A diatom morphological classification method for medico-legal inference of drowning sites

Abstract

The application relates to the technical field of morphological classification, and discloses a diatom morphological classification method for forensic inference of a drowning site, which comprises the following steps: acquiring diatom vector data and tissue vector data; extracting three principal component variables from the diatom vector data and the tissue vector data respectively to obtain a first coordinate point and a second coordinate point; calculating the distance between the first coordinate point and the second coordinate point corresponding to each sampling point; and taking the sampling point with the shortest distance from the first coordinate point as a potential drowning site. According to the application, principal component analysis is performed on the tissue vector data and the diatom vector data to obtain the first coordinate point and the second coordinate point formed by the three principal component variables; the distance between the first coordinate point and each second coordinate point is calculated; and the sampling point where the second coordinate point with the shortest distance from the first coordinate point is located is taken as the potential drowning site. In the foregoing manner, the application can realize quick, accurate and easy-to-operate inference of the drowning site.

Description

Technical Field

[0001] This application relates to the field of morphological classification technology, and in particular to a morphological classification method for diatoms used in forensic drowning location deduction. Background Technology

[0002] In forensic practice, determining the location of drowning is crucial in clarifying the circumstances of waterborne deaths, especially when the location where a submerged body is found is far from the initial drowning site. The presumed drowning location is invaluable in confirming or refuting witness testimonies, accurately estimating the time elapsed since death, and revealing environmental factors that may have contributed to the accident. Furthermore, accurately determining the drowning location makes a significant contribution to public safety efforts, helping to identify high-risk areas for water accidents. This valuable information supports targeted prevention strategies, such as optimizing safety signage, strategically deploying lifeguards, and conducting comprehensive public education campaigns. By utilizing these insights, authorities can strengthen water safety measures and potentially reduce the number of drowning-related deaths.

[0003] Diatoms are single-celled algae with unique siliceous cell walls, widely distributed in aquatic environments. During drowning, these microorganisms may be inhaled into the alveolar cavities, subsequently entering the bloodstream through alveolar capillaries and distributing to organs such as the liver, kidneys, and bone marrow. In some countries, drowning diagnosis heavily relies on diatom detection in these organs (especially the lungs, liver, and kidneys), although the reliability of diatom detection remains controversial. Furthermore, forensic experts can infer the location of drowning by comparing diatom groups found in organs with those in water samples. Currently, some researchers are using molecular biology techniques to diagnose drowning and infer drowning locations by identifying diatom species, specifically employing DNA barcoding techniques such as 16S rDNA, 18S rDNA, and rbcL. However, these methods are questioned due to the production of non-specific products during PCR amplification. Moreover, the high cost of equipment and labor hinders the widespread application of these methods in forensic medicine.

[0004] In contrast, morphological definition of diatom species offers a more economical alternative, requiring less specialized equipment than molecular techniques and facilitating its adoption at the grassroots level of forensic medicine. Morphological identification and classification of diatoms involves a systematic examination of diatom shells under high magnification (>1000×), typically using an oil immersion microscope or electron microscope. The conventional process generally follows these steps: (1) identifying the presence of diatom shells; (2) distinguishing key physical features, such as diameter and suture orientation (central or off-center); (3) comparing features, including the number of dotted rows, shell valve length, stripe diameter, and width; and (4) verifying symmetry after diatom identification, confirming whether it is bilateral or radial symmetry. Other features, such as shape and size, should also be analyzed to further refine the classification. This method requires considerable expertise to discern subtle morphological differences between species and often necessitates reference to taxonomic atlases and other sources to ensure accuracy. This method is extremely complex, time-consuming, and requires extensive aquatic knowledge. Especially in time-sensitive applications such as forensic investigations, there is an urgent need to develop faster and easier-to-use diatom classification techniques for forensic drowning location deduction. Summary of the Invention

[0005] The purpose of this application is to provide a diatom morphological classification method for forensic drowning location inference, so as to achieve rapid, accurate and easy-to-operate drowning location inference.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] This application provides a morphological classification method for diatoms used in forensic drowning location deduction, the method comprising:

[0008] Acquire diatom vector data and tissue vector data;

[0009] Three principal component variables are extracted from the diatom vector data and the tissue vector data respectively. The three extracted principal component variables are represented as coordinate points in three-dimensional space to obtain the first coordinate point and the second coordinate point.

