CN102353957A - Method for processing multi-beam bathymetric data based on variable-bandwidth filter - Google Patents
Method for processing multi-beam bathymetric data based on variable-bandwidth filter Download PDFInfo
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- CN102353957A CN102353957A CN2011102733450A CN201110273345A CN102353957A CN 102353957 A CN102353957 A CN 102353957A CN 2011102733450 A CN2011102733450 A CN 2011102733450A CN 201110273345 A CN201110273345 A CN 201110273345A CN 102353957 A CN102353957 A CN 102353957A
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Abstract
The invention aims to provide a method for processing a multi-beam bathymetric data based on a variable-bandwidth filter. The method comprises the following steps: transmitting a signal to underwater; performing band-pass sampling on a seabed backscatter signal; after performing orthogonal transformation and low-pass filtering, acquiring a multi-beam complex signal with a channel number being M; calculating a bandwidth of each wave beam at a beam forming angle according to a depth value; designing a group of filters with same orders and different cut-off frequencies as sub-filters of the variable-bandwidth filter; selecting cut-off frequencies of the sub-filters and generating a group of filter selecting coefficients; by adopting the filter coefficients and selecting coefficients, performing filtering treatment on each channel signal, and then performing beam forming on the channel signal, and adopting a bathymetric algorithm to acquire the depth value as a depth initial value of the next period. By adopting the method, the principle defect of a fixed-bandwidth filter can be made up and an engineering feasible filter can further promote the precision of a multi-beam bathymetric system.
Description
Technical field
What the present invention relates to is a kind of depth detecting method under water.
Background technology
In multibeam sounding system, the signal to noise ratio (S/N ratio) of seabed involuting wave directly influences multibeam echosounding result's precision.Must improve signal to noise ratio (S/N ratio) in order to improve the multibeam echosounding precision, it is a kind of effective means that signal is carried out Filtering Processing.
Present multibeam sounding system both domestic and external extensively adopts the fixed-bandwidth Filtering Processing; Its method is: according to the bandwidth of exomonental length selecting filter; Its weak point is: because bandwidth depends on beam angle, seabed depth, wave beam and several factors such as vertical direction angle, pulse width; Seabed involuting wave signal to noise ratio (S/N ratio) from different beams direction on the band is also inequality, so the effect of fixed-bandwidth wave filter is not optimum.
VariableBandwidthFilterforMultibeamEcho-soundingBottomDe tection one literary composition and ICIA meeting EstimationofMultibeamPhaseDifferenceUsingVariableBandwid thFilter one literary composition in 2010 have proposed the employing variable bandwidth filter in the OCEANS meeting in 2004; Its method is: after wave beam forms; Has different bandwidth to different beams; Adopting variable bandwidth filter that phase difference sequence is carried out adaptive-filtering handles; Its weak point is: because filtering is carried out after wave beam forms; Amount of calculation is very big, is difficult to real-time implementation and is applied to engineering reality.
Summary of the invention
The object of the present invention is to provide a kind of deficiency that can either remedy on the fixed-bandwidth wave filter principle, the wave filter that has engineering feasibility again can further improve a kind of multibeam echosounding data processing method based on variable bandwidth filter of the precision of multibeam sounding system.
The objective of the invention is to realize like this:
A kind of multibeam echosounding data processing method based on variable bandwidth filter of the present invention is characterized in that:
(1) to transmitting under water; And the seabed back-scattered signal carried out bandpass sampling, after orthogonal transformation and low-pass filtering, obtaining port number is the multi-beam complex signal of M; In following signal Processing step, will carry out wave beam to signal and form, the angle that wave beam forms is θ
1, θ
2,, θ
n, in first cycle of measuring default depth initial value H is set, be θ according to depth value H compute beam angulation
1, θ
2,, θ
nThe bandwidth of each wave beam;
(2) by identical, the cutoff frequency different filter of one group of exponent number of bandwidth Design of each wave beam of step (1), as the subfilter of variable bandwidth filter;
(3) wave beam that arrives for each sampling instant echo, the cutoff frequency according to wherein maximum bandwidth selecting filter produces one group of wave filter and selects coefficient, is used for selecting the different subfilters that adopt constantly;
(4) adopt above filter coefficient and select coefficient, each channel signal is carried out Filtering Processing, afterwards signal is carried out wave beam and form, and obtain the degree of depth initial value that depth value is used for next cycle through the depth measurement algorithm.
