. There is a 0.5h interval between adjacent groups; if the number of invalid groups exceeds the number of groups or the instrument stops working for more than 4h, the previous observations will be invalid and the observations will be restarted; d) The observation equation is composed of the distance and time pairs collected for each drop, and the observed gravity value g at the initial position of the falling body is solved to make solid tide corrections ( c) The observation results at the height of the initial position of the falling body are corrected for the observation height (see C.4) and converted to a height of 1.3 m from the pier surface:
The group mean and its mean error are obtained from each group of grid-observed gravity values after various corrections (see 6.5, 2), and the total mean and its mean error are calculated from all the group means (see 6.5.3) to obtain the observation results at the height of the initial position of the falling body; g) The mean error of the total mean at each point should not exceed 5×10-tns-. Adjustment and correction of gravimeter
During the measurement process, the operation of the instrument should be checked in a timely manner according to the stability of the observation environment at the measuring point. If any problems are found (such as bubble offset, frequency parameter deviation, laser verticality deviation, etc.), they should be adjusted and corrected in time, and the "Absolute Gravimetry Measurement Observation Record Form" (see Appendix D) should be filled in carefully and in detail
6.4.3 End of absolute gravity observation
After obtaining enough observation groups and the observation results meet the accuracy requirements, disassemble the instrument and end the absolute gravity observation work at this point. h
6.4.4 Laser and time frequency calibration
GB/T 20256—2006
After the entire measurement task is completed, the laser and time frequency calibration should be recalibrated. If there is any change, the results should be corrected accordingly. 6.5 Observation value processing and accuracy assessment
6. 5. 1 Add solid tide correction to the original observed gravity value obtained by each drop solution (see C. 1) and air pressure correction 2g. See C.2), polar motion correction 8g, (see C.3), finite light speed correction 8g: (adopt the value given by the manufacturer) and altitude correction 8g (see C.4), and obtain the gravity value glga =g.+ag.+ag.+ag,+gr +agh on the pier surface or at a distance of 1.3m from the pier surface
group average value (the average value of each group of observed gravity values) calculation and accuracy estimation, the formula is as follows: 6.5.21
(gu - gde)e
wherein:
group average value, unit is 10\tus3;
the observed gravity value of the ith fall, unit is 10-\ ms-zthe mean error of the single fall observation value, unit is 10-\ tns-2; the mean error of the group average value, unit is 10-ms-2·the number of effective falls observed in this group.
6.5.3 Calculation of total average value and accuracy estimation, the formula is as follows:>gh
M = mb
The total average value at a given height, unit is 10-ms-1, the group average value, unit is 10\ms\, the mean error of a single group of observed gravity values, unit is 10-\ ms-\, the mean error of the total average value of the group, unit is 10-\ms-\; the number of groups of observation results.
6.6 Determination of vertical gravity gradient
6.6. 1 Technical requirements
The determination of vertical gravity gradient shall meet the following technical requirements: The vertical gravity gradient shall be measured between two points on the tender surface and at a height of 1.3m from the pier surface: a)
-（6)
The vertical gravity gradient shall be measured using a relative gravity meter with a nominal accuracy of +20×10-8ms-\. The number of instruments shall not be less than 2: b)
The number of qualified results of the step difference measured by each instrument shall not be less than 5, and the error in the average value of the step difference shall not exceed R×10 1s-2. 5
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GB/T 20256—2006
6.6.2 Observation outline
The determination of vertical gravity gradient shall include:
a) Install the observation instrument plate at a height of 1.3 m from the pier surface, measure the height from the plate surface to the surface, and read the reading to millimeters (mm): observe in the order of low point (pier surface) → high point (plate) → low point or high point → low point → high point, which is an independent survey line; b) Calculate the step difference and obtain an independent result; b) Obtain the specified number of results, and after various corrections (see Appendix C), calculate the average value of the step difference and its error, the formula is as follows: 124g
D, - Agi- Age
ng-=±n(n-1)
Wherein:
Agg—average value of segment difference, unit is 10-\ms-\; the i-th observation value of a segment difference, unit is 10-l ms-3, Ag:
-the difference between the first observation value and the average value of the observation value, unit is 10- ms-2mar
error in segment difference observation, unit is 10-ms-; number of observation values.
6.6.3 Calculation of vertical gradient
The formula for calculating the vertical gradient of gravity is as follows: 0
Wherein:
8——vertical gradient of gravity, unit is 10-8s-2, Aggr
-average value of segment difference observation value, unit is 10-ms-\the height between the plate and the pier surface, unit is meter (). 6.7 Results collation and technical summary
6.7.1 Results collation
After the absolute gravity measurement is completed, the measurement results should be checked and the data collated. The results collation should include: Check whether the number of observation groups and the measurement accuracy meet the specified requirements! a) Check whether the observation records are complete: e) Collect the geological structure of the Cexun point area and the ground attack, groundwater changes and meteorological conditions during the observation period. (8)
-(10)
（l1）
l) Collate the data of absolute gravity measurement and gravity vertical gradient measurement disk, and compile the absolute gravity measurement results table (see Appendix E). 6.7.2 Technical summary
After the absolute re-measurement is completed, a technical summary should be made. The main contents should include: description of the measuring point, including: point name, point number, the year of establishment of the point and relevant historical information, point location, groundwater fluctuations and regional meteorological conditions, longitude and latitude and elevation of the measuring point and its system, and the existing gravity points in the surrounding area; h) absolute gravity measurement, including the operation of the instrument and the parameters used; absolute gravity measurement results, including results table, observation result distribution change diagram, group mean residual histogram, analysis of absolute gravity measurement results and comparison and analysis with the existing measurement results of the point; d) gravity vertical gradient measurement, including the number of instruments, results and accuracy. 6.8 Results and materials to be submitted The results and materials to be submitted should include: Absolute gravity measurement observation record CD: Gravity vertical gradient observation notebook (paper); Absolute gravity measurement observation calculation data (paper and electronic documents); Gravity vertical gradient calculation data (paper and electronic documents); e) Absolute gravity measurement results table and analysis (paper and electronic documents); f) Points (paper and electronic documents); Absolute gravimeter test data (paper and electronic documents); Relative gravimeter test data (paper and electronic documents); h) Technical summary (paper and electronic files); Inspection and acceptance report. 7 Relative gravity meter 7.1 Selection and requirements of instruments GB/T 20256—2006
Relative gravity is measured by using a relative gravity instrument with a nominal accuracy of ±20×10-.Used S-1. The mean error of the consistent performance of multiple instruments should be less than 2% of the mean error of the joint measurement.