[0010] Calculate the distance between the first coordinate point and the second coordinate point corresponding to each sampling point;

[0011] The sampling point that is closest to the first coordinate point is taken as the potential drowning location.

[0012] Furthermore, diatom vector data and tissue vector data were obtained in the following ways:

[0013] Water samples were collected from multiple sampling points in the target area and prepared into water smears.

[0014] The number of diatoms in the water sample smears at each sampling point was counted;

[0015] The diatoms in the water sample smear were classified using a diatom classification system, and the percentage of each type of diatom was calculated.

[0016] Arrange the percentage values ​​of each type of diatom in a set order to obtain diatom vector data for each sampling location;

[0017] Tissue samples of the human body to be tested were extracted and prepared into tissue smears, and then classified using a diatom classification system to obtain tissue vector data.

[0018] Furthermore, the number of diatoms in the water sample smear at each sampling point shall not be less than 500.

[0019] Furthermore, the methods for classifying diatoms in the water smear or tissue sample using a diatom classification system include:

[0020] Extract diatom shell features, contour features, and texture features from the water smear or the tissue sample;

[0021] Diatom shell characteristics are used to determine the symmetry classification of diatoms;

[0022] Diatom outline classification is determined based on the outline features;

[0023] The texture classification of diatoms is determined based on the texture features.

[0024] Furthermore, the method of classifying diatoms in the water smear or tissue sample using a diatom classification system also includes:

[0025] The symmetry, contour, and texture classifications of diatoms are represented by a three-dimensional variable, wherein the three-dimensional variable includes three variable values, which represent the numbers of the symmetry, contour, and texture classifications of diatoms, respectively.

[0026] Furthermore, the symmetry classification of diatoms is determined based on the characteristics of the diatom shells, including:

[0027] If the diatom shell is characterized by rotating around a central point at any angle while maintaining its shape and appearance, then the symmetry is classified as central symmetry.

[0028] If the diatom shell is characterized by symmetry on both the apical axis and the transverse apical axis, such that it remains unchanged when rotated at a specific angle of less than 360 degrees, then the symmetry is classified as biaxial symmetry.

[0029] If the diatom shell is characterized by having an inverted portion aligned along the apical axis or transverse apical axis, such that it remains unchanged when rotated at an angle less than 360 degrees, then the symmetry is classified as reverse symmetry.

[0030] If the diatom shell is characterized by symmetry on the apical axis or transverse axis, such that it remains unchanged after being rotated at an angle less than 360 degrees, then the symmetry is classified as uniaxial symmetry.

[0031] If the diatom shell is characterized by being asymmetrical on the apical axis and the transverse apical axis, and does not appear identical after being rotated at any angle less than 360 degrees, then the symmetry is classified as asymmetric.

[0032] Further, the diatom outline classification is determined based on the outline features, including:

[0033] If the outline is classified as a circular two-dimensional graphic and all points are equidistant from the center point, then the outline is classified as a circle.

[0034] If the contour is classified as a two-dimensional elliptical curve, and the sum of the distances from any point on the curve to two fixed points remains constant, then the contour is classified as elliptical.

[0035] If the outline is classified as an elongated symmetrical shape, tapering at both ends and bulging on the sides, then the outline is classified as a spindle shape.

[0036] If the outline is classified as a long and thin shape, tapering gradually at both ends and with relatively straight sides, then the outline is classified as needle-shaped.

[0037] If the outline is classified as a long, straight rectangle with flat ends, then the outline is classified as a rod-shaped outline.

[0038] If the contour is classified as a smooth, flowing line or shape without sharp angles, and can be open or closed, and may gradually change direction, then the contour is classified as curved.

[0039] If the outline is classified as a two-dimensional shape with four sides and four right angles, then the outline is classified as a square.

[0040] If the outline is classified as a long and slender shape with sharp ends, then the outline is classified as a willow leaf shape.

[0041] If the outline is classified as a boat shape, characterized by a slender, curved structure, wider in the middle and tapering to a point at both ends, then the outline is classified as a crescent shape.

