GB 12898-1991 National third- and fourth-class level measurement specifications
Some standard content:
National Standard of the People's Republic of China
National Specifications for the
third and fourth order levelingQuestion Content and Scope of Application
1
This standard specifies the layout principles, surveying methods and accuracy indicators for establishing third and fourth order leveling networks. This standard is applicable to the layout of third and fourth order leveling networks. 2 Reference standards
GB3160 Level series and basic parameters
GB3161 Theodolite series and basic parameters
GB12897 National first and second class leveling specifications 3 Layout of leveling network
3.1 Layout principles
GB12898-91
3.1.1 The third and fourth class leveling network is further encrypted on the basis of the first and second class leveling network. According to the needs, the line, loop or node network is laid out in the high-level leveling network to directly provide the necessary elevation control points for topographic mapping and various engineering construction. 3.1.2 The length of a single third class leveling line should not exceed 150km, and the circumference of the loop should not exceed 200km; the distance between nodes in the same level network should not exceed 70km.
3.1.3 The length of a single fourth-class leveling route should not exceed 80km; the circumference of the loop should not exceed 100km; the distance between nodes in the same-level network should not exceed 30km; it can be appropriately relaxed in mountainous areas. 3.1.4 Large locations, hydrological stations, meteorological observatories (stations), etc. (hereinafter collectively referred to as other fixed points) within 50km of the leveling route should be included in the leveling route for continuous measurement as needed. If continuous measurement is indeed difficult, branch measurement can be carried out. The level of branch measurement can be determined based on the required elevation accuracy and branch line length of "other fixed points". If the user unit has no special accuracy requirements, when the branch line length is within 20km, it shall be measured according to the fourth-class leveling accuracy; when the branch line length is more than 20km, it shall be measured according to the third-class leveling accuracy. 3.2 Density of leveling points
On third- and fourth-class leveling routes, ordinary leveling stone bases must be buried every 4 to 8 km. In densely populated and economically developed areas, this can be shortened to 2 to 4 km; in desert areas and leveling branches, this can be increased to about 10 km. Branches within 15 km do not need to be buried. 3.3 Route naming and leveling point numbering
3.3.1 The abbreviation of the starting and ending place names is used as the line name, and the order of the starting and ending place names is "starting from the west and ending in the east" or "starting from the north and ending in the south". The name of the loop line is the largest place name in the loop line followed by the word "loop". The grades of third- and fourth-class leveling routes are indicated by II and N written before the line name. 3.3.2 The leveling points on the route should be numbered in the order of 1, 2, and 3 starting from the starting leveling point of the line. The point numbers on the loop line are in a clockwise direction, and the point numbers are written after the line name. 3.3.3 The branch line of leveling shall be named after the name of the elevation point it measures with the word "branch" added to it. The leveling stones on the branch line shall be numbered in the order of 1, 2, and 3 from the starting leveling point to the measured elevation point. Approved by the State Bureau of Technical Supervision on May 5, 1991 and implemented on January 1, 1992
GB12898-91
3.3.4 When using old leveling points, the old names may be used. If re-edited, the old name of the point when it was buried shall be indicated in brackets after the new name.
3.4 ??Connection between new routes and measured routes
3.4.1 The starting point and end point of the newly established leveling route shall be the leveling points of the higher or equal leveling routes that have been measured. 3.4.2 When the newly established third and fourth leveling routes are within 4km of the measured leveling points of each level, they shall be measured in conjunction or connected. 3.4.3 For the leveling points on the measured route, the measurement shall be carried out according to the lower level accuracy requirement of the new measured route and the measured leveling route. 3.4.4 When the new route and the measured route overlap, if the old markers meet the requirements, the old points should be used as much as possible. If the old markers do not meet the requirements, they should be buried separately, but the old points with intact marks must be measured continuously. 3.5 Elevation system and elevation datum
The elevation of the leveling points adopts the normal elevation system and is calculated according to the 1985 national elevation datum. The elevation of Qingdao origin is 72.260m. 3.6 Accuracy of levelingwww.bzxz.net
For third and fourth leveling, the accidental mean error M per kilometer of leveling. and the total mean error Mw shall not exceed the values ??specified in Table 1: Table 1
Surveying grade
M
Mw
Third grade
3.0
6.0
For the calculation method of M and Mw, see the provisions of Articles 9.5.2 and 9.5.3. 3.7 Technical design of leveling network
Fourth grade
5. 0
10.0
mm
Before laying out the leveling network, technical design must be carried out to obtain the best layout plan for the leveling network and leveling route. The requirements, contents and approval procedures of technical design shall be implemented in accordance with ZBA75001 "Surveying and Mapping Technical Design Regulations". 4 Point selection and stone burial
4.1 Selection of leveling route and leveling point
The leveling route should be laid out along highways, main roads and rural roads with a small slope that are conducive to surveying. The leveling route should avoid crossing obstacles such as rivers, lakes, swamps, etc. over 500m. The leveling point should be selected at a location with solid soil, safe and quiet, convenient for observation and conducive to long-term preservation. The following locations should not be selected for leveling points: a. Places that are prone to flooding, dampness or high groundwater levels; places prone to landslides, landslides, and subsidence; b.
