Surface flow velocity and direction mapping method

Abstract

This invention relates to a method for mapping surface flow velocity and direction, comprising the following steps: S1, obtaining the engineering grid coordinates (X, X, Y) of the measuring point P using the forward intersection method or GNSS positioning measurement method. n Y n S2, based on the engineering grid coordinates (X) of two adjacent points. n Y n ), (X n+1 Y n+1 Given the time difference Δt, calculate the corresponding surface velocity and direction; S3, create a surface velocity and direction result file. The mathematical model of this invention is reasonably designed, highly applicable, and produces accurate calculations and results, improving work efficiency and saving costs.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrological observation of water transport engineering, and more particularly to a surface flow velocity and flow direction mapping method. BACKGROUND

[0002] Surface flow velocity and flow direction measurement is one of the important contents of hydrological observation, and surface flow velocity and flow direction mapping results are important basic data for planning, design, construction and operation management of port, channel, bridge, water conservancy, flood control and other engineering, and the observation results have a direct impact on the determination of the wharf front line and the analysis of riverbed evolution in water transport engineering.

[0003] The classical surface flow velocity and flow direction measurement method is the float method. The float method generally uses two modes of forward intersection method and satellite positioning method, wherein the forward intersection method, although low in accuracy and efficiency, is simple to operate, especially suitable for areas with weak or no satellite signals, so it has been used. The satellite positioning method is widely used due to its high measurement accuracy and convenient operation. The results of the two methods are drawn, and the traditional surface flow velocity and flow direction measurement result drawing method mainly includes manual observation, recording, inputting and compiling. The main problems of the traditional method are that the data reading, conversion and calculation processes are prone to errors, and the labor intensity is large, the work efficiency is low, and the results are not elegant. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a surface flow velocity and flow direction mapping method which is simple and efficient, not prone to errors and has universality compared with the traditional method.

[0005] The technical solution adopted by the present application to solve the technical problem is that a surface flow velocity and flow direction mapping method is constructed, comprising the following steps:

[0006] S1, obtaining the engineering grid coordinates (X n , Y n ) of the flow measurement point P by the forward intersection method or GNSS positioning measurement method;

[0007] S2, calculating the corresponding surface flow velocity and flow direction according to the engineering grid coordinates (X n , Y n ), (X n+1 , Y n+1 ) and the time difference Δt of the adjacent two points;

[0008] S3, establishing a surface flow velocity and flow direction result file.

[0009] According to the above scheme, in the step S1, the forward intersection method comprises the following steps:

[0010] S1-a1, using two or more stations with a recording card total station or electronic theodolite, according to the agreed time period, the drift flow of the buoy is measured by synchronous forward intersection, and positioning measurement strip number, point number and angle data are obtained;

[0011] S1-a2, calculating the engineering coordinates (X n ,Y n ) of the point according to the mathematical model of the forward intersection method;

[0012] The mathematical model of the forward intersection method is established as follows:

[0013]

[0014]

[0015] In the formula, X a , Y a are the known engineering longitudinal and transverse coordinates of the station A;

[0016] X b , Y b are the known engineering longitudinal and transverse coordinates of the station B;

[0017] α is the included angle of the station A viewing B and intersecting the flow point P;

[0018] β is the included angle of the station B viewing A and intersecting the flow point P;

[0019] X n , Y n are the to-be-determined engineering longitudinal and transverse coordinates of the flow point P;

[0020] The engineering coordinates (X n , Y n ) of the flow point P are calculated according to the formulas (1) and (2).