[0042] If the outline is classified as a long and thin shape, with two rounded and bulging ends connected by a narrower middle section, then the outline is classified as peanut-shaped.

[0043] If the outline is classified as a symmetrical shape with a circular or elliptical center and twisted ends, then the outline is classified as candy-shaped.

[0044] If the outline is classified as a smooth, teardrop-shaped shape with a rounded bottom and a gradually tapering top, then the outline is classified as teardrop-shaped.

[0045] If the contour is classified as a shape consisting of two parallel, slender, equal-length and uniformly wide rods, then the contour is classified as a double-rod shape.

[0046] If the outline is classified as having a sharp triangular shape, with a wide base that gradually narrows to a sharp tip, and a noticeable protrusion at the bottom, then the outline is classified as a dart shape.

[0047] Further, the texture classification of diatoms is determined based on the texture features, including:

[0048] If the texture feature is no texture, then the texture classification of the diatom is determined to be an empty texture;

[0049] If the texture feature is a pattern with equal, short, fence-like structures along the edge, and the fence-like structures are located on the inner or outer side, then the texture of the diatom is classified as a jagged texture.

[0050] If the texture feature is a pattern of straight, uniform lines running through the entire body at equal intervals, forming stripes or lines, then the texture of the diatom is classified as a striped texture.

[0051] If the texture feature is a pattern of straight, uniform lines running through the entire body at equal intervals, forming stripes or lines, then the texture of the diatom is classified as a vertical line texture.

[0052] If the texture feature is a pattern with a prominent single vertical line running from top to bottom through the entire body and located in the center, then the texture of the diatom is classified as a cross-shaped texture.

[0053] If the texture feature is a pattern defined by the intersection of uniformly distributed horizontal lines and a single vertical line running from top to bottom, then the texture of the diatom is classified as a fence-like texture.

[0054] If the texture feature is a pattern composed of two concentric circles, and the edge of each circle may be decorated with radial patterns, then the texture of the diatom is classified as a concentric circle texture.

[0055] Furthermore, the method of extracting three principal component variables from the diatom vector data and the tissue vector data respectively includes extracting the first three principal component variables from the diatom vector data and the tissue vector data respectively based on principal component analysis.

[0056] Furthermore, the method for calculating the distance between the first coordinate point and the second coordinate point corresponding to each sampling point includes cosine distance or Euclidean distance.

[0057] The beneficial effects of this application are:

[0058] This application utilizes a diatom classification system to classify diatoms in tissue smears and water sample smears from various sampling points, obtaining tissue vector data and diatom vector data. Principal component analysis is then performed on the tissue vector data and diatom vector data to obtain a first coordinate point and a second coordinate point formed by three principal component variables. Based on the distance between the first coordinate point and each of the second coordinate points, the sampling point located at the second coordinate point with the shortest distance to the first coordinate point is taken as the potential drowning location. Through the above method, this application can achieve rapid, accurate, and easy-to-operate drowning location inference. Attached Figure Description

[0059] Figure 1 A flowchart illustrating a diatom morphological classification method for forensic drowning location deduction provided in this application embodiment;

[0060] Figure 2 A flowchart illustrating the classification of diatoms in water smears or tissue samples using a diatom classification system, provided for embodiments of this application;

[0061] Figure 3 A schematic diagram of symmetry classification provided for embodiments of this application;

[0062] Figure 4 A schematic diagram of contour classification provided for embodiments of this application;

[0063] Figure 5 This is a schematic diagram of texture classification provided in an embodiment of this application;

[0064] Figure 6 The following are renderings of a diatom morphological classification method for forensic drowning location inference provided in this application embodiment; wherein, A, PCA scatter plot in vitro; B, PCA scatter plot in vivo; C, confusion matrix diagram for drowning location inference in vitro; D, confusion matrix diagram for drowning location inference in vitro. Detailed Implementation

[0065] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0066] The specific implementation methods of this application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0067] Please see Figure 1 This is a flowchart illustrating a diatom morphological classification method for forensic drowning location deduction, provided in an embodiment of this application. The method can be implemented through the following steps S100 to S103.

