RU2615050C2 - Method of detecting underwater ferromagnetic objects and system for detecting underwater ferromagnetic objects - Google Patents

Abstract

FIELD: physics, instrument-making.

SUBSTANCE: invention relates to reconnaissance using magnetic fields and can be used to detect underwater ferromagnetic objects. Method comprises towing two magnetic field sources along an investigation strip. The boundaries of the investigation strip are set by spreading ferromagnetic material, formed in the form of 1 m³ heaps, placed at a distance of 80-170 m from each other along the axis of the boundary to form a quadrangle. A unit for controlling alternate operation of the towed magnetic field sources is used to record the overall magnetic field of the towed sources and the ferromagnetic heaps with a primary three-component magnetic field converter. Method includes amplifying and converting the detected signals of the overall magnetic field of the towed sources and the ferromagnetic heaps with a secondary converter. The amplified and converted signals of the overall magnetic field of the towed sources and the ferromagnetic heaps are transmitted to a computing unit. The computing unit determines the signal caused by the presence of ferromagnetic heaps or an underwater ferromagnetic object. The signal is transmitted from the computing unit to an actuating unit followed by relaying thereof to the control unit. The control unit provides movement of the towed magnetic field sources within the boundaries of the investigation strip by determining signal coordinates in a navigation module. Method includes preliminary bathymetric survey using a multi-beam echo sounder, acoustic probing of the bottom relief using side-scan sonar, based on the echo and shadow contacts, identifying the detected underwater objects, mapping the bottom relief with identification of watershed lines and weir lines, further probing of the detected object using a laser beam source with transmission of the image to a video system with highlighting of the boundaries on the image using a Sobel operator and a Canny detector. The system for detecting underwater ferromagnetic objects consists of a magnetic field measuring system, which includes two towed magnetic field sources respectively connected by conducting ropes to a power unit through a control unit, two towed primary three-component magnetic field converters, respectively connected by conducting ropes to the secondary converter through the control unit, a computing unit, the input of which is connected to the output of the secondary converter, and the output is connected to the input of the actuating unit, a multi-beam echo sounder and side-scan sonar, which are connected through the control unit and the secondary converter to the computing unit, characterised by that it includes a laser beam module, a video system, an image processing unit, which is connected through the control unit to the laser beam module, the multi-beam echo sounder, the side-scan sonar and the computer.

EFFECT: invention increases accuracy of detecting underwater objects.

3 cl, 6 dwg

Description

The invention relates to methods and devices for reconnaissance and inspection of the seabed using magnetic fields and can be used to detect underwater ferromagnetic objects.

The development of the resources of the oceans is an indispensable and necessary condition for maintaining and expanding the raw material base of the Russian Federation, ensuring its economic and food independence. In addition, it is known that the prospect of depletion of hydrocarbon reserves and other mineral resources on the continental part has predetermined the reorientation of exploration and mining of mineral resources on the continental shelf of the Russian Federation, as well as on international areas of the seabed.

This circumstance led to the need for widespread use of underwater equipment for engineering surveys and inspection of the bottom of individual seas to detect objects of natural origin (stones, boulders, etc.), objects of technogenic origin (ships, ships, other objects that have sunk as a result of natural disasters or military operations, other property, explosive objects, including mines, fragments of trawls, etc.).

The need to inspect the bottom of individual seas in the interests of detecting and eliminating explosive objects is caused, on the one hand, by the residual mine risk and the other explosiveness, and the restriction in navigation and production activities of ships, established by regulatory documents of the Navy, on the other hand.

When performing such tasks, search tools are used, which include multi-beam echo sounders, side-scan sonars, towed and lowered magnetometric devices, as well as remote-controlled underwater vehicles (Survey technology for cleaning bottom from explosive objects in the exclusive economic zone of the Russian Federation in the Gulf of Finland / V. Blinkov / ., Bystrov B.V., Pirozhenko V.A. // SPb., NGO-11, OJSC GNINGI, 2011, pp. 653-657 [1]).

The use of underwater vehicles in the interests of detecting and eliminating explosive objects involves significant material costs and the complexity of performing these works due to the need for their positioning relative to underwater objects.

Known methods for detecting underwater ferromagnetic objects (copyright certificate SU No. 1073607 A1, 02/15/1984 [2]; Geophysical research methods. Textbook. Edited by V.K. Khmelevsky. - M .: Nedra, 1988, p. 57 [3 ]; copyright certificate SU No. 506820 A1, 03/15/1976 [4]; patent BE No. 1011126 A, 05/05/1999 [5]; patent RU No. 2030583 C1, 03/10/1995 [6]).

A known method of underwater mining of minerals [2], includes moving along a landmark of an underwater mining unit along the bottom in parallel stripes and collecting minerals, in which the boundaries are set by dispersing the ferromagnetic material, and a device is installed on the unit for monitoring the presence of ferromagnetic material and measuring the magnitude magnetic field, while moving the unit, the boundary of the next strip is set from the board of the unit simultaneously with the collection of ferromagnetic material and Leznov fossil of the previous strip.

The disadvantage of this method is the small width of the strip of the survey, which significantly increases the time of the process, and, accordingly, material costs.

There is also a method of detecting underwater objects from ferromagnetic materials, based on measuring the magnetic field along the survey strip using a magnetometer [3]. This method also has a small inspection width, in particular, when searching for ferromagnetic objects having a negligible intrinsic field.

To detect and measure a useful signal in the known methods, a magnetic system [4] is used, comprising a three-component magnetic field converter, a power supply, a signal amplification and conversion unit, an executive unit, a second three-component magnetic field converter, two magnetic field sources, a control unit and a computing unit in which the outputs of the first and second magnetic field sources and the outputs of the first and second three-component magnetic field transducers are connected through a control unit respectively, with a power supply unit and a signal amplification and conversion unit, the output of which is connected through the computing unit to the input of the executive unit. In this case, three-component transducers and magnetic field sources are located at the vertices of the corners of a rectangle oriented across the survey strip, the lower side of which is formed by a source and a three-component magnetic field transducer.

