Some standard content:
GB/T17944--2000
This standard is formulated on the basis of the "Detailed Rules for Geodetic Gravity Measurement" (revised version) issued by the State Administration of Surveying, Mapping and Geoinformation in March 1975 and CH/T20031999 "National First-Class Gravity Measurement Specification", combined with the latest scientific research and production results. This standard shall be implemented from August 1, 2000
Appendix A and Appendix B of this standard are both appendices to the standard. This standard is proposed and managed by the State Administration of Surveying, Mapping and Geoinformation. This standard is drafted by the Surveying and Mapping Standardization Institute of the State Administration of Surveying, Mapping and Geoinformation. The main drafters of this standard are Zhang Yaomin, Dai Qichao, Yang Zhendai and Wang Zhongliang. 337
1 Scope
National Standard of the People's Republic of China
Specifications for the dense gravity measurement
Specifications for the dense gravity measurement GB/T17944—2000
1.1 This standard specifies the measurement principles, accuracy requirements, and measurement methods for dense gravity measurement on land. 1.2 This standard is applicable to dense gravity measurement throughout the country, and other regional uniform gravity measurements can be implemented as a reference. 2 Reference standards
GB128971991 National first and second class leveling specification GB/T17942-2000 National triangulation specification GB/T17943-2000 Geodetic and astronomical survey specification CH1001-1991 Surveying and mapping technical summary writing regulations CH1002-1995 Surveying and mapping product inspection and acceptance regulations CH1003-1995 Surveying and mapping product quality assessment standards CH/T1004-1999 Surveying and mapping technical design regulations CH2001—1992 Global Positioning System (GPS) Measurement Specifications CH/T2003--1999 National First-Class Gravity Measurement Specifications CH8016—1995 Global Positioning System (GPS) Measurement Receiver Calibration Procedures 3 Measurement Principles
3.1 Purpose and Tasks
3.1.1 Densified gravity measurement is a gravity measurement conducted by encrypting certain gravity points on the basis of gravity control points at all levels in the relevant areas for various scientific purposes.
3.1.2 Densified gravity measurement is mainly used to determine the fine structure of the earth's gravity field, and provide earth gravity field data for gravity anomalies, vertical deviations, elevation anomalies, and space disturbance gravity fields required in fields such as geodesy, geophysics, geology, seismology, oceanography, and space technology.
3.1.3 The main tasks of the national encrypted gravity survey are: a) Comprehensive gravity survey to establish a digital average gravity anomaly model of 5\×5' national basic grid (for some difficult areas with large areas of blank gravity measurement, a 30°×30° grid can be established); b) Intensified gravity survey to refine the geoid and determine the elevation anomaly value across the country using astronomical, gravity, and GPS leveling methods;
c) Local encrypted gravity survey to interpolate the astronomical geodetic vertical deviation of large locations; d) Local encrypted gravity survey for the correction of the normal height system of precision leveling. 3.2 Use of Datum
3.2.1 The gravity datum of the encrypted gravity survey adopts the "1985 National Gravity Basic Network System". 3.2.2 The geodetic coordinates of the encrypted gravity points adopt the "1980 Xi'an Coordinate System": the plane coordinates adopt the Gaussian plane coordinate system, and are divided into six zones according to the six-degree National Quality and Technical Supervision Bureau approved on January 3, 2000 338
2000-08-01 implementation
GB/T17944-2000
3.2.3 The elevation system of the encrypted gravity points adopts the normal height system, and the elevation datum adopts the "1985 National Elevation Datum" 3.2.4 The normal ellipsoid adopts the "1975 International Ellipsoid". 3.3 Accuracy requirements
3.3.1 The mean error of gravity joint measurement of the dense gravity point relative to the starting point shall not exceed 0.60×10-5ms-2, and it can be relaxed to 1.00×10-5ms-2 in difficult areas. When it is necessary to jointly measure the second-class gravity points (including the lead-in points), the mean error of gravity joint measurement of the second-class gravity points relative to the starting point shall not exceed 0.30×10-5ms-2.