[0068] S100: Acquire diatom vector data and tissue vector data.

[0069] In some embodiments, step S100 includes the following steps S101 to S105.

[0070] S101: Collect water samples from multiple sampling points in the target area and prepare water smears;

[0071] S102: Count the number of diatoms in the water sample smear at each sampling point;

[0072] S103: Classify the diatoms in the water sample smear using a diatom classification system and calculate the percentage of each type of diatom in the total number of diatoms;

[0073] S104: Arrange the percentage values ​​of each type of diatom in a set order to obtain the diatom vector data for each sampling location;

[0074] S105: Extract human tissue samples to be tested, prepare tissue smears, and classify them using a diatom classification system to obtain tissue vector data.

[0075] S101: Extract three principal component variables from the diatom vector data and the tissue vector data respectively, and represent the three extracted principal component variables as coordinate points in three-dimensional space to obtain the first coordinate point and the second coordinate point.

[0076] S102: Calculate the distance between the first coordinate point and the second coordinate point corresponding to each sampling point.

[0077] S103: The sampling point with the shortest distance to the first coordinate point is selected as the potential drowning location.

[0078] In some embodiments, such as Figure 2 As shown, the method for classifying diatoms in the water smear or tissue sample using a diatom classification system includes the following steps:

[0079] S201: Extract diatom shell features, contour features, and texture features from the water sample smear or the tissue sample;

[0080] S202: Determine the symmetry classification of diatoms based on the characteristics of the diatom shells;

[0081] S203: Determine the contour classification of diatoms based on the contour features;

[0082] S204: Determine the texture classification of diatoms based on the texture features.

[0083] In this embodiment, the diatom classification system can classify diatoms in human tissues and water smears under conventional microscopes with magnification up to 400x. It identifies diatoms by extracting diatom shell features, contour features, and texture features from the smears. Each type of diatom can be defined by a three-dimensional vector, for example, the three-dimensional vector can be (a,b,c), where a, b, and c are vector values ​​representing the symmetry classification, contour classification, and texture classification number of the diatom.

[0084] Specifically, such as Figure 3 As shown, Figure 3 In this context, Radial represents central symmetry, Double-axis represents biaxial symmetry, Single-axis represents uniaxial symmetry, Asymmetry represents asymmetry, Symmetry represents symmetry, and Example represents an example. Symmetry is classified into five types, with the corresponding symmetry classification number 'a' being any natural value from 1 to 5, as detailed below:

[0085] 1) Central symmetry: Diatom shells can rotate around a central point at any angle while maintaining their shape and appearance;

[0086] 2) Biaxial symmetry: Diatom shells exhibit symmetry on both the apical axis and the transverse axis, which keeps them unchanged when rotated at a specific angle of less than 360 degrees;

[0087] 3) Reverse symmetry: Diatom shells have inverted portions aligned along the apical axis or transverse apical axis, which keeps them unchanged when rotated at a specific angle of less than 360 degrees.

[0088] 4) Uniaxial symmetry: Diatom shells exhibit symmetry on the apical axis or transverse axis, making them appear unchanged after being rotated at a specific angle of less than 360 degrees;

[0089] 5) Asymmetry: Diatom shells are asymmetrical on the apical axis and the transverse axis, which makes them not appear the same after being rotated at any angle less than 360 degrees.

[0090] like Figure 4 As shown, Figure 4 In this context, Circle represents a circle, Ellipse represents an ellipse, Spindle represents a spindle shape, Needle represents a needle shape, Rod represents a rod shape, Curve represents a curve shape, Square represents a square shape, Outline represents a contour, Example represents an example, Willow leaf represents a willow leaf shape, Navicular represents a crescent shape, Peanut represents a peanut shape, Candy represents a candy shape, Drop represents a teardrop shape, Double-bar represents a double-bar shape, and Dart represents a dart shape. Regarding contour classification, there are mainly 14 types, and the corresponding contour classification number 'b' is any natural value from 1 to 14, as detailed below:

[0091] 1) Circle: A perfect circular two-dimensional shape in which all points are equidistant from the center point;

[0092] 2) Ellipse: A two-dimensional elliptical curve, where the sum of the distances from any point on the curve to two fixed points remains constant;

[0093] 3) Spindle shape: An elongated symmetrical shape that tapers gradually at both ends and bulges on the sides;

[0094] 4) Needle-shaped: A slender shape that tapers gradually at both ends, with relatively straight sides;

[0095] 5) Rod-shaped: A long, straight rectangle with flat ends;

[0096] 6) Curved shape: A smooth, flowing line or shape without sharp angles; it can be open or closed and may gradually change direction.