This system compared with the known methods [2, 3] through the use of two three-component magnetic field transducers increases the accuracy of detection of underwater objects and increases the width of the survey strip. However, when searching for ferromagnetic objects with a small intrinsic field, the width of the survey strip is also characterized by an insignificant value. In addition, this system is practically not applicable for the detection of weakly magnetized objects.

In the known method of underwater mining and detection of underwater objects in magnetic fields, including moving along a landmark of a magnetic field measurement carrier, defining boundaries by dispersing ferromagnetic material or natural sources of a magnetic field, followed by measuring the magnitude of the magnetic field with the creation of an alternating magnetic field in two diagonally located vertices of a quadrangle oriented across the examination strip formed by the borders, the lower side of the cat It is formed by a magnetic field source and a meter and is located on the survey horizon, and the upper side is formed by the primary three-component transducers of the magnetometer - before setting the boundaries by dispersing the ferromagnetic material, masses of one cubic meter are formed from the ferromagnetic material, which are placed at distances of 80-170 m each from each other along the axis of the border (patent RU No. 2297650 C2, 04/20/2007 [7]).

The essence of the known method [7] is that two sources of a magnetic field are towed along the survey strip. Moreover, the boundaries of the survey strip are set by dispersing the ferromagnetic material formed in the form of masses of 1 m ³ located at a distance of 80-170 m from each other along the axis of the border with the formation of a quadrangle. By means of the control unit for alternating operation of the towed sources of the magnetic field, the total magnetic field of the towed sources and ferromagnetic masses is recorded by a primary three-component magnetic field transducer. The recorded signals of the total magnetic field of the towed sources and ferromagnetic masses are amplified and converted by a secondary converter. The amplified and converted signals of the total magnetic field of the towed sources and ferromagnetic masses are transmitted to the computing unit. In the computing unit, a signal is determined due to the presence of ferromagnetic masses or an underwater ferromagnetic object. A signal is transmitted from the computing unit to the executive unit, followed by its relay to the control unit. The control unit provides the movement of the towed sources of the magnetic field at the specified boundaries of the survey strip by determining the coordinates of the signal in the navigation module. Technical result: expanding the survey strip of the seabed.

In contrast to the methods [2-6] in the known method [7], before defining the boundaries of the survey area by dispersing the ferromagnetic material, masses of one cubic meter are formed from it, which are placed at distances of 80-170 m from each other along the boundary axis.

It is known [1] that the range of the magnetometer is not constant and is determined by the magnetic characteristics of the object, the noise environment and sensitivity.

A significant advantage of the magnetometer in comparison with acoustic means is its effectiveness in conditions of reverberation interference of the shallow sea.

The disadvantages of magnetometric surveys include the impossibility of accurately determining the location of the object, as well as a significant dependence on variations in the Earth's magnetic field.

A technical solution is also known in which a bathymetric survey by means of a multi-beam echo sounder and acoustic sounding of the bottom topography by a side-scan sonar are preliminarily performed, and detected underwater objects are detected by echo and shadow contacts. At the same time, bottom topography is mapped to identify lines of watersheds and overflow lines (S. A. Mikolenko, G. A. Grin. Experience of using modern hydrographic equipment when examining underwater crossings of pipelines. II Scientific and Technical Conference “Welding Related Technologies for Underwater Crossings and offshore oil and gas facilities. ”November 19-20, 2009, resort-park of the Ministry of Foreign Affairs of the Russian Federation“ Union ”, Moscow Region, pp. 5-16 [8]). The known technical solution [8] allows you to identify underwater objects either by the amplitude method, when the target strength of the underwater object and, sometimes, its length are determined. At the same time, it is practically unrealistic to identify underwater objects silted up and brought in by bottom sediments, including mine torpedo weapons and containers with poisonous waste.

In addition, according to GOST 17.1.3.08-82, in selected monitoring points, observations are carried out in full and shortened programs. Observations should be carried out at horizons of 0, 5, 10, 20, 50, 100, 500, 1000 m and at the bottom.

The full control program (with the exception of hydrobiological indicators) includes the following parameters:

- petroleum hydrocarbons, mg / dm ³ (mg / l),

- dissolved oxygen, mg / dm ³ (mg / l) and% saturation,

- hydrogen indicator (pH), units pH

- visual observations of the surface state of the marine water body,

- chlorinated hydrocarbons, including pesticides, μg / dm ³ (μg / l),

- heavy metals (mercury, lead, cadmium, copper), μg / dm ³ (μg / l),

- phenols, μg / dm ³ (μg / l),

- synthetic surfactants (SAS), μg / dm ³ (μg / l),

- additional ingredients specific to the area,

- nitrite nitrogen, μg / dm ³ (μg / l),

- silicon, μg / dm ³ (μg / l),

- salinity of water,%,

- temperature of water and air, ° C,

- wind speed and direction, m / s,

- water transparency, m,

- color of water, units chroma

- excitement, score.

During visual observations, phenomena unusual for this region of the sea are noted (the presence of floating impurities, films, oil spots, inclusions and other impurities; the development, accumulation and death of algae; the death of fish and other animals; the mass release of mollusks (mussels) onto the shore; the appearance of increased turbidity, unusual coloring, foam, etc.).

Known methods and devices do not allow to fully perform the necessary observations due to their limited information content.

In addition, the source data for creating digital sea maps of the bottom topography (DEM) are the data of hydrographic surveys. At the same time, the following DTM construction technology was adopted (Suvorov S.G., Dvoretsky E.M., Kovalenko S.A. Methodology for creating digital elevation models of high accuracy // Information and Space. No. 1, 2005, p. 52-54). All available information is digitized. The data obtained from various sources are combined into a single set of coordinates of points and heights in them. This set is triangulated (usually by the Delaunay method). The triangulation procedure gives a system of disjoint triangles covering the considered region of the earth's surface (TIN model). As a result, the relief appears as a multifaceted (elementary face - a triangle) surface with elevations (depth marks) at the nodes of the triangular network. Each face of this surface is described either by a linear function (polyhedral model) or by a polynomial surface, the coefficients of which are determined by the values at the vertices of the triangle faces. This technology in various versions is implemented in all GIS used in practice.

