CN106092061A - River water surface flow field calibrating method based on lens imaging model under oblique viewing angle - Google Patents

Abstract

The invention discloses a kind of river water surface flow field calibrating method based on lens imaging model under oblique viewing angle.First two marker posts are set on fiver survey section for orienting；Then a laser range finder and industrial camera are carried out being connected as image measuring device, and be erected on the Measure section of side, riverbank；Next the distance by laser range finder measurement apparatus to intersection point between marker post and the water surface, and the angle of pitch being recorded by built-in sensors calculates device to the elevation of the water surface；Solve every the line image scale factor at section and downbeam that tests the speed in image respectively finally according to the lens imaging model under oblique viewing angle, and then demarcate corresponding start point distance and flow speed value, complete flow field calibration.Compare existing method, it is not necessary at laying control point, two sides, river and survey its coordinate by complex device such as total powerstations, greatly reduce workload and the demand to equipment, be particularly suitable for the emergency monitoring periodically patrolling under survey and extreme condition of river flow, flow.

Description

River water surface flow field calibrating method based on lens imaging model under oblique viewing angle

Technical field

The present invention relates to a kind of river water surface flow field calibrating method, particularly relate to a kind of test the speed for river water surface imaging Water surface flow field calibrating method, belongs to vision measurement field.

Background technology

In the river water surface imaging velocity measuring technique utilizing video image measurement river water surface velocity field, flow field calibration be by Motion vector in image light flow field is converted to world coordinate system from image coordinate system, and obtains velocity vector field divided by frame period Process.Comparing the machine vision in industrial detection, there is following difficult point in the vision measurement of the river water surface: 1. measurand is height The water surface that journey dynamically changes, the water level of high flood phase flashy stream rises suddenly and sharply and breaks, and interior in short-term luffing is up to several meters；2. the tested water surface On be difficult to laying control point, same field, can only disperse to be laid in two sides and it needs to use the professional equipment such as total powerstation or DGPS exploration Its world coordinates；3. for covering perfect measurement section, camera is generally set up in bank and treats with a less oblique viewing angle shooting Surveying the water surface, perspective distortion not only causes the reduction of far field space resolution ratio, and causes its skewness in region to be measured；④ There is nonlinear distortion in the optical system of non-metric camera, especially with the distortion aberration away from picture centre during wide-angle lens Often can not ignore.

At present in the river water surface imaging velocity-measuring system of application, it is fixed that main employing following two mode carries out water surface flow field Mark:

(1) measurement mode, feature is to be considered as measuring camera on the basis of Accurate Calibration camera inside and outside parameter to make With.For example, homography matrix is decomposed into inside and outside parameter matrix by Bechle et al., demarcates intrinsic parameter first with indoor standardization plate, Then the dial on site control point and The Cloud Terrace is utilized to demarcate outer parameter.But, generally require according to water in applying at the scene The shooting angle of the focal length of the change regulation camera lens of position elevation and illumination condition, aperture and camera, thus cause imaging optical path With the change of inside and outside parameter, therefore measurement mode is generally difficult to be suitable in emergency monitoring.

(2) non-measurement mode, feature is directly to use ordinary digital camera as non-metric camera, general use based on The integral calibrating method of direct linear transformation (Direct Linear Transformation, DLT) solves one group not clearly The intermediate parameters of physical significance, sets up the mapping relations between image space coordinate and object coordinates.For example, the water surface is approximated by Fujita etc. Regard the plane of a constant elevation as, and use the method for 2 d dlt (DLT) to solve the plane of delineation and physical Model is singly answered between face.The method only need to lay 4 ground control points in two sides, river, but needs to ensure control point with the water surface altogether Face, otherwise their projections on image can not reflect real water level elevation.As improvement, also been proposed a kind of three-dimensional DLT method, it is contemplated that the distance at control point to the water surface simultaneously uses water level and than the water surface in fall parameters revision Perspective transformation model Elevation, can significantly improve under less shooting inclination angle the photogrammetric accuracy of (< 10 °).It is simple fast that non-measurement mode has calculating Speed, it is not necessary to the feature of inside and outside element of orientation initial value, therefore camera can be positioned over optional position and be not necessarily to measure its coordinate, It is particularly suitable for field emergency measurement.Also more sensitive to the laying mode and exploration precision at control point so that the measurement of big visual field Precision is limited.

