Stratum chromatography method by synthetic aperture

Technical Field

The invention belongs to the seabed stratum detection, new Technical Field marine survey, is mainly a synthetic aperture formation chromatography method.

Background Art

In ocean mineral resource rich, understanding of the marine structure to the seabed strata investigation (probe petroleum, natural gas, etc.) is very important; at the same time our oceans are also of the platform of the various kinds of maritime activities, knowledge of ocean engineering structure to the seabed strata (construction of the marine terminal, seawall platform; submarine pipeline laying, such as the opening of the tunnel), seabed threat detection (submarine volcano distribution structure, such as buried mine arrangement) is important.

Seabed stratum chromatography the corresponding method, means to understand the seabed stratum sedimentary deposit sequence, stratum stratification characteristics of geological analysis technology of a door. At present, the most commonly used is to carry out drilling, sampling analysis for obtaining formation information, however, because of the marine complicated situations, transmitting low frequency penetrate the acoustic wave, on a large scale for echo inversion is the best way to submarine stratum chromatography. In the International is not mature seabed stratum chromatography system, applying a comparison generally splits shallowly system, the system is faced with splits shallowlynavigation Uygur imaging resolution problem, and some small target or the texture formation cannot distinguish, thereby realizing seabed stratum chromatography, the key is to breakthrough imaging resolution limit. The innovation of the present invention in a synthetic aperture technique to seabed stratum chromatography, in order to improve its in the resolution of the navigation Uygur , at the same time in the synthetic aperture processing layered on the basis of the two-dimensional forward normalized post-treatment in order to further solve interface fuzzy problems and raise the stratum resolution. The synthetic aperture technical application seabed strata in the chromatographic process still belongs to the first example of the world, there are many key problems to be solved. If the stratum is change in velocity, when penetrating between the acoustic wave in a layered modulation, and the synthetic aperture formation chromatography caused by sea water, such as fuzzy problem of the submarine interface, all these factors will affect the output gain of synthetic aperture. Strong these key issue to be solve the technical application range of synthetic aperture, creatively make it from traditional detecting terrain, geomorphologic field of chromatographic field extended to the stratum.

Synthetic aperture formation chromatography technology, first of all, the low-frequency band signal depth Uygur pulse compression processing to obtain high resolution, and adequate penetrability of stratum of the can; and then the different hierarchical data employ different synthetic aperture processing the obtained velocity to high resolution navigation Uygur ; finally through the layered two-dimensional forward normalized post-processing further improve the seabed formation resolution.

Content of the invention

The purpose of this invention is to overcome the technical defects, and to provide a synthetic aperture formation chromatography method.

To solve the technical problems of the present invention adopts the technical proposal: this kind of synthetic aperture formation chromatography method, comprising the steps of as follows:

(1), obtaining formation echo signal: transmitting low frequency broadband signal, by linear frequency modulation signal bandwidth is 1-15kHz, the obtained layered interface reflection echo throughout the frequency band of the matched filter processing;

(2), synthetic aperture formation chromatography: using acoustic shock the vertical downward wide beam transmitting/receiving the working mode, the stratum echo synthetic aperture processing, to the same time receiving a three-dimensional arc wavefront echo, in the signal processing method of the synthetic aperture algorithm using conventional synthetic aperture focusing beam-forming processing;

(3), layered synthetic aperture processing: application bottom tracing method, the echo data is divided into two part of the sea water and the seabed, then, according to the sea water, the sound velocity of the submarine data value corresponding to synthetic aperture processing, in order to raise the stratum chromatography resolution;

(4), the synthetic aperture processing layered on the basis of the two-dimensional forward normalized post-processing; against seawater, seabed are respectively normalized processing, the depth of the seabed strata solve different echo attenuation is very quick question, at the same time the initial inhibition by synthetic aperture processing fuzzy problem of the interface, and improve the formation resolution, highlight formation chromatography effect.

As preferred, the combined transmitting transducer, the transmitting mode, in sequence: a group of heat transmitting first 1kHz -5kHz of the LFM signal, total pulse width emission time of about 1/3; immediately before the other group of transducer transmitting 5kHz -15kHz of the LFM signal, transmission time accounts for about of total pulse width 2/3.