[0097] 7) Square: A two-dimensional shape with four sides and four right angles;

[0098] 8) Willow leaf shape: A slender and elongated shape, similar to a willow leaf, with sharp ends, often gently curved like the letter 'S';

[0099] 9) Crescent shape: A boat-shaped form characterized by a slender, curved structure, wider in the middle and tapering to a point at both ends;

[0100] 10) Peanut-shaped: A long and thin shape with two rounded and bulging ends connected by a narrower middle section, similar to the shape of the number '8';

[0101] 11) Candy-shaped: A small, symmetrical shape with a round or oval center and twisted ends, resembling a wrapped candy;

[0102] 12) Teardrop shape: A smooth, teardrop-shaped form with a rounded bottom and a gradually tapering top;

[0103] 13) Double rod shape: A shape consisting of two parallel, slender rods of equal length and uniform width;

[0104] 14) Dart shape: A shape similar to a Chinese dart, with a sharp triangular shape, wide at the bottom and gradually narrowing to a sharp top, with a noticeable protrusion at the bottom.

[0105] like Figure 5 As shown in the diagram, Empty represents an empty texture, Serrated represents a jagged texture, Strip represents a striped texture, VD represents a vertical line texture, CD represents a cross-shaped texture, Fence-like represents a fence-like texture, CC represents a concentric circle texture, and Pattern represents a texture. Regarding texture classification, there are mainly 7 types, and their corresponding texture classification number c is any natural value from 1 to 7, as detailed below:

[0106] 1) Empty texture: No texture whatsoever;

[0107] 2) Serrated texture: A pattern with equal, short, fence-like structures along the edges, which can be located on the inside or outside;

[0108] 3) Striped texture: A pattern in which straight, uniform lines run through the entire body at equal intervals, forming a striped or linear appearance;

[0109] 4) Vertical line texture: A pattern in which straight, uniform lines run through the entire body at equal intervals, forming a striped or linear appearance;

[0110] 5) Cross-shaped texture: A pattern in which a single, prominent vertical line runs from top to bottom through the entire body and is located in the center.

[0111] 6) Fence-like texture: A pattern defined by the intersection of evenly distributed horizontal lines and a single vertical line running from top to bottom;

[0112] 7) Concentric circle pattern: A pattern consisting of two concentric circles, each of which may be decorated with a radial pattern along its edge.

[0113] In one exemplary embodiment, by means of... Figure 1 Steps S101 to S104 in the illustrated process can construct a diatom water sample database for the target area, and then the drowning location can be inferred through the following steps:

[0114] (1) Extract human tissue samples to be tested, prepare smears, and use a diatom classification system to generate tissue vector data;

[0115] (2) Principal component analysis was used to analyze the database and human tissue vector data respectively, and the first three principal component variables were extracted. The values ​​of these variables can be represented as coordinate points (x,y,z) in three-dimensional space.

[0116] (3) Calculate the distance between the coordinate points formed by the three principal component values ​​of the human tissue sample to be tested and the coordinate points formed by the three principal component values ​​of each water sample point in the database;

[0117] (4) The water sampling point that is closest to the human tissue sample to be tested is the potential drowning location.

[0118] The final result is as follows Figure 6 As shown.

[0119] Figure 6 The diagram shows 3D scatter plots generated after principal component analysis (PCA) of diatom abundance data from four sampling points (CF, ZS, CY, and TS), revealing the characteristics of diatom communities in different water bodies. In these plots, large dots represent the centroids of reference water samples, while small dots correspond to samples from in vitro and in vivo experiments. The PCA results show that diatom communities at different sampling points formed clear and independent clusters, indicating that the water source has a significant impact on diatom communities, making it an effective marker for forensic water body identification. For example, samples from the CY sampling point formed a tight and independent cluster, indicating that its unique diatom composition can distinguish CY from other sampling points (CF, ZS, and TS) (including samples from in vitro and in vivo experiments).