[0021] According to the above scheme, in the step S1, the GNSS positioning measurement method specifically comprises the following steps of: reading the time and geodetic coordinates (B, L) in the positioning measurement data in the cloud server or the recording card, converting the geodetic coordinates (B, L) into reference ellipsoid grid coordinates (X0, Y0), and then converting the reference ellipsoid grid coordinates (X0, Y0) into engineering grid coordinates (X n ,Y n ):

[0022] S1-b1, the mathematical model for converting the satellite positioning automatic measurement geodetic coordinates (B, L) into reference ellipsoid grid coordinates (X0, Y0) is as follows:

[0023]

[0024]

[0025] wherein:

[0026]

[0027] l = L - L0, L0 is the central meridian

[0028]

[0029] t = tan B

[0030] η = e' cos B

[0031]

[0032]

[0033]

[0034]

[0035]

[0036] S1-b2, convert the reference ellipsoid grid coordinates (X0, Y0, H0) into engineering coordinates (X, Y, H), using two ways of conversion, four parameters or seven parameters, two mathematical models are obtained: n n n

[0037] ① Four-parameter conversion model:

[0038]

[0039] wherein: Δx, Δy: translation parameters;

[0040] θ: rotation parameter;

[0041] k: scale transformation parameter;

[0042] ② Seven-parameter conversion model:

[0043]

[0044] wherein: Δx, Δy, Δh: translation parameters;

[0045] ε x , ε y , ε z : rotation parameters;

[0046] k: scale transformation parameter;

[0047] ​​​The geodetic coordinates of GNSS positioning are converted to grid coordinates (X0, Y0) according to formulas (3) and (4), and the grid coordinates (X0, Y0) of GNSS positioning are converted to engineering coordinates according to formulas (5) or (6), to obtain the engineering coordinates (X n , Y n ) of the flow measuring point P of the satellite positioning measurement method.

[0048] According to the above scheme, in the step S2, the flow velocity mathematical model of the adjacent two points is:

[0049]

[0050] In the formula, (X n , Y n ) is the coordinate of the nth point of the drift point P, with the unit of meter;

[0051] (X n+1 , Y n+1 ) is the coordinate of the (n+1)th point of the drift point P, with the unit of meter;

[0052] Δt is the time experienced by the drift point P from the nth point to the (n+1)th point, with the unit of second;

[0053] V n～n+1 is the average flow velocity of the drift point P from the nth point to the (n+1)th point, with the unit of meter / second.

[0054] According to the above scheme, in the step S2, the flow direction mathematical model of the adjacent two points is:

[0055]

[0056] In the formula, X n , Y n is the coordinate of the nth point of the drift point P, with the unit of meter;

[0057] X n+1 , Y n+1 is the coordinate of the (n+1)th point of the drift point P, with the unit of meter;

[0058] α n～n+1 is the flow direction from the nth point to the (n+1)th point of the drift point P, with the unit of radian, which can be converted to degree and minute and second as needed;

[0059] The flow direction value is the coordinate direction value in the engineering plane system, which is related to the coordinate difference value of the adjacent flow measuring points, and the value rule is:

[0060] Let: ΔX n = (X n+1 -X n ), ΔYn= (Y n+1 -Y n )

[0061] Then, the flow direction value method is:

[0062] ① When ΔX n > 0, ΔY n = 0: α n～n+1 = 0 (8-1)

[0063] ② When ΔX n > 0, ΔY n > 0:

[0064] ③ When ΔX n = 0, ΔY n > 0: α n～n+1 = π / 2 (8-3)

[0065] ④ When ΔX n < 0, ΔY n > 0:

[0066] ⑤ When ΔX n < 0, ΔY n = 0: α n～n+1 = π (8-5)

[0067] ⑥ When ΔX n < 0, ΔY n < 0:

[0068] ⑦ When ΔX n = 0, ΔY n < 0: α n～n+1 = 3π / 2 (8-7)

[0069] ⑧ When ΔX n > 0, ΔY n < 0:

[0070] According to the above scheme, the calculation method of the surface flow velocity and flow direction in the step S2 is as follows:

[0071] ① Calculation method of average flow velocity

[0072]

[0073] In the formula, k: total number of measuring points of the measuring line;