3.3.2 The layout accuracy of astronomical gravity leveling and GPS gravity leveling can meet the requirement that the cumulative mean error of elevation anomaly calculated from the origin of the earth to the farthest point of the country shall not exceed 1.0m, and the mean error of the gravity correction item of each side of the layout route shall not exceed 0.020/X10-5 ms-2 (where: s——route side length, km). 3.3.3 For the 5°×5° national basic grid, the mean error of average spatial gravity anomaly should not exceed 5.0×10-5ms~2, and can be relaxed to 10.0×10-5ms-2 in difficult areas; for the 30°×30 grid, the mean error of average spatial gravity anomaly should not exceed 3.0×10-5 ms-2
3.3.4 The mean error of the position of the dense gravity point relative to the plane point of the national astronomical location should not exceed 100m, and the mean error relative to the elevation point with an accuracy not lower than that of the national fourth-class leveling point should not exceed 1.0m, and can be relaxed to 2.0m in difficult areas. 3.4 Principles of point layout
3.4.1 The layout plan of the dense gravity point should be determined according to different uses, characteristics of the gravity field and different terrain categories. 3.4.2 The representative error coefficient of gravity anomaly is one of the characteristics that reflects the fluctuation of gravity field equipotential surface, and is an important basis for the layout plan of dense gravity points. The representative error coefficient of spatial gravity anomaly is calculated as follows: C = AH/(90 Va)
Where: d-the side length of the smallest grid, km;
△H is the maximum height difference in the smallest grid, m. 1
For a 30°×30° grid, it can be divided into 5'°×5° grids, and the representative error coefficient of spatial gravity anomaly of each grid is calculated respectively, and the average value is taken as the representative error coefficient of spatial gravity anomaly of 30°×30° grid. 3.4.3 The corresponding relationship between terrain category and representative error coefficient shall be implemented according to Table 1. Table 1 Terrain categories and representative error coefficients
Representative error coefficient
Terrain category
Small mountain area
Middle mountain area
Large mountain area
Extra-large mountain area
Bouguer anomaly
Spatial anomaly
3.4.4 The encrypted gravity points should be evenly distributed as much as possible on the characteristic points of the gravity field and the existing large points (triangulation points, astronomical points, leveling points, GPS points). The distribution density should be increased as much as possible in economically developed areas and areas with large changes in the gravity field. 3.4.5 In areas with drastic changes in vertical deviation and large vertical deviation, in addition to arranging encrypted gravity points on first-class astronomical large points, appropriate encrypted gravity points should be arranged around astronomical large points according to the accuracy requirements of the interpolated vertical deviation. 3.4.6 In mountainous areas, encrypted gravity points should be arranged on each leveling point along second-class and above leveling routes. For the layout of the encrypted gravity points on the national first and second class leveling routes, they should be laid out in accordance with the provisions of GB12897. 339
GB/T 17944—2000
3.4.7 For F comprehensive gravity measurement, in general areas, a density of gravity points should be laid out every 5°×5°, and it can be appropriately relaxed in difficult areas. In mountainous areas, the minimum point density for comprehensive gravity measurement of 30°×30° grid shall be implemented according to Table 2, and they shall be evenly laid out at different elevations of the grid, and the average elevation value of the points shall not differ from the average elevation of the grid by more than ±200m. Table 2 Point density in mountainous areas
Convenient transportation, many large sites
Tibet, desert border and other areas with difficult transportation Special difficult areas
Small mountainous areas
Medium mountainous areas
Large mountainous areas
Extra-large mountainous areas
3.4.8 Astronomical gravity leveling should be carried out on the basis of comprehensive gravity measurement. Gravity points should be appropriately increased in the area of 15°×15° around the astronomical point.
3.4.9GPS gravity leveling should use GPS positioning and GPS leveling methods to determine the coordinates and elevation of gravity points on the basis of comprehensive gravity measurement.
3.5 Gravity joint measurement
3.5.1 The starting point of the increased gravity measurement is the gravity control points of each level. If the density of gravity basic points and first-class gravity control points is not enough, second-class gravity points can be arranged, and their positions can be determined according to the needs of increased gravity measurement. The measurement of second-class gravity points shall be carried out in accordance with the relevant provisions of this standard and the corresponding provisions of first-class gravity measurement in CH/T2003. 3.5.2 The gravity survey line should form a closed or attached route, that is, starting from a high-level gravity control point or a point to be determined, and returning to the starting point after measuring a number of points, or starting from a high-level gravity control point and attaching to another high-level gravity control point, and the closing or attaching time for the second-level gravity measurement should generally not exceed 36 hours, and can be relaxed to 48 hours in difficult areas; the intensive gravity measurement should generally not exceed 60 hours, and can be relaxed to 84 hours in difficult areas.
