CN100470215C - Measurement method and measurement system for video wave - Google Patents

Abstract

This invention relates to a image frequency wave measuring means and measuring system, which could process convenient digital image processing to collective sea surface image, to gain more wave measuring parameter. Method includes: pick sea surface image ( S1), pretreat image to enhance sea surface vein ( S2), isotropical cut sea surface image ( S30), execute Radon transform to gotten image ( S31), drawn wavelength parameter ( s32), pile time-time image follow wave propagating orientation ( s40), isotropic cut the time-stack image (S41), execute Radon transform to the gotten time-stack image ( s42), drawn wave direction, wave celerity, cycle parameter ( s43), outgoing wave direction, wave celerity, wavelength, cycle parameter ( s5) . The measuring system include sea surface image pick device, image processing and wave parameter extractpiston and measurement result final assembly.

Description

Video wave measuring method and measuring system

Technical field

The present invention relates to the ocean wave measuring technique, particularly relate to the method and system that adopts sequential frame image to carry out wave measurement.

Background technology

The generation of ocean wave and motion are one of modal physical phenomenons in the ocean, and wave measurement all is very important for marine engineering design, marine transportation and fishing operation, marine environmental forecasting and scientific research of seas etc.

Traditional ocean wave monitoring equipment is that wave-measuring sensor is directly put into seawater, comes the Measuring Oceanic wave parameter by the motion of detection seawater particle and the SEA LEVEL VARIATION on sea.Traditional ocean wave monitoring equipment adopts the spot measurement mode, and measurement range is little.Even multiple spot is laid surveying instrument, its measurement range also is limited, and measurement data data globality is poor.

Along with the development of remote sensing and telemetry, adopt the method for video image Measuring Oceanic wave parameter further to be used.With video image Measuring Oceanic parameter, with the metering system of traditional marine monitoring equipment relatively, the advantage that measurement range is big, globality is strong is arranged.At present the image that adopts multiple mode to obtain comprises the fixedly image etc. of camera head shooting of satellite remote sensing images, aircraft aviation photographic images, ship's navigation photographic images, bank or platform, can be used for the ocean wave parameter measurement.

Use the static information that video image can not only write down wave of the sea, but also write down the multidate information of wave of the sea, can measure the kinematic parameter of wave.In the sea level chart picture, crest has constituted the image texture structure with the different brightness of trough, particularly wave breaking generally all occurs in crest, the breaker whitecap is the pixel of high brightness in image, formed the wire textural characteristics of wave peak valley in the vertical direction of wave propagation direction, research wave video image can obtain the wave motion parameter.

The video image wave measurement research work of having reported at present comprises: by detecting the breaker whitecap that produces in the wave motion, follow the tracks of the crest band with high luminance values in Flame Image Process, obtain the method for kinematic parameter; By Fourier (Fourier) change detection wave motion intermediate frequency spectrum and related function, obtain the method for kinematic parameter; Separate the method that wave motion intermediate frequency spectrum anisotropy is obtained direction parameter by small echo (Wavelet) conversion.

But the video image wave measurement method of above-mentioned prior art exists problems such as calculation of complex, measurement parameter are few.

Summary of the invention

The existing problem of video image wave measurement method at above-mentioned prior art, the present invention releases the new video wave measuring method that digital video wave image is carried out more convenient processing, its purpose be by the isotropy clip image is carried out Radon conversion (Radon transform) and to the time stack image carry out the Radon conversion, to obtain the wave parameter of wave direction, velocity of wave, wavelength and period of wave.Simultaneously, the present invention also releases the video wave measuring system of implementing above-mentioned video wave measuring method.

Video wave measuring method involved in the present invention is to handle and extract the wave parameter of wave direction, velocity of wave, wavelength, period of wave etc. by the wave of the sea image that computing machine is taken ccd video camera.Described video wave measuring method may further comprise the steps:

1, gathers the sea level chart picture

Take the sea level chart picture with ccd video camera, then image data transmission is arrived computing machine.

