CN111983686A - SEGY-based visual display method for shallow stratum profile original data - Google Patents
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Abstract
The invention discloses a SEGY-based visual display method for shallow stratum profile original data, which comprises the steps of firstly, referring to ocean survey regulations, combining the situation of on-site water depth and terrain surveying, acquiring and obtaining shallow stratum profile original data under the condition of meeting the parameter requirements of survey line layout and observation systems, and storing the shallow stratum profile original data in an SEGY file format; importing an SEGY shallow stratum profile original data file of a certain measuring line, using Matlab programming to realize data reading and decoding, and extracting all echo signal data of the measuring line by taking Ping as a horizontal coordinate and taking depth of time as a vertical coordinate; and programming the extracted echo signal data to carry out surging static correction, multiple wave suppression and true amplitude recovery processing to generate a shallow stratum profile map, thereby realizing image visualization of the shallow stratum profile data. The method can be applied to analysis of SEGY-based deep and shallow water type shallow stratum profiles and single-channel and multi-channel seismic raw data, and can also provide necessary reference for analysis of XTF-based side-scan sonar raw data.
Description
Technical Field
The invention relates to an ocean mapping method, in particular to a SEGY-based visual display method for shallow stratum profile original data.
Background
With the development of the science of marine surveying and mapping and the need of marine engineering exploration, the detection of seabed sediments is an important content developed aiming at the type and the property of seabed shallow surface sediments. The traditional method for detecting the seabed sediment is a method which is most direct and effective in obtaining the classification and the property of the sediment by using clam type, box type, gravity and other samplers to take sediment samples on site and transporting the samples to a laboratory for analysis and test, but has the disadvantages of large manpower consumption, high financial resources, long required time and only can obtain discrete data of the seabed sediment data. The method is a technology for acquiring the backscattering intensity or sonar images of the seabed by using acoustic telemetry means such as single beam, multi-beam and side scan sonar and identifying and dividing the category, distribution and property of the substrate, has high measurement efficiency and relatively low cost, and realizes the expansion of substrate detection from discrete points to continuous lines and surfaces.
The shallow stratum profile detection is used as one of acoustic telemetry, and uses a normal incidence signal which has a relatively lower transmitting frequency compared with a depth measuring device, the acoustic signal can penetrate through the surface of a seabed and enter the interior of a seabed settled layer, and is reflected and scattered at a stratum layer, the echo carries richer information of sediments in the stratum, and the physical properties of the seabed sediments can be inverted with higher confidence.
The shallow stratum profile original data is mostly subjected to internal processing by adopting the current mainstream international business software (such as Sonarwiz, Triton and the like), the original data is directly read and imaged only for a user, the function of independently acquiring each parameter in the original shallow stratum profile data is not opened for the user, the user is not convenient to carry out secondary development on the subsequent shallow stratum profile image processing function, and the software is high in price and easy to lose, so that the great economic safety hidden danger exists.
Disclosure of Invention
Aiming at the prior art and aiming at solving the problem that the internal processing of the original data of the shallow stratum profile excessively depends on international business software, the invention provides a visual display method of the original data of the shallow stratum profile based on SEGY. The shallow stratum profile data extracted by the method can also be used for classification research of seabed shallow sediments.
In order to solve the technical problems, the invention provides a SEGY-based visual display method for shallow stratigraphic section original data, which relates to equipment comprising a shallow stratigraphic profiler, a GPS and a computer, wherein the shallow stratigraphic profiler is provided with data acquisition software, and the computer is provided with Matlab programming software, and comprises the following steps:
step 2, importing a SEGY shallow stratum profile original data file of a certain measuring line into a computer, reading and decoding the SEGY shallow stratum profile original data file by using Matlab programming software, and extracting all echo signal data of the measuring line by taking Ping as a horizontal coordinate and taking depth as a vertical coordinate;
and 3, programming the echo signal data extracted in the step 2 by using Matlab programming software, realizing the surge static correction, random noise suppression, multiple wave suppression and true amplitude recovery processing, generating a shallow stratum profile, and realizing the image visualization of the shallow stratum profile data of the measuring line.