[0074] n: current point number of the measuring line

[0075] V n～n+1 : segment flow velocity of the measuring line, calculated according to formula (7);

[0076] ② Selection rule of maximum flow velocity

[0077] Let the total number of measuring lines be k, and the maximum flow velocity be V MAX The initial value is 0;

[0078] V MAX The filtering method is:

[0079] If V MAX -V n～n+1 ≥ 0

[0080] V MAX = V MAX

[0081] If V MAX -V n～n+1 <0

[0082] V MAX = Vn ～n+1 (n = 1, 2,..., k-1) (10);

[0083] 3. The selection rule of the minimum flow velocity

[0084] Let the total number of measuring lines be k, and the minimum flow velocity be V MIN The initial value is 0;

[0085] V MIN The filtering method is:

[0086] If V MIN -V n～n+1 ≤ 0

[0087] V MIN = V MIN

[0088] If V MIN -V n～n+1 >0

[0089] V MIN = V n～n+1 (n = 1, 2,..., k-1) (11)

[0090] According to the above scheme, in the step S3, the achievement file includes: the surface flow velocity and flow direction calculation book, the surface flow velocity and flow direction graph, and the surface flow velocity and flow direction table.

[0091] According to the above scheme, the surface flow velocity and flow direction calculation book is expressed in text form, the surface flow velocity and flow direction table is expressed in table form, the surface flow velocity and flow direction calculation book includes the measuring section number, distance, time, flow velocity, average value, maximum value, and minimum value, and the information of the surface flow velocity and flow direction table includes: the flow line number, date, water level, wind force and direction, maximum flow velocity, minimum flow velocity, average flow velocity, and buoy style.

[0092] According to the above scheme, the surface flow velocity and flow direction diagram is expressed in the form of a DXF graphic file, and the graphic file content includes: flow line number, flow velocity point position, flow direction line and flow velocity value.

[0093] The surface flow velocity and flow direction mapping method of the present application has the following beneficial effects:

[0094] 1. The mathematical model of the present application is correct, and the calculation results meet the specification requirements, ensuring the quality of the results.

[0095] 2. The judgment rule of the present application is comprehensive, the judgment method is simple, the search logic is rigorous, and the running speed is fast;

[0096] 3. The algorithm of the present application has strong compatibility, taking into account different mapping methods and different data conversion modes;

[0097] 4. The digital and intelligent mode of the present application is strong, completely replacing the traditional manual and semi-automatic operation mode;

[0098] 5. The work efficiency of the present application is significantly improved, and the automatic integration of field and office work is efficient and cost-saving;

[0099] 6. The present application is not only suitable for ordinary PC, but also suitable for smart phones, which is convenient for field measurement operation;

[0100] 7. The present application has significant benefits, full-automatic data processing, avoiding traditional manual errors, and providing standardized mapping results. BRIEF DESCRIPTION OF DRAWINGS

[0101] The present application will be further described below in conjunction with the drawings and examples, wherein:

[0102] Figure 1 is a forward intersection measurement schematic diagram of the surface flow velocity and flow direction mapping method of the present application;

[0103] Figure 2 is a calculation book schematic diagram of the surface flow velocity and flow direction mapping method of the present application;

[0104] Figure 3 is a trajectory schematic diagram of the surface flow velocity and flow direction mapping method of the present application;

[0105] Figure 4 is a flow velocity and flow direction representation schematic diagram of the surface flow velocity and flow direction mapping method of the present application. DETAILED DESCRIPTION

[0106] In order to have a clearer understanding of the technical features, purposes and effects of the present application, the specific embodiments of the present application will be described in detail with reference to the drawings.