c. Within 50m from the railway and 30m from the highway (special circumstances can be handled as appropriate); d. Locations where the marker may be destroyed or observation may be obstructed due to construction and development in the short term. 4.2 Marking stone types
The types of marker stones used for the third and fourth leveling points and the applicable areas are shown in Table 2. No.
1
2
3
4
5
6
4.3 Buried marker
Standard
Type
Stone
Concrete ordinary water marker
Rock stratum ordinary leveling marker
Concrete column ordinary leveling marker
Steel pipe ordinary leveling marker
CB12898—91
Table 2
Explosive type concrete marker Concrete column ordinary leveling mark
Leveling mark at the foot of the wall
Applicable area
Areas where the soil layer is not frozen or the frozen soil depth is less than 0.8mAreas where the rock layer is exposed or buried no deeper than 1.5m in the groundAreas where the frozen soil depth is greater than 0.8m
Solid buildings or vertical stone banks
4.3.1 The land occupied by the mark stone must obtain the consent of the land management department and the ten land-using units or individuals, and go through the land acquisition procedures. 4.3.2 The mark stone column can be prefabricated in advance, and the base must be poured on site. The specifications and material consumption of the mark stone shall be implemented in accordance with the provisions of A5 to A6 in Appendix A (Supplement).
4.3.3 The level mark on the top of the mark stone shall be a copper or stainless steel hemispherical top mark with an iron root network, or a glass fiber reinforced plastic or stone mark. The marking specifications are shown in A4 in Appendix A (Supplement). 4.3.4 After the marker is buried, the detailed map should be recorded at the site survey point in the format of A2 in Appendix A (Supplement). 4.4 External finishing of the marker
4.4.1 After the marker is buried, the protective ditch should be dug and the indicator monument should be buried in accordance with the specifications of A7 in Appendix A (Supplement). 4.4.2 For leveling markers buried in government agencies, schools, residential courtyards, and in cultivated land and water network areas, no protective ditch is dug and no indicator monument is set. However, a protective well must be built and an indicator plate must be covered in accordance with the specifications of A7 in Appendix A (Supplement). 4.4.3 In open areas such as grasslands, deserts, and Gobi, in addition to digging protective ditches and setting up indicator monuments as required, 2 to 3 azimuth stakes can be set nearby, or small beautiful markers can be built.
4.4.4 When burying markers in mountainous and forested areas, azimuth stakes can be set on the roadside closest to the leveling point. 4.4.5 Azimuth stakes and markings can be made of wood, stone, concrete or metal materials. The point number and direction of the point should be written in a conspicuous place by red paint or stamping. In the point record, indicate the direction and distance of the setting of the azimuth object. 4.5 Trusteeship of the benchmark stone
After the stone is buried, the procedures for entrusting the stone to the local government and relevant individuals should be completed in accordance with regulations. The format of the entrustment and custody document is shown in A8 in Appendix A (Supplement).
4.6 Materials to be submitted after the stone is buried:
a.
The record of the leveling points, route map and node connection map surveyed after the stone is buried; b.