Further, the invention relates to a method for visually displaying raw data of a shallow stratum profile based on SEGY, wherein,
in the step 1, the data acquisition software is Discover software, and the specific process of acquiring the shallow stratum profile original data of a certain sea area and storing the shallow stratum profile original data in an SEGY file format is as follows:
setting the water depth of a measurement area to be less than 100m, wherein the main survey line direction is vertical to the general trend direction of deep lines such as submarine topography when the survey lines are laid; before measurement of a survey line, selecting and adjusting the total gain of a receiver, the TVG gain and the receiving frequency band of the shallow stratum profiler to ensure that the detection profile obtains the optimal penetration rate and resolution; during towing operation, the water inlet angle of a transducer of the shallow stratum profiler is 15-20 degrees, so that a towed array is kept stable, the sailing speed is kept at 5kn, the frequency band of the shallow stratum profiler is 4kHz, the beam opening angle is 16 degrees, the pulse length is 20ms, the detection recording depth is 30m below the vertical sea floor, and the recording resolution is 20 cm; the height of the towed fish from the sea bottom is always kept at 5m, and the horizontal distance from the towed fish to the GPS is 20 m; acquiring, displaying and playing back the original data of the shallow stratum section in real time by using the Discover software, and automatically generating a JSF file format; and converting the JSF file format into an SEGY file format by using Discover software, and copying the SEGY file format onto a computer for storage, thereby forming an SEGY shallow stratum profile original data file of each measuring line.
In step 2, after acquiring the number of sampling points, the sampling rate, the total track number, the line number, the track number and the XY coordinates from the parameters contained in the coil head and the track head in the SEGY shallow profile original data file, writing a program by utilizing Matlab programming software to read the data of the SEGY shallow profile original data file.
The specific process of reading the data of the SEGY shallow stratigraphic section original data file by utilizing a Matlab programming software program is as follows:
step 2-1, with fopen function: the file id (fopen) imports the shallow profile raw data file of the SEGY, and the fopen function represents to open the file or obtains information about the open file, where: fileID represents a file identifier; the filename represents the local path of the file to be opened; the permission indicates that the access authority type of the opened file is specified, wherein the access authority type is 'r', namely the access authority type of the opened file is specified to be read;
step 2-2, using fseek function: fseek (fileID, offset, origin) and fread functions: a ═ fread (fileID, sizeA, precision, skip, machinefmt) reads the number of sample points SampleNumber and the sample rate, the fseek function represents the pointer movement to a specified position in the file, where: offset represents the number of bytes of specified offset, and the number of bytes of sampling rate and sampling point offset is 3200 and 3216 respectively, which means that a file header of 3200 bytes is followed by a file header of 400 bytes containing key information, wherein the sampling rate and the number of sampling points respectively start from 16 th byte and 20 th byte, and each occupy 4 bytes; origin indicates an offset from a specified position, which is represented by "bof" indicating an offset from the header; the fread function represents that data are read from the opened binary file into an array A, and the array A is filled in a column mode; wherein: the sizeA represents the dimension of the output array A, and the dimension of the output data is 1; precision represents the type of data to be read is specified, and the data types are all 16-bit integer data; skip represents the number of bytes needing to be adjusted, and the default is 0; the macchinefmt represents the arrangement mode of the data bytes to be read, the arrangement mode is represented by 'b', the arrangement mode of the data bytes to be read is represented by arranging the low-order bytes at the high address end of the memory, and arranging the high-order bytes at the low address end of the memory;
step 2-3, using a ftell function: calculating the total byte number and the total track number of the SEGY shallow stratigraphic section original data file, wherein the A is ftell (fileID), and the ftell function is used for obtaining the offset byte number of the current position of the file position pointer relative to the file head so as to obtain the total byte number of the file; the total channel number calculation method comprises the following steps: subtracting the byte number occupied by the character string file header and the binary file header from the total byte number, and dividing the byte number occupied by each track by the byte number occupied by the character string file header and the binary file header, wherein the byte number occupied by the binary file header is 3600, the byte number occupied by each track is the byte number of a sampling point plus the byte number of track header information, and the calculation formula of the total track number is as follows:
TotalTrace＝(TotalBytes-3600)/(SampleNumber*4+240)；
step 2-4, reading the line number, the track number and the XY coordinates, and using the fseek function and the fread function; starting to circulate from 1 until the total number of tracks, and traversing all tracks; the offset calculation formula in the fseek function is:
3600+(i-1)*240+(i-1)*SampleNumber*4+site
wherein, i is the total track number, and the sites are respectively 8, 20, 72 and 76 which sequentially represent the initial positions of the line number, the track number, the X coordinate and the Y coordinate in the track head information;
and 2-5, after decoding the data of the SEGY shallow stratum profile original file, extracting all echo signal data of the survey line by taking Ping as a horizontal coordinate and taking depth of time as a vertical coordinate, and storing the echo signal data in a CSV file format.