2, pretreatment image strengthens the sea texture

Sea level chart is looked like to carry out pre-service,, take the method for enhancing contrast ratio to strengthen the sea texture, improve image picture quality for darker image.

3, isotropy clip image

The sea level chart picture that strengthens texture is sheared maximum available circular image in the original image scope, realize that the isotropy of sea level chart picture is sheared.

4, image is carried out the Radon conversion

The image that isotropy is sheared is carried out the Radon conversion, is projected image in the Radon transform domain with digital service unit.

Be specially: in two dimensional image plane, the definition coordinate system is the coordinate axis of horizontal direction with the x axle, is the coordinate axis of vertical direction with the y axle, and (x is in (x, the brightness of image of y) locating y) to f.The Radon conversion is that (x is y) on same two dimensional image plane, along the transform method of projection on the specified angle directions of rays for the computed image function f.(x, projection y) is it in line integral of determining on the direction to image function f, and the pixel intensity in the image is carried out the result of integration gained, is the drop shadow intensity in the Radon transform domain.For example, and f (x, y) two-dimentional line integral in vertical direction is exactly f (x, y) projection on the x axle; (x, y) two-dimentional line integral in the horizontal direction is exactly f (x, y) projection on the y axle to f.Can (this that is to say for x, projection y), all has function f (x, Radon conversion y) on arbitrarily angled along 0 °～360 ° arbitrarily angled θ computing function f.If the coordinate system that x axle and y axle are formed is the center at grade with the initial point, rotates with angle θ, the x axle is an x ' axle with angle θ rotation gained, the y axle is a y ' axle with angle θ rotation gained, thereby an x ' axle and a new coordinate system of y ' axle composition, here define f (x, y) angle be the Radon conversion of θ be f (x y) is parallel to a projection line integration on x ' axle of y ' axle:

$R_{\mathrm{\θ}}(x\′)={\∫}_{-\∞}^{\∞}f(x\′\cos \mathrm{\θ}-y\′\sin \mathrm{\θ},x\′\sin \mathrm{\θ}+y\′\cos \mathrm{\θ})\mathrm{dy}\′$

In the formula:

$\left[\begin{array}{c}x\′\\ y\′\end{array}\right]=\left[\begin{array}{cc}\cos \mathrm{\θ}& \sin \mathrm{\θ}\\ -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]\left[\begin{array}{c}x\\ y\end{array}\right]$

With angle θ is that the projected image in the width of cloth Radon transform domain is made in the Radon conversion of variable, and its transverse axis is angle θ, and the longitudinal axis is x ', the intensity R of the projection line integration of Radon conversion _θ(x ') is exactly the projected image brightness in the Radon transform domain.

5, extract wavelength parameter

Go up the extraction wavelength parameter in wave propagation orientation (Orientation).

In the projected image in the Radon transform domain, detect maximum intensity R _θ(x ') extracts maximum intensity R in the Radon transform domain _θThe angle θ that (x ') is corresponding _M, θ _MBe the wave propagation orientation.θ _MThere is ± 180 ° polysemy in the angle, may be along the wave propagation direction, also may be the head sea wave direction of propagation.

That the extraction wavelength parameter is selected for use on the wave propagation orientation is the θ that is orientated along wave propagation _MThe angle, that is, with the corresponding angle θ of wave progresses path parallel direction _MIntensity in detected intensity peak value or valley, calculate peak separation or valley spacing to draw wavelength.

Stack image when 6, piling up

From the sea level chart picture that strengthens texture, according to the corresponding angle θ of wave progresses path parallel direction _MIntercepting line strip image slices on the wave propagation orientation, again the continuous adjacent frame is used the same manner intercepting line strip image slices at the same position place, and to the linear image slices of continuous adjacent frame, time sequencing according to original picture frame, be similar to the push operation process of computing machine, one by one the linear image slices piled up, stack when being integrated into (time-stack) image.

7, to the time stack image carry out isotropy and shear

When two dimension, shear maximum available circular image in the image range of the stack plane of delineation.

8, to the time stack image carry out the Radon conversion

To cut time stack image carry out the Radon conversion, be projected image in the Radon transform domain with digital service unit.