The entrustment and custody document of the benchmark stone and the document approving the requisition of land; c
Summary of the stone burial work (a brief description of the stone burial work, special problems in the stone burial and suggestions for observation work, etc.). 5 Technical requirements for instruments
5.1 Selection of instruments
The instruments used in leveling measurements shall be in accordance with the provisions of Table 3. Serial number
2
3
4
Instrument name
Automatic leveling instrument
or bubble level
Double-sided Area format
Wooden scale
Theodolite
Photoelectric distance meter
Inspection of 5.2 instruments
GB12898—91
Table 3|| tt||Lowest model
Third class
DSZ3
DS3
DJ2
Fourth class
DSZ3
DS3| | tt | For elevation wire measurement and cross-river leveling measurement, the basic parameters are shown in GB3161 | The inspection of the distance meter shall be carried out in accordance with the regulations of ZBA76002. Third-class standard metal linear rulers used for instrument inspection should be sent to the relevant verification unit for verification every two years. 5.2.2 For newly shipped instruments and their inspection items before operation and cross-river leveling measurement, the inspection items shall be carried out as specified in Table 4. Table 4
Serial number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15|| tt||16
17
instrument
water
accurate
standard
foot
water||tt| |Accurate
Servant
Longitude
Latitude
Instrument
Inspection
Inspection of the ruler
ruler (see appendix B1) in B (Supplement) | B3) Determination of the zero-point unequal difference of a pair of scales and the difference between the base and auxiliary division readings [see B4 in Appendix B (Supplement)
Determination of the nominal meter length of a pair of scales, see Appendix B (Supplement) B5) Determination of decimeter division error of the scale [See B6 in Appendix B (Supplement)) Inspection of the level C See B7 in Appendix B (Supplement)) General calibration of the level on the level [See Appendix B8 in B (Supplement)] Calibration of the crosshair (see B9 in Appendix B (Supplement)) Determination of viewing distance constant [See B10 in Appendix B (Supplement)) Determination of operating error of the focusing lens [See B11 in Appendix B (Supplement)) Calibration of cross error of bubble level See B12 in Appendix B (Supplement)) Calibration of i angle [See B13 in Appendix B (Supplement)) Measuring station Determination of error and vertical axis error in height difference observation (see B14J in Appendix B (Supplement)
Determination of magnetic error of Baidong Anping level Determination of vertical dial micrometer line error (see Appendix B (B15 in Supplement) - Determination of errors in vertical angle observations [See B16 in Appendix B (Supplement)] New instrument
+
+
+
+
+
+
+
+
+
+
+|| tt||+
+
+
+
Before homework
+
+
×||tt ||+
+
+
+
+
+
+
+
Cross-river level
Before measurement
+
×
+
x
X
+||tt| |+
+
+
+
+
+
Ten in Table 4 indicates the items that should be inspected. When used If the instruments and methods are irrelevant to the test, no test is required. The 15th inspection item in Table 4 should be sent to the relevant verification unit for inspection. GB12898-91
5.2.3 The relevant items affected by the repaired instrument should be inspected. Item 15 must be checked. 5.2.4 The i angle should be checked once a day within a week after the operation starts (item 13 in Table 4). If the i angle remains within 10\, it can be checked once every 15 days in the future.
5.2.5 During the operation, you should always pay attention to items 2 and 8 in the calibration table 4. If there is any doubt about the quality of a certain part of the instrument, the corresponding items should be inspected at any time.
5.2.6 Items 3.5 in Table 4 should be inspected once each after each period of operation. If the operation period exceeds three months, these two items should be added once in the middle of the operation period.
5.3 Instrument technical indicators
Instrument technical indicators shall be implemented in accordance with Table 5.