And 3, programming the extracted echo signal data by using Matlab programming software to realize surge static correction, random noise suppression, multiple wave suppression and true amplitude recovery processing, wherein the surge static correction and the random noise suppression processing are respectively carried out by adopting a surge filter and a band-pass filter. Performing multiple suppression by adopting a method for predicting deconvolution, wherein the process comprises the following steps: and predicting a pure interference part according to the information of the recorded primary reflection and interference, and subtracting the pure interference part from the seismic record comprising the primary wave and the interference to obtain a primary reflection signal after the interference is eliminated so as to eliminate the multiple interference behind the primary reflection and realize multiple suppression. Realizing true amplitude recovery processing by adopting one of the following methods, namely 1) compensating and correcting acoustic wave energy by adopting any one of wave front diffusion energy compensation, stratum absorption energy compensation and surface consistency performance adjustment; 2) the amplitude energy abnormity between adjacent channels is eliminated by using an amplitude statistical method, the influence of sound wave spherical diffusion on the amplitude is eliminated by using spherical diffusion compensation, and the phenomenon of uneven amplitude of the measuring line caused by seabed geological factors is eliminated by using earth surface consistency amplitude compensation.
Compared with the prior art, the invention has the beneficial effects that:
the method directly completes all internal processing work of the original data of the shallow stratum profile in Matlab by programming, does not need high cost to purchase international business software, and does not need to worry about huge economic loss caused by the loss of the dongle. In addition, the method can open the function of independently acquiring each parameter in the original shallow stratum profile data for the user, and is convenient for the user to carry out secondary development, subsequent related numerical simulation and other scientific research works on the subsequent shallow stratum profile image processing function. The method can be applied to analysis of deep and shallow water type shallow stratum profiles mainly in SEGY format and single-channel seismic raw data, and can also provide necessary reference for analysis of side-scan sonar raw data mainly in XTF format.
Drawings
FIG. 1 is a flow chart of the SEGY-based method for visually displaying raw shallow stratigraphic profile data according to the present invention;
FIG. 2 is a schematic diagram of the operation of a shallow profiler used in the method of the present invention;
FIG. 3 is a schematic representation of the overall system of shallow profile formation in the method of the present invention;
FIG. 4 is a diagram of a shallow profile raw data acquisition in the method of the present invention;
FIG. 5 is a flow chart of Matlab writing shallow profile raw data analysis codes in the method of the present invention;
FIG. 6 is a flow chart of the post-processing of shallow profile data in the method of the present invention;
FIG. 7 is a cross-sectional view of a shallow formation produced by the method of the present invention.
Detailed Description
The invention will be further described with reference to the following figures and specific examples, which are not intended to limit the invention in any way.