[0120] Furthermore, the centroids (large points) of each cluster provide a central reference point, facilitating distance-based classification analysis. Specifically, these centroids can be used to calculate the Mahalanobis distance, thereby classifying unknown samples to the most probable drowning location. By comparing the distance of each unknown sample to the nearest centroid in in vivo and in vitro experiments, it can be associated with the corresponding water source with high confidence. Based on Mahalanobis distance calculations, both in vivo and in vitro experiments demonstrated high classification accuracy in drowning location identification. Specifically, the in vitro experiment (n=44) achieved a classification accuracy of 0.98, indicating that almost all samples could be accurately identified as belonging to their respective water bodies; in contrast, the in vivo experiment (n=40) had a slightly lower classification accuracy of 0.95. Furthermore, Figure 6The CD model shows the confusion matrix of classification results for in vitro and in vivo experiments, demonstrating high classification accuracy for the three sampling points (CY, ZS, and TS), where all samples were correctly classified. However, the CF sampling points showed slight misclassification in both confusion matrices: in in vitro experiments (… Figure 6 In the in vivo experiment (C), one CF sample was misclassified as CY; while in the in vivo experiment (C) Figure 6 In the middle (D) category, two CF samples were misclassified as TS.

[0121] The above embodiments are only used to illustrate this application and are not intended to limit this application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this application. Therefore, all equivalent technical solutions also fall within the scope of this application, and the patent protection scope of this application should be defined by the claims.

Claims

1. A morphological classification method for diatoms used in forensic drowning location deduction, characterized in that, The method includes: Acquire diatom vector data and tissue vector data; Three principal component variables are extracted from the diatom vector data and the tissue vector data respectively. The three extracted principal component variables are represented as coordinate points in three-dimensional space to obtain the first coordinate point and the second coordinate point. Calculate the distance between the first coordinate point and the second coordinate point corresponding to each sampling point; The sampling point with the shortest distance to the first coordinate point is taken as the potential drowning location; Diatom vector data and tissue vector data are obtained using the following methods: Water samples were collected from multiple sampling points in the target area and prepared into water smears. The number of diatoms in the water sample smears at each sampling point was counted; The diatoms in the water sample smear were classified using a diatom classification system, and the percentage of each type of diatom was calculated. Arrange the percentage values ​​of each type of diatom in a set order to obtain diatom vector data for each sampling location; Tissue samples of the human body to be tested were extracted and prepared into tissue smears, and then classified using a diatom classification system to obtain tissue vector data; The methods for classifying diatoms in the water smear or tissue sample using a diatom classification system include: Extract diatom shell features, contour features, and texture features from the water smear or the tissue sample; Diatom shell characteristics are used to determine the symmetry classification of diatoms; Diatom outline classification is determined based on the outline features; The texture classification of diatoms is determined based on the texture features.

2. The diatom morphological classification method for forensic drowning location deduction as described in claim 1, characterized in that, The number of diatoms in the water sample smear at each sampling point shall not be less than 500.

3. The diatom morphological classification method for forensic drowning location deduction as described in claim 1, characterized in that, The methods for classifying diatoms in the water smear or tissue sample using a diatom classification system also include: The symmetry, contour, and texture classifications of diatoms are represented by a three-dimensional variable, wherein the three-dimensional variable includes three variable values, which represent the numbers of the symmetry, contour, and texture classifications of diatoms, respectively.

4. The diatom morphological classification method for forensic drowning location deduction as described in claim 1, characterized in that, Diatom shell characteristics are used to determine the symmetry classification of diatoms, including: If the diatom shell is characterized by rotating around a central point at any angle while maintaining its shape and appearance, then the symmetry is classified as central symmetry. If the diatom shell is characterized by symmetry on both the apical axis and the transverse apical axis, such that it remains unchanged when rotated at a specific angle of less than 360 degrees, then the symmetry is classified as biaxial symmetry. If the diatom shell is characterized by having an inverted portion aligned along the apical axis or transverse apical axis, such that it remains unchanged when rotated at an angle less than 360 degrees, then the symmetry is classified as reverse symmetry. If the diatom shell is characterized by symmetry on the apical axis or transverse axis, such that it remains unchanged after being rotated at an angle less than 360 degrees, then the symmetry is classified as uniaxial symmetry. If the diatom shell is characterized by being asymmetrical on the apical axis and the transverse apical axis, and does not appear identical after being rotated at any angle less than 360 degrees, then the symmetry is classified as asymmetric.