In sum, the difficult point existing in view of river water surface vision measurement, existing method or precision be not high, is difficult to reality With, or waste time and energy, be difficult to rapid deployment.Therefore, study and propose a kind of rapid water surface current field calibration side exempting from control point Method, the emergency monitoring periodically patrolling flood under survey and extreme condition for river, field is significant.

Content of the invention

Goal of the invention: the present invention is directed to the difficult point of river water surface vision measurement and the deficiency of existing method existence, provide A kind of river water surface flow field calibrating method based on lens imaging model under oblique viewing angle.

Technical scheme: a kind of river water surface flow field calibrating method based on lens imaging model under oblique viewing angle, including with Lower five key steps:

(1) section marker post is set, Measure section arranges two marker posts intersecting with the water surface, is used for indicating section Direction, and using the intersection point of one of them marker post and the water surface as water level reference point；

(2) set up image measuring device, first an industrial camera and a laser range finder are connected and constitute imaging survey Amount device, and it is erected at side, riverbank；Secondly the position of tripod and the level of The Cloud Terrace are regulated so that after individually changing the angle of pitch The target spot of laser range finder can sight two marker posts successively, to guarantee that camera optical axis is positioned on Measure section；Then use and swash Optar measure its to oblique distance D of water level reference point and angle of pitch δ, and by built-in triangulation program calculate rangefinder to The vertical range of the water surface:

H_L=D sin δ

Next select the suitable optical lens of focal length f and regulate the shooting angle of pitch so that viewing field of camera covers complete Measure section simultaneously has spatial resolution high as far as possible, and then obtains industry phase according to the current angle of pitch α ' of laser range finder The angle of pitch of machine optical axis:

α=α '+Δ α

Wherein, Δ α represents the angle difference between the two demarcated in advance；Finally calculate industrial camera to the water surface vertical away from From:

H=H_L-d·cosα

Wherein, d represents laser range finder measuring center to the distance of industrial camera imaging center；

(3) gather image sequence, after image measuring device is stable, with Δ t for time interval be continuously shot total when a length of T N width image is used for flow-speed measurement；

(4) demarcate the line start point distance that tests the speed, first read the piece image in image sequence, and according to the demand of testing the speed at figure The line L that tests the speed that I bar is parallel with downbeam and size is M × 1 is set along section direction in Xiang_i(1≤i≤I), with (x_i,y_i) table Show the image coordinate at line midpoint of testing the speed；Then image coordinate (the x of water level reference point is extracted in the picture₀,y₀) test the speed as calculating The reference zero of line start point distance；Finally according to the lens imaging model under oblique viewing angle, utilize in image ordinate j from y₀To y_i Each pixel demarcate, at image scale factor Δ Y (j) of section Y-direction, the start point distance of line of testing the speed:

${\mathrm{Dist}}_i=\underset{j=y_0}{\overset{y_i}{\&Sigma;}}\mathrm{\&Delta;}Y\left(j\right)=\underset{j=y_0}{\overset{y_i}{\&Sigma;}}H\&CenterDot;\{1/tan\&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-j-1)s}{f}\&rsqb;-1/tan\&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-j)s}{f}\&rsqb;\}$

Wherein, m × n represents the image resolution ratio of camera, and s represents the pixel dimension of imageing sensor；

(5) the line flow speed value that tests the speed is demarcated, for every the line L that tests the speed_i, first with the space of pixel on the line that tests the speed for horizontal seat Mark, the time of every two field picture are ordinate, set up the time-space image that size is M × N；Then time-space image velocimetry is used to estimate Test the speed the size of motion vector on line:

