A DEM image generation method based on streak tube lidar

Abstract

The present disclosure provides a method for generating a DEM image based on a streak tube lidar. The method comprises: obtaining multiple original streak images scanned by the streak tube lidar; filtering the original streak images for non-ground streaks to generate a first processed image, wherein the first processed image retains only ground streaks; supplementing adjacent areas of the first processed image with ground information where ground signals are missing to obtain a second processed image; and performing point cloud inversion on multiple second processed images corresponding to the multiple original streak images to generate a DEM. The present disclosure can accurately and quickly generate a DEM image using the original echo signals of the streak tube lidar.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a DEM image generation method based on a streak tube laser radar. Background Art

[0002] Compared to traditional microwave radar, lidar offers high precision, high resolution, high detection sensitivity, high confidentiality, and a compact size and light weight, making it suitable for airborne and shipborne deployment. Furthermore, due to its different operating mechanism, the laser pulses emitted by lidar are more resistant to interference than traditional microwave radar signals and capture richer data, resulting in higher detection and recognition capabilities. Given these characteristics of lidar, how to use it to generate relevant topographic and geomorphological products has become a hot topic.

[0003] A digital elevation model (DEM) is a finite sequence of three-dimensional vectors representing terrain. It describes ground elevation information and has a wide range of applications in surveying and mapping, hydrology, meteorology, geomorphology, geology, soil science, engineering construction, communications, military affairs, and other fields, including national economy and national defense, as well as the humanities and natural sciences. Currently, DEMs are generated based on LiDAR point cloud data. Airborne LiDAR measurement systems acquire continuous sequence footstep information through scanning operations. However, this footstep information is discrete and irregularly distributed in space, with large amounts of data and dense distribution. Filtering this footstep information is complex and time-consuming, resulting in inefficient DEM generation and a struggle to keep up with the rapid advancement of LiDAR hardware. Summary of the Invention

[0004] The present invention aims to provide a method for generating a DEM image based on a streak tube lidar, which can solve at least one of the above-mentioned technical problems. The specific solution is as follows:

[0005] The present invention provides a DEM image generation method based on a streak tube laser radar, comprising:

[0006] Acquire a plurality of original streak images generated by scanning a target area with the streak tube laser radar;

[0007] filtering out non-ground stripes from each of the original stripe images to generate a first processed image, wherein only ground stripes are retained in the first processed image;

[0008] Supplementing ground information to an area adjacent to the first processed image where ground signals are missing, to obtain a second processed image;

[0009] Point cloud inversion is performed on the plurality of second processed images corresponding to the plurality of original fringe images to generate a DEM.

[0010] In some optional embodiments, filtering out non-ground stripes from the original stripe image to generate a first processed image includes:

[0011] According to the connected domain of the original fringe image, non-ground fringe signals in the original fringe image are determined and filtered out to obtain a first processed image.

[0012] In some optional embodiments, determining and filtering out non-ground fringe signals in the original fringe image based on the connected domain of the original fringe image to obtain a first processed image includes:

[0013] Reading the connected domain of the original fringe image;

[0014] Determining a connected domain to be processed in the connected domain of the original fringe image according to the area of the connected domain;

[0015] According to the position of the centroid of the connected domain to be processed, determining the ground connected domain and the non-ground connected domain in the connected domain to be processed and marking them;

[0016] The non-ground connected domain is filtered out to obtain the first processed image.

[0017] In some optional embodiments, determining the ground-type connected domain and the non-ground-type connected domain in the connected domain to be processed according to the position of the centroid of the connected domain to be processed includes:

[0018] In the connected domain to be processed, a target connected domain with the largest centroid coordinate X value is determined, where the centroid coordinate X value includes elevation information of the centroid from the streak tube laser class;

[0019] Determine whether the X value of the centroid coordinate of the connected domain to be processed is greater than or equal to a critical value, where the critical value includes the sum of the X value of the centroid coordinate of the target connected domain and a preset offset value;

[0020] When the X value of the centroid coordinate of the connected domain to be processed is greater than or equal to a critical value, the connected domain to be processed is marked as a non-ground connected domain; or

[0021] When the X value of the centroid coordinate of the connected domain to be processed is not greater than or equal to a critical value, the connected domain to be processed is marked as a ground-type connected domain.

[0022] In some optional embodiments, the step of supplementing ground information in an adjacent ground signal-deficient region in the first processed image to obtain a second processed image includes:

[0023] Obtaining the number of connected components in the first processed image;

[0024] determining whether the number of connected domains is greater than 1, and when the number of connected domains is greater than 1, performing pixel supplementation on a first defective region between adjacent ground signals in the first processed image to obtain an intermediate image;

[0025] Pixels of a second defective area between adjacent ground signals in the intermediate image are supplemented to obtain the second processed image; wherein the range of the second defective area is larger than the range of the first defective area.

[0026] In some optional embodiments, the step of supplementing pixels of a first defective region in an adjacent ground signal in the first processed image to obtain an intermediate image includes:

[0027] Opening and closing operations are performed on the first processed image to supplement ground information in the first incomplete area between adjacent ground signals to obtain the intermediate image.