Table 5
Serial number
1
2
3
4
5
6| |tt||7
8
9
10
11
12
Scale bending difference
Instrument indicators Item
zero point unequal difference of a pair of scales
base and auxiliary division constant deviation of the scale
nominal length deviation of a pair of scales
decision division error of the scale| |tt||Operation error of focusing lens
Angle
Error in height difference observation of measuring station
Vertical axis error
Magnetic error of automatic leveling level||tt| |Vertical dial micrometer line error
Error in vertical angle observation in one measurement round
Limited
Third grade
8.0mm
1.0mm| |tt||0.5mm
0.50mm
1.0mm
1.0mm
20\
1.0mm
0.3mm|| tt||0.12r
2.0
3.0″
poor
fourth grade
8.0mm
1.0mm
0.5mm
0.50mm
1.0mm
1.0mm
20″
1.5mm
0.5mm
0.20 *
2. 0%
3.0*
Apply corrections
Adjust
Use actual measured values
Prohibited use
Prohibited use
Prohibited use
Excessive handling measures
Calibration, the self-leveling level should be sent to the factory for calibration
Prohibited use
Prohibited use||tt| |Prohibited use
Prohibited use
Prohibited use
The magnetic error of the automatic leveling instrument in the above table refers to the steady magnetic field effect of the automatic leveling instrument in the horizontal direction with a magnetic induction intensity of 0.05mT. down, causing the maximum deviation of the line of sight. 6 Level Observation
6.1 Observation Method
6.1.1 The third-class level measurement adopts the middle wire reading method for round-trip measurement. When using a level with an optical micrometer and a linear Invar level rod for observation, one-way double-turn point observation can also be performed. 6.1.2 The fourth-grade leveling uses the middle wire reading method for single-pass observation. The branch line must be a round-trip survey or a one-way double-turn point survey. 6.2 Requirements for setting up measuring stations
The third and fourth grade leveling measurements use a ruler platform as the pivot point support. Observation should be carried out when the image of the ruler reticle is clear and stable. If the image is not good, the length of sight should be shortened as appropriate. The line-of-sight length and line-of-sight height of the measuring station shall be as specified in Table 6. Level
Third class
Fourth class
Sight length
Instrument type
DS3
DS1,DS05
S3| | tt | Sight distance
75
100
100
150
6.3.1 The order of sighting scale divisions at each survey station in third-class leveling is as follows: black surface of rearsight scale (basic divisions);
b.
c
d.
6.3.2
a.
b.
c.
d.
6.3.3
a.
b.
black surface of frontsight scale (basic divisions)
red surface of frontsight scale (auxiliary divisions);
red surface of rearsight scale (auxiliary divisions).
The order of the sighting scale divisions at each station of the fourth-order leveling measurement is as follows: black face of the rear sight scale (basic division):
red face of the rear sight scale (auxiliary division);
black face of the front sight scale (basic division);
red face of the front sight scale (auxiliary division).
Operational procedures for one station:
2.0
3.0
The accumulated difference of sight distance before and after each station
5.0
10.0
m
Line of sight height
Three-wire energy reading
Three-wire energy reading
First, adjust the vertical axis of the instrument to the vertical position (when the telescope rotates around the vertical axis, the level bubble The two ends are separated by no more than 1cm): Aim the telescope at the black face of the rear sight ruler, use the inclined spiral level bubble to accurately center it, and read the ruler readings accurately according to the sight line and the middle line (the fourth-order observation does not require reading the upper and lower line readings, and the distance can be read directly); c.
d.
Aim at the black face of the front sight ruler and operate according to item b; aim at the red face of the front sight ruler and operate according to item b. At this time, only read the middle line reading; aim at the red face of the rear sight ruler and operate according to item d. e.
When observing with the Invar scale with a single row of scales, take two sighting readings of the single row of scales instead of the Kiev scale readings. 6.3.4 The operating procedure of the automatic leveling level is the same as that of the bubble level. Before observing at each station, first guide the roughly leveled level bubble to the center, and then aim at the scale and take readings in the prescribed order. The operating procedure of the rotating mirror level is to aim at the scale in the prescribed order, and the observation of the black and red scales should be carried out at two mirror positions (or positions) respectively. 6.3.5 When the third and fourth leveling measurements are made by the one-way double turning point method, two scale platforms 0.5m apart are placed at each turning point, corresponding to the two leveling routes on the left and right. Each measuring station shall follow the prescribed observation method and operating procedures; first complete the observation of the right route, and then carry out the observation of the left route.
6.4 Interval and inspection
During the work interval, it is best to end the observation at the leveling point. Otherwise, two fixed points that are firm, reliable, smooth and protruding, and convenient for placing the scale should be selected as the intermission points. After the interval, the inspection should be carried out, and the measurement can be started if the inspection results meet the tolerance requirements. If there is no fixed point to choose, wooden stakes with cap nails are driven into the turning points of the last two measuring stations before the interval as the intermission points. After the interval, the test is carried out, and the height difference measured before and after the interval between any two turning points is compared. If it meets the tolerance requirements, the test can be started from this point. Otherwise, the test starts from the previous leveling point. The height difference is not adopted.