3.5.3 The starting point of the equal joint measurement is the gravity basic point, equal gravity point or its leading point. The number of second-level gravity points in the attached route and closed loop route of the second-level joint measurement shall not exceed 4, and 2 second-level gravity points are allowed to be measured in the branch measurement route. In general, the three-pass circulation method should be used as much as possible for the second-level joint measurement, that is, AB-A, BAB is calculated as two measurement lines. When the zero drift is stable, it is allowed to add and encrypt gravity points in individual equal measurement lines in difficult areas.
3.5.4The number of instruments and qualified step differences for gravity joint measurement shall be in accordance with Table 3. Table 3 Instruments and step differences
LCR gravimeter
Number of instruments
Number of step differences
Other instrumentswww.bzxz.net
Number of instruments
Number of step differences
3.5.5When the error in joint measurement exceeds the limit, the grouped step difference observation value exceeding the limit shall be discarded, and the corresponding step difference shall be re-measured; the number of discarded step differences shall not exceed one third of the total number of step differences, otherwise the entire survey line shall be re-measured. 3.6 Technical design
Technical design must be carried out before the dense gravity measurement layout. Technical design requirements, contents and approval procedures shall be implemented in accordance with CH/T1004. 4 Technical requirements for gravimeters
4.1 Selection of gravimeters
Quartz spring gravimeters (such as: ZSM, Worden) or metal spring gravimeters (such as: LCR) can be used for gravity joint measurement of second-class gravity points and encrypted gravity points.
4.2 Inspection and adjustment of gravimeters
GB/T 17944—2000
4.2.1 Before and during gravity joint measurement, inspection and adjustment shall be carried out at least once a month according to the specified items. 4.2.2 Inspection and adjustment of L.CR type gravimeters shall be carried out in accordance with CH/T2003. 4.2.3 The following inspections and adjustments shall be carried out for quartz spring gravimeters: a) Inspection and adjustment of panel position (see Appendix A); b) Inspection and adjustment of longitudinal and transverse levels (see Appendix A); c) Inspection and adjustment of bright line sensitivity (see Appendix A); d) Adjustment of measurement range (see Appendix A). 4.3 Gravimeter calibration
4.3.1 New and repaired gravimeters must be calibrated. Operational gravimeters should be calibrated every two years.
4.3.2 The calibration field should generally be a national gravity baseline field. For LCR-G gravimeters, the scale factor must be calibrated between national basic (accurate) points or national long gravity baseline fields, and an airplane should be used as a means of transportation. 4.3.3 It is allowed to test the scale factor of LCR-G gravimeters on the national short baseline field. When the ratio of the difference between the test result and the previous calibration result to the scale factor is not greater than 2×10-4, calibration may be omitted and the previous calibration result may be used. 4.3.4 Gravimeter calibration conditions shall be implemented in accordance with Table 4. Table 4 Grid value calibration conditions
Number of segment differences
Mutual difference of segment differences
Relative mean error≤
Over-limit processing
LCR-G gravimeter
2, 4 during detection
0. 04×10 5ms 2
5×105
4.3.5 Grid value or proportional factor is calculated as follows:LCR-D gravimeter
1X10-4
Re-measurement shall not exceed 2 segment differences
C = C' X aG/Ag
Where: C\—…approximate grid value or proportional factor, AG—known gravity difference of the measuring section;
—average observed value of gravity difference, calculation of gravity difference shall be carried out in accordance with 7.1, Ag
4.3.6 The relative mean error of grid value or proportional factor determination shall be calculated as follows: m./C = ma/g
Where: m-…---mean error of gravity joint measurement, calculation shall be carried out in accordance with 7.1.6 Ag——average observed value of gravity difference.
4.4 Performance test of gravimeter
Other gravimeters
6X10-4
Re-test shall not exceed 2 difference
(3)
4.4.1 For the newly manufactured gravimeter, performance test shall be carried out before operation every year, and it is required to be carried out after the inspection and adjustment of the gravimeter. 4.4.2 Static test
4.4.2.1 The test should be conducted indoors without external interference, with stable foundation and small temperature change. 4.4.2.2 Read ~- times every 30 minutes, and observe continuously for more than 16 hours. During the observation, the LCR gravimeter should be kept in a loose swing state.