[0107] As Figures 1-4As shown, the surface flow velocity and direction mapping method of the present application is based on the float method, involves the multi-disciplinary fields of engineering surveying, hydrological observation, computer software engineering, etc., and mainly includes the design of field data collection and calculation method, the design of drawing algorithm, etc. The technical route of the present application is: extracting the float positioning original data collected by the forward intersection method or GNSS positioning measurement method; extracting the collection time and coordinates or angles from the original data to calculate the average flow velocity and direction of the adjacent two points, and statistically analyzing the characteristic values of the flow velocity; outputting the surface flow velocity and direction calculation book; drawing the flow velocity and direction diagram; and drawing the flow velocity and direction table. The key technologies of the present application are: establishing the mathematical model of observation data form conversion; establishing the mathematical model of surface flow velocity calculation; establishing the mathematical model of surface flow direction calculation; establishing the logical judgment rule of surface flow direction; and establishing the characteristic value calculation and interpretation rule. The main technical steps of the present application are: firstly, establishing the mathematical model of observation data form conversion to convert the original observation data into engineering system coordinate data; secondly, establishing the flow velocity calculation model of adjacent observation points to analyze and calculate the characteristic values of flow velocity and direction; thirdly, establishing the flow direction calculation model of adjacent observation points and the flow direction logical judgment formula; and finally, establishing the surface flow velocity and direction result file, i.e. the calculation book, the flow line diagram and the flow velocity and direction table.

[0108] Embodiment:

[0109] The surface flow velocity and direction mapping method comprises the following steps:

[0110] S1, obtaining the engineering grid coordinates (X n , Y n ) of the flow measuring point P by the forward intersection method or GNSS positioning measurement method; and analyzing and determining the surface flow velocity and direction measurement method according to the field environment conditions.

[0111] The forward intersection method comprises the following steps:

[0112] S1-a1, using two or more total stations or electronic theodolites with recording cards to perform synchronous forward intersection measurement on the drifting floating float according to the agreed time period, such as 60 seconds, to obtain positioning measurement strip number, point number and angle data;

[0113] S1-a2, calculating the engineering coordinates (X n , Y n ) of the point position according to the mathematical model of the forward intersection method;

[0114] The mathematical model of the forward intersection method is established as follows:

[0115]

[0116]

[0117] In the formula, X a , Y aThe known longitudinal and transverse coordinates of station A;

[0118] X b Y b The known longitudinal and transverse coordinates of station B;

[0119] α is the angle between the backsight of station A and the intersection of the flow measurement point P with the flow measurement point;

[0120] β is the angle between the backsight of station B and the flow measurement point P.

[0121] X n Y n The coordinates of the undetermined project at the flow measurement point P are:

[0122] The engineering coordinates (X, X) of the flow measurement point P are calculated according to formulas (1) and (2). n Y n ).

[0123] The GNSS positioning and measurement method specifically involves: reading the time and geodetic coordinates (B, L) from the positioning and measurement data on a cloud server or recording card; converting the geodetic coordinates (B, L) into reference ellipsoidal grid coordinates (X0, Y0); and then converting the reference ellipsoidal grid coordinates (X0, Y0) into engineering grid coordinates (X...). n ,Y n ).

[0124] The specific steps of the GNSS positioning and measurement method are as follows:

[0125] S1-b1, The mathematical model for converting the geodetic coordinates (B, L) obtained from automatic satellite positioning measurements into reference ellipsoidal grid coordinates (X0, Y0) is as follows:

[0126]

[0127]

[0128] In the formula:

[0129]

[0130] l = L - L0, where L0 is the central meridian.

[0131]

[0132] t = tanB

[0133] η=e′cosB

[0134]

[0135]

[0136]

[0137]

[0138]

[0139] S1-b2, converting the reference ellipsoid grid coordinates (X0, Y0, H0) into engineering coordinates (X n , Y n , H n ), which is obtained by using two conversion methods of four parameters or seven parameters, and the two mathematical models are:

[0140] ① Four-parameter conversion model:

[0141]

[0142] In the formula: Δx, Δy: translation parameters;

[0143] θ: rotation parameter;

[0144] k: scale transformation parameter;

[0145] ② Seven-parameter conversion model:

[0146]

[0147] In the formula: Δx, Δy, Δh: translation parameters;

[0148] ε x , ε y , ε z : rotation parameters;

[0149] k: scale transformation parameter;

[0150] According to the formulas (3) and (4), the geodetic coordinates of GNSS positioning are converted into grid coordinates (X0, Y0); according to the formulas (5) or (6), the grid coordinates (X0, Y0) of GNSS positioning are converted into engineering coordinates, and the engineering coordinates (X n , Y n ) of the flow point P of satellite positioning measurement method are obtained.