The present invention can also comprise:
1, described beam angle θ
1, θ
2,, θ
nSelection satisfy θ
1, θ
2,, θ
nThe angular range that wave beam is formed covers comprehensively.
2, described is θ according to depth value H compute beam angulation
1, θ
2,, θ
nThe method of bandwidth of each wave beam be: c is the velocity of sound, and τ is a pulse width, and λ is the wavelength of signal, is the uniform straight line array of L for array length, and H is the degree of depth, β
iFor beam position is θ
iThe time-the 3dB half beam width:
2β
i≈2sin
-1(0.443λ/L)secθ
i (i＝1，2，·，n)，
t
iBe the echo duration the in-3dB beam angle:
t
i＝2(cos
-1(θ
i+β
i)-cos
-1(θ
i-β
i))H/c+τ (i＝1，2，·，n)，
θ
iThe direction beamformer output signal-three dB bandwidth Δ f
iFor: Δ f
i=1/t
i(i=1,2,, n).
3, one group of exponent number of described design method identical, the cutoff frequency different filter is: adopt the FIR low-pass filter, the cutoff frequency f of subfilter
CiBandwidth according to each wave beam is chosen f
Ci=k * Δ f
i, k is a constant, the scope of k is between 1 to 2.
4, one group of wave filter of described generation selects the method for coefficient to be: the degree of depth of current period is approximately equal to the depth value that the last cycle obtains, and is θ to beam angle
iObtain it-3dB beam angle β
i, the echo angular range of this wave beam is [θ
i-β
i, θ
i+ β
i]; The time that echo arrives at first is t
1=2Hcos
-1(θ
i-β
i)/c, the time of Dao Daing is t at last
2=2Hcos
-1(θ
i+ β
i)/c+ τ, sample frequency is f
s, then the lasting sampled point of echo is n
1=t
1/ f
sTo n
2=t
2/ f
sThe cutoff frequency of big bandwidth selective filter in the effective echo of the wave beam of same sampling instant, the numbering of preserving the wave filter that adopts according to time sequencing.
Advantage of the present invention is: the echo-signal of considering each wave beam comes from different angles; Sequencing is arranged the time of advent of echo; Such as under receive echo at first; And the later echo of receiving of outer beams direction; Therefore before wave beam forms; Echo to the different beams direction on time shaft is divided the time of advent; Adopt the bandwidth of this beam direction echo to adopt the cut-off frequency of the bandwidth of another beam direction echo to certain as wave filter as the cut-off frequency of wave filter, to another time period time period; By that analogy; Can either reach the effect of bandwidth varying filtering like this, again greatly degree reduce amount of calculation.
Description of drawings
Fig. 1 is the bandwidth of different beams angle echoed signal of the present invention;
The different cutoff frequencys of wave filter constantly of Fig. 2;
Fig. 3 process flow diagram of the present invention;
The frequency spectrum of Fig. 4 signal;
The contrast of Fig. 5 phase differential curve.
Embodiment
For example the present invention is done description in more detail below in conjunction with accompanying drawing:
In conjunction with Fig. 1～5,, realize by the following technical programs for realizing purpose according to the invention:
1. multibeam sounding system is to transmitting under water; And the seabed back-scattered signal carried out bandpass sampling, after orthogonal transformation and low-pass filtering, obtaining port number is the multi-beam complex signal of M; In follow-up signal is handled, will carry out wave beam to signal and form, the angle that wave beam forms is θ
1, θ
2,, θ
n, in first cycle of measuring default depth initial value H being set, in each cycle thereafter, H was measured by the last cycle, was θ according to depth value H compute beam angulation
1, θ
2,, θ
nThe bandwidth of each wave beam;
2. the one group of exponent number of bandwidth Design by each wave beam is identical, and the cutoff frequency different filter is as the subfilter of variable bandwidth filter;
3. for each sampling instant, there is the echo of several wave beams to arrive, the cutoff frequency according to wherein maximum bandwidth selecting filter produces one group of wave filter and selects coefficient, is used for selecting the different subfilters that adopt constantly;
4. adopt above filter coefficient and select coefficient, each channel signal is carried out Filtering Processing, afterwards signal is carried out wave beam and form, and obtain the processing that depth value H is used for next cycle through the depth measurement algorithm.