Preferably, the time delay focusing synthetic aperture processing method, after the data of the matched filtering said discrete form for ss (n, m), m, and n are respectively said sample points depth Uygurwalks navigation Uygur specimen point (m=1, 2, the   M; n=1, 2, the   N), the Image output

ff(n,m)=Σi=1LSAss(n+τ(n,i),m+i)---(2)

In the formula L_SA to position to the synthetic aperture length, τ (i, n) is defined as the distance from the time delay of the migration curve variation amount caused by

τ(n,i)=n2+[2fs[!CenterDot!]i[!CenterDot!]d/c]-n,i=1,2,[!CenterDot!][!CenterDot!][!CenterDot!]LSA---(3)

The distance d of the space a, c is a sound velocity, said rounding operation [·], in order to obtain precise time delay interpolation samples in the processing operation.

As a preference, the stratum echo seawater in the separation of data and seabed data, different sound velocity value to its application synthetic aperture processing;

The seawater * bottom tracking processing, seabed data separation:

The post-filter data match energy and short-time integration

Ess(m,n)=1JΣj=1J|ss(m,n+j)|---(4)

EEss(m)=1NΣn=1NEss(m,n)---(5)

When the Ess ≥ 0.707 *EEss (m, n) (m) found N_s (θ) =n time of the submarine;

* lamination synthetic aperture processing:

After separating the sea water, different sound velocity data seabed data applications synthetic aperture formation chromatography, the synthetic aperture processing, sea water and of the seabed a fuzzy belt is formed in the vicinity of the interface, this fuzzy with normalization processing by the rear-mounted.

The beneficial effect of the invention is: the technology of the invention relates to synthetic aperture technique is applied to the formation in the field of chromatography. In this invention the velocity of different hierarchical data employ different synthetic aperture processing method to seabed stratum chromatography, in order to raise the stratum chromatography system in the resolution of the navigation Uygur ; at the same time in the synthetic aperture processing layered on the basis of the two-dimensional forward normalized post-treatment in order to further solve interface fuzzy problems and raise the stratum resolution.

Description of drawings

Figure 1: the stratum echo synthetic aperture processing geometrical relationships;

Figure 2: sound speed changes on the synthetic aperture beam impact;

Figure 3: layered synthetic aperture formation chromatography processing flow;

Figure 4: large area formation section data stratum chromatography results;

Figure 5: seabed buried target imaging result of the three-dimensional formation.

Mode of execution

The embodiment of Figure and with the further description of this invention:

The present invention adopts a synthetic aperture technique to seabed stratum chromatography, in order to raise the stratum chromatography system in the resolution of the navigation Uygur , at the same time in the synthetic aperture processing layered on the basis of the two-dimensional forward normalized post-treatment in order to further solve interface fuzzy problems and raise the stratum resolution. Seabed stratum chromatography the corresponding method, means to understand the seabed stratum sedimentary deposit sequence, stratum stratification characteristics of geological analysis technology of a door. At present, the most commonly used is to carry out drilling, sampling analysis for obtaining formation information, however, because of the marine complicated situations, transmitting low frequency penetrate the acoustic wave, on a large scale for echo inversion is the best way to submarine stratum chromatography. In the International is not mature seabed stratum chromatography system, applying a comparison generally splits shallowly system, the system is faced with splits shallowlynavigation Uygur imaging resolution problem, and some small target or the texture formation cannot distinguish, in the present invention the synthetic aperture technique applied to submarine stratum chromatography in order to break through the imaging resolution is limited. Synthetic aperture formation chromatography method, first of all, the low-frequency band signal depth Uygur pulse compression processing to obtain high resolution, and adequate penetrability of stratum of the can; then, for seawater, seabed hierarchical data employ different synthetic aperture processing the obtained velocity to high resolution navigation Uygur ; finally through the layered two-dimensional forward normalized post-processing solution interface fuzzy problem of the seabed can be further improved and the formation resolution.

As shown, this kind of synthetic aperture formation chromatography method, comprising the steps of as follows:

1. Obtaining formation echo signal

Transmitting low frequency broadband signal, in order to obtain sufficient penetrating the stratum and the stratum chromatography resolution. The bandwidth for the linear FM signal 1-15kHz, the obtained layered interface reflection echo frequency band through the full theory distance matched filter processing the obtained resolving power is 5.3 centimeter

Because the transducer is very difficult to realize process problem of low frequency broadband, here the combined transmitting transducer, in order to realize broadband 1-15kHz work, the programme with sequential launching means in:a group of heat transmitting first 1kHz -5kHz of the LFM signal (emission time total pulse width of about 1/3), immediately before the other group of transducer transmitting 5kHz -15kHz of the LFM signal (transmission time accounts for about of total pulse width 2/3).