$v_i=\frac{s_i}{T}=\frac{s_i}{N\&CenterDot;\mathrm{\&Delta;}t}=\frac{tan\mathrm{\&theta;}}{\mathrm{\&Delta;}t}$

Wherein, s_iThe pixel distance that expression time T internal object moves along downbeam, θ represents the texture master of time-space image Direction；Finally according to the lens imaging model under oblique viewing angle, utilize on the line that tests the speed pixel at the image yardstick of following current X-direction Factor Δ X (y_i) demarcate the size of the physics flow velocity on line of testing the speed:

$V_i=v_i\&CenterDot;\mathrm{\&Delta;}X\left(y_i\right)=v_i\&CenterDot;\frac{Hs}{\sqrt{{\&lsqb;(n/2-y_i)s\&rsqb;}^2+f^2}}/tan\&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-y_i)s}{f}\&rsqb;$

Wherein, V_iThe positive and negative direction reflecting flow velocity on the line that tests the speed.

Described image measuring device, the case top of industrial camera and bottom all have one 1/4 " mounting seat of screw, The mounting seat of bottom is connected with tripod, and the mounting seat at top passes through a Double-end connecting piece and laser range finder is connected, and passes through Adjustment makes camera optical axis parallel with the optical axis of laser range finder；Industrial camera uses the cmos image sensing with global shutter Device, to eliminate the image deformation of moving target；The optical lens of camera uses the industrial tight shot of 8mm～16mm, to reduce The impact of non-linear aberration；Camera used USB 3.0 interface is connected with field data acquiring terminals such as panel computers；Laser ranging Instrument uses outdoor measurement type laser range finder, and measurement distance is better than 3mm more than 200m, range accuracy；Built-in measurement of dip angle module, Can measure the angle of pitch in the range of-45 °～+45 °, angle measurement accuracy is better than 0.1 °.

The present invention uses technique scheme, has the advantages that

1st, rapid deployment: compare existing method, it is not necessary at laying control point, two sides, river and use the equipment such as total powerstation to survey Observing and controlling point coordinates, greatly reduces workload, can complete measuring point and lay, be suitable for river flow, the determining of flow in several minutes Phase patrols the emergency monitoring surveyed and under extreme condition.

2nd, equipment is simple: only need a camera and a laser range finder with measurement of dip angle function, and without full station Complicated and the valuable instrument of surveying and mapping such as instrument or DGPS, not only reduces measurement cost and is easy to one-man service.

Brief description

Fig. 1 is the river water surface flow field calibrating method schematic diagram of the present invention, label title in figure: 1 is Measure section；2、3 For section marker post；4 is water level reference point；5 is image measuring device；6 is camera optical axis.

Fig. 2 is the image measuring device hardware architecture diagram of the present invention, label title in figure: 51 is industrial camera；52 For laser range finder；53 is Double-end connecting piece.

Fig. 3 be the present invention oblique viewing angle under lens imaging model schematic, (a) is pixel p_i,jIt is positioned at image far field Cross section view, (b) is pixel p_i,jBeing positioned at image near field cross section view, (c) is pixel p_i,jIt is positioned at the three-dimensional view on the left of image, D () is pixel p_i,jIt is positioned at the three-dimensional view on the right side of image.

Detailed description of the invention

It below in conjunction with specific embodiment, is further elucidated with the present invention, it should be understood that these embodiments are merely to illustrate the present invention Rather than restriction the scope of the present invention, after having read the present invention, the various equivalences to the present invention for the those skilled in the art The modification of form all falls within the application claims limited range.