7.2 Inspection and adjustment of the instrument
7.2.1 To ensure the best working condition of the gravity instrument, the instrument should be inspected and adjusted every month before and during operation. 7.2.2 Inspection and adjustment content (taking LCR-G instrument as an example) The inspection and adjustment content of the gravimeter should include: a) Determination and adjustment of optical displacement sensitivity (see Appendix F); h) Inspection and adjustment of the correct reading line (see Appendix (G); Inspection and adjustment of the horizontal water thruster (see Appendix H); d) Inspection and adjustment of the electronic reading zero position and the galvanometer fog position (see Appendix I); Determination and adjustment of electronic sensitivity (see Appendix J) e) Inspection of optical displacement linearity (see Appendix K); g) Inspection of electronic reading linearity (see Appendix L). The record format of the above inspections and adjustments is shown in Appendix M.7.3 Instrument performance test
7.3.1 Static test
The contents of the static test include:
8) Place the instrument in a stable place indoors with little temperature change and dynamic interference! b) Read the number every half an hour after the instrument is stable, and observe continuously for 48 hours. The instrument is in the open state during the entire test process; c) After the solid tide correction, the static multi-point drift curve of the instrument is drawn in combination with the readings to check the zero drift accuracy. 7.3.2 Dynamic test
The contents of the dynamic test include:
a) Conduct round-trip symmetrical observations at a site with a step difference of not less than 50 × 10-5 ms-2 and a point number of not less than 10, with a direction finding number of not less than 3, and a round-trip closing time of not less than 1 b) After the solid tide correction and zero drift correction, calculate the step difference value of each instrument. Calculate the dynamic observation accuracy of each instrument separately. The calculation formula is as follows:
md-Vn）
Where:
The dynamic observation accuracy of the instrument, the unit is 10-ms-\++---(12 )
GB/T 20256--2006
u-—The difference between the observed values of each segment difference between the same two adjacent points (called the measurement section) of the instrument and the average value, the unit is 10-ms-1——The number of segment difference observation values of all measurement sections of the instrument;-The number of measurement sections in the test site.
For the same instrument, if the mutual difference of the segment difference observation values of each measurement section is not greater than ma, 2.5 times.It can be assumed that the zero of the instrument is linear.
7.3.3 Test of consistency of multiple instruments
The test of consistency of multiple instruments can be carried out together with the dynamic test. The calculation formula of the mean error of consistency between instruments is as follows: ±
(m—n)
The mean error of consistency between instruments, single pull is 1-8 s-\: The difference between the standard value of the section difference of each instrument on the same measuring section and the average value, the unit is 10-ms. The total number of section difference observation values of all instruments and all settings; II—The number of sections in the test site.
II-The mean error of consistency should be less than 2 times the mean error of joint measurement. 7.3. 4 Instrument use
When the static test, dynamic test and consistency test of multiple instruments meet the requirements, the instrument can be put into use. 7. 4 Calibration of gravimeter scale factor
Calibration of gravimeter scale factor should include: -(13
Before operation, the scale factor must be calibrated between the benchmark points or basic points of the long baseline (taking LCR-G as an example). b) The selected setting difference should benefit the reading range of the gravimeter in the working area to avoid extrapolation of the scale factor. When the two basic points are measured by aircraft, each instrument should measure two independent results of the round trip, and the difference between the two results should not be greater than e
40X10-ms-2. When the benchmark point and basic point in the same city are measured by car, each instrument should measure two independent results, and the difference should not be greater than ×10- tns\2. d) Proportional factor calculation formula:
C = AGA/Ag12
Wherein:
C--proportional factor of a load-bearing instrument;
△G12——the difference in known gravity values between two points of the long baseline, the unit is 10-trs\, Ag
the average value of the segment difference between two points of the long baseline measured by the relative gravity instrument, the unit is 1Q~°ms-2. 7.5 Observation outline
7.5.1 Technical provisions for relative gravity joint measurement
Relative gravity measurement should meet the following technical requirements: a) The number of instruments and results used in the relative gravity joint measurement of the control point of the Han family are shown in Table 2. Table 2 Number of instruments and results used in joint survey of basic points, first-class points and second-class points Grade
Number of instruments
Number of results
Basic points
Second-class points
-( 14 )
In the joint survey of short baselines, the number of instruments shall not be less than 6, the number of qualified results of each instrument shall not be less than 4, and the total number of results shall not be less than 24. b)
The joint survey route of basic points shall form a closed loop, and the number of measurement sections of the closed loop shall not exceed 5. d)--The joint survey route of equal points can form a closed loop or be attached between two basic points, and the number of its sections generally does not exceed 5: in special cases, it can be measured in a radial pattern·one first-class point. 8
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