At the same time, the goal of building a DEM — obtaining adequate direct and indirect terrain information in automated systems — is not achieved. The source of all the disadvantages of this technology is the triangulation stage. In this case, the relief is represented as a continuous function, but with discontinuities already in the corresponding function of the first differential on the edges of the triangulation (i.e., a nonsmooth function). This contradicts the relief model, which is accepted when constructing topographic or navigation maps, where the relief surface appears to be a smooth function. In addition, the true purpose of triangulation is to set the order (network) according to the degree of proximity and relative position on a set of points in the plane, therefore, the relationship of heights (depths) between points is not taken into account, which leads to a distortion of the spatial direction and a shift in the location of structural relief lines. The main types of structural lines of relief include ridge and keel lines, lines of convex and concave bends. By ridge lines, or watersheds, we mean lines of planned correlation of points with maximum heights. Keel lines (thalwegs, beds) connect the points with minimum heights. In addition, the result of triangulation will change dramatically and unpredictably with a change in the initial set of points, i.e. when deleting, adding points (points) or when changing coordinates in the original array of points. This property of triangulation does not allow “controlling” (editing) the construction of a local landform. In addition, if the DEM was constructed using triangulation, then the results of calculating relief differentials of various orders are not reliable. It can be stated that in this area of geoinformatics there is a problem situation, which is expressed in the fact that the technology of DEM construction using the triangulation procedure does not allow achieving the desired goal. This problematic situation can be resolved by using such DTM construction tools that do not use the triangulation procedure and which lead to the construction of an everywhere smooth surface.

In addition, in materials devoted to the identification and classification of underwater objects (A SYSTEM FOR AUTOMATIC DETECTION AND CLASSIFICATION FOR A MINE COUNTERMEASURE AUV Konstantinos Siantidis, Ursula Holscher-HobingATLAS ELEKTRONIK GmbH Sebaldsbrucker Heerstra.e 235 D-28309 Bremen, The drawback of the mission to detect, identify or classify an underwater object and to make decisions by the methods currently in use is to double the total search time due to the delay between the time of inspection of the underwater object and the assessment of the received data. Therefore, it is recommended that detection and classification be done online. This is all the more relevant because at present the most complex tasks, such as independent decision-making in conditions of uncertainty, pattern recognition, identification and classification of objects, are usually solved by means of a medium with the participation of a person and, which is typical, according to insufficiently reliable data.

The objective of the proposed technical solution is to expand the functionality of known methods for detecting underwater objects by magnetic fields while increasing the reliability of detection of ferromagnetic objects.

The problem is solved due to the fact that in the method for detecting underwater ferromagnetic objects, including towing two sources of a magnetic field along the survey strip with setting boundaries by dispersing ferromagnetic material formed in the form of masses of one cubic meter, placed at a distance of 80-170 m each from each other along the axis of the border with the formation of a quadrangle, implementation by means of a control unit of alternating operation of towed sources of a magnetic field, registration of the total magnetic fields of towed sources and ferromagnetic masses by a primary three-component magnetic field transducer, amplification and conversion of registered signals of the total magnetic field of towed sources and ferromagnetic masses by a secondary transducer, transmission of amplified and converted signals of the total magnetic field of towed sources and ferromagnetic masses to a computing unit that determines the signal due to the presence of ferromagnetic masses or an underwater ferromagnetic object, signal transmission with a calculating unit to an executive unit with its subsequent relaying to a control unit that provides towed magnetic field sources movement at predetermined boundaries of the survey strip by determining the signal coordinates in the navigation module, preliminarily perform a bathymetric survey, using a multi-beam echo sounder, acoustic sounding of the bottom topography by side-scan sonar, along echo and shadow contacts detect detected underwater objects, perform mapping of the bottom topography with line detection of the watershed and overflow lines, they additionally perform sounding of the detected object by means of a laser beam source with image transmission to the video system with bordering on the image by means of the Sobel operator and Canne detector, and to the system for detecting underwater ferromagnetic objects, consisting of a magnetic field measuring system, which includes two towed magnetic field sources connected via cable cables respectively to the power supply through the control unit, two tug primary three-component magnetic field transducers connected via cable cables respectively to the secondary transducer through a control unit, a computing unit whose input is connected to the output of the secondary transducer, and the output is connected to the input of the executive unit, multi-beam echo sounder and side-scan sonar, which are connected through the unit control and a secondary Converter to the computing unit, introduced a laser beam module, a video system, an image processing unit, which through the control unit it is connected to a laser beam module, a multi-beam echo sounder, side-scan sonar and a computer. In this case, the laser beam module consists of a laser radiation generating unit, a laser emitter, a reflected beam receiving antenna, a reflected beam concentrator, and an optical fiber cable.

The invention is illustrated by drawings (Fig. 1-6).

FIG. 1 is a block diagram of a magnetic field measuring system, which includes two towed magnetic field sources 1 and 2, connected via cable cables 3 to a power supply unit 5 through a control unit 6, a laser beam module 4, two towed primary three-component magnetic field transducers 7, connected via cable cables 9, respectively, to the secondary Converter 11 through the control unit 6, the video system 8, the image processing unit 10, the computing unit 12, the input of which is connected to the output again about the Converter 11, and the output is connected to the input of the Executive unit 13, the multi-beam echo sounder 14 and the side-scan sonar 15, connected through the control unit 6 and the secondary Converter 11 to the computing unit 12, which is connected through the control unit 6 to the image processing unit 10, which is connected with a laser beam module 4, a multi-beam echo sounder 14, side-scan sonar 15 and a video system 8.