Low frequency broadband signal in the earth penetrating in the process, will be layered in the stratum strong reflection on the interface, including the stratum information so as to obtain the echo signal, the echo signal through the matched filter processing can be preliminary inversion stratum medium the hierarchical information.

2. Synthetic aperture formation chromatography

In order to realize the stratum chromatography, using acoustic shock the vertical downward wide beam transmitting/receiving operating mode, compared with the traditional sidescan the synthesis of the aperture there is a big difference in the working mode. The stratum echo synthetic aperture processing, receiving a simultaneous three-dimensional arc wavefront echo, its geometrical relationship as shown in Figure 1 is shown in schematic diagram. In the Figure is the position of the sonar platform A, its perpendicular to the moving direction of the wave front of the upper arc of two arbitrary point target P1 and P2, the soundpath equal to their receive (r1=r2), to B position when the movement of the platform, the two target soundpath remains equal (r1     =r2   [...]), the receive the echo signal upward navigation side still meet the parabola focus criteria.

R=r2+x2---(1)

Visible, although formation echo is multi-target superimposed together, however, each a reflective target delay curve of the conventional sidescan mode synthetic aperture processing the obtained delay relationship curve is the same, therefore, in signal processing method, we can still use the conventional synthetic aperture algorithm synthetic aperture focusing beam-forming processing.

This scheme adopts the time delay focusing synthetic aperture processing method, after the data of the matched filtering said discrete form for ss (n, m), m, and n are respectively said sample points depth Uygurwalks navigation Uygur specimen point (m=1, 2, the   M; n=1, 2, the   N), the Image output

ff(n,m)=Σi=1LSAss(n+τ(n,i),m+i)---(2)

In the formula L_SA to position to the synthetic aperture length, τ (i, n) is defined as the distance from the time delay of the migration curve variation amount caused by

τ(n,i)=n2+[2fs[!CenterDot!]i[!CenterDot!]d/c]-n,i=1, 2,     L_SA     (3)

The distance d of the space a, c is a sound velocity, said rounding operation [·]. In order to obtain precise time delay in the processing operation to up-sample interpolation.

3. Layered synthetic aperture processing

Seawater, the sound velocity of the submarine in the synthetic aperture processing gain changes in a great impact, Figure 2 simulation sea water depth of 100 meters, formation depth 10 meters, the velocity of sound in water is 1500 m/sec, the sound velocity stratum 1550 meters/seconds, simulating the actual formation echo velocity of sound are 1500 meters/seconds, 1550 meters/seconds, 1600 m/sec, 1650 m/sec, a point target echo synthetic aperture processing of the beam pattern (horizontal coordinates as shipboard direction length, ordinate is the output of beam abeam), analysis shows that, the error need to control the velocity of 6.4% is within the range, in order to make the synthetic aperture processing influence is very small.

For this, in a synthetic aperture formation in the chromatography process, different echo data the need to employ different velocity of sound velocity value changes in the synthetic aperture processing, the data may be approximately that of sea water c=1500 m/sec, and for submarine data, different layered medium there is a large change in velocity, however, the shallow stratum (30 m) changes in general velocity 1550-1650 meters/seconds, averaging c=1600 m/sec, the error in velocity of 6.4% range, on the synthetic aperture processing is very small. To this end we need the stratum echo seawater in the separation of data and seabed data, different sound velocity value to its application synthetic aperture processing. .

The seawater * bottom tracking processing, seabed data separation

The post-filter data match energy and short-time integration

Ess(m,n)=1JΣj=1J|ss(m,n+j)|---(4)

EEss(m)=1NΣn=1NEss(m,n)---(5)

When the Ess ≥ 0.707 *EEss (m, n) (m) found N_s (θ) =n time of the submarine.