[0151] S2, according to the engineering grid coordinates (X n , Y n ) and (X n+1 , Y n+1 ) of the adjacent two points and the time difference Δt, the corresponding surface flow velocity and flow direction are calculated;

[0152] The mathematical model of the flow velocity of the adjacent two points is:

[0153]

[0154] In the formula: (X n Y n () represents the coordinates of the nth point of drift point P, in meters;

[0155] (X n+1 Y n+1 () represents the coordinates of the (n+1)th point of drift point P, in meters;

[0156] Δt is the time taken for drift point P to travel from point n to point n+1, in seconds;

[0157] V n～n+1 The average flow velocity from point n to point (n+1) of drift point P is expressed in meters per second.

[0158] The mathematical model for the flow direction between two adjacent points is:

[0159]

[0160] In the formula: X n Y n Let n be the coordinates of the nth point of drift point P, in meters;

[0161] X n+1 Y n+1 Let be the coordinates of the (n+1)th point of drift point P, in meters;

[0162] α n～n+1 The direction of the flow from point n to point (n+1) of drift point P is expressed in radians, which can be converted to degrees, minutes, and seconds as needed.

[0163] The flow direction value is taken as the coordinate direction value in the engineering plane system. The value is related to the coordinate difference between adjacent flow measurement points, and the rule for taking the value is as follows:

[0164] Let: ΔX n =(X n+1 -X n ), ΔYn=(Y n+1 -Y n )

[0165] Therefore, the method for determining the flow direction is as follows:

[0166] ①When ΔX n >0, ΔY n =0: α n～n+1 =0 (8-1)

[0167] ②When ΔX n >0, ΔY n >0:

[0168] ③When ΔX n =0, ΔYn > 0: a = π / 2 (8-3) n～n+1

[0169] IV. When ΔX < 0, ΔY > 0: n n

[0170] V. When ΔX < 0, ΔY = 0: n n n～n+1 n～n+1 = 3π / 2 (8-7)

[0171] VI. When ΔX < 0, ΔY < 0: n n

[0172] VII. When ΔX = 0, ΔY < 0: n n n～n+1 = 3π / 2 (8-7)

[0173] VIII. When ΔX > 0, ΔY < 0: n n

[0174] The calculation method of surface flow velocity and flow direction is as follows:

[0175] I. The calculation method of average flow velocity

[0176]

[0177] In the formula: k: total number of measuring points of the measuring line;

[0178] n: the current point number of the measuring line

[0179] V n～n+1 : the flow velocity of the measuring line section, calculated according to formula (7).

[0180] II. The selection rule of maximum flow velocity

[0181] Let the total number of measuring points of the measuring line be k, and the maximum flow velocity V MAX The initial value is 0;

[0182] V MAX The filtering method is:

[0183] If V MAX -V n～n+1 ≥ 0

[0184] V MAX = V MAX

[0185] If V MAX -V​​​​​​​​​​n～n+1 <0

[0186] then V MAX = V n～n+1 (n = 1, 2, …, k-1) (10).

[0187] ③, the minimum flow rate selection rule

[0188] Let the total number of lines is k, the minimum flow rate V MIN The initial value is 0.

[0189] V MIN The filter selection method is:

[0190] If V MIN -V n～n+1 ≤0

[0191] then V MIN = V MIN

[0192] If V MIN -V n～n+1 >0

[0193] then V MIN = V n～n+1 (n = 1, 2, …, k-1) (11).