6.5 Number of reading digits and observation tolerance of measuring station
6.5.1 The reading position shall be carried out in accordance with the provisions of Table 7. Grade
Grade
Sight wire
Third grade
Fourth grade
1
1
GB12898-91
Table 7
Middle wire reading method
Middle wire
1
1
6.5.2 The observation tolerance of measuring station shall be carried out in accordance with the provisions of Table 8. Table 8
Basic and auxiliary scales
Grade
Third grade
Fourth grade
Observation method
Middle thread reading method
Optical micrometry
Middle thread reading method
(black and red surface)
Difference in readings
2.0
1.0
3.0
Basic and auxiliary scales
(black and red surface)
Difference in measured height difference
3.0
1.5
5.0| |tt||Sight line
1
1
Optical micrometer method
When observing
by single-pass double-turn point method, the difference between the left and right route turning points
1.5
4.0
Bisector
0.1
1
mm
mm
Difference in height difference between detection inter-stimulus points
3.0
5.0
Because the observation error of the measuring station exceeds the limit, it can be re-measured immediately after inspection at this station. If it is found after the station is moved, it should be re-observed from the leveling point or intermittent point (which must be tested to meet the limit difference). 6.6 Matters to be observed during observation
6.6.1 During observation, a white measuring umbrella should be used to block the sunlight, and a white instrument cover should be used when moving the station. 6.6.2 For a level with a tilting screw, the zero point of the tilting screw should be measured and marked before observation. The zero point should be adjusted at any time as the temperature changes. For the level of an automatic leveling level, it must be strictly leveled before observation. 6.6.3 When placing the tripod of the level at each consecutive measuring station, two of the legs should be parallel to the direction of the leveling route, and the third leg should be placed alternately on the left and right sides of the route direction.
6.6.4 Except for the turning point of the route, the three positions of the instrument and the front and rear sight scales at each measuring station should be as close to a straight line as possible. 6.6.5 When observing at the same measuring station, it is generally not allowed to adjust the focus twice. Only when the line of sight length is less than 10m and the difference in front and rear sight distances is less than 1m, the focus can be adjusted when observing the front and rear scales.
6.6.6 The number of measuring stations for the forward and return measurements of each measuring section should be an even number. When switching from the forward measurement to the return measurement, the two scales must be exchanged and the instrument should be re-set.
6.6.7 When conducting third- and fourth-class leveling in areas with large elevation differences, the optical micrometry method should be used as much as possible to measure using the Invar leveling rod. 6.7 Observation and detection of route connection points
6.7.1 When observing the intersection of two leveling routes, the connection situation must be recorded in detail on the "Leveling Network Node Connection Map". 6.7.2 When the third- and fourth-class leveling routes (or branches) are connected to the measured leveling points, a single-way detection of a measured section must be performed. If it exceeds the limit, another single-way detection should be performed. If it still exceeds the limit, the detection should continue forward to determine a reliable measured point as the connection point. If the intersection changes, the relevant measurement section must be re-measured.
For high-level routes, the inspection shall be carried out according to the grade of the newly established routes; for low-level routes, the inspection shall be carried out according to the grade of the measured routes. The tolerance of the difference between the height differences of the measured sections is shown in Table 9. 6.8 The tolerance of the difference between the round-trip height difference and the loop closure error 6.8.1 The tolerance of the difference between the round-trip height difference and the loop closure error shall be implemented in accordance with the provisions of Table 9. Grade
Third grade
Fourth grade
Measurement section, route round-trip
Discordance value of height difference
±12Vk
±20/k
Note: K is the length of the route or measurement section, km; L is the length of the attached route (loop), km; R is the length of the detection measurement section, km;
GB12898—91
Table 9
Measurement section, route
Left and right routes
Height difference does not match the value
±8k
±14K
Closure difference of matching route or loop line
Original
Level
±12V
±20V
Mountainous area refers to the area with an altitude of more than 1000m or the maximum height difference in the route exceeds 400m. Mountain
±15V
±25VE
mm
Detect the difference in height of the measured
section
±20VR
±30VR
6.8.2 When the leveling loop is composed of routes of different grades, the tolerance of the loop closure error shall be calculated according to the length of each grade of route, and then the square root of the sum of their squares shall be taken as the tolerance.
