CN103345759B - Accurate detection method for submarine large complex sandwave landforms - Google Patents

Abstract

The invention discloses a survey research method for hydrographic surveying and charting and submarine landforms, and specifically relates to an accurate detection method for submarine large complex sandwave landforms. The method disclosed by the invention comprises the following steps: through a specific detecting instrument, determining the layout of a tide station, and carrying out sound velocity profile survey; then, carrying out submarine sandwave landform detection; establishing a submarine DDM according to detected data; carrying out sandwave character extraction based on the submarine DDM; and finally, carrying out profile-based sandwave FFT (fast Fourier transform algorithm) decomposition and fitting. The method disclosed by the invention has the advantages that a fine detection scheme for submarine sandwave characters is solved, and a frequency decomposition and fitting method for submarine sandwaves is further given. The method disclosed by the invention has an important practical application value in marine engineering construction, hydrographic surveying and charting, oceanographic survey, and submarine scientific researches, and achieves an actual application effect in the detection, decomposition and fitting of various sandwaves such as cycloid sandwaves, bimodal sandwaves and cosine sandwaves and the like.

Description

The accurate detection method of the large complicated bed ripples landforms in a kind of seabed

Technical field

The present invention relates to the technical fields such as marine charting, the research of submarine topography topographic feature survey and submarine science, specifically refer to the accurate detection method of the large complicated bed ripples landforms in a kind of seabed.

Background technology

Seabed sand waves is a kind of seabed form extensively distributing under trend environment, is the extremely strong sea-bed topography type of a kind of activity, and the appearance of seabed sand waves has characterized the intense activity in seabed.Bed ripples is grown the characteristic morphology on the bed surface of seabed, is to adapt to current shear action to produce the form that distortion changes bed surface pests occurrence rule thereby be considered to seabed bed surface sediment.Feature and the rule of research bed ripples, safety assessment for the construction of the oceanographic engineering such as subsea pipeline and oil platform has extremely important using value, the seabed sand waves of high behaviour area easily causes the even unstability of oil platform of suspended span of subsea pipeline, even causes pipeline breakage and platform to collapse when serious.

Multibeam echosounding (MBES, Multi-Beam Echo Sounding) technology represents the high-tech achievement of contemporary depth measurement field recent development, is the complicated integrated total system merging with multi-source data height of multisensor.Multibeam sounding system, in the rudiment sixties of 20th century in USN's demand, starts commercialization the eighties, introduces China large-scale application the nineties.Multibeam echosounding has the distinguishing feature of high resolving power, high precision, high-level efficiency and all standing compared with traditional single beam depth measurement.This technology is widely used in the investigation of seabed bathymetric survey and topography and geomorphology at present, as the detection of seabed sand waves, dune ridge landforms etc.

Seabed sand waves form and complex genesis, the widely different bed ripples of scale often being caused by different dynamic is superimposed, and some type bed ripples is stable, and some bed ripples is high activity.How to take rational technical method accurately to survey seabed sand waves, decompose the composition of bed ripples, very helpful for the origin cause of formation that discloses seabed sand waves, and then provide reliable suggestion and foundation for the enforcement of seabed engineering.From the open source information analysis of retrieval, there is no at present with the on all four method of the present invention and be applicable to seabed sand waves detection and resolution problem.

Summary of the invention

The present invention is directed to Seafloor Sandwaves and be difficult to accurate detection and complicated components problem, propose accurate detection and the FFT decomposition method of the large complicated bed ripples landforms in seabed.

The present invention is achieved by following technical proposals:

The accurate detection of the large complicated bed ripples landforms in seabed and FFT decomposition method, comprise the following steps:

Step 1: seabed sand waves is prepared before surveying

(1) equipment Inspection and demarcation: multibeam sounding system is a kind of submarine topography landforms detection system of complexity; select multi-beam detectoscope, length measuring instrument, sound velocimeter etc.; before measuring, all appts equipment all need carry out self-correcting or send legal metering mechanism to demarcate according to standard GB/T/T12763.10-2007; to guarantee that all the sensors, in normal operating conditions, guarantees that accuracy of instrument meets GB requirement.The total accuracy of sounding of multiple-beam system reaches even centimetre-sized of decimeter grade, and GPS positioning precision reaches sub-meter grade or decimeter grade.

(2) lay at tidal level station: lay 2～4 interim tidal stations around bed ripples measurement zone, obtain interim tide gauge Tide={tide _i} _i=1,4, survey district's tidal level to control.