9, extract wave direction, velocity of wave, cycle parameter

In the projected image in the Radon transform domain, detect maximum intensity;

Extract the angle of maximum intensity correspondence in the Radon transform domain, determine that according to this angle value with on the wave propagation orientation direction of wave propagation is wave direction;

The angle of the maximum intensity correspondence of in the Radon transform domain, extracting, according to this angle value calculate corresponding the time the slope of the crest direction of propagation in the stack image, obtain velocity of wave; Calculate the merchant of wavelength and velocity of wave again, obtain the cycle.

10, output wave parameter

According to pairing the earth yardstick of actual imaging and orientation angle, the wave parameter of extracting is converted to actual terrestrial coordinate, and on output unit, shows and printing.The wave parameter of output is wave direction, velocity of wave, wavelength, cycle.

Video wave measuring system involved in the present invention comprises sea image collecting device, Flame Image Process and wave parameter extraction element and measurement result output unit.

The sea image collecting device is a ccd video camera, has the data transfer mode or the embedded network transmission mode of USB, IEEE1394 (Firewire) standard, view data can be transferred to computing machine directly, fast.The sea image collecting device is installed in above beacon, ocean platform, offshore buildings or the support etc. that are higher than the sea, and taking lens is taken the sea image sequence of measured zone to the locating tab assembly sea.

Flame Image Process and wave parameter extraction element are made of microcomputer, have the function of implementing above-mentioned video wave measuring method: pretreatment image strengthens the sea texture, the isotropy clip image, stack image when piling up, to the sea level chart picture and the time stack image carry out the Radon conversion, extract wave parameters such as wavelength, wave direction, velocity of wave, cycle in the wave propagation orientation.

The measurement result output unit is display and the printer that is connected with the microcomputer of Flame Image Process and wave parameter extraction element, can wave parameters such as wave direction, velocity of wave, wavelength, cycle be converted to actual terrestrial coordinate according to pairing the earth yardstick of actual imaging and orientation angle.

Video wave measuring method involved in the present invention and measuring system can look like to carry out video digital images processing more easily to the sea level chart of gathering, to obtain more wave measurement parameter.

Description of drawings

Fig. 1 is the process flow diagram of the video wave measuring method that the present invention relates to.

Fig. 2 is the block diagram of the video wave measuring system that the present invention relates to.

Fig. 3 is the wave simulation image graph.

Fig. 4 shears the image that obtains to Fig. 3 image isotropy.

Fig. 5 carries out the intensity map that the Radon conversion obtains to Fig. 4 image.

Fig. 6 is the intensity that Fig. 5 detection peak intensity corresponding angle is obtained.

Fig. 7 is along wave propagation orientation intercepting line strip image slices and piles up stack image when obtaining.

Fig. 8 shears the image that obtains to Fig. 7 image isotropy.

Fig. 9 carries out the intensity map that the Radon conversion obtains to Fig. 8 image.

Description of symbols in the accompanying drawing:

S ₁, gather sea level chart as S ₂, pretreatment image

S ₃₀, isotropy clip image S ₃₁, image is carried out the Radon conversion

S ₃₂, extract wavelength parameter S ₄₀, stack image when piling up

S ₄₁, to the time stack image isotropy shear S ₄₂, to the time stack image carry out the Radon conversion

S ₄₃, extract wave direction, velocity of wave, cycle S ₅, output wave parameter

The projection straight line distance of the angle x ' of θ, Radon conversion, Radon conversion

The intensity of R ', peak strength corresponding angle

Embodiment

Now in conjunction with the accompanying drawings the present invention is done further detailed elaboration.

Fig. 1 shows the process flow diagram of the video wave measuring method that the present invention relates to.Fig. 3～Fig. 9 shows the image of handling in the video wave measuring method application process of the present invention.

As shown in Figure 1, the video wave measuring method may further comprise the steps:

S ₁-collection sea level chart picture

Fig. 3 is the wave simulation image, is that the brightest pixel is represented crest according to a two field picture of the numerical simulation image of linear water waves theory, and the darkest pixel is represented trough.