The present invention can also comprise:
(1) each beam angle θ in the step 1
1, θ
2,, θ
nBe the angular range that forms according to wave beam and carry out precision of filtering and select, satisfy θ
1, θ
2,, θ
nThe angular range that wave beam is formed covers comprehensively.
(2) depth value that records according to the last cycle in the step 1 is asked each wave beam θ of current period
1, θ
2,, θ
nThe bandwidth method following:
If c is the velocity of sound, τ is a pulse width, and λ is the wavelength of signal, is the uniform straight line array of L for array length, and H is the degree of depth, β
iFor beam position is θ
iThe time-the 3dB half beam width:
2β
i≈2sin
-1(0.443λ/L)secθ
i (i＝1，2，·，n)
t
iBe the echo duration the in-3dB beam angle:
t
i＝2(cos
-1(θ
i+β
i)-cos
-1(θ
i-β
i))H/c+τ (i＝1，2，·，n)
θ
iThe direction beamformer output signal-three dB bandwidth Δ f
iFor: Δ f
i=1/t
i(i=1,2,, n).
(3) method for designing of step 2 median filter is: adopt the FIR low-pass filter, the cutoff frequency f of subfilter
CiBandwidth according to each wave beam is chosen f
Ci=k * Δ f
i, wherein k chooses according to ambient conditions.
(4) step 3 median filter selects coefficient to calculate as follows:
(a) suppose that the degree of depth is gradual change, it is H that the degree of depth of current period is approximately equal to the depth value that the last cycle obtains, and is θ to beam angle
i, can obtain it-3dB beam angle β by the computing method in the claim 2
i, the echo angular range of this wave beam is [θ
i-β
i, θ
i+ β
i];
(b) time of arriving at first of echo is t
1=2Hcos
-1(θ
i-β
i)/c, the time of Dao Daing is t at last
2=2Hcos
-1(θ
i+ β
i)/c+ τ, sample frequency is f
s, then the lasting sampled point of echo is n
1=t
1/ f
sTo n
2=t
2/ f
s
(c) have all effective echo of several wave beams in same sampling instant,, preserve the numbering of the wave filter that adopts according to time sequencing according to the cutoff frequency of wherein bigger bandwidth selective filter.
(5) Filtering Processing in the step 4 is before wave beam forms, to carry out; The signal filtering of each passage is handled identical; In each numbering of selecting the coefficient median filter constantly according to wave filter, adopt corresponding filter coefficient and signal to carry out multiply accumulating, obtain filtered signal.
Multibeam sounding system adopts T-shape combination acoustics basic matrix, and the emission basic matrix is polynary arc battle array, and receiving battle array is the even linear array of being made up of 80 array elements, sound source transponder pulse length 1ms, sampling rate 40kHz.Songhua Lake test figure in 2009 is handled.
1. obtain depth of water H=58.6 rice, each beam angle θ by the last cycle
1, θ
2,, θ
nTo carry out the beam angle of 128 spot beams when forming is example, calculates bandwidth such as Fig. 1 of current period different beams angle echoed signal, and visible along with beam angle increases, signal bandwidth reduces;
2. design the subfilter of variable bandwidth filter: with 100 rank FIR low-pass filters is example, and the cutoff frequency of subfilter is chosen f
Ci=k * Δ f
i, be example with k=1;
3. for each sampling instant; Have the echo of several wave beams to arrive, the cut-off frequency based on wherein maximum bandwidth selecting filter produces one group of wave filter and selects coefficient; Being used for selecting the different subfilters that adopt constantly, is the different cut-off frequencies of wave filter constantly like Fig. 2;
4. adopt above filter coefficient and select coefficient, each channel signal is carried out Filtering Processing, process flow diagram such as Fig. 3.