5. The diatom morphological classification method for forensic drowning location deduction as described in claim 1, characterized in that, Determining the contour classification of diatoms based on the aforementioned contour features includes: If the outline is classified as a circular two-dimensional graphic and all points are equidistant from the center point, then the outline is classified as a circle. If the contour is classified as a two-dimensional elliptical curve, and the sum of the distances from any point on the curve to two fixed points remains constant, then the contour is classified as elliptical. If the outline is classified as an elongated symmetrical shape, tapering at both ends and bulging on the sides, then the outline is classified as a spindle shape. If the outline is classified as a long and thin shape, tapering gradually at both ends and with relatively straight sides, then the outline is classified as needle-shaped. If the outline is classified as a long, straight rectangle with flat ends, then the outline is classified as a rod-shaped outline. If the contour is classified as a smooth, flowing line or shape without sharp angles, whether open or closed, and gradually changes direction, then the contour is classified as a curved shape. If the outline is classified as a two-dimensional shape with four sides and four right angles, then the outline is classified as a square. If the outline is classified as a long and slender shape with sharp ends, then the outline is classified as a willow leaf shape. If the outline is classified as a boat shape, characterized by a slender, curved structure, wider in the middle and tapering to a point at both ends, then the outline is classified as a crescent shape. If the outline is classified as a long and thin shape, with two rounded and bulging ends connected by a narrower middle section, then the outline is classified as peanut-shaped. If the outline is classified as a symmetrical shape with a circular or elliptical center and twisted ends, then the outline is classified as candy-shaped. If the outline is classified as a smooth, teardrop-shaped shape with a rounded bottom and a gradually tapering top, then the outline is classified as teardrop-shaped. If the contour is classified as a shape consisting of two parallel, slender, equal-length and uniformly wide rods, then the contour is classified as a double-rod shape. If the outline is classified as having a sharp triangular shape, with a wide base that gradually narrows to a sharp tip, and a noticeable protrusion at the bottom, then the outline is classified as a dart shape.

6. The diatom morphological classification method for forensic drowning location deduction as described in claim 1, characterized in that, Determining the texture classification of diatoms based on the aforementioned texture features includes: If the texture feature is no texture, then the texture classification of the diatom is determined to be an empty texture; If the texture feature is a pattern with equal, short, fence-like structures along the edge, and the fence-like structures are located on the inner or outer side, then the texture of the diatom is classified as a jagged texture. If the texture feature is a pattern of straight, uniform lines running through the entire body at equal intervals, forming stripes or lines, then the texture of the diatom is classified as a striped texture. If the texture feature is a pattern of straight, uniform lines running through the entire body at equal intervals, forming stripes or lines, then the texture of the diatom is classified as a vertical line texture. If the texture feature is a pattern with a prominent single vertical line running from top to bottom through the entire body and located in the center, then the texture of the diatom is classified as a cross-shaped texture. If the texture feature is a pattern defined by the intersection of uniformly distributed horizontal lines and a single vertical line running from top to bottom, then the texture of the diatom is classified as a fence-like texture. If the texture feature is a pattern composed of two concentric circles, with each circle's edge decorated with a radial pattern, then the texture of the diatom is classified as a concentric circle texture.

7. The diatom morphological classification method for forensic drowning location deduction as described in claim 1, characterized in that, The method of extracting three principal component variables from the diatom vector data and the tissue vector data respectively includes extracting the first three principal component variables from the diatom vector data and the tissue vector data respectively based on principal component analysis.

8. The diatom morphological classification method for forensic drowning location deduction as described in claim 1, characterized in that, The methods for calculating the distance between the first coordinate point and the second coordinate point corresponding to each sampling point include cosine distance or Euclidean distance.

Images