(3) Sound speed profile is measured: start, before exploration, must near Ce district, carry out Sound speed profile measurement, at least obtain and survey one, district Sound speed profile Svp={v _i} _{i=1, n1}, n1 is the Sound speed profile number of plies.

Step 2: Seafloor Sandwaves is surveyed

Take rectangular area wire laying mode to carry out the multi-beam echo sounding of seabed sand waves.In laying rectangular area, bed ripples district, the long limit of rectangle should be moved towards by parallel bed ripples, the vertical bed ripples trend of minor face, and the horizontal expansion that the long limit A of rectangle should be greater than bed ripples is apart from l, and the minor face B of rectangle should be greater than the twice of bed ripples wavelength d.Require line navigation, ship's speed 6 joint left and right, driftage is less than 5m, the exploration of multi-beam full opened corner, omnidistance GPS has differential signal.Form and survey raw data set Raw={raw _i.

Step 3: build seabed DDM

(1) data processing: to the raw data set Raw={raw obtaining _icarry out after the processing such as tidal level correction, drinking water correction, correction of sounding wave velocity and noise spot editor the discrete bathymetric data set Proc={ (x after formation processing _i, y _i, z _i) _{i=1, n}, data demand after treatment retains all available discrete beam points as far as possible.

(2) build DDM:IDW (Inverse Distance Weighted) method discrete bathymetric data set Proc is processed, form DDM={dep _{(i, j)}} _{i=1, n, j=1, m}.

IDW method computing formula is:

${\mathrm{dep}}_{(i,j)}=\left[\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{w}_k{z}_k\right]/\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{w}_k;$

$w_k=1/d_k^2;$

$d_k=\sqrt{{(x_{(i,j)}-x_k)}^2+{(y_{(i,j)}-y_k)}^2}$

In formula, x _k, y _k, z _kfor horizontal ordinate, ordinate and the water depth value of discrete depth of water point, from set Proc.W _kfor the weighted value of discrete bathymetric data point.Dep _{(i, j)}for grid value, x _{(i, j)}and y _{(i, j)}for grid horizontal ordinate and ordinate value.

Step 4: the bed ripples feature extraction based on DDM

(1) graphing: on drawing formation system, draw seabed three-dimensional land map based on the seabed DDM building.

(2) Pick up Profile: based on three-dimensional land map, observation seabed sand waves trend.Vertical bed ripples trend, builds and extracts terrain section line, forms topographic profile data acquisition Prof={x _i, y _i, dis _i, z _i} _{i=1, n2}, n2 is that topographic profile is counted, x _i, y _i, dis _iand z _ibe respectively the coordinate figure of section point, apart from threshold value and water depth value.

(3) profile drawing: based on data acquisition Prof={x _i, y _i, dis _i, z _i} _{i=1, n2}, with dis _iand z _ifor horizontal ordinate and ordinate are drawn topographic profile.

Step 5: the bed ripples based on section decomposes and matching

The present invention adopts Fast Fourier Transform (FFT) (FFT) to decompose seabed sand waves bed ripples section, carrys out matching in the spike part of bed ripples with cycloid equation.

(1) bed ripples topographic profile decomposes and matching

The topographic profile Prof={x obtaining on step 4 basis _i, y _i, dis _i, z _i} _{i=1, n2}, adopt FFT function f (x) to carry out matching.F (x) is the combination by a series of sine function and cosine function.

f(x)=f ₁(x)+f ₂(x)

$f_1\left(x\right)={\mathrm{\Σ}}_{k=1}^8{b}_k\sin \left(\mathrm{kx}\right)$

$f_2\left(x\right)=a_0+{\mathrm{\Σ}}_{k=1}^8{a}_k\cos \left(\mathrm{kx}\right)$

F ₁(x) odd function sine series, f ₂(x) be even function cosine series.

A ₀for initial offset values, a _kand b _kbe respectively the component parameters of FFT function, need to actual bed ripples topographic profile curve Prof={x _i, y _i, dis _i, z _i} _{i=1, n2}after matching, determine;

In the ridge peak of bed ripples part, adopt cycloid equation to carry out matching, cycloid equation is as follows:

$\left\{\begin{array}{c}x=\frac{\mathrm{\λ}}{2\mathrm{\π}}(t-k\sin t)\\ d=d_u+A(1-\cos t)\end{array}\right.$

X is horizontal shift; D is the depth of water; T is angle parameter; λ is bed ripples wavelength; A is bed ripples amplitude (half of bed ripples wave height); K is the undetermined parameter relevant with bed ripples form; d _ufor the bed ripples crest place depth of water.