S ₂-pretreatment image strengthens the sea texture

S ₃₀-isotropy clip image

Because the image that collects has isotropy or anisotropic feature, for making method isotropy of the present invention, the image execution is sheared based on the isotropy of circle, in image range, shear maximum available circular image.Fig. 4 shears the image that obtains to Fig. 3 image isotropy.

S ₃₁-to cut image carry out the Radon conversion

The Radon conversion has the advantages that to be projected in 360 ° of circles along 180 ° of symmetries, so computational short cut is in 180 ° of scopes.Fig. 5 is the projected image in the Radon transform domain that obtains by the conversion to Fig. 4 image execution Radon.The initial point of digital picture coordinate axis is at the center of image, is that the center is 1 ° of rotation counterclockwise with angle step with the initial point with the digital picture coordinate axis, is the projection of Radon transform domain with digital service unit in 180 ° of scopes.

S ₃₂-extraction wavelength parameter

In the projected image in the Radon transform domain, detect maximum intensity.Among Fig. 5, at angle θ ₁=123 ° peak value occurs, extract the angle of maximum intensity correspondence in the Radon transform domain.Among Fig. 5, for the angle θ that extracts according to grain direction ₁=123 °, can not determine wave propagation be from upper left to the bottom right, still from the bottom right to upper left, therefore there is ± 180 ° polysemy in this angle, may be the direction along wave propagation, also may be the direction that the head sea wave is propagated, and this time is to obtain along wave propagation to be orientated.Fig. 6 is this angle intensity by Fig. 5 detection peak intensity corresponding angle is obtained, detected intensity peak value or valley in the intensity that is orientated corresponding angle along wave propagation, and calculating peak separation or valley spacing draw the wavelength result and are L=32.29.

S ₄₀-stack image when wave propagation orientation is piled up

Along wave propagation orientation intercepting line strip image slices, again the continuous adjacent frame is used the same manner intercepting line strip image slices at the same position place, and to the linear image slices of continuous adjacent frame, time sequencing according to original picture frame, to be similar to the push operation process of computing machine, one by one the linear image slices is piled up stack image when being integrated into.Fig. 7 is for passing through along wave propagation orientation θ ₁=123 ° of intercepting line strip image slices are also piled up stack image when obtaining, and time sequencing is for from top to bottom.

S ₄₁-to the time stack image isotropy shear

To the time stack image carry out the isotropy clip image, in image range, shear maximum available circular image.Fig. 8 shears the image that obtains to Fig. 7 image isotropy.

S ₄₂-to cut time stack image carry out the Radon conversion

To cut time stack image carry out the Radon conversion.Fig. 9 is the projected image in the Radon transform domain that obtains by the conversion to Fig. 8 image execution Radon.

S ₄₃-extract wave direction, velocity of wave, cycle

In the projected image in the Radon transform domain, detect maximum intensity.Among Fig. 9, at angle θ ₂=172 ° peak value occurs; Extract the angle of maximum intensity correspondence in the Radon transform domain.Among Fig. 9, according to angle θ ₂=172 ° angle value and along the orientation θ of wave propagation ₁=123 °, determine the direction of wave propagation, be specially and calculate tan θ ₂=-0.14, symbol is for negative, and the direction of promptly judging wave propagation to upper left, is determined wave direction=123 ° from the bottom right.The angle θ of the maximum intensity correspondence of in the Radon transform domain, extracting ₂=172 °, according to this angle value calculate corresponding the time the slope tan θ of the crest direction of propagation in the stack image ₂=-0.14, and calculate velocity of wave=0.14, cycle=229.72.

S ₅-output wave parameter: wave direction, velocity of wave, wavelength, cycle

Output wave parameter: wave direction=123 °, velocity of wave=0.14, wavelength=32.29, cycle=229.72.According to pairing the earth yardstick of actual imaging and orientation angle, wave parameter can be converted to actual terrestrial coordinate.

Fig. 2 is the block diagram of the video wave measuring system that the present invention relates to.As shown in Figure 2, the ingredient of video wave measuring system comprises sea image collecting device, Flame Image Process and wave parameter extraction element and measurement result output unit.