The river water surface flow field calibrating method schematic diagram of the present invention is as shown in Figure 1.Method includes following five key steps:

(1) section marker post is set, Measure section 1 arranges the marker posts that two and the water surface intersect the 2nd, 3, is used for indicating Section direction, and using the intersection point of marker post 2 and the water surface as water level reference point 4；When being embodied as, for transform through side slope The artificial section of concrete, directly can draw in the two sides side slope of Measure section and be perpendicular to river course and crossing notable of the water surface Markings are used for replacing above-mentioned marker post；

(2) set up image measuring device, first an industrial camera and a laser range finder are connected and constitute imaging survey Amount device 5, and it is erected at side, riverbank；Secondly the position of tripod and the level of The Cloud Terrace are regulated so that individually change the angle of pitch The target spot of rear laser range finder can sighting target bar the 2nd, 3 successively, to guarantee that camera optical axis 6 is positioned on Measure section 1；Then use Laser range finder measures its oblique distance D arriving water level reference point 4 and angle of pitch δ, and is calculated range finding by built-in triangulation program Instrument is to the vertical range of the water surface:

H_L=D sin δ

Next select the suitable optical lens of focal length f and regulate the shooting angle of pitch so that viewing field of camera covers complete Measure section simultaneously has spatial resolution high as far as possible, and then obtains industry phase according to the current angle of pitch α ' of laser range finder The angle of pitch of machine optical axis:

α=α '+Δ α

Wherein, Δ α represents the angle difference between the two demarcated in advance；Finally calculate industrial camera to the water surface vertical away from From:

H=H_L-d·cosα

Wherein, d represents laser range finder measuring center to the distance of industrial camera imaging center；

(3) gather image sequence, after image measuring device is stable, with Δ t for time interval be continuously shot total when a length of T N width image is used for flow-speed measurement；

(4) demarcate the line start point distance that tests the speed, first read the piece image in image sequence, and according to the demand of testing the speed at figure The line L that tests the speed that I bar is parallel with downbeam and size is M × 1 is set along section direction in Xiang_i(1≤i≤I), with (x_i,y_i) table Show the image coordinate at line midpoint of testing the speed；Then image coordinate (the x of water level reference point 4 is extracted in the picture₀,y₀) survey as calculating The reference zero of speed line start point distance；Finally according to the lens imaging model under oblique viewing angle, utilize in image ordinate j from y₀Arrive y_iEach pixel image scale factor Δ Y (j) (m/pixel) in the Y direction demarcate the start point distance of the line that tests the speed:

${\mathrm{Dist}}_i=\underset{j=y_0}{\overset{y_i}{\&Sigma;}}\mathrm{\&Delta;}Y\left(j\right)=\underset{j=y_0}{\overset{y_i}{\&Sigma;}}H\&CenterDot;\{1/tan\&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-j-1)s}{f}\&rsqb;-1/tan\&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-j)s}{f}\&rsqb;\}$

Wherein, m × n represents the image resolution ratio of camera, and s represents the pixel dimension of imageing sensor；

(5) the line flow speed value that tests the speed is demarcated, for every the line L that tests the speed_i, first with the space of pixel on the line that tests the speed for horizontal seat Mark, the time of every two field picture are ordinate, set up the time-space image that size is M × N pixel；Then time-space image velocimetry is used Estimate to test the speed the size of motion vector on line:

$v_i=\frac{s_i}{T}=\frac{s_i}{N\&CenterDot;\mathrm{\&Delta;}t}=\frac{tan\mathrm{\&theta;}}{\mathrm{\&Delta;}t}$

Wherein, s_iThe pixel distance that expression time T internal object moves along downbeam, θ represents the texture master of time-space image Direction；Finally according to the lens imaging model under oblique viewing angle, utilize on the line that tests the speed pixel in the image scale factor of X-direction ΔX(y_i) demarcate the size of the physics flow velocity on line of testing the speed:

$V_i=v_i\&CenterDot;\mathrm{\&Delta;}X\left(y_i\right)=v_i\&CenterDot;\frac{Hs}{\sqrt{{\&lsqb;(n/2-y_i)s\&rsqb;}^2+f^2}}/tan\&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-y_i)s}{f}\&rsqb;$

Wherein, V_iThe positive and negative direction reflecting flow velocity on the line that tests the speed.