(2) contrast before and after the matching of bed ripples topographic profile

By forming new topographic profile Prof after step (1) matching ₁={ x1 _i, y1 _i, dis1 _i, z1 _i} _{i=1, n2}, with former landform profile P rof={x _i, y _i, dis _i, z _i} _{i=1, n2}counted identically, then adopt section stack control methods to observe fitting effect, synchronously adopt section differential technique quantitatively to judge the effect of decomposing with matching.

In section depth of water difference before and after matching, error is:

In section depth of water difference number percent before and after matching, error is:

In the time of △ δ > δ, return to step (1) matching again.δ is external variable, by the given initial value of system, can be modified as required by user.When this step cycle number of times reaches n3 time, automatically increase δ value, and return to step (1).N3 is external variable, can be revised by user, but can given initial value.

In the time of △ δ < δ, record bed ripples and decompose and fitting parameter, power cut-off.

Beneficial effect

Distinguishing feature of the present invention is based on multibeam echosounding technology, adopts the navigation positioning system of sub-meter grade precision, has realized the accurate detection of seabed sand waves topography and geomorphology.For disclosing the fine-feature of bed ripples, adopt the mode of rectangular area to survey.On this basis, adopt IDW method to carry out the gridding of multibeam bathymetric data, and based on DDM, vertical bed ripples moves towards to extract topographic profile, and then based on topographic profile, adopt FFT and the cycloid equation mode of combining to decompose and matching seabed sand waves.This invention has solved the meticulous detecting strategy of seabed sand waves feature, has further provided frequency resolution and the approximating method of seabed sand waves.This invention has important actual application value in marine charting, oceanographic survey and submarine science research.

Accompanying drawing explanation

Fig. 1 workflow diagram of the present invention

Fig. 2 gerotor type bed ripples of the invention process decomposes and fitted figure

Fig. 3 bimodal molded line bed ripples of the invention process decomposes and fitted figure

Fig. 4 longitudinal cosine type bed ripples of the invention process decomposes and fitted figure

Embodiment

Illustrate below in conjunction with enforcement of the present invention:

Embodiment 1

Accurate detection and the FFT decomposition method of the large complicated bed ripples landforms in seabed are realized according to following step.

Detailed step of the present invention and flow process are as shown in Figure 1.

Step 1: seabed sand waves is prepared before surveying

(1) equipment Inspection and demarcation: multibeam sounding system is a kind of submarine topography landforms detection system of complexity; select multi-beam detectoscope, length measuring instrument, sound velocimeter; before measuring, all appts equipment all need carry out self-correcting or send legal metering mechanism to demarcate according to standard GB/T/T12763.10-2007; to guarantee that all the sensors, in normal operating conditions, guarantees that accuracy of instrument meets GB requirement.The total accuracy of sounding of multiple-beam system reaches decimeter grade, and GPS positioning precision reaches sub-meter grade.

(2) lay at tidal level station: lay 2 interim tidal stations around bed ripples measurement zone, obtain interim tide gauge Tide={tide _i} _i=1,4, survey district's tidal level to control.

(3) Sound speed profile is measured: start, before exploration, must near Ce district, carry out Sound speed profile measurement, at least obtain and survey one, district Sound speed profile Svp={v _i} _{i=1, n1}, n1 is the Sound speed profile number of plies.

Step 2: Seafloor Sandwaves is surveyed

Take rectangular area wire laying mode to carry out the multi-beam echo sounding of seabed sand waves.In laying rectangular area, bed ripples district, the long limit of rectangle should be moved towards by parallel bed ripples, the vertical bed ripples trend of minor face, and the horizontal expansion that the long limit A of rectangle should be greater than bed ripples is apart from l, and the minor face B of rectangle should be greater than the twice of bed ripples wavelength d.Require line navigation, ship's speed 6 joint left and right, driftage is less than 5m, the exploration of multi-beam full opened corner, omnidistance GPS has differential signal.Form and survey raw data set Raw={raw _i.