As shown in fig. 1, the method for visually displaying raw data of a shallow stratigraphic section based on SEGY according to the present invention is characterized in that the related devices include a shallow stratigraphic section instrument, a GPS and a computer, wherein the shallow stratigraphic section instrument is installed with data acquisition software, and the computer is installed with Matlab programming software, and the method comprises the following steps:
step 2, importing a SEGY shallow stratum profile original data file of a certain measuring line into a computer, reading and decoding the SEGY shallow stratum profile original data file by using Matlab programming software, and extracting all echo signal data of the measuring line by taking Ping as a horizontal coordinate and taking depth as a vertical coordinate;
and 3, programming the echo signal data extracted in the step 2 by using Matlab programming software, realizing the surge static correction, multiple wave suppression and true amplitude recovery processing, generating a shallow stratum profile map, and realizing the image visualization of the shallow stratum profile data of the measuring line.
For easy understanding, the working principle of the shallow profile instrument and the structure and characteristics of the echo signal are firstly analyzed, the main technical indexes of the shallow profile instrument are known, and the SEGY shallow profile original file structure is deeply researched. The specific contents are as follows:
the working principle of the shallow stratum profiler is as follows: as shown in fig. 2, the whole system structure diagram of the device for detecting the bottom strata of the ocean, the river and the lake by using the cross-sectional structure instrument for detecting the shallow bottom strata by using sound waves is shown in fig. 3, and is specifically explained as follows:
the shallow profile system consists of user equipment (AC power supply and GPS), a portable deck unit, a transducer, a towing cable, a fish and a data acquisition computer, wherein the transmitting transducer and the receiving transducer are both positioned at the fish. In the process of sailing of the detection ship, an alternating current power supply keeps constant 220V voltage and 50Hz discharge frequency, the GPS provides positioning data in real time, and the towed fish is always positioned in the underwater part and keeps constant distance from the sea bottom. The transducer on the fish can emit sound wave of high-power low-frequency pulse to underwater vertically, when it reaches seabed, it is partially reflected, and partially propagated to deep position of stratum, and because the stratum structure is complex, on different interfaces some sound waves are reflected, and according to the characteristics and depth of these reflected interfaces the time and intensity of receiving echo signal on the ship are different, and after the echo signal is undergone the processes of amplification and filtering, etc., it can be fed into recorder, and can display the lines formed from points with different grey levels on the mobile dry-type recording paper, so that the sectional structure of stratum can be clearly described.
The structure and characteristics of the echo signal: the first echo signal received by the sonar transducer generally comes from the position right below the towed fish, the intensity of the first echo signal is high, the intensity of the later received echo is good in continuity, the height information of the towed fish can be obtained by calculating the position of the first echo, and an echo sequence obtained by one-time measurement is called as 1Ping echo. In the course of sailing, the towed fish continuously transmits and receives echo signals, and converts the collected echo signals of each Ping into gray information, namely, an echo image sequence is formed.
The shallow stratum profiler related in the invention has the main technical indexes that: the field measurement adopts 3100P shallow stratum profiler with working frequency of 2-16 kHz; is provided with 216S dragfish, the weight is 72kg, and the pressure resistance is 300 m; the towing cable is standard-matched with 35m, the bending radius is 25cm, the working tension is 300kg, and the breaking force is 1500 kg.
SEGY File Format analysis: the SEGY file format is established by the exploration geophysical Association and is a de facto standard in the current geophysical exploration industry. The file format data is stored in binary system, and the data in each part are closely connected without any separator.
Binary data types in the SEGY file are divided into three types as a whole, the first type is unsigned integer, the second type is unsigned short integer, and the third type is character type. As shown in table 1, the standard SEGY file format employed in the present invention generally includes three parts: (1)3200 bytes of character string file header records the relevant information of the data acquisition system by EBCDIC coding, consists of 40 cards and is used for storing some information describing the data body; (2) the 400-byte binary file header stores some key information describing the SEGY file in 16-bit and 32-bit binary numbers, including the data format, the sampling point number, the sampling interval, the measurement unit and the like of the SEGY file, and the information is generally stored at a fixed position of the binary file header; (3) each track actually contains 240 bytes of track header information. The track head data generally stores information such as a line number, a track number, a sampling point number, geodetic coordinates and the like corresponding to the track, but the positions of some key parameter positions (such as the line number and the track number) in the track head are not fixed. The trace data is obtained by sampling the waveform of the signal at certain time intervals Δ t and recording the series of discrete amplitude values in some manner.