Signal is carried out carrying out wave beam formation after the bandwidth varying filtering; Form 128 wave beams; Because longer duration at the big direction signal of echo angle; And little direction echo duration of angle is shorter; In different beams has the scope of echo; Signal is carried out frequency analysis, and the frequency spectrum that Fig. 4 has provided each wave beam carries out the normalization result.From figure, can see, under the wave beam bandwidth maximum, be approximately 1kHz, along with the bandwidth of the increase signal of beam angle constantly reduces, with the theoretical analysis result basically identical.
Multibeam sounding system adopts variable bandwidth filter of the present invention and adopts phase difference sequence behind the fixed-bandwidth wave filter to such as Fig. 5.The cutoff frequency of fixed-bandwidth wave filter is got the inverse of transponder pulse length, i.e. 1kHz.(a) and (b) are No. 124 wave beams among the figure, and promptly beam position is 67.2 ° a phase differential curve, and (c), (d) be No. 105 wave beam, promptly beam position is 38.7 ° a phase differential curve.
Contrast above result, after bandwidth varying filtering, phase difference sequence is more level and smooth, and the signal to noise ratio (S/N ratio) of signal has clear improvement.
Claims (5)
1. multibeam echosounding data processing method based on variable bandwidth filter is characterized in that:
(1) to transmitting under water; And the seabed back-scattered signal carried out bandpass sampling, after orthogonal transformation and low-pass filtering, obtaining port number is the multi-beam complex signal of M; In following signal Processing step, will carry out wave beam to signal and form, the angle that wave beam forms is θ
1, θ
2,, θ
n, in first cycle of measuring default depth initial value H is set, be θ according to depth value H compute beam angulation
1, θ
2,, θ
nThe bandwidth of each wave beam;
(2) by identical, the cutoff frequency different filter of one group of exponent number of bandwidth Design of each wave beam of step (1), as the subfilter of variable bandwidth filter;
(3) wave beam that arrives for each sampling instant echo, the cutoff frequency according to wherein maximum bandwidth selecting filter produces one group of wave filter and selects coefficient, is used for selecting the different subfilters that adopt constantly;
(4) adopt above filter coefficient and select coefficient, each channel signal is carried out Filtering Processing, afterwards signal is carried out wave beam and form, and obtain the degree of depth initial value that depth value is used for next cycle through the depth measurement algorithm.
2. a kind of multibeam echosounding data processing method based on variable bandwidth filter according to claim 1 is characterized in that: described beam angle θ
1, θ
2,, θ
nSelection satisfy θ
1, θ
2,, θ
nThe angular range that wave beam is formed covers comprehensively.
3. a kind of multibeam echosounding data processing method based on variable bandwidth filter according to claim 2 is characterized in that: described is θ according to depth value H compute beam angulation
1, θ
2,, θ
nThe method of bandwidth of each wave beam be: c is the velocity of sound, and τ is a pulse width, and λ is the wavelength of signal, is the uniform straight line array of L for array length, and H is the degree of depth, β
iFor beam position is θ
iThe time-the 3dB half beam width:
2β
i≈2sin
-1(0.443λ/L)secθ
i (i＝1，2，·，n)，
t
iBe the echo duration the in-3dB beam angle:
t
i＝2(cos
-1(θ
i+β
i)-cos
-1(θ
i-β
i))H/c+τ (i＝1，2，·，n)，
θ
iThe direction beamformer output signal-three dB bandwidth Δ f
iFor: Δ f
i=1/t
i(i=1,2,, n).
4. a kind of multibeam echosounding data processing ten thousand methods according to claim 3 based on variable bandwidth filter; It is characterized in that: one group of exponent number of described design is identical, ten thousand methods of cutoff frequency different filter are: adopt the FIR low-pass filter, the cutoff frequency f of subfilter
CiBandwidth according to each wave beam is chosen f
Ci=k * Δ f
i, k is a constant, the scope of k is between 1 to 2.