The image measuring device hardware architecture diagram of the present invention is as shown in Figure 2.The case top of industrial camera 51 and the end Portion all has one 1/4, and " mounting seat of screw, the mounting seat of bottom is connected with tripod, and the mounting seat at top passes through a double end Connector 53 and laser range finder 52 are connected, and make camera optical axis parallel with the optical axis of laser range finder 52 through adjustment.Industry Camera 1 uses the cmos image sensor with global shutter, to eliminate the image deformation of moving target；Can adopt when being embodied as The black and white industrial camera MV-CA013-20UM regarding by Haikang prestige, camera have employed the cmos image sensor of 1,300,000 pixels, figure As resolution ratio is 1280 × 1024 pixels, pixel dimension is 4.8 μm；The optical lens of camera uses the industry of 8mm～16mm fixed Zoom lens, to reduce the impact of non-linear aberration；The field data acquiring terminals such as camera used USB 3.0 interface and panel computer It is connected.Laser range finder 52 uses outdoor measurement type laser range finder, and measurement distance is better than 3mm more than 200m, range accuracy；In Putting measurement of dip angle module, can measuring the angle of pitch in the range of-45 °～+45 °, angle measurement accuracy is better than 0.1 °；Can adopt when being embodied as With the DISTO D5 type laser range finder of Leica company.

Under the oblique viewing angle of the present invention, lens imaging model schematic is as shown in Figure 3.Model describes camera primary optical axis OOO ' is perpendicular to X-direction and only exists the situation of the angle of pitch.Wherein, photo coordinate system is with (x y) represents, object plane coordinate System is represented by (X, Y)；O is the photocentre of lens plane, and o, O ' are respectively its subpoint in image plane and object plane；C is picture Plane extended line and the horizontal intersection point passing through photocentre；H is photocentre to the vertical range of object plane, and C is corresponding intersection point point； The angle of pitch α of camera is defined as the angle between camera primary optical axis and object plane.When object distance is much larger than image distance, focal length f and image distance Approximately equal, in image, coordinate is (i, pixel p j)_i,jImage scale factor can be with its object point P_i,jWith phase in X, Y-direction The distance of the corresponding object point of adjacent pixel represents, it may be assumed that

$\left\{\begin{array}{c}\mathrm{\&Delta;}X(i,j)=|X_{i+1,j}-X_{i,j}|\\ \mathrm{\&Delta;}Y(i,j)=|Y_{i,j+1}-Y_{i,j}|\end{array}\right.---\left(1\right)$

Assume pixel p_i,jBeing positioned at the far field (Fig. 3 a) of image, it is at y direction neighbor p_i.j+1Corresponding object point is used P_i,j+1Representing, 2 subpoints on the main ordinate of object plane are respectively P_jAnd P_j+1, it is respectively β and γ with the angle of object plane, Subpoint on the main ordinate of image plane is respectively p_jAnd p_j+1.According to formula (1), p_i,jImage scale factor in y direction can table It is shown as:

Δ Y (i, j)=P_j+1C-P_jC=H (1/tan γ-1/tan β) (2)

For subpoint p_j, meet following triangle relation:

$tan\&angle;p_{j}Oo=tan(\&angle;cOo-\&angle;{\mathrm{cOp}}_j)=\frac{p_{j}o}{Oo}=\frac{(j-n/2)s}{f}---\left(3\right)$

Wherein, s represents the pixel dimension of imageing sensor.Due to α=∠ cOo, β=∠ cOp_j, substitute into above formula and obtain:

$\mathrm{\&beta;}=\mathrm{\&alpha;}-\arctan \frac{(j-n/2)s}{f}---\left(4\right)$

In like manner, for subpoint p_j+1, have:

$\mathrm{\&gamma;}=\mathrm{\&alpha;}-\arctan \frac{(j+1-n/2)s}{f}---\left(5\right)$

Formula (4), formula (5) are substituted into formula (2):

$\mathrm{\&Delta;}Y(i,j)=\mathrm{\&Delta;}Y\left(j\right)=H\&CenterDot;\{1/tan\&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-j-1)s}{f}\&rsqb;-1/tan\&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-j)s}{f}\&rsqb;\}---\left(6\right)$

Owing to arctan () is odd function, work as pixel p_i,jAbove formula is met equally when being positioned at image near field (Fig. 3 b).