TABLE 1
In the step 1, the data acquisition software is Discover software, and the specific process of acquiring and storing the shallow stratum profile original data of a certain sea area in an SEGY file format is as follows:
setting the water depth of a measurement area to be less than 100m, wherein the main survey line direction is vertical to the general trend direction of deep lines such as submarine topography when the survey lines are laid; before measurement of a survey line, selecting and adjusting the total gain of a receiver, the TVG gain and the receiving frequency band of the shallow stratum profiler to ensure that the detection profile obtains the optimal penetration rate and resolution; during towing operation, the water inlet angle of a transducer of the shallow stratum profiler is 15-20 degrees, so that a towed array is kept stable, the sailing speed is kept at 5kn, the frequency band of the shallow stratum profiler is 4kHz, the beam opening angle is 16 degrees, the pulse length is 20ms, the detection recording depth is 30m below the vertical sea floor, and the recording resolution is 20 cm; the height of the towed fish from the sea bottom is always kept at 5m, and the horizontal distance from the towed fish to the GPS is 20 m; acquiring, displaying and playing back the original data of the shallow stratum section in real time by using the Discover software, and automatically generating a JSF file format; and converting the JSF file format into an SEGY file format by using Discover software, and copying the SEGY file format onto a computer for storage, thereby forming an SEGY shallow stratum profile original data file of each measuring line.
In step 2, after acquiring the number of sampling points, the sampling rate, the total track number, the line number, the track number and the XY coordinates from the parameters contained in the reel head and the track head in the SEGY-based shallow profile original data file, as shown in fig. 5, the data of the SEGY-based shallow profile original data file is read by using a Matlab programming software program, and the specific process is as follows:
step 2-1, with fopen function: the file id (fopen) imports the shallow profile raw data file of the SEGY, and the fopen function represents to open the file or obtains information about the open file, where:
fileID represents a file identifier; the filename represents the local path of the file to be opened; the permission indicates that the access permission type of the opened file is designated, the access permission type is "r", that is, the access permission type of the opened file is designated as read.
Step 2-2, using fseek function: fseek (fileID, offset, origin) and fread functions: a, read the number of sampling points SampleNumber and sampling rate,
the fseek function represents the movement of a pointer to a specified location in a file, where: offset represents the number of bytes of specified offset, and the number of bytes of sampling rate and sampling point offset is 3200 and 3216 respectively, which means that a file header of 3200 bytes is followed by a file header of 400 bytes containing key information, wherein the sampling rate and the number of sampling points respectively start from 16 th byte and 20 th byte, and each occupy 4 bytes; origin indicates an offset from a specified position, which is represented by "bof" indicating an offset from the header;
the fread function represents that data are read from the opened binary file into an array A, and the array A is filled in a column mode; wherein: the sizeA represents the dimension of the output array A, and the dimension of the output data is 1; precision represents the type of data to be read is specified, and the data types are all 16-bit integer data; skip represents the number of bytes needing to be adjusted, and the default is 0; the machinefmt indicates the arrangement of the data bytes to be read, the arrangement is indicated by "b", and indicates that the arrangement of the data bytes to be read is that the low-order bytes are arranged at the high address end of the memory, and the high-order bytes are arranged at the low address end of the memory.