FIG. 2 - exposure strip survey. The masses of the ferromagnetic material 16, the axis of the boundary 17, the carrier 18 of the measuring system of the magnetic field.

FIG. 3. Illustration of the discrepancy between the results of numerical differentiation with true values. Here, the function L _n (x) is a function that interpolates the “true” function y (x) at the measurement points x _i .

FIG. 4. The initial surface is represented by a regular set of 15 × 15 points.

FIG. 5. Calculated position: troughs — local minima 19, passes — saddles 20, peaks — local maxima 21, ridges 22 — chains of triangles, thalwegs 23 — chains of segments “-”>, vector field 24 for the discrete Morse function (shown as arrows , the numbers near the triangulation nodes are elevation values of 25.

FIG. 6. The block diagram of the laser beam module. The laser beam module 2 consists of a laser radiation generating unit 26, a laser emitter 27, a reflected beam receiving antenna 28, a reflected beam concentrator 29, and an optical fiber cable 30.

The essence of the method is as follows.

Preliminary, a bathymetric survey is performed by means of a multi-beam echo sounder, and acoustic sounding of the bottom topography by a side-scan sonar, the detected underwater objects are detected by echo and shadow contacts, the bottom topography is mapped to identify watershed lines and overflow lines, and then, as in the prototype [7], carry out the towing of two sources of the magnetic field along the survey strip with the assignment of its boundaries by dispersing the ferromagnetic material formed in the form of masses of one cubic meter, p located at a distance of 80-170 m from each other along the axis of the border with the formation of a quadrangle, using the control unit for alternating operation of the towed sources of the magnetic field to register the total magnetic field of the towed sources and ferromagnetic masses with the primary three-component magnetic field converter, amplification and conversion of the recorded signals of the total magnetic field towed sources and ferromagnetic masses by a secondary converter, amplified transmission and conversion signals of the total magnetic field of the towed sources and ferromagnetic masses to the computing unit, which determines the signal due to the presence of ferromagnetic masses or an underwater ferromagnetic object, the transmission of the signal from the computing unit to the executive unit and its subsequent relaying to the control unit, providing the movement of the towed magnetic field sources in the specified the boundaries of the survey strip by determining the coordinates of the signal in the navigation module.

Survey of the bottom topography is carried out by regular ship multi-beam echo sounders without passes with overlapping adjacent bands. To capture the bottom topography, multi-beam echo sounders can be used (see, for example: Sea Beam 1180, Simrad EM 3002). Acoustic sounding is performed using a side-scan sonar (HBO) with a frequency of 500-780 kHz, for example, a C-max side-scan sonar to detect explosive objects at a frequency of 780 kHz.

A feature of detecting objects at the bottom of the sea with the help of HBO is that the HBO display shows echo and shadow contacts of detected objects, and their sizes, including height, can be determined, depending on the length of the shadow cast.

The height of the object along the length of the cast shadow is determined from the expression:

where: Δ _t - the length of the projection of the shadow;

H - the distance of the antenna from the ground;

d ₀ is the measured slant range.

The calculations showed that for the effective detection of bottom objects it is advisable to tow the HBO antenna at a speed of no more than 6 knots at a slight distance of the antenna from the ground (up to 5 m).

One of the drawbacks of this side-scan sonar sample is the presence of a slight dead zone, which should be taken into account when planning, while it is advisable to search for bottom objects on mutually perpendicular tacks.

This shortcoming of HBO in terms of the presence of a dead zone is eliminated through the use of an antenna with a synthesized aperture.

The experience of using a side-scan sonar showed its high efficiency in detecting bottom objects, however, their recognition presents certain difficulties in conditions of sea bottom contamination with boulders and stones, which are close in size to the size of explosive objects.

The main positive properties of HBO include the following:

relatively high search performance;

sufficiently high accuracy in determining the coordinates of detected objects;

the ability to determine the size of objects.

The disadvantages of HBO of this type include: the presence of "dead zones"; difficulty in interpreting detected objects.

The composition of the area survey complex includes sound velocity meters and vertical pitch and roll - trim sensors, which provide corrections to the data of the area bathymetric survey and acoustic sounding.

Heading and dynamic displacement sensor of the Octans type vessel with compensation of dynamic displacements of 0.01 degrees on the course, vertical movement, roll and pitching with a data frequency of 40 Hz.

Sound speed meter type "SVP 15" or type "OLD-1".

Sea level meter type "GMU-2".

The measured depths in post-processing are corrected by depths at sea level according to the data of temporary level posts. Based on the survey results, depth plates are compiled on a scale of 1: 2000.

In mapping the relief, the structural lines of the relief play an important role (see, for example: Leontyev OK, Rychagov GI General geomorphology. - Moscow: Higher school, 1976. - 288 p.). Among these lines, two types of lines are the most significant. These are the lines of the watersheds - the intersection of two opposite slopes of the ridge, its crest, forming a dividing line, and the spillway, or thalweg — a line that runs along the bottom of depressions, bounded by slopes on both sides.

Typically, the structural lines of land and sea topography are determined by experts, experts - cartographers and geomorphologists. However, the introduction of computers into cartographic activities necessitates the development of automated methods for detecting structural lines.

Automated determination of structural lines is associated with the resolution of the problem of discreteness of the source data representing the relief. This circumstance is especially important in problems of constructing the bottom topography. Here, the surface of the relief is not accessible to direct visual inspection.

The methods used in geographic information systems are reduced to a sequence of operations: obtaining an array of depths (heights) on a regular coordinate grid with subsequent two-dimensional triangulation of the initial set of points of depths (heights) and interpolation based on some kind of smoothing algorithm (splines, nearest neighbor, etc.) ) Based on this array, the vector field of surface gradients is found by numerical differentiation, which is the basis for an interactive way of revealing structural lines.