5. a kind of multibeam echosounding data processing method according to claim 4 based on variable bandwidth filter; It is characterized in that: one group of wave filter of described generation selects the method for coefficient to be: the degree of depth of current period is approximately equal to the depth value that the last cycle obtains, and is θ to beam angle
iObtain it-3dB beam angle β
i, the echo angular range of this wave beam is [θ
i-β
i, θ
i+ β
i]; The time that echo arrives at first is t
1=2Hcos
-1(θ
i-β
i)/c, the time of Dao Daing is t at last
2=2Hcos
-1(θ
i+ β
i)/c+ τ, sample frequency is f
s, then the lasting sampled point of echo is n
1=t
1/ f
sTo n
2=t
2/ f
sThe cutoff frequency of big bandwidth selective filter in the effective echo of the wave beam of same sampling instant, the numbering of preserving the wave filter that adopts according to time sequencing.
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| CN102927974A (en) * | 2012-10-31 | 2013-02-13 | 山东科技大学 | Detection method for multi-beam sounding detection method |
| CN105044705A (en) * | 2015-06-09 | 2015-11-11 | 哈尔滨工程大学 | Multibeam depth measuring sonar multi-subarray wave beam sharpening method |
| CN105071782A (en) * | 2015-07-29 | 2015-11-18 | 无锡思泰迪半导体有限公司 | Variable-bandwidth filter chip |
| CN108627839A (en) * | 2017-03-16 | 2018-10-09 | 中国科学院声学研究所 | A kind of object detection method and device based on sound wave Gao Gengxin rate emission mode |
| CN109029387A (en) * | 2018-09-01 | 2018-12-18 | 哈尔滨工程大学 | A kind of wave beam is interior to be fitted multibeam echosounding algorithm |
| CN109471114A (en) * | 2018-11-06 | 2019-03-15 | 哈尔滨工程大学 | A kind of multibeam sonar bathymetric surveying quality real time evaluating method based on amplitude method |
| CN109902335A (en) * | 2019-01-11 | 2019-06-18 | 中冶南方连铸技术工程有限责任公司 | Realize the filtering method and system of online control model technology stability |
| CN112945153A (en) * | 2021-02-08 | 2021-06-11 | 国家深海基地管理中心 | Cobalt-rich crust thickness measuring method based on multi-beam receiving technology |
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| CN102927974A (en) * | 2012-10-31 | 2013-02-13 | 山东科技大学 | Detection method for multi-beam sounding detection method |
| CN102927974B (en) * | 2012-10-31 | 2015-03-11 | 山东科技大学 | Detection method for multi-beam sounding detection method |
| CN105044705A (en) * | 2015-06-09 | 2015-11-11 | 哈尔滨工程大学 | Multibeam depth measuring sonar multi-subarray wave beam sharpening method |
| CN105044705B (en) * | 2015-06-09 | 2018-12-07 | 哈尔滨工程大学 | A kind of multibeam echosounding sonar multiple submatrixes beam sharpening method |
| CN105071782A (en) * | 2015-07-29 | 2015-11-18 | 无锡思泰迪半导体有限公司 | Variable-bandwidth filter chip |
| CN108627839A (en) * | 2017-03-16 | 2018-10-09 | 中国科学院声学研究所 | A kind of object detection method and device based on sound wave Gao Gengxin rate emission mode |
| CN109029387A (en) * | 2018-09-01 | 2018-12-18 | 哈尔滨工程大学 | A kind of wave beam is interior to be fitted multibeam echosounding algorithm |
| CN109029387B (en) * | 2018-09-01 | 2020-12-08 | 哈尔滨工程大学 | Wave beam internal fitting multi-beam sounding algorithm |
| CN109471114A (en) * | 2018-11-06 | 2019-03-15 | 哈尔滨工程大学 | A kind of multibeam sonar bathymetric surveying quality real time evaluating method based on amplitude method |
| CN109902335A (en) * | 2019-01-11 | 2019-06-18 | 中冶南方连铸技术工程有限责任公司 | Realize the filtering method and system of online control model technology stability |
| CN109902335B (en) * | 2019-01-11 | 2023-02-28 | 中冶南方连铸技术工程有限责任公司 | Filtering method and system for realizing on-line control model process stability |
| CN112945153A (en) * | 2021-02-08 | 2021-06-11 | 国家深海基地管理中心 | Cobalt-rich crust thickness measuring method based on multi-beam receiving technology |
| CN112945153B (en) * | 2021-02-08 | 2022-07-29 | 国家深海基地管理中心 | Cobalt-rich crust thickness measuring method based on multi-beam receiving technology |
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