Step 2-3, using a ftell function: calculating the total byte number and the total track number of the SEGY shallow stratigraphic section original data file, wherein the A is ftell (fileID), and the ftell function is used for obtaining the offset byte number of the current position of the file position pointer relative to the file head so as to obtain the total byte number of the file; the total channel number calculation method comprises the following steps: subtracting the byte number occupied by the character string file header and the binary file header from the total byte number, and dividing the byte number occupied by each track by the byte number occupied by the character string file header and the binary file header, wherein the byte number occupied by the binary file header is 3600, the byte number occupied by each track is the byte number of a sampling point plus the byte number of track header information, and the calculation formula of the total track number is as follows:
TotalTrace＝(TotalBytes-3600)/(SampleNumber*4+240)；
step 2-4, reading the line number, the track number and the XY coordinates, and using the fseek function and the fread function; starting to circulate from 1 until the total number of tracks, and traversing all tracks; the offset calculation formula in the fseek function is:
3600+(i-1)*240+(i-1)*SampleNumber*4+site
wherein, i is the total track number, and the sites are respectively 8, 20, 72 and 76 which sequentially represent the initial positions of the line number, the track number, the X coordinate and the Y coordinate in the track head information;
and 2-5, after decoding the data of the SEGY shallow stratum profile original file, extracting all echo signal data of the survey line by taking Ping as a horizontal coordinate and taking depth of time as a vertical coordinate, and storing the echo signal data in a CSV file format.
In the step 3, Matlab programming software is used for programming the echo signal data Matlab extracted in the step 2 to realize processing of surge static correction, multiple wave suppression, true amplitude recovery and the like, and a shallow stratum profile is generated to realize image visualization of the shallow stratum profile data of the measuring line. As shown in fig. 6, firstly, introducing CSV format echo signal data of the survey line into Matlab, defining parameters of an observation system and a reduced fish towing position according to technical indexes of a shallow profiler, and adjusting gain of an image by properly adjusting a gray value; compiling a visual image code and traversing all Ping, checking Ping with obvious abnormality and repairing, and operating a program to generate a shallow stratum profile image preliminarily; and designing a surge filter and a band-pass filter to respectively carry out surge static correction and random noise suppression on the image, and carrying out energy compensation and correction on the amplitude of the echo.
The relative time displacement between the tracks is generated by time shift caused by the influence of fluctuation of the cable and the sound energy converter caused by surge on recording, and the condition has the characteristic of static time shift and is also one of static correction. The existence of the relative time displacement obviously reduces the signal-to-noise ratio and the resolution of the section, so that the in-phase axis is not clear enough.
Multiples are the most common interfering waves in shallow profile exploration, and are suppressed by a method of predictive deconvolution. The prediction deconvolution is to predict a pure interference part by a prediction method according to information of recording primary reflection and interference, and then subtract the pure interference part from the seismic record comprising primary waves and interference to obtain a primary reflection signal after interference elimination so as to eliminate multiple interference such as marine singing behind the primary reflection and realize multiple suppression.
In the process of stratum propagation, the sound wave is continuously subjected to attenuation and distortion of amplitude energy, and the purpose of true amplitude recovery is to compensate and correct the sound wave energy as much as possible, mainly comprising wave front diffusion energy compensation, stratum absorption energy compensation and surface consistency performance adjustment. The amplitude energy abnormity between adjacent channels can be eliminated by using an amplitude statistical method, the influence of sound wave spherical diffusion on the amplitude is eliminated by using spherical diffusion compensation, and the phenomenon of uneven amplitude of the measuring line caused by seabed geological factors is eliminated by using earth surface consistency amplitude compensation.
Fig. 4 is a diagram of a shallow profile raw data acquisition. It can be seen that the reflective layer interfaces in the figure are continuous, indicating good raw data acquisition quality.
Fig. 7 is a shallow profile generated by analyzing, processing and visualizing the raw data of the shallow stratum. It can be seen that the figure shows a clear regional strong reflection interface, the internal reflection structure, form, energy, frequency and the like of the same layer group are basically similar, and the contrast difference of adjacent layers is obvious, so that the result to be realized by the invention is achieved.