In this sequence of operations, the most problematic is the operation of numerical differentiation. This operation is a classic example of an incorrect mathematical problem according to Hadamard (see, for example: Shilov G.E. Jacques Hadamard and the formation of functional analysis. Speech at the memorial meeting of the Moscow Mathematical Society on March 10, 1964 // Advances in Mathematical Sciences. - 1964. - 19. - No. 3. - S. 183-185.). The fact is that the fact that the values of the measured depths are close to the true values does not imply that the calculated and "true" derivatives (differentials) will be close even with a high density of depth measurement points. Moreover, the “true” biases and the calculated derivatives can have different signs at the same point (Fig. 3).

Therefore, to automatically determine the location of the structural lines of the bottom topography, an algorithm is needed that does not require the use of incorrect algorithms for numerical differentiation. It is proposed to use methods for computing a discrete vector field as a basic basis for such an algorithm.

The arguments for this are the following circumstances. The initial data structure is the two-dimensional triangulation of the initial array of coordinates of the depth measurement points used in existing algorithms. The operations of interpolation, smoothing, reduction to a regular network of point coordinates, and differentiation are not used. Instead of these operations, only combinatorial methods of calculation are used, which are based on the mathematical theory of combinatorial topology.

For the constructive description of the proposed algorithm, it is required to provide several explanatory concepts from the field of discrete geometry.

From a mathematical point of view, the cartographic representation of the relief is a smooth Morse function (see, for example: Zhukov Yu.N. Mathematical tools for describing the cartographic display of the Earth's relief. // Navigation and Hydrography, 2011, No. 32, pp. 60-69.). The lines of the watersheds and thalwegs are identical to the lines of separatrices on the corresponding relief of the Morse function. Lines of watersheds and thalwegs connect mountain peaks with passes, and passes with the lowest point of the basin. Similarly, the separatrix lines connect the maximum points with saddle points, and the saddle points with the minimum points of the Morse function.

For a smooth function of the surface of the relief, it is possible to use methods of differential geometry. However, in practice, the relief surface is represented at discrete points, and the methods of differential geometry are not applicable to the discretely presented surface. Therefore, it is natural to describe the discrete relief presented in the form of an analog — the discrete Morse function, which in turn is the discrete analog of the smooth Morse function.

A discrete Morse function is a combinatorial object - a simplicial complex obtained by simplicial decomposition of the corresponding smooth Morse function. In practice, this means that a smooth surface is specified at the nodes of the triangulation of the coordinates of the points of measurement of the relief. But there are abstract concepts that are included in the description of the discrete Morse function, for which there is no simple practical analogue, but without which it is impossible to describe the method of finding the lines of watersheds and thalwegs on a discretely defined triangulated relief surface.

We give far from a complete minimal set of concepts necessary for describing a discrete Morse function and computing a vector field on it. The theory of discrete Morse functions was developed by Forman in 1998 (see, for example: Forman R. Morse theory for cell complexes. // Advances in Mathematics. 1998, No. 134, 90-145 pp.).

The triangulated set of surface points is represented by the simplicial complex K (in our case, necessarily finite), in which each triangular element consists of independent objects a with different topological dimension p, called p-simplexes. In our case, the two-dimensional relief surface with p-simplexes will be: the vertices of the triangulation nodes are points (separate) with p = 0, the sides of the triangles (without end points and the inner region of the triangle) are edges with p = 1, and the region inside the triangle (without vertices and sides) with p = 2.

A discrete Morse function f on K is a map

such that for each σ ^(p) ∈K _p and two conditions:

Here R is the set of real numbers, σ ^{(p) is a} simplex of dimension p, K _p is a subcomplex of complex K consisting of simplexes of dimension p, the sign # determines the number of simplexes satisfying the conditions indicated in curly brackets. The discrete Morse function f can be represented as a function increasing with the dimension of simplexes in the sense that there is no more than one direction in which f decreases when passing from the p-simplex σ to the (p + 1)-simplex τ.

The structural points of the relief are the lowest points of the basins, the points of the passes, and the peak points of the peaks. An analogue of these points can be represented as critical points of the discrete Morse function f, which are simplexes σ ^(p) (dimension p) for which the equalities hold:

In other words, the lowest points of the basins correspond to the points of the vertices of the triangles with the minimum values of f in comparison with the values of f on adjacent edges and triangles; the points of the passes correspond to edges on which the values of f are strictly not greater than at their endpoints, and the values of f on the triangles adjacent to the edges are strictly greater than on the corresponding edges; peak points of mountain peaks correspond to the inner regions of triangles, the values of f on which are strictly greater than on the edges forming them.

The vector in the discrete Morse function f is an ordered pair of simplexes (σ, τ) such that σ ^(p) <τ ^{(p + 1)} and f (τ) ≤f (σ). It is said that the vector is directed from σ ^(p) to τ ^{(p + 1)} . A discrete vector field V on K is a collection of vectors {σ ^(p) <τ ^{(p + 1)} } such that each simplex K belongs to no more than one vector from V. If a discrete vector field V on K is given, then K -by called an ordered sequence of simplexes

.such that for each i = 0, ..., r the vector {σ ^(p) <τ ^{(p + 1)} } ∈V and $${\tau }_i^{\left(p+\mathrm{one}\right)}>{\sigma }_{i+\mathrm{one}}^{\left(p\right)}\ne {\sigma }_i^{\left(p\right)}$$

.

An essential circumstance is that, as Forman showed in 1998 (see, for example: Forman R. Morse theory for cell complexes. // Advances in Mathematics. 1998, No. 134, 90-145 pp.) V for a discrete Morse function f is equivalent to the vector half of the gradients for the smooth Morse function corresponding to f.

The latter circumstance allows us to obtain the following rigorous method for calculating the location of the lines of watersheds and thalwegs, which is as follows.

Two-dimensional Delaunay triangulation is calculated for the depth measurement coordinates.