4.4.2.3 After adding tidal correction to the reading, draw a static zero drift curve. 4.4.3 Dynamic test
4.4.3.1 The test should be conducted at points A and B with a gravity difference of not less than 50×10-5ms-\ according to the round-trip symmetric observation method, and no less than three round trips.
4.4.3.2 Carry out calculations according to the requirements of 7.1, and calculate the joint measurement mean error of each gravimeter separately, and calculate the consistency mean error between each gravimeter according to the following formula:
GB/T 179442000
m = VV/(n- 1)
Wherein: V is the difference between the average gravity step difference of a certain gravimeter and the average gravity step difference of each gravimeter; number of gravimeters.
4.4.3.3 The consistency mean error between instruments must meet the requirements of the highest level of gravity point joint measurement accuracy used by the instrument. 4.5 Maintenance of gravimeter
4.5.1 Establish strict gravimeter handover procedures, clarify responsibilities, and be responsible for the safety of gravimeters. 4.5.2 Gravimeters must be wiped clean when put into storage, with complete accessories, and moisture-proof during storage. 4.5.3 Anti-vibration measures should be taken when transporting the gravimeter over long distances, and a dedicated person should be responsible to prevent accidents. 4.5.4 When using the gravimeter, the movements should be gentle and steady, and collisions are strictly prohibited. 4.5.5 It is prohibited to tilt the gravimeter at a large angle or place it horizontally, and it is strictly prohibited to carry the LCR gravimeter in a loose state. 4.5.6 In case of sticking of the gravimeter, you can tap the panel with your fingers, and it is prohibited to knock the panel with tools (4)
4.5.7 When a gravimeter fails, the cause should be carefully analyzed and carefully eliminated. Blind disassembly is not allowed. General faults should be eliminated by experienced operators. Major faults must be sent back to the team with a detailed report. 5 Gravity Observation
5.1 Preparation before Observation
5.1.1 Preparation before measurement of LCR type gravimeter: a) The instrument must be powered on and kept at constant temperature 24 hours before observation, and the battery must be charged; b) At least 30 minutes before observation, the charging power must be cut off and replaced with battery power; c) Check whether the optical reading system, level and lighting of the instrument are normal; d) The static instrument must be moved for 5 minutes before observation; e) Whether various tools and related materials and correspondence are complete. 5.1.2 Preparation before measurement of quartz spring gravimeter: a) Check whether each working system is normal:
b) According to the arrangement of the survey line, estimate the approximate gravity difference between each point to be determined and the starting point, adjust the instrument reading at the starting point, and try to avoid adjusting the measurement range in the survey line.
5.2 Observation Procedure
5.2.1 Observation Procedure of LCR Instrument:
a) Clean the site and eliminate unsafe factors; b) Install the chassis and instrument. Carefully lift the instrument out of the instrument box, gently place it on the chassis, and make the instrument's horizontal level parallel to the magnetic north direction;
c) Accurately level the instrument;
d) Loosen the pendulum and adjust the bright line to the vicinity of the reading line; e) Reading: Generally, you should read according to the following procedures after loosening the pendulum for 5 minutes, and return the reading wheel to zero in the same direction: 1) Turn the reading wheel clockwise (or counterclockwise) to align the bright line accurately with the reading line (or return the galvanometer or digital voltmeter to zero), and read the counter and reading wheel readings;
2) Turn the reading wheel half a turn in the opposite direction, and then turn the reading wheel clockwise (or counterclockwise) to zero, and read the second reading; 3) Repeat the above operation and read the third reading. f) After each reading, immediately record the reading and time, and record the time to the whole minute; g) Lock the pendulum and pack the instrument;
h) Check the handbook records;
i) The observation is over.
5.2.2 Observation procedure of quartz spring gravimeter: 342
a) Install the chassis;
b) Level the instrument;
GB/T 17944 --2000
c) Rotate the reading wheel clockwise to align the bright line with the zero line accurately, and read the reading of the reading wheel; d) Rotate the reading wheel in the opposite direction one circle, and then rotate the reading wheel clockwise to return the bright line to zero accurately, and read the second and third readings; e) Check whether the longitudinal and transverse levels are centered. If the deviation is greater than 0.2 grids, re-level the instrument and read the reading; f) After each reading, immediately record the reading and time, and record the time to the whole minute; g) Check the notebook record and pack the instrument; h) End of observation.