[0194] S3, the surface flow velocity and flow direction result file is established.

[0195] The result file includes: surface flow velocity and flow direction calculation, surface flow velocity and flow direction graph and surface flow velocity and flow direction table. The surface flow velocity and flow direction calculation is expressed in text form, and the surface flow velocity and flow direction table is expressed in table form.

[0196] The surface flow velocity and flow direction calculation includes section, distance, time, flow velocity, flow direction, average value, maximum value, minimum value.

[0197] The surface flow velocity and flow direction graph is expressed in DXF graphic file form, and the graphic file content includes: flow line number, flow velocity point position, flow direction line, flow velocity value; the legend specification is as follows:

[0198] ① Flow line number annotation: black body, height is 5mm on the graph, the direction is north;

[0199] ② Flow velocity value annotation: black body, height is 3mm on the graph, the direction is perpendicular to the flow direction line;

[0200] ③ Flow velocity point position: the figure is a hollow circle + point, the hollow circle diameter is 1.5mm on the graph;

[0201] ④ Flow direction line: automatically calculated according to the sampling time interval, the length is 10-30mm on the graph.

[0202] The information of the surface flow velocity flow direction table includes: flow line number, date, water level, wind force, wind direction, maximum flow velocity, minimum flow velocity, average flow velocity, buoy style.

[0203] The embodiments of the present application are described above with reference to the drawings, but the present application is not limited to the specific embodiments described above, and the specific embodiments described above are merely illustrative, but not restrictive, and those skilled in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, which all belong to the protection of the present application.

Claims

1. A method of surface velocity flow direction mapping, the method comprising: obtaining a plurality of surface velocity flow direction measurements; and determining a surface velocity flow direction map based on the plurality of surface velocity flow direction measurements. The method comprises the following steps: S1, obtain the engineering grid coordinates of the flow measuring point P by the forward intersection method or GNSS positioning measurement method ; S2, calculating the corresponding surface flow velocity and flow direction according to the engineering grid coordinates of the two adjacent points and the time difference At​ In the step S2, the mathematical model of the flow direction of the two adjacent points is: wherein: X n , Y n are the coordinates of the n-th point of the drift point P in meters; X n+1 , Y n+1 is the coordinate of the n+1 point of the drift point P, in meters; a n~n+1 is the drift angle from the nth point to the n+1th point of the drift point P, in radians; The flow direction value is the coordinate direction value in the engineering plane system, and is related to the coordinate difference of the adjacent flow measuring points. The value rule is: Let: ΔX n = (X n+1 - X n ), ΔYn = (Y n+1 - Y n ) The flow direction value method is: X n 0, Δ Y n =0: α n~n+1 =0 (8-1)​ ii) when Δ X n 0, Δ Y n 0: α n~n+1 = (8-2) X n = 0, Δ Y n 0: α n~n+1 = π / 2 (8-3)​ IV. When Δ X n 0, Δ Y n 0: α n~n+1 = π + (8-4) • when Δ X n • when Δ n Y n~n+1 α n (8-5)​​ (6) when Δ X n 0, Δ Y n 0: α n~n+1 = π+ (8-6) = 0, Δ X n = 0, Δ Y n 0: α n~n+1 = 3π / 2 (8-7) (8) when Δ X n 0, Δ Y n 0: α n~n+1 = 2π+ (8-8); In the step S2, the calculation method of the surface flow velocity and the flow direction is as follows:

1. The average flow velocity calculation method (9) In the formula, k represents the total number of measuring points of the measuring line; n represents the current point number of the measuring line : measured line segment flow rate, calculated from equation (7) 2. The selection rule of the maximum flow velocity Let the total number of measuring lines be k, and the maximum flow rate The initial value is 0; The filtering method is as follows: If then If then (10); 3. The selection rule of the minimum flow velocity Let the total number of measuring lines be k, the minimum flow rate The initial value is 0; The selection method is as follows: If then If then (11) ; S3, Establishing the surface flow velocity and flow direction result file.