* lamination synthetic aperture processing flow

After separating the sea water, different sound velocity data seabed data applications synthetic aperture formation chromatography, flow as shown in Figure 3. In the synthetic aperture processing, to the interface between the sea water and the seabed is added reasons for the parabola aperture focusing, will form a near the interface fuzzy belt , this fuzzy with our inhibit through the post-normalization processing

4, a layered bottom tracing-based two-dimensional forward normalized

Layered two-dimensional forward normalized solves the problem that the three issues, a submarine of different depth stratum echo attenuation is very fast, water of the seabed is in close to the virtual Image (due to the synthetic aperture processing to form the fuzzy belt) can not be too obvious, three water stratum with the seabed target in a normalized result to the position of discrete problems. (This technological invention the success of the programme and multi-beam process combining construction into a three-dimensional formation chromatography system, the following formula the angle θ multi-beam the result after processing)

* bottom tracking processing

Layered two-dimensional forward normalized before multi-beam first of all it is necessary to sequence the output time do the oblique distance amendment and submarine tracking. Oblique distance correction need for interpolating resampled, unified display into the depth. Submarine tracking adopts the slide window short-term average amplitude (32 point) the threshold detection method, the threshold is set to a time axis corresponding to the azimuth (not containing arteries drift) average of 0.707, and recording the position of the seabed of the beam. (As far as possible the seabed above the seabed strata artifact).

Ey[!theta!](n)=1MΣj=1My[!theta!](n+j)Θ =1:K, n=1:N-M     (6)

EEy[!theta!]=1NΣn=1Ny[!theta!](n)---(7)

When the Ey_θ (n) ≥ 0.707 *EEy_θ sentenced N₀ (θ) =n time of the submarine

Ey_θ (n) is a matching filter process, layered synthetic aperture processing and after multi-beam treatment, the direction of the angle θ the energy of the sequence value.

Seawater * data normalization

Water (target) in the Image display only the normalization process of the whole, the average value of the whole of the background (not containing arteries drift) normalization

To 16. The calculation of two times the background average requirements, does not include statistics 2nd last average value is greater than 3 times that of the point.

ESy[!theta!]=1N0([!theta!])Σn=1N0([!theta!])y[!theta!](n)---(8)

ESy=1KΣ[!theta!]=1KESy[!theta!]---(9)

For K includes an effective sea water beam data of the data.

y_θ '(n) = y_θ (n) when y_θ' (n) ≥ 3 *ESy   y_θ ' (n) =ESy     (10)

ESy′=1KΣ[!theta!]=1K1N0([!theta!])Σn=1N0([!theta!])y[!theta!]′(n)---(11)

y_θ '(n) = y_θ (n)/ ESy' * 16n     N₀ (θ) (12)

* sea bottom data normalization

Normalized reverberation of the seabed different directions, taking the azimuth the entire submarine stratum average value of intensity of the reverberation 1/2 power as a normalization factor.

EDy([!theta!])=1N-N0([!theta!])Σn=1N-N0([!theta!])y[!theta!](n)---(13)

y '_θ (n) = y_θ (n)/ sqrt (EDy (θ)) n≥N₀ (θ) (14)

Seabed stratum display in different directions at the same time the beam the normalization factor, calculating the position of the time shaft a short-term average (32 point), then the position of the azimuth normalization factor weighting statistical average, the average value of 1/2 power as a normalization factor. Near-distance on average according to the actual beam number.

EDy(n)=1K(n)Σ[!theta!]=1K(n)Ey[!theta!](n)/sqrt(EDy([!theta!]))---(15)

y "_θ (n) = y_θ ' (n)/ sqrt (EDy (n-5)) n≥N₀ (θ) (16)

Before final discharge a large amount of function normalizes the mean value of the seabed strata 64.

EEy′′=1KΣ[!theta!]=1K1N-N0([!theta!])Σn=N0([!theta!])Ny[!theta!]′′(n)---(17)

y "'_θ (n) = y_θ" (n)/ EEy "* 64n     N₀ (θ) (18)

5. Seabed stratum chromatography the sea tries results

This technological invention with the multi-beam technology can be combined with an imaging system for building three-dimensional seabed strata, Figure 4, Figure 5 for this technical invention is applied to three-dimensional seabed stratum imaging system, in 2010 year 10 month zhoushan sea area to a rich stratum areas and buried mines stratum of the target area on the imaging detection test results, in the map the technology invention has good formation chromatography effect is obtained.

Finally, it should be note, the above embodiment is only used to illustrate the technical scheme of the invention and with the open-ended, but the application can be extended to other modification, change, application, and that all such modifications, changes, application, in instances of this invention within the spirit and scope.