5.3 Precautions in observation
5.3.1 All operations during the observation process must be cautious, and collision with the instrument is strictly prohibited. 5.3.2 After the instrument is placed on the chassis, the observer must not leave to prevent accidents. 5.3.3 During the observation of LCR type gravimeter, the pendulum must be locked before the reading wheel rotates one circle or more. It is forbidden to move the instrument when the pendulum is loose. 5.3.4 During the operation of ILCR type gravimeter, the temperature must be kept constant and the power must not be cut off. If the battery needs to be replaced, it must be replaced at least 30 minutes before the observation:
In a measurement line, except for the measurement range of the quartz spring gravimeter, the rest shall not be adjusted. 5.3.6 When reading the quartz spring gravimeter, the counter's extreme position should be avoided as much as possible. 5.3.7 When the instrument is left stationary for more than 3 hours in the measurement line, the reading must be taken before and after the stationary state, and the static zero drift is calculated. 5.3.8 Before the measurement line is closed for observation, if it is found that the reading is wrong, the memory is wrong, or the instrument is subjected to severe vibration, it should be returned to the previous station for re-measurement, and the static zero drift is calculated.
5.3.9 At the measurement station, attention should be paid to the sun protection and rain protection of the instrument. 5.4 Observation requirements
5.4.1 When observing at control points, the instrument should be placed at the center of the mark. When multiple instruments are observing at the same time, they should be close to the center of the mark. 5.4.2 When making repeated observations or check observations at encrypted points, the instrument should be placed at the same position and at the same height. 5.4.3 When the encrypted points are observed at various triangulation points or leveling points and the instrument cannot be placed on the benchmark, it can be observed next to the benchmark, but the height of the instrument from the benchmark must be noted in the record. 5.4.4 The readings of various instruments at the measuring station are estimated to 0.1 grid, and the mutual difference of the three readings shall not be greater than 0.5 grid. If the limit is exceeded, it can be re-measured once. If it still exceeds the limit, the instrument must be re-leveled and re-measured. 6 Coordinate and elevation determination
6.1 General provisions
6.1.1 The coordinates and elevations of various gravity points must be measured. 6.1.2 The following methods can be generally used for coordinate determination: a) measurement on the map; b) intersection method; c) wire method; d) lock grid method; e) GPS positioning method. 6.1.3 The following methods can be generally used for elevation determination: a) elevation wire method; b) independent intersection point elevation method; c) GPS leveling method. 6.1.4 The observation instruments can be DJ2, DJ6 theodolites and I, class rangefinders, as well as corresponding total station electronic tachometers or GPS positioning receivers with an accuracy of not less than 10mm+3×10-°D. 343
GB/T 17944---2000
6.1.5 In addition to the provisions of this standard, other matters such as observation methods and inspection of observation instruments in coordinate and height determination shall be carried out in accordance with the relevant standards cited in Chapter 2.
6.1.6 The tolerances for coordinate and height determination shall be carried out in accordance with Table 5. Table 5 Coordinate and elevation measurement tolerances
Horizontal angle observation
Vertical angle observation
Coordinate calculation
Elevation calculation
Number of measurement rounds
Name of tolerance
Semi-measurement regression zero difference
2C variation range
Each measurement direction is poor
Triangle closure difference
Early and new angles of the starting point of the wire are poor
Number of measurement rounds
Difference of index difference
Early vertical angle difference of each measurement round
Number of measurement rounds||tt ||Relative accuracy of distance measurement
Position closure error, m
Azimuth closure error
Relative closure error of the entire length of the line
Round trip height difference is poor, m
The maximum height of a single point is poor. m
Height closure error, m
1/20000
1/15000
n is the number of azimuth transmissions
D is the round trip measurement side length km
L. is the route length km
6.1.7 Coordinate height points are divided into three levels. The starting control points of the first level points are the national triangulation points and national leveling points, and other points of each level can be measured on the basis of the control of the higher level points. All grid-shaped coordinate points, attached or closed traverse coordinate elevation points, and GPS points can be used as first, second, and third level points. Intersection coordinate points and independent elevation points can be used as second and third level points, and branch traverse coordinate elevation points can only be used as third level points. Intersection coordinate points and independent elevation points shall not be used as the starting control points for grid-shaped points and traverse coordinate elevation points. 6.2 Measurement method on the map
6.2.1 The scale of the topographic map used for measuring coordinates on the map should generally not be less than 1:50,000, and can be relaxed to 1:100,000 in special areas. 6.2.2 Gravity points should be selected on reliable and obvious ground targets and ground features on the map. The determination of point positions and coordinate measurement should be checked by a second person, and the difference between the two people's measurement results should not exceed 0.3mm on the map. 6.2.3 There should be no cracks in the coordinate measurement parts on the topographic map. 6.3 Intersection method
6.3.1 The intersection method can be used to determine coordinates by using the rear intersection of four known points, the front intersection of three known points, and the side intersection, that is, observing a single triangle with three angles.