From the triangulation data and the measured depths, the discrete Morse function f is calculated. Next, critical points f, a discrete vector field V for f, and vector paths (according to formula 6) are calculated that lead from the minima to the saddles, and from the saddles to the maxima f.

The sequence of simplexes of these vector paths will represent the locations of the desired lines of the watersheds and thalwegs. It follows from expression (6) that the separatrices connecting the maximum with the saddle are formed by a sequence of triangles, and the separatrices connecting the saddles and minima are a sequence of edges.

The presented method is implemented in several algorithms described in the literature (see, for example, King N., Knudson K., Mramor N. Generating Discrete Morse Function from Point Dat // Experimental Mathematics, 2005, v. 14, No. 4. - 435 -444 pp .; Gyulassy A., Levine J., Pascucci V. Visualization of Discrete Gradient Construction // Proceedings of the 27th annual ACM symposium on Computational geometry, 2011, 289-290 pp.).

For the illustrative calculations shown in FIG. 3-5, the algorithm proposed by A. Gyulassy was used (see, for example: Gyulassy A., Levine J., Pascucci V. Visualization of Discrete Gradient Construction // Proceedings of the 27th annual ACM symposium on Computational geometry, 2011, 289 -290 pp). Its advantage over others is that, unlike other algorithms, it does not require any additional information, except for an array of point measurements of depths. All other necessary information, for example, the location of critical points, is calculated during the execution of the algorithm.

The proposed method can serve as the basis for the development of effective rigorous automated algorithms for cartographic relief generalization.

The task of searching for objects at the bottom is performed using C-max type side-scan sonar (Great Britain) and a Sea Spy type towed magnetometer (Canada), laser beam module 4 and video system 8.

The side-scan sonar is equipped with a parametric emitter and a parametric receiver, which have a wide band of operating frequencies, small dimensions, a constant and smooth directivity pattern at different frequencies.

Underwater objects are recognized by their physical characteristics by analyzing the spectrum of echo signals in the low frequency region (tens of Hz - units of kHz) or by measuring the phase distortion in the received echo signal.

However, parametric emitters and receivers have a significant drawback, namely, low conversion efficiency. But the losses of the conversion of the primary wave into differential-frequency sound can be compensated either by using a broadband or multicomponent probing signal, which allows increasing the energy of converting a high-frequency signal into a difference-frequency signal, thereby increasing the sonar range by 1.5-2 times, or by amplifying the echo signal when processing.

Since some features are difficult to recognize either due to hydrological conditions, or due to the presence of natural or artificial interference, the proposed system for detecting underwater ferromagnetic objects also contains a laser beam module 4 and a video system 8 for identifying the material and configuration of the underwater object.

The task of distinguishing ferromagnetic objects from underwater objects, mainly of natural origin, is assigned to towed magnetometers, which are used in conjunction with side-scan sonars and laser beam module 4 and video system 8.

To accomplish these tasks, a towed magnetometer of the Sea Spy type by Marine Magnetics was used, which measures the magnetic field of an object using special nuclear magnetic resonance technology using the Overhauser effect.

The tracks are worked out with a distance between the profiles of 10 m. Then, up to the corridor widths of 400 and 2000 m (expansion sections), the step between the profiles is 50 m. This allows you to confidently track linearly elongated objects - pipes, cables, etc. For monitoring, we perform measurements along longitudinal tacks in 1 km

A significant advantage of the magnetometer in comparison with acoustic means is its effectiveness in conditions of reverberation interference of the shallow sea.

Detection ranges of ferromagnetic objects using the SeaSpy magnetometer are:

for an object weighing 250 kg - 30 m;

for an object weighing 50 kg - 18 m;

for an object weighing 18 kg - 12 m;

In a gondola designed for towing a magnetometer the following are also located: sonar or parametric sonar profiler; underwater navigation transponder beacon; video system 8, for example, a color video camera; depth sensors; laser rangefinder; halogen lights; electromagnetic finder type "Pepi Tracker TSS-340/440"; metal detector type "Innovatum", which has a search strip with a width of 8-10 m, laser beam module 4.

In the laser beam module 4 (Fig. 6), the laser radiation generating unit 26 contains n-lasers intended, respectively, for detecting explosives (BB), metal and wood structures, concrete, paraffin, and oiled paper. The reflected signals from the detected object are received by the antenna 28 receiving the reflected beam and through the hub 29 of the reflected rays are fed to the fiber optic cable 30 and then to the image processing unit 10.

The image processing unit 10 also receives signals from the video system 8.

The digital image obtained by the video system 8 is pre-processed to eliminate noise by anisotropic diffusion.

In order for temperature equalization (smoothing) to be performed inside homogeneous regions without violating the boundaries between the regions, it is necessary that the conductivity inside the regions is high and low at the boundaries. This can be achieved by choosing a diffusion coefficient in the form of a monotonically decreasing function of the intensity gradient. The diffusion equation is solved numerically. The next step is to highlight the borders in the image using the Sobel operator and Canne detector (C. John Canny. A Computation Approach to Edge Detection // EEE Transaction Analysis and Machine Intelligence, No. 6, vol. 8, November 1986, p. 689).

In this case, only the maximum points of the image gradient are left in the boundary contour, and not the maximum points lying near the border are deleted. Here, information is used about the direction of the boundary in order to remove points precisely with the boundary and not tear the boundary itself near the local maximums of the gradient.

The attribution of the detected object to a certain class is carried out on the basis of the analysis of signs inherent in explosive objects. The main features by which the identification (recognition) of objects is carried out is its "image" (image), characterized by: the shape of the object; the size of the object, as well as other individual distinguishing features (galvanic shock caps, combat charging compartment, tail units, torpedo propulsion, etc.).

The location of the carrier vehicle search means is determined using the SNA in differential mode.