The sea image collecting device can be transferred to view data the microcomputer of composing images processing and wave parameter extraction element directly, fast, and the measurement result output unit is display and the printer that is connected with the microcomputer of Flame Image Process and wave parameter extraction element.

Claims (9)

1, a kind of video wave measuring method is characterized in that comprising: gather sea level chart picture (S ₁), pretreatment image strengthens sea texture (S ₂), isotropy is sheared sea level chart picture (S ₃₀), to cut image carry out Radon conversion (S ₃₁), extract wavelength parameter (S ₃₂), stack image (S when on the wave propagation orientation, piling up ₄₀), to the time stack image isotropy shear (S ₄₁), to cut time stack image carry out Radon conversion (S ₄₂), extract wave direction, velocity of wave, cycle parameter (S ₄₃), output wave is to, velocity of wave, wavelength, cycle parameter (S ₅).

2, video wave measuring method according to claim 1 is characterized in that, gathers sea level chart picture (S ₁) be to take the sea level chart picture with ccd video camera, then image data transmission is arrived computing machine.

3, video wave measuring method according to claim 1 is characterized in that, image is carried out Radon conversion (S ₃₁) be that the image that isotropy is sheared is carried out the Radon conversion, be projected image in the Radon transform domain with digital service unit.

4, video wave measuring method according to claim 1 is characterized in that, extracts wavelength parameter (S ₃₂) be on wave propagation orientation, to extract wavelength parameter, with the corresponding angle θ of wave progresses path parallel direction _MIntensity in detected intensity peak value or valley, calculate peak separation or valley spacing to draw wavelength.

5, video wave measuring method according to claim 1 is characterized in that, stack image (S when piling up ₄₀) be corresponding angle θ according to wave progresses path parallel direction _MIntercepting line strip image slices on the wave propagation orientation, again the continuous adjacent frame is used the same manner intercepting line strip image slices at the same position place, and to the linear image slices of continuous adjacent frame, time sequencing according to original picture frame is one by one piled up the linear image slices, stack image when being integrated into.

6, video wave measuring method according to claim 1 is characterized in that, to the time stack image carry out Radon conversion (S ₄₂) be to isotropy shear circular the time stack image carry out the Radon conversion, be projected image in the Radon transform domain with digital service unit.

7, video wave measuring method according to claim 1 is characterized in that, extracts wave direction, velocity of wave, cycle parameter (S ₄₃) comprising: in the projected image in the Radon transform domain, detect maximum intensity; Extract the angle of maximum intensity correspondence in the Radon transform domain, determine that according to this angle value with on the wave propagation orientation direction of wave propagation is wave direction; According to the angle value of the maximum intensity correspondence of extracting in the Radon transform domain, calculate corresponding the time the slope of the crest direction of propagation in the stack image, obtain velocity of wave; Calculate the merchant of wavelength and velocity of wave again, obtain the cycle.

8, video wave measuring method according to claim 1 is characterized in that, output wave parameter (S ₅) be according to pairing the earth yardstick of actual imaging and orientation angle, the wave parameter of extracting is converted to actual terrestrial coordinate, and shows on output unit and printing that the wave parameter of output is wave direction, velocity of wave, wavelength, cycle.

9, a kind of video wave measuring system of implementing video wave measuring method according to claim 1 is characterized in that, comprises sea image collecting device, Flame Image Process and wave parameter extraction element and measurement result output unit; The sea image collecting device is a ccd video camera, has the data transfer mode or the embedded network transmission mode of USB, IEEE1394 (Firewire) standard, view data can be transferred to computing machine directly, fast; Flame Image Process and wave parameter extraction element are made of microcomputer, have the function of implementing above-mentioned video wave measuring method; The measurement result output unit is display and the printer that is connected with the microcomputer of Flame Image Process and wave parameter extraction element, according to pairing the earth yardstick of actual imaging and orientation angle wave parameters such as wave direction, velocity of wave, wavelength, cycle is converted to actual terrestrial coordinate.

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