6.3.2 The intersection angle of various intersection points should not be less than 30° or greater than 150°; when it is difficult, the individual intersection angle should not be less than 20° or greater than 160°. The rear intersection point should not be located near the circumference of the three known points, that is, the sum of the two intersection angles and the corresponding known angles should not be between 170° and 190°.
6.4 Conductor method
6.4.1 Conductor layout - generally adopts the form of attached conductors. In areas with few large points, it can be laid out in the form of closed conductors or branch conductors. The side length of the conductor 344
is determined by an electromagnetic wave rangefinder.
GB/T17944——2000
6.4.2 At the starting and closing points of the traverse, two known directions should generally be measured together. The comparison of the new and old angles between the two known directions shall not exceed 30\. In case of difficulty, only one known direction may be measured.
6.4.3 Traverse measurement should generally be carried out simultaneously with the elevation traverse measurement. The graphic conditions of the traverse are consistent with the requirements of the elevation traverse. 6.5 Locking net shape method
6.5.1 The locking net shape should start from two points and close at two points. In case of difficulty, it can also start from one point and close at another point. 6.5.2 The number of triangles in the locking net shall not exceed 15. The total length shall not exceed 150km. 6.5.3 The graphic conditions of the triangles in the locking net shall meet the requirements of 6.3.2. 6.6GPS positioning and GPS leveling method
6.6.1GPS positioning can adopt GPS static carrier phase positioning or fast static positioning method. Positioning accuracy shall not be lower than the accuracy requirement of Class E.
6.6.2 For the baseline side of 15~30km, the observation period shall not be less than 10min; for the baseline side of less than 15km, it shall not be less than 5min.
6.6.3 The coordinate conversion between WGS84 coordinate system and 1980 Xi'an coordinate system can adopt conversion parameters with an accuracy of not less than 5m or at least three national astronomical locations shall be measured in the GPS network for coordinate conversion. 6.6.4 A certain number of national leveling points shall be measured evenly in the GPS network, and the layout density of the leveling points shall generally meet the requirements of Table 6. For leveling points in difficult areas, it can be relaxed to 2 times. Table 6
Layout density of leveling points in GPS network
Terrain type
Spacing, km
Minimum number of points
Small mountain area
6.6.5 The GPS network should try to conduct joint measurement with nearby national GPS network points. 6.7 Elevation traverse and independent elevation method
Middle mountain area
High mountain area
6.7.1 Elevation traverse should be laid out as a contiguous route as far as possible, and in difficult areas it can also be laid out as a closed route or branch traverse. Extra large mountain area
6.7.2 The total length of the elevation traverse shall not exceed 60km, and the side length shall not exceed 3km. Branch traverses are allowed to develop two sides from the starting point. 6.7.3 Independent elevation should have two starting points, one opposite and one unidirectional vertical angles, or three starting points, or three unidirectional vertical angles. The vertical angles of the elevation traverse should be observed in opposite directions.
6.7.The side length of the four conductors and independent points should not exceed 10km. In case of difficulty, the individual side length can be relaxed to 15km, and the independent points with relaxed side lengths shall not be used as the starting control points.
7 Data processing
7.1 Survey line calculation
7.1.1 The solid tide correction of the station observation value is calculated as follows: 8t -- - 1. 16L165. 17F(B)(C/r)3(cos2Z -- 1/3)+ 1. 37F2(B)(C/r)*cosZ(5cos2Z - 3)+ 76.08F(B)(C./r.)3(cos2Z, - 1/3)J + 4. 83-- 15.73sin\ + 1.59sin*g
F(B)-0. 998 327+0. 001 67cos2B=tg-1(0. 993 306tgB)
wherein: 8t--—solid tide correction value, 10-8ms-2; B-geod latitude of the measuring station (accurate to arc minute); C, C, a are the average distances from the center of the earth to the center of the moon and to the center of the sun, respectively, km; · (5))
GB/T 17944—2000
r, r- are the distances from the center of the earth to the center of the moon and to the center of the sun, respectively, km; Z, Z, a are the geocentric zenith distances of the measuring station to the moon and to the sun, respectively. 7.1.2 The instrument height correction of the measuring station observation value is calculated according to the following formula: 8h =- 0. 308 6h
-instrument height correction value, 10~5ms-2;
wherein. 8h--
instrument height of the measuring station, m.