Step 3: build seabed DDM

(3) data processing: to the raw data set Raw={raw obtaining _icarry out after the processing such as tidal level correction, drinking water correction, correction of sounding wave velocity and noise spot editor the discrete bathymetric data set Proc={ (x after formation processing _i, y _i, z _i) _{i=1, n}, data demand after treatment retains all available discrete beam points as far as possible.

(4) build DDM:IDW (Inverse Distance Weighted) method discrete bathymetric data set Proc is processed, form DDM={dep _{(i, j)}} _{i=1, n, j=1, m}.

IDW method computing formula is:

${\mathrm{dep}}_{(i,j)}=\left[\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}{w}_k{z}_k\right]/\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}{w}_k;$

$w_k=1/d_k^2;$

$d_k=\sqrt{{(x_{(i,j)}-x_k)}^2+{(y_{(i,j)}-y_k)}^2}$

In formula, x _k, y _k, z _kfor horizontal ordinate, ordinate and the water depth value of discrete depth of water point, from set Proc.W _kfor the weighted value of discrete bathymetric data point.Dep _{(i, j)}for grid value, x _{(i, j)}and y _{(i, j)}for grid horizontal ordinate and ordinate value.

Step 4: the bed ripples feature extraction based on DDM

(1) graphing: on drawing formation system, draw seabed three-dimensional land map based on the seabed DDM building.

(2) Pick up Profile: based on three-dimensional land map, observation seabed sand waves trend.Vertical bed ripples trend, builds and extracts terrain section line, forms topographic profile data acquisition Prof={x _i, y _i, dis _i, z _i} _{i=1, n2}, n2 is that topographic profile is counted, x _i, y _i, dis _iand z _ibe respectively the coordinate figure of section point, apart from threshold value and water depth value.

(3) profile drawing: based on data acquisition Prof={x _i, y _i, dis _i, z _i} _{i=1, n2}, with dis _iand z _ifor horizontal ordinate and ordinate are drawn topographic profile.

Step 5: the bed ripples based on section decomposes and matching

The present invention adopts Fast Fourier Transform (FFT) (FFT) to decompose seabed sand waves bed ripples section, carrys out matching in the spike part of bed ripples with cycloid equation.

(1) bed ripples topographic profile decomposes and matching

The topographic profile Prof={x obtaining on step 4 basis _i, y _i, dis _i, z _i} _{i=1, n2}, adopt FFT function f (x) to carry out matching.F (x) is the combination by a series of sine function and cosine function.

f(x)=f ₁(x)+f ₂(x)

$f_1\left(x\right)={\mathrm{\&Sigma;}}_{k=1}^8{b}_k\sin \left(\mathrm{kx}\right)$

$f_2\left(x\right)=a_0+{\mathrm{\&Sigma;}}_{k=1}^8{a}_k\cos \left(\mathrm{kx}\right)$

F ₁(x) odd function sine series, f ₂(x) be even function cosine series.

In the ridge peak of bed ripples part, adopt cycloid equation to carry out matching, cycloid equation is as follows:

$\left\{\begin{array}{c}x=\frac{\mathrm{\&lambda;}}{2\mathrm{\&pi;}}(t-k\sin t)\\ d=d_u+A(1-\cos t)\end{array}\right.$

X is horizontal shift; D is the depth of water; T is angle parameter; λ is bed ripples wavelength; A is bed ripples amplitude (half of bed ripples wave height); K is the undetermined parameter relevant with bed ripples form; d _ufor the bed ripples crest place depth of water.

(2) contrast before and after the matching of bed ripples topographic profile

By forming new topographic profile Prof after step (1) matching ₁={ x1 _i, y1 _i, dis1 _i, z1 _i} _{i=1, n2}, with former landform profile P rof={x _i, y _i, dis _i, z _i} _{i=1, n2}counted identically, then adopt section stack control methods to observe fitting effect, synchronously adopt section differential technique quantitatively to judge the effect of decomposing with matching.

In section depth of water difference before and after matching, error is:

In section depth of water difference number percent before and after matching, error is:

In the time of △ δ > δ, return to step (1) matching again.δ is external variable, by the given initial value of system, can be modified as required by user.When this step cycle number of times reaches n3 time, automatically increase δ value, and return to step (1).N3 is external variable, can be revised by user, but can given initial value.

In the time of △ δ < δ, record bed ripples and decompose and fitting parameter, power cut-off.

Adopt the method to gerotor type bed ripples, as shown in Figure 2, bimodal pattern bed ripples, as shown in Figure 3 with longitudinal cosine type bed ripples, wait as shown in Figure 4 three kinds of compound type bed ripples to carry out effective decomposition and matching.