While the present invention has been described with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are illustrative only and not restrictive, and various modifications which do not depart from the spirit of the present invention and which are intended to be covered by the claims of the present invention may be made by those skilled in the art.
Claims (7)
1. A visual display method of shallow profile original data based on SEGY is characterized in that related equipment comprises a shallow profiler, a GPS and a computer, wherein data acquisition software is installed in the shallow profiler, Matlab programming software is installed in the computer, and the method comprises the following steps:
step 1, referring to ocean survey regulations, combining with the on-site water depth and terrain surveying conditions, acquiring shallow stratum profile original data of a certain sea area by using a shallow stratum profiler and data acquisition software thereof under the condition of meeting the parameter requirements of survey line layout and observation systems, and storing the shallow stratum profile original data in an SEGY file format, thereby forming an SEGY shallow stratum profile original data file of each survey line;
step 2, importing a SEGY shallow stratum profile original data file of a certain measuring line into a computer, reading and decoding the SEGY shallow stratum profile original data file by using Matlab programming software, and extracting all echo signal data of the measuring line by taking Ping as a horizontal coordinate and taking depth as a vertical coordinate;
and 3, programming the echo signal data extracted in the step 2 by using Matlab programming software, realizing the surge static correction, random noise suppression, multiple wave suppression and true amplitude recovery processing, generating a shallow stratum profile, and realizing the image visualization of the shallow stratum profile data of the measuring line.
2. The SEGY-based visual display method for shallow profile raw data according to claim 1, wherein the data acquisition software is Discover software in step 1, and the specific process of acquiring shallow profile raw data of a certain sea area and storing the shallow profile raw data in SEGY file format is as follows:
setting that the water depth of a measuring area is less than 100m, and the main measuring line direction is vertical to the general trend direction of deep lines such as submarine topography when the measuring lines are laid;
before measurement of a survey line, selecting and adjusting the total gain of a receiver, the TVG gain and the receiving frequency band of the shallow stratum profiler to ensure that the detection profile obtains the optimal penetration rate and resolution;
during towing operation, the water inlet angle of a transducer of the shallow stratum profiler is 15-20 degrees, so that a towed array is kept stable, the sailing speed is kept at 5kn, the frequency band of the shallow stratum profiler is 4kHz, the beam opening angle is 16 degrees, the pulse length is 20ms, the detection recording depth is 30m below the vertical sea floor, and the recording resolution is 20 cm; the height of the towed fish from the sea bottom is always kept at 5m, and the horizontal distance from the towed fish to the GPS is 20 m; acquiring, displaying and playing back the original data of the shallow stratum section in real time by using the Discover software, and automatically generating a JSF file format;
and converting the JSF file format into an SEGY file format by using Discover software, and copying the SEGY file format onto a computer for storage, thereby forming an SEGY shallow stratum profile original data file of each measuring line.
3. The SEGY-based visual display method for shallow stratigraphic section raw data according to claim 2, wherein in step 2, after acquiring the number of sampling points, the sampling rate, the total track number, the line number, the track number and the XY coordinates from the parameters contained in the header and the track head in the SEGY-based shallow stratigraphic section raw data file, the data of the SEGY-based shallow stratigraphic section raw data file is read by using a Matlab programming software.