7.1.3 The station observation reduction value is calculated according to the following formula: g = RC + α × 10-3 +8h
where: g'
-station observation reduction value, 10~5ms-2;
station observation value, grid or 10-5ms-2;
grid value, or proportional factor.
7.1.4 The station observation reduction value is calculated according to the following formula for zero drift correction: g' + K(ti - ta)
K(G-GA)-(g\-gA)-2(gl\-g0)
where; GA,G-
(tg-tA) -E(tn--tt)
-the known gravity value at the beginning and end of the survey line, 10~5ms-? , - the calculated value of the observation at the beginning, end and to-be-determined points of the measuring station, 10-5ms-2; the calculated value of the beginning and unobserved points of each static adjustment point, 105ms-2; the observation time of the beginning, end and to-be-determined points of the measuring line; the beginning and end observation time of each static adjustment point.
ictn---
7.1.5 Gravity step difference and gravity value of each undetermined point of the survey line are calculated according to the following formula: Gi = Ga + Agi
Agigi\\ga
In: Ag: —-
Gravity step difference, 10-5ms-2,
G;----Gravity value of the undetermined point, 10-5ms2
7.1.6 The error in gravity joint measurement is calculated according to the following formula: ma V[VV/[n(n - 1)]
Difference between gravity step difference and average value, 10-5ms2; In: V—
Number of step difference.
When the number of step difference is 1, m is calculated by half of the gravity closure difference. 7.1.7 The error in gravity value of gravity point is calculated according to the following formula: my
In: m. --The mean error of gravity value of the starting control point is 10-\ms-"; the mean error of gravity joint measurement is 10-5ms-2.
ma-—
7.2 Gravity anomaly calculation
7.2.1 The normal gravity in gravity anomaly calculation is calculated as follows:,- 978 032.68(1 + 0. 005 302 4sinB -- 0. 000 005 8sin*2B) Where: B is the geodetic latitude of the calculation point.
7.2.2 The spatial anomaly is calculated as follows:
Agh - G - Y. + [0. 308 6(1 + 0. 000 7cos2B) - 0. 72 X 10-7HJH Where: G- measured gravity value of the calculation point, 10-5ms-\,. ——- normal gravity value of the calculation point on the normal ellipsoid, 105ms-\; 346
(9)
(10)
H- normal height of the calculation point, m.
7.2.3 Bouguer anomaly is calculated according to the following formula:
8 Data collation and submission
8.1 Achievement record
GB/T 17944-2000
Age Ag 0. 111 6H
8.1.1 All numbers and text records in the results should be correct, clear, neat and in a uniform format—(12)
8.1.2 All original data and record items of field observations must be recorded completely on site in the specified format. Copying and supplementary recording are strictly prohibited.
8.1.3 When correcting errors in the results, the wrong characters should be crossed out neatly with a horizontal line and the correct numbers or words should be written on top. Do not change the characters or use erasers. It is strictly prohibited to change the numbers in a row. Strike through with a horizontal line. The entire station and the entire page of results shall be invalidated by crossing out with a red pencil (from the upper left to the lower right) and indicating the reason. The names of the observations, micrometer readings and observation time in the observation records shall not be changed. The observation time of 12 hours that is recorded incorrectly and the incorrect scale reading of the LCR gravimeter are allowed to be changed once. 8.1.4 All original data and calculation results recorded on the computer shall be strictly checked. The program used for calculation shall be strictly debugged and approved before use.
8.2 Results collation
8.2.1 All records, The calculation and result description materials shall be bound into books (or packed into bags) and packaged collectively by project of the same period.
8.2.2 The bound materials shall be numbered and cataloged by project and time, and shall be accompanied by inspection and acceptance opinions and relevant instructions. 8.2.3 The gravity result table shall be organized in the format specified in Appendix B. 8.3 Inspection and acceptance, quality assessment and technical summary After the gravity measurement work is completed, inspection and acceptance, quality assessment shall be carried out in accordance with the requirements of CH1003, CH1002 and CH1001.