6.8.3 Detect the tolerance of the difference in height of the measured sections, which is applicable to both one-way and two-way detection. 6.9 Re-measurement and selection of measurement results
If the leveling measurement results exceed the tolerances specified in Article 6.8 and Article 3.6, they shall be re-measured. The operator shall make a specific analysis of the reasons for the exceeding of the limits and re-measure and select according to the following principles: If the difference in the round-trip height measurement of the measuring section does not meet the limit, the whole measuring section shall be re-measured for the forward or return measurement with a lower degree of reliability. If the re-measured height a.
If the discrepancy between the difference and the original height difference in the same direction exceeds the limit of the round-trip height difference discrepancy, but the discrepancy with the other one-way height difference does not exceed the limit, the re-measurement result will be used. If it is re-measured If the discrepancy between the measured height difference and the original measured height difference in the same direction does not exceed the discrepancy of the round-trip height difference, and the discrepancy between the measured height difference and the other one-way original measured height difference does not exceed the limit, then the middle number is taken. as the height difference for that one-way trip. If the above limit is exceeded, another one-way measurement must be re-measured;
b. In the one-way double-turn point observation, if the height difference between the left and right routes of the measurement section does not match the value and exceeds the limit, only one one-way single line can be re-measured and combined with The median of the original test results that meets the tolerance will be used; if the retest results and the original test results both meet the tolerance, the median of the three single-line results will be taken. When the remeasurement results exceed the limits of the original two single-line measurements, the reasons should be analyzed and a one-way single-line measurement should be re-measured; c. Accidental measurement of each kilometer calculated by the discrepancy between the round-trip height difference (or the height difference between the left and right routes). Error M. When the limit is exceeded, some measurement sections with larger discrepancy values ??should be re-measured;
d. When the loop closure error exceeds the limit, the measurement sections on the route that are less reliable (those with large round-trip height difference discrepancies or poor observation conditions) on the route should be re-measured first. When the closure error of the conforming route exceeds the limit, the reasons should be analyzed and the relevant measurement sections should be re-measured. In areas with large altitude differences, attention should be paid to the influence of ruler length errors and gravity anomalies. If conditions permit, gravity anomaly correction should be added. 7 Cross-river leveling
7.1 General provisions
When the leveling route crosses a river (or lake, pond, wide ditch, depression, valley, etc.) and the sight length is within 200m, general observation methods can be used. However, the instrument height should be changed once at the measuring station and observed twice. The difference between the two height differences should not exceed 7mm, and the median of the two results will be used. If the line of sight length exceeds 200m, the method described in this chapter should be used for observation based on the width of the river and the conditions of the instrument and equipment. The cross-river leveling measurement method, its scope of application, number of observation rounds, and tolerance regulations are in accordance with Table 10. Serial number
1
2
square
method
direct ruler reading method
micro-moving plate method
theodolite Inclination method or
ranging trigonometric elevation method
level
three
four
three
four
three| |tt||four
GB12898—91
Table 10
Maximum sight length 5
km
0.3
0.3||tt ||0. 5
1.0
2.0
2.0
Single test
Number of times
2
2|| tt||4
8
8
half test round
number of observation groups
3
mutual difference in height difference between test rounds| |tt||not larger than
mm
8
16
30·5
50·8
24s||tt| |40s
Prepare
Note
See 7.3 for the measurement method
See 7.4 for the measurement method
The measurement method is in accordance with 8.8 and 8.9 in GB12897
When the line of sight across the river exceeds 2000m, the methods and requirements used must be specially designed based on the conditions of the survey area. 7.2 Selection and layout of cross-river sites
7.2.1 Cross-river sites should be selected in river sections with narrow water surface, solid soil, and easy installation of stations. Eye level should be as high as possible. The placement of rulers and instrument points should be as high as possible.