The position of the towed nacelle relative to the carrier vessel is determined using HANS with an ultrashort base (USBL) of the Hipap type (Kongsberg, Norway), which determines the range, bearing and elevation angle of the nacelle relative to the HANS receiver placed on the provided vessel. The specified HANS sample determines a distance of up to 4000 m, while the standard deviation for determining the range can be 0.25 percent of the range, and the standard deviation for determining the elevation angle to 0.25 degrees. The indicated errors, in fact, are instrumental and are given for “ideal” conditions that do not take into account errors due to reverberation, refraction of acoustic rays, etc. The experience of using this type of HANS showed their unstable operation at shallow depths of the sea up to 10-12 m.

Magnetometry is performed using a Sea SPY or Marine Magnetic Explorer proton gradiometer. The towed body (gondola) of the gradiometer in deep water is towed at a distance of 5 m from the bottom. For stable holding of the towed body at a given distance from the bottom, a DT VARINE 2005EHLWR winch with remote control is used. In shallow areas, the working body of the gradiometer is towed to the surface, its location is determined by the length of the cable and the distance to the GPS antenna.

To determine the position of the vessel and the information sensors with the necessary accuracy, the GPS satellite navigation system in differential mode (DGPS) is used, operating on two independent control and correction stations, as well as geodetic control and correction stations for working in RTK mode or for receiving Starfix HP corrections via satellite channel.

Such a coordination system ensures the determination of a place with a mean square error of not more than 0.3 m at any point in the district during round-the-clock operation.

For navigation support, the MS 750 Base type geodetic station, Trimble 5700 RTK and Trimble DSM 2121 shipborne receivers, a navigation computer with software, electronic navigation information system (ECDIS), and ECS-1000 with “dKart Navigator” software, ultra-short-range underwater navigation system of the type “Simrad HRP 4 UR” for high-precision positioning of the gondola of a magnetometer with two beacon transponders or a geodetic station of the type “Trimble 4600LS”, as well as mathematical software Trimble Geomatics Office software, Mapinfo v.7-type geographic information system, Octans type heading and dynamic displacement sensor with dynamic displacement compensation of 0.01 degrees heading, vertical displacement, side and keel pitching with data frequency 40 Hz, a sound velocity meter of the type "SVP 15" or of the type "OLD-1", a sea level meter of the type "GMU-2", a multi-beam echo sounder of the type "Simrad EM 3002" or "SEA BEAM".

Further, the method is implemented, as in the prototype [7].

From the theory of permanent magnets it is known (see, for example: Gordin V.M., Rose E.N., Uglov B.D. Marine magnetometry. M., Nedra, 1986, p.232), which is one of the main characteristics of permanent magnets is the specific magnetic energy:

where B is the magnetic induction, H is the magnetic field strength.

This energy characterizes the potential ability of a magnet to store magnetic energy.

Wherein

where B _r is the residual magnetic induction, μ ₀ is the magnetic permeability of the magnet rock.

Based on the values of the maximum specific energy that these or those magnets can create, we can estimate the magnitude of the magnetic moment. Given that the magnetic moment is directly proportional to the volume of the ferromagnetic material, the results of the assessment for one cubic meter of magnetic material, taking into account that

where ξ is the magnetization, M is the magnetic moment, V is the volume of the magnetic material.

The results of calculating the maximum magnetic moment that can be created by one cubic meter of ferromagnetic material have the following values:

- for Fe-Al-Ni-Co alloys (Wmax = 40-10 ³ J / m ³ ; Mmax = 500 kA / m ² ; K = 2⋅10 ^-8 );

- for rare-earth compounds of the SmCo type (Wmax = 72⋅10 ³ J / m ³ ; Mmax = 670 kA / m ² ; K = 1.5⋅10 ^-8 );

- compounds based on Fe, Fe-Co (Wmax = 26⋅10 ³ J / m ³ ; Mmax = 400 kA / m ² ; K = 2.5⋅10 ^-8 );

- various steels of the ЕХЗ, Е7В6 type and others (Wmax = 1 ÷ 2 10 ³ J / m ³ ; Mmax = 80 ÷ 110 kA / m ² ; К = 9 ÷ 12⋅10 ^-8 ).

The highest energy intensity are compounds of rare-earth metals (coefficient 1.5⋅10 ^-8 ) and steel (coefficient 9 ÷ 12⋅10 ^-8 ).

Estimation of the volume of ferromagnetic material necessary to create at various distances r from the center of a magnetic field source having values of 1.10 and 100 nT, based on the dependence:

where k = 10 ^-5 / M is a coefficient depending on the magnetic material used;

showed that to create a constant magnetic field with the required strength of 10 nT at a distance from the center of the source of about 200 m, approximately ten cubic meters of steel or two cubic meters of rare-earth metals are needed.

Given that the average length of the support vessel is about 150 m, and the error of modular magnetic sensors is 0.1-0.01 nT (see, for example, Semevsky RB, Averkiev V.V., Yarotsky V.A. Special magnetometry (St.P., Nauka, 2002, p. 164), the length of the ferromagnetic material along the recommended course of motion for detecting a useful signal will be about 300 m. Moreover, the value of the inspection bandwidth when using a magnetometer will be 214 m.

Unlike the known methods in the present method, a bathymetric survey is preliminarily performed, using a multi-beam echo sounder, acoustic sounding of the bottom topography by a side-scan sonar, detected underwater objects by echo and shadow contacts, bottom topography mapping with revealing watershed lines and overflow lines, as well as as in the prototype [7], before setting the boundaries of the survey area by dispersing the ferromagnetic material, masses of one cubic meter are formed from it, some are placed at distances of 80-170 m from each other along the axis of the border.

The measuring system operates as follows. In the process of towing along the survey strip by means of the control unit 6, the magnetic sources 1 and 2 are alternately operated. The total magnetic field of the source 1 and the ferromagnetic masses 16 acts on the primary track component transducer of the magnetic field 8, and the total magnetic field of the source 2 and ferromagnetic masses 14 affects primary track component magnetic field transducer 7. The signals arising from this are fed to the input of the secondary transducer And, which amplifies and converts the signal Ala. From the secondary Converter 11, the signals alternately enter the computing unit 12, which determines the signal due to the presence of ferromagnetic masses or an underwater ferromagnetic object (when searching for underwater objects). Next, the signal is fed to the Executive unit 13, where it is recorded and transmitted to the media control system 6, which provides media movement within the specified boundaries of the survey area (work). When searching for underwater objects, the signal enters the navigation module, where its coordinates are determined.