2. The surface flow velocity and flow direction mapping method of claim 1, wherein, In the step S1, the forward intersection method comprises the following steps: S1-a1, Using two or more total stations or electronic theodolites with recording cards, synchronous forward intersection measurement is performed on the floating buoy in the drift flow according to the agreed time period to obtain the positioning measurement strip number, point number and angle data; S1-a2, calculate the engineering coordinates (X n ,Y n ) of the point according to the mathematical model of the resection method; The mathematical model of the forward intersection method is established as follows: （1） （2） wherein: X a , Y a are the known engineering longitudinal and transversal coordinates of the station A; X b , Y b are the known engineering longitudinal and transversal coordinates of station B; Alpha is the included angle of the intersection of the measuring station A looking at B to the flow measuring point P; Beta is the included angle of the intersection of the measuring station B looking at A to the flow measuring point P; X n , Y n are the unknown longitudinal and transversal coordinates of the measuring point P; The engineering coordinates of the measuring point P are calculated according to the formulas (1) and (2) .

3. The surface velocity flow direction mapping method of claim 1, wherein, In the step S1, the GNSS positioning measurement method specifically comprises: reading time and geodetic coordinates in the positioning measurement data in the cloud server or the recording card , converting the geodetic coordinates into reference ellipsoid grid coordinates , and converting the reference ellipsoid grid coordinates into engineering grid coordinates (X n ,Y n ), comprising the following steps: S1-b1, geodetic coordinates automatically measured by satellite positioning converted into reference ellipsoid grid coordinates The mathematical model is: （3） （4） In the formula, ； S1-b2, the reference ellipsoid grid coordinates converted into engineering coordinates , two ways of four parameters or seven parameters are adopted to convert and obtain two mathematical models:

1. Four-parameter conversion model: （5） In the formulae: , : translation parameters; : rotation parameters; : scale transform parameter; 2. Seven-parameter conversion model: （6） In the formulae: , , : translation parameters; , , : rotation parameters; : scale transform parameter; According to formulas (3) and (4), the geodetic coordinates of GNSS positioning are converted to grid coordinates. According to formula (5) or (6), the grid coordinates of GNSS positioning are ( Converting to engineering coordinates yields the engineering coordinates of the flow measurement point P obtained using the satellite positioning measurement method. .

4. The surface velocity flow direction mapping method of claim 1, wherein, In the step S2, the mathematical model of the flow velocity of the two adjacent points is: wherein: Pn is the coordinate of the n-th point of the drift point P in meters; is the coordinate of the (n+1)th point of the drift point P, in meters;​ t is the time, in seconds, experienced by the drift point P from the nth point to the n+1th point; V n~n+1 Vn+1is the average flow velocity for the n+1th point of the drift point P, in meters per second.

5. The surface flow velocity and flow direction mapping method of claim 1, wherein, In the step S3, the result file comprises the surface flow velocity and flow direction calculation book, the surface flow velocity and flow direction graph and the surface flow velocity and flow direction table.

6. The surface flow velocity and flow direction mapping method of claim 5, wherein, The surface flow velocity and flow direction calculation book is expressed in the form of text, the surface flow velocity and flow direction table is expressed in the form of table, the surface flow velocity and flow direction calculation book comprises the measuring section number, distance, time, flow velocity, average value, maximum value and minimum value, and the information of the surface flow velocity and flow direction table comprises the flow line number, date, water level, wind power and direction, maximum flow velocity, minimum flow velocity, average flow velocity and buoy style.

7. The surface flow velocity and flow direction mapping method of claim 6, wherein, The surface flow velocity and flow direction graph is expressed in the form of DXF graph file, and the content of the graph file comprises the flow line number, flow velocity point position, flow direction line and flow velocity value.

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