7.2.2 The positions of cross-river leveling instruments and rulers should generally be laid out in a "Z\" shape or similar graphics. As shown in Figure 1, 1, and I are the rotation placement points for instruments and far rulers, 1 , b2 is the nearest ruler placement point, 1,61.bz, and is about 10~20m; each point in Figure 1 should be firmly driven into the ground with wooden piles with a diameter of not less than 5cm and a length of about 30~50cm. The iron cap nail is attached to the end for placing the ruler d
1
Figure 1
7.3 Direct ruler reading method
7.3.1 Observation method
The observation method for each measurement round is as follows,
ob
first level the level at a point between I, and 6 (or 1. and 6a) and equidistant from I; and b, and then use Use the same ruler to measure the height difference hi between T and br according to the general a. Press the middle wire to read the base and auxiliary divisions of the scale once; c. Turn the instrument to the opposite shore and aim at the far scale on point I. After adjusting the focus, use tape to fix the focusing screw, and press the middle wire to read the base and auxiliary divisions of the scale. Make two strokes each;
d. While ensuring that the focusing screw is not touched, immediately move the instrument to point 1 on the other side, and at the same time move the ruler at point b to point 1. After the instrument is precisely leveled, first aim at the far scale at point I on the other side, and read in the reverse order of c, b, a and the operating requirements; e. Move the instrument to a point equidistant between 1. and b2. , according to the general operation method, measure the height difference h, b between 1. and ba. The above a, b, c are the observations of the upper half of the test, and d and e are the observations of the lower half of the test.bz, and is about 10~20m; at each point in Figure 1, wooden piles with a diameter of no less than 5cm and a length of about 30~50cm should be firmly driven into the ground, and iron cap nails are nailed on the top ends for placing the ruler. d
1
Figure 1
7.3 Direct ruler reading method
7.3.1 Observation method
The observation method for each measurement round is as follows, ||tt| |ob
After leveling the level at a point between I, and 6 (or 1. and 6a) and equidistant from I; and b, use the same ruler to press a.||tt| |Operating procedures, measure the height difference hi,,b of T,br. Move the instrument to 11 o'clock. After leveling the instrument precisely, aim at the near scale at 6 o'clock on the local shore. Press the middle wire to read the base and auxiliary scale of the scale once. c. Turn the instrument to the opposite shore and aim at the far scale at point I. , after focusing, use tape to fix the focusing screw, press the middle wire to read the base and auxiliary divisions of the ruler twice;
d. Under the requirement of ensuring that the focusing screw is not touched, immediately turn the instrument Move to the other side1. Point on, and the ruler on point b is also moved to 1, point on. After the instrument is precisely leveled, first aim at the far scale at point I on the opposite bank, and read in the reverse order of c, b, a and the operating requirements; e. Move the instrument to a point equidistant between 1. and b2, and measure the height difference h and b between 1. and ba according to the general operating method. The above a, b, and c are the observations of the first half of the round, and d and e are the observations of the second half of the round. -bz, and is about 10~20m; at each point in Figure 1, wooden piles with a diameter of no less than 5cm and a length of about 30~50cm should be firmly driven into the ground, and iron cap nails are nailed on the top ends for placing the ruler. d
1
Figure 1
7.3 Direct ruler reading method
7.3.1 Observation method
The observation method for each measurement round is as follows, ||tt| |ob
After leveling the level at a point between I, and 6 (or 1. and 6a) and equidistant from I; and b, use the same ruler to press a.||tt| |Operating procedures, measure the height difference hi of T,br,,b. Move the instrument to 11 o'clock. After leveling the instrument precisely, aim at the near scale at 6 o'clock on the local shore. Press the middle wire to read the base and auxiliary scale of the scale once. c. Turn the instrument to the opposite shore and aim at the far scale at point I. , after focusing, use tape to fix the focusing screw, press the middle wire to read the base and auxiliary divisions of the ruler twice;
d. Under the requirement of ensuring that the focusing screw is not touched, immediately turn the instrument Move to the other side1. Point on, and the ruler on point b is also moved to 1, point on. After the instrument is precisely leveled, first aim at the far scale at point I on the other side, and read in the reverse order of c, b, a and the operating requirements; e. Move the instrument to a point equidistant between 1. and b2, and measure the height difference h and b between 1. and ba according to the general operating method. The above a, b, and c are the observations of the first half of the round, and d and e are the observations of the second half of the round. -
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