Assume pixel p_i,jBeing positioned at the left side (Fig. 3 c) of image, it is at x direction neighbor p_i+1.jCorresponding object point is used P_i+1,jRepresent, ray P_i,jO and P_i+1,jO and projection line P_jThe angle of O is used respectivelyRepresent with φ.According to formula (1), p_i,jIn x side To image scale factor be represented by:

For pixel p_i,j, meet following triangle relation::

$tan\&angle;p_{i,j}{\mathrm{Op}}_j=\frac{p_{i,j}{p}_j}{p_{j}O}=\frac{(m/2-i)s}{p_{j}O}---\left(8\right)$

Due to φ=∠ p_i,jOp_j, and:

$p_{j}O=\sqrt{{\left(p_{j}o\right)}^2+{\left(Oo\right)}^2}=\sqrt{{\&lsqb;(n/2-j)s\&rsqb;}^2+f^2}---\left(9\right)$

Substitution formula (8), has:

In like manner, for pixel p_j+1, have:

$tan\mathrm{\&phi;}=\frac{(m/2-i-1)s}{\sqrt{{\&lsqb;(n/2-j)s\&rsqb;}^2+f^2}}---\left(11\right)$

According to formula (4), have:

$tan\mathrm{\&beta;}=tan\&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-j)s}{f}\&rsqb;---\left(12\right)$

Formula (10), formula (11) and formula (12) are substituted into formula (7):

$\mathrm{\&Delta;}X(i,j)=\mathrm{\&Delta;}X\left(j\right)=\frac{Hs}{\sqrt{{\&lsqb;(n/2-j)s\&rsqb;}^2+f^2}}/tan\&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-j)s}{f}\&rsqb;---\left(13\right)$

Visible, and Δ X (i, j) unrelated with image coordinate i.Work as pixel p_i,jOn meeting equally when being positioned at (Fig. 3 d) on the right side of image Formula.

Claims (3)

1. the river water surface flow field calibrating method based on lens imaging model under oblique viewing angle, it is characterised in that include with Lower five key steps:

(1) section marker post is set, Measure section 1 arranges the marker posts that two and the water surface intersect the 2nd, 3, is used for indicating section Direction, and using the intersection point of marker post 2 and the water surface as water level reference point 4；

(2) set up image measuring device, first an industrial camera and a laser range finder are connected and constitute imaging measurement dress Put 5, and be erected at side, riverbank；Secondly the position of tripod and the level of The Cloud Terrace are regulated so that swash after individually changing the angle of pitch The target spot of optar can sighting target bar the 2nd, 3 successively, to guarantee that camera optical axis 6 is positioned on Measure section 1；Then laser is used Stadia surveying its to oblique distance D of water level reference point 4 and angle of pitch δ, and by built-in triangulation program calculate rangefinder to The vertical range of the water surface:

H_L=D sin δ

Next select the suitable optical lens of focal length f and regulate the shooting angle of pitch so that viewing field of camera covers complete measurement Section simultaneously has spatial resolution high as far as possible, and then obtains industrial camera light according to the current angle of pitch α ' of laser range finder The angle of pitch of axle:

α=α '+Δ α

Wherein, Δ α represents the angle difference between the two demarcated in advance；Finally calculating industrial camera is to the vertical range of the water surface:

H=H_L-d·cosα

Wherein, d represents laser range finder measuring center to the distance of industrial camera imaging center；

(3) gather image sequence, after image measuring device is stable, with Δ t for time interval be continuously shot total when a length of T N width Image is used for flow-speed measurement；