4. The SEGY-based method for visually displaying raw data of a shallow stratigraphic section according to claim 3, wherein the specific process of reading the SEGY-based raw data file of the shallow stratigraphic section by using a Matlab programming software program is as follows:
step 2-1, with fopen function: the file id (fopen) imports the shallow profile raw data file of the SEGY, and the fopen function represents to open the file or obtains information about the open file, where:
fileID represents a file identifier;
the filename represents the local path of the file to be opened;
the permission indicates that the access authority type of the opened file is specified, wherein the access authority type is 'r', namely the access authority type of the opened file is specified to be read;
step 2-2, using fseek function: fseek (fileID, offset, origin) and fread functions: a, read the number of sampling points SampleNumber and sampling rate,
the fseek function represents the movement of a pointer to a specified location in a file, where:
offset represents the number of bytes of specified offset, and the number of bytes of sampling rate and sampling point offset is 3200 and 3216 respectively, which means that a file header of 3200 bytes is followed by a file header of 400 bytes containing key information, wherein the sampling rate and the number of sampling points respectively start from 16 th byte and 20 th byte, and each occupy 4 bytes;
origin indicates an offset from a specified position, which is represented by "bof" indicating an offset from the header;
the fread function represents that data are read from the opened binary file into an array A, and the array A is filled in a column mode; wherein:
the sizeA represents the dimension of the output array A, and the dimension of the output data is 1;
precision represents the type of data to be read is specified, and the data types are all 16-bit integer data;
skip represents the number of bytes needing to be adjusted, and the default is 0;
the macchinefmt represents the arrangement mode of the data bytes to be read, the arrangement mode is represented by 'b', the arrangement mode of the data bytes to be read is represented by arranging the low-order bytes at the high address end of the memory, and arranging the high-order bytes at the low address end of the memory;
step 2-3, using a ftell function: calculating the total byte number and the total track number of the SEGY shallow stratigraphic section original data file, wherein the A is ftell (fileID), and the ftell function is used for obtaining the offset byte number of the current position of the file position pointer relative to the file head so as to obtain the total byte number of the file;
the total channel number calculation method comprises the following steps: subtracting the byte number occupied by the character string file header and the binary file header from the total byte number, and dividing the byte number occupied by each track by the byte number occupied by the character string file header and the binary file header, wherein the byte number occupied by the binary file header is 3600, the byte number occupied by each track is the byte number of a sampling point plus the byte number of track header information, and the calculation formula of the total track number is as follows:
TotalTrace＝(TotalBytes-3600)/(SampleNumber*4+240)；
step 2-4, reading the line number, the track number and the XY coordinates, and using the fseek function and the fread function;
starting to circulate from 1 until the total number of tracks, and traversing all tracks; the offset calculation formula in the fseek function is:
3600+(i-1)*240+(i-1)*SampleNumber*4+site
wherein, i is the total track number, and the sites are respectively 8, 20, 72 and 76 which sequentially represent the initial positions of the line number, the track number, the X coordinate and the Y coordinate in the track head information;
and 2-5, after decoding the data of the SEGY shallow stratum profile original file, extracting all echo signal data of the survey line by taking Ping as a horizontal coordinate and taking depth of time as a vertical coordinate, and storing the echo signal data in a CSV file format.
5. The SEGY-based visual display method for shallow stratum profile raw data according to claim 1, wherein in step 3, Matlab programming software is used to program the extracted echo signal data, and a surge filter and a band-pass filter are used to perform surge static correction and random noise suppression respectively.
6. The SEGY-based method for visually displaying raw data of a shallow stratigraphic section according to claim 1, wherein in step 3, Matlab programming software is used to program the extracted echo signal data, and the method of predictive deconvolution is used to perform multiple suppression, wherein the steps are as follows: and predicting a pure interference part according to the information of the recorded primary reflection and interference, and subtracting the pure interference part from the seismic record comprising the primary wave and the interference to obtain a primary reflection signal after the interference is eliminated so as to eliminate the multiple interference behind the primary reflection and realize multiple suppression.
7. The SEGY-based method for visually displaying raw data of a shallow stratigraphic section according to claim 1, wherein in step 3, Matlab programming software is used to program the extracted echo signal data, and the true amplitude recovery processing is performed by one of the following methods:
1) compensating and correcting the acoustic wave energy by adopting any one of wave front diffusion energy compensation, stratum absorption energy compensation and earth surface consistency performance adjustment;
2) the amplitude energy abnormity between adjacent channels is eliminated by using an amplitude statistical method, the influence of sound wave spherical diffusion on the amplitude is eliminated by using spherical diffusion compensation, and the phenomenon of uneven amplitude of the measuring line caused by seabed geological factors is eliminated by using earth surface consistency amplitude compensation.
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