The creation of a magnetic field in two diagonally located vertices of a quadrangle oriented across the survey strip formed by the boundaries, the lower side of which is formed by the magnetic field source 1 and the primary three-component transducer 8 with its location on the survey horizon, and the upper side is formed by the magnetic field 2 and the primary three-component transducer 7 with the formation of boundaries by dispersing ferromagnetic material with a volume of one cubic meter at a distance of 80 ÷ 170 m a friend from each other along the axis of the border, allows you to create a constant magnetic field with a strength of 10 nT using magnetometers with a sensitivity of 0.001 ÷ 0.0001 gamma, which allows the detection of ferromagnetic objects with a survey bandwidth of up to 5000 m and low-magnetic objects with a survey bandwidth of 1000 m and more.

According to the data obtained by means of the laser beam module 4 and video system 8, the detection limits of underwater objects and their classification are specified.

In the proposed method, systematic errors and errors due to the Earth’s magnetic field and its variations due to the compensation principle of the measuring system’s functioning in combination with the location of the ferromagnetic material forming the boundaries of the survey area in a certain order are excluded from the processing results, which increases the reliability of the survey results. The creation of an artificial magnetic field from the masses of ferromagnetic material located in a certain order allows, when approaching unchallenged marine loading and unloading buoy terminals of the BTL and STL type, to ensure navigational safety of ships and reduces the time to exit to these stations. In this embodiment, the use of the proposed method, the magnetometers can be installed in the underwater part of the shaft lag or sonar equipment in the bow of the vessel. When the magnetometers are located in ship conditions, the created artificial magnetic field from the masses of ferromagnetic material can also be used as a cable measuring line for field tests of ship technical navigation aids (see, for example, Korablev A.E., Massarov V.F. Electromagnetic navigation systems and instruments. L., VMA, p. 9.).

Using the proposed method, the search and detection of underwater objects consisting of ferromagnetic materials (iron, steel, etc.), underwater hazards (banks, reefs, rocks) containing low-magnetic materials (sand, clay, pebbles, etc.) can be carried out. .p.), as well as underwater exploration of minerals.

Information sources.

1. Technology for inspection of cleaning the bottom of explosive objects in the exclusive economic zone of the Russian Federation in the Gulf of Finland / Blinkov V.I., Bystrov B.V., Pirozhenko V.A. // SPb., NGO-11, OJSC GNINGI, 2011, p. 653-657.

2. Copyright certificate SU No. 1073607 A1, 02.15.1984.

3. Geophysical research methods. Textbook allowance under the editorship of VK. Khmelevsky. - M .: Nedra, 1988, p. 57.

4. Copyright certificate SU No. 506820 A1, 03/15/1976.

5. BE patent No. 1011126 A, 05/04/1999.

6. Patent RU No. 2030583 C1, 03/10/1995.

7. Patent RU No. 2297650 C2, 04.20.2007.

8. S.A. Mikolenko, G.A. Grin. The experience of using modern hydrographic equipment in the examination of underwater crossings of pipelines. II Scientific and Technical Conference "Welding related technologies for underwater crossings and offshore oil and gas facilities." November 19-20, 2009, resort-park of the Ministry of Foreign Affairs of the Russian Federation “Union”, Moscow Region, p. 5-16.

Claims (3)

1. A method for detecting underwater ferromagnetic objects, including towing two sources of a magnetic field along a survey strip with setting boundaries by dispersing ferromagnetic material formed in the form of masses of one cubic meter, located at a distance of 80-170 m from each other along the axis of the border with the formation the quadrangle, the implementation of the alternating operation of the towed sources of the magnetic field through the control unit, registration of the total magnetic field of the towed sources and ferromagnetic m as a primary three-component magnetic field transducer, amplification and conversion of recorded signals of the total magnetic field of towed sources and ferromagnetic masses by a secondary converter, transmission of amplified and converted signals of the total magnetic field of towed sources and ferromagnetic masses to a computing unit that determines the signal due to the presence of ferromagnetic masses or underwater ferromagnetic object, signal transmission from the computing unit to the executive unit with by its subsequent relaying to the control unit, ensuring the movement of towed magnetic field sources within the specified boundaries of the survey strip by determining the coordinates of the signal in the navigation module, preliminary performing bathymetric surveys using a multi-beam echo sounder and acoustic sounding of the bottom topography with a side-scan sonar, which can be detected by echo and shadow contacts discovered underwater objects, perform mapping of the bottom topography with the identification of the watershed lines and weir lines, about Leach in that it additionally operate sensing object detected by the laser-beam source of the transfer image on the video system with allocation boundaries in the image by Sobel operator and Canne detector. 2. A system for detecting underwater ferromagnetic objects, consisting of a magnetic field measuring system, which includes two towed magnetic field sources connected via cable cables respectively to a power supply unit through a control unit, two towed three-component primary magnetic field transducers connected via cable cables respectively, to the secondary converter through a control unit, a computing unit, the input of which is connected to the output of the secondary converter, and the output is connected to the input of the executive unit, multi-beam echo sounder and side-scan sonar, which are connected through the control unit and the secondary converter to the computing unit, characterized in that the laser beam module, video system, image processing unit, which is connected through the control unit to the laser beam module, multi-beam echo sounder, side-scan sonar and calculator. 3. The system for detecting underwater ferromagnetic objects according to claim 2, characterized in that the laser beam module consists of a laser radiation generating unit, a laser emitter, a reflected beam receiving antenna, a reflected beam concentrator, and an optical fiber cable.

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