8.4 Submission of Materials
After the gravity measurement work is completed, the following materials must be submitted: a) Records and calculation data of instrument inspection and adjustment, scale factor determination, etc.; b) Various observation notebooks, calculation notebooks, accuracy calculations, gravity results tables, calculation procedure instructions, etc.; c) Gravity point records, entrusted custody documents; d) Data for determining the average height of terrain and the type of terrain; e) Coordinates, height measurement data and topographic maps of measured coordinates; f) Technical design, technical summary, inspection and acceptance report. 347
A1 Inspection and adjustment of panel position
GB/T17944—2000
Appendix A
(Appendix of the standard)
Inspection and adjustment method of quartz spring gravimeter The panel position of the gravimeter shall be inspected and adjusted according to the following steps: a) Set the instrument horizontally;
b) Turn the foot screw of the vertical level clockwise (counterclockwise) to tilt the instrument forward (or backward) (to the observer), and observe the moving direction of the horizontal bubble;
c) If the horizontal bubble moves to the left (or right), move the main body of the instrument horizontally. d) Repeat steps a) to c) until the horizontal bubble is centered when the foot screw of the vertical level is turned clockwise or counterclockwise. A2 Inspection and adjustment of vertical and horizontal levels
A2.1 Before measuring, the instrument should be fully inspected and adjusted by measuring the bubble curve. The steps are as follows (taking the vertical level as an example:
a) Draw a circular disk with a diameter of about 5 cm, divide the circumference into 16 equal parts, take any division as zero, and mark .+1~+8 in the clockwise direction.Mark numbers such as -1 to -8 in the counterclockwise direction, and stick the circular disk to the foot screw of the longitudinal level so that the center of the foot screw coincides with the center of the circular disk;
b) Set the instrument horizontally and make a fixed mark on the foot screw of the longitudinal level opposite to the zero scale line of the circular disk; c) Read out the corresponding readings of the instrument when the longitudinal foot screw is at each scale position of the scale in sequence; d) With the instrument inclination (the scale of the circular disk of the longitudinal foot screw) as the horizontal coordinate and the corresponding reading of the instrument as the vertical coordinate, draw a curve of the relationship between the instrument reading and the instrument inclination, namely the bubble curve; e) Align the fixed mark on the longitudinal foot screw with the scale of the circular disk corresponding to the maximum value of the instrument reading on the bubble curve, and adjust the adjusting screw of the longitudinal level to center the bubble. The inspection and adjustment steps of the horizontal level are basically the same as those of the vertical level. The difference is that after a horizontal level foot screw is attached to the circular disk and a fixed mark is made, it is not allowed to move the other horizontal foot screw during the measurement of the bubble curve; at the same time, after each change of the scale of the horizontal foot screw, the vertical level must be centered before reading. The precautions in inspection and adjustment are as follows: a) During the measurement of the bubble curve, the foot screw must be rotated in the same direction to eliminate the influence of the foot screw gap difference; b) After the bubble is adjusted, it must be rechecked; c) The vertical bubble curve often cannot measure a complete symmetrical curve, mainly because the instrument sensitivity is related to the longitudinal inclination. When the inclination increases to a certain limit, the zero sensitivity of the instrument will tend to infinity and cannot be read. A2.2 During field operations, the vertical and horizontal bubbles should be checked regularly according to the following operating steps. Take the horizontal bubble as an example: a) Set the instrument horizontally and rotate the counter so that the bright line coincides with the zero line. b) Rotate the foot screw of the horizontal level to move the horizontal level bubble one grid to the left (or right), and observe the direction of movement of the bright line; then rotate the foot screw of the horizontal level to move the horizontal level two grids to the right (or left) (i.e. one grid away from the center position), and observe the direction of movement of the bright line. When moving the horizontal bubble, the vertical bubble should always be kept in the center. c) When the horizontal level bubble deviates to the left and right, if the bright line moves from the zero line to the left, the position of the horizontal level is correct. If the bright line moves in different directions when the horizontal level bubble deviates to the left and right, the horizontal level should be adjusted. d) Adjustment method: gradually rotate the foot screw of the horizontal level to make the bright line gradually move to the right to the maximum distance and no longer move to the right.
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