Claims (1)

1. an accurate detection method for the large complicated bed ripples landforms in seabed, is characterized in that comprising the following steps: step 1: seabed sand waves is prepared before surveying

(1) select multi-beam detectoscope, length measuring instrument, sound velocimeter, the rower of going forward side by side is fixed;

(2) lay 2～4 interim tidal stations around bed ripples measurement zone, survey district's tidal level to control;

(3) near Ce district, carry out Sound speed profile measurement, at least obtain and survey one, district Sound speed profile;

Step 2: Seafloor Sandwaves is surveyed

Take rectangular area wire laying mode to carry out the multi-beam echo sounding of seabed sand waves; In laying rectangular area, bed ripples district, the long limit of rectangle should be moved towards by parallel bed ripples, the vertical bed ripples trend of minor face, and the horizontal expansion that the long limit A of rectangle should be greater than bed ripples is apart from l, and the minor face B of rectangle should be greater than the twice of bed ripples wavelength d; Detection direction is line navigation, the exploration of multi-beam full opened corner, and omnidistance GPS has differential signal; Form and survey raw data set Raw={raw _i;

Step 3: build seabed DDM

(1) to the raw data set Raw={raw obtaining _iprocess, form discrete bathymetric data set Proc={ (x _i, y _i, z _i) _{i=1, n};

(2) adopt IDW method to process discrete bathymetric data set Proc, form DDM={dep _{(i, j)}} _{i=1, n, j=1, m};

Step 4: the bed ripples feature extraction based on DDM

(1), on drawing formation system, draw seabed three-dimensional land map based on the seabed DDM building;

(2) vertical bed ripples trend, extracts terrain section line, forms topographic profile data acquisition Prof={x _i, y _i, dis _i, z _i} _{i=1, n2};

(3) based on data acquisition Prof={x _i, y _i, dis _i, z _i} _{i=1, n2}, with dis _iand z _ifor horizontal ordinate and ordinate are drawn topographic profile;

Step 5: the bed ripples FFT based on section decomposes and matching

Adopt Fast Fourier Transform (FFT) (FFT) to decompose seabed sand waves bed ripples section, carry out matching in the spike part of bed ripples with cycloid equation;

(1) bed ripples topographic profile decomposes and matching

The topographic profile Prof={x obtaining on step 4 basis _i, y _i, dis _i, z _i} _{i=1, n2}, adopt FFT function f (x) to carry out matching, x is horizontal shift dis _i, f (x) is water depth value z _i;

f(x)=f ₁(x)+f ₂(x)

$f_1\left(x\right)={\mathrm{\&Sigma;}}_{k=1}^8{b}_k\sin \left(\mathrm{kx}\right)$

$f_2\left(x\right)=a_0+{\mathrm{\&Sigma;}}_{k=1}^8{a}_k\cos \left(\mathrm{kx}\right)$

A ₀for initial offset values, a _kand b _kbe respectively the component parameters of FFT function;

In the ridge peak of bed ripples part, adopt cycloid equation to carry out matching, cycloid equation is as follows:

$\left\{\begin{array}{c}x=\frac{\mathrm{\&lambda;}}{2\mathrm{\&pi;}}(t-k\sin t)\\ d=d_u+A(1-\cos t)\end{array}\right.$

X is horizontal shift, with dis _icorresponding; D is the depth of water, with z _icorresponding; T is angle parameter; λ is bed ripples wavelength; A is bed ripples amplitude; K is the undetermined parameter relevant with bed ripples form; d _ufor the bed ripples crest place depth of water;

(2) contrast before and after the matching of bed ripples topographic profile

After matching, form new topographic profile Prof ₁={ x1 _i, y1 _i, dis1 _i, z1 _i} _{i=1, n2}; Adopt section stack control methods to observe fitting effect, synchronously adopt section differential technique quantitatively to judge the effect of decomposing with matching;

In section depth of water difference before and after matching, error is:

In section depth of water difference number percent before and after matching, error is:

In the time of Δ δ > δ, return to step (1) matching again; δ is external variable, by the given initial value of system, when this step cycle number of times reaches n3 time, automatically increases δ value, and returns to step (1); N3 is external variable, can be revised by user, but can given initial value;

In the time of Δ δ < δ, record bed ripples and decompose and fitting parameter, power cut-off.

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