(4) the line start point distance that tests the speed is demarcated, first the piece image in reading image sequence, and according to the demand of testing the speed in the picture The line L that tests the speed that I bar is parallel with downbeam and size is M × 1 is set along section direction_i(1≤i≤I), with (x_i,y_i) represent and survey The image coordinate at speed line midpoint；Then image coordinate (the x of water level reference point 4 is extracted in the picture₀,y₀) test the speed line as calculating The reference zero of start point distance；Finally according to the lens imaging model under oblique viewing angle, utilize in image ordinate j from y₀To y_i's Each pixel demarcates, at image scale factor Δ Y (j) of section Y-direction, the start point distance of line of testing the speed:

${\mathrm{Dist}}_i=\underset{j=y_0}{\overset{y_i}{\&Sigma;}}\mathrm{\&Delta;}Y\left(j\right)=\underset{j=y_0}{\overset{y_i}{\&Sigma;}}H\&CenterDot;\left\{1/\tan \&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-j-1)s}{f}\&rsqb;-1/\tan \&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-j)s}{f}\&rsqb;\right\}$

Wherein, m × n represents the image resolution ratio of camera, and s represents the pixel dimension of imageing sensor；

(5) the line flow speed value that tests the speed is demarcated, for every the line L that tests the speed_i, first with the space of pixel on the line that tests the speed as abscissa, every frame The time of image is ordinate, sets up the time-space image that size is M × N；Then time-space image velocimetry is used to estimate to test the speed line The size of upper motion vector:

$v_i=\frac{s_i}{T}=\frac{s_i}{N\&CenterDot;\mathrm{\&Delta;}t}=\frac{tan\mathrm{\&theta;}}{\mathrm{\&Delta;}t}$

Wherein, s_iThe pixel distance that expression time T internal object moves along downbeam, θ represents the texture principal direction of time-space image； Finally according to the lens imaging model under oblique viewing angle, utilize on the line that tests the speed pixel in the image scale factor of following current X-direction ΔX(y_i) demarcate the size of the physics flow velocity on line of testing the speed:

$V_i=v_i\&CenterDot;\mathrm{\&Delta;}X\left(y_i\right)=v_i\&CenterDot;\frac{Hs}{\sqrt{{\&lsqb;(n/2-y_i)s\&rsqb;}^2+f^2}}/tan\&lsqb;\mathrm{\&alpha;}+\arctan \frac{(n/2-y_i)s}{f}\&rsqb;$

Wherein, V_iThe positive and negative direction reflecting flow velocity on the line that tests the speed.

2. the river water surface flow field calibrating method based on lens imaging model under oblique viewing angle according to claim 1, its It is characterised by, the artificial section for the concrete transformed through side slope, can directly draw in the two sides side slope of Measure section It is perpendicular to river course the distinctive marks line crossing with the water surface for replacing above-mentioned marker post.

3. the river water surface flow field calibrating method based on lens imaging model under oblique viewing angle according to claim 1, its Being characterised by, the case top of industrial camera 5 and bottom all have one 1/4 " mounting seat of screw, the mounting seat of bottom and three pin Frame is connected, and the mounting seat at top passes through a Double-end connecting piece 53 and laser range finder 52 is connected, and makes camera light through adjustment Axle is parallel with the optical axis of laser range finder；Industrial camera 51 uses the cmos image sensor with global shutter, to eliminate fortune The image deformation of moving-target；The optical lens of camera uses the industrial tight shot of 8mm～16mm, to reduce non-linear aberration Impact；Camera used USB 3.0 interface is connected with field data acquiring terminals such as panel computers；Laser range finder 2 uses outdoor Measurement type laser range finder, measurement distance is better than 3mm more than 200m, range accuracy；Built-in measurement of dip angle module, can measure pitching Angle is in the range of-45 °～+45 °, and angle measurement accuracy is better than 0.1 °.