[0028] In some optional embodiments, the performing pixel supplementation on the second defective area between adjacent ground signals in the intermediate image to obtain the second processed image includes:

[0029] Marking a first connected domain and a second connected domain adjacent to the first connected domain;

[0030] Obtaining a first feature point of a minimum circumscribed rectangle of the first connected region and a second feature point of a minimum circumscribed rectangle of the second connected region;

[0031] A straight line is fitted between the first feature point and the second feature point, and a predetermined width value is assigned to the straight line to supplement a second incomplete region between the first connected domain and the second connected domain, thereby obtaining a second processed image.

[0032] In some optional embodiments, the method further includes:

[0033] When the number of connected domains of the first processed images corresponding to all original fringe images is equal to 1, point cloud inversion is directly performed on all the first processed images to generate a DEM image.

[0034] In some optional embodiments, before obtaining the original stripe image generated by the stripe tube laser radar scanning the target area, the method further includes: receiving a first folder address input by the user end for storing the original stripe image.

[0035] In some optional embodiments, the method further includes:

[0036] After filtering out non-ground fringes from the original fringe image to generate a first processed image, and before supplementing ground information in adjacent ground signal-deficient regions in the first processed image to obtain a second processed image, the method further includes:

[0037] receiving a second folder address input by a user terminal for storing the first processed image;

[0038] Based on the second folder address, the first processed image is acquired.

[0039] Compared with the prior art, the above solution of the embodiment of the present invention has at least the following beneficial effects:

[0040] The DEM image generation method provided by the present invention directly generates a DEM using the original echo signals of the streak tube lidar, eliminating the tedious process of converting all the original echo signals into point cloud data maps, thereby quickly generating a DEM; based on the integrity of the original echo signals, the accuracy and precision of the generated DEM are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present invention, and together with the specification, are used to explain the principles of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can derive other drawings based on these drawings without inventive effort. In the drawings:

[0042] Figure 1 A DEM image generation method based on a streak tube lidar provided by an embodiment of the present invention is shown;

[0043] Figure 2 A flow chart of a method for generating the original fringe image provided by an embodiment of the present invention is shown;

[0044] Figure 3 A diagram showing the detection principle scene of scanning by a streak tube laser radar provided by an embodiment of the present invention is shown;

[0045] Figure 4a shows an original stripe image of a plain type provided by an embodiment of the present invention;

[0046] Figure 4b shows an original stripe image of a slope type provided by an embodiment of the present invention;

[0047] Figure 4c shows an original stripe image of a building type provided by an embodiment of the present invention;

[0048] Figure 4dshows an original stripe image of a tree type provided by an embodiment of the present invention;

[0049] Figure 5 A schematic diagram of a scanning method of a rectangular area by the streak tube laser radar provided in an embodiment of the present invention is shown;

[0050] Figure 6 A flow chart of a method for obtaining a first processed image based on a connected domain of the original stripe image provided by an embodiment of the present invention is shown;

[0051] Figure 7 A flow chart of a method for determining ground-type connected domains and non-ground-type connected domains in a connected domain to be processed based on the position of the centroid of the connected domain to be processed, provided by an embodiment of the present invention, is shown;

[0052] Figure 8 A flow chart of a method for supplementing ground information in adjacent areas of the first processed image where ground signals are missing, to obtain a second processed image, is shown, according to an embodiment of the present invention;

[0053] Figure 9 A flowchart of a method for performing pixel supplementation on a second defective region between adjacent ground signals in the intermediate image to obtain the second processed image is shown, provided by an embodiment of the present invention;

[0054] Figure 10 shows a scanning effect diagram of a target area in an embodiment of the present invention;

[0055] Figure 11 Shows the Figure 10 The scanned image shown is the image after non-ground stripes are filtered out;

[0056] Figure 12 Shows the Figure 11 The effect picture shown is the DEM point cloud image after the ground stripe information is supplemented. DETAILED DESCRIPTION

[0057] To make the objectives, technical solutions, and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the embodiments described are only some, not all, of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0058] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a," "an," "the," and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, and unless the context clearly indicates otherwise, "a plurality" generally includes at least two.

[0059] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0060] It should be understood that although the terms first, second, third, etc. may be used to describe the embodiments of the present invention, they should not be limited to these terms.

[0061] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or device. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or device comprising the element.

[0062] In related technologies, when generating DEM based on point cloud data, the original echo signal needs to be converted into a point cloud data map, and this conversion process is relatively cumbersome. In addition, when using commercial single-point scanning lidar scanning, for the sake of technical confidentiality, the original laser echo signal will not be provided, only the processed point cloud data will be provided. The DEM is generated based on part of the point cloud data, which makes the generated DEM less accurate and precise.

[0063] The optional embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0064] Figure 1 FIG1 shows a flow chart of a DEM image generation method based on a streak tube laser radar provided by an embodiment of the present invention. Figure 1 As shown, the method includes:

[0065] S100, acquiring a plurality of original streak images generated by scanning the streak tube laser radar;

[0066] In this step, the streak tube lidar is used to collect the full waveform of the echo signal. The data volume of the full waveform echo signal of each ground target can reach 1000 times that of the non-waveform sampling signal, and about 30G of data can be generated in 1 minute, so more feature details of the ground target can be obtained. With more feature details, the ground targets can be filtered out more accurately and the ground information can be retained, which helps to generate DEM more accurately. Figure 2 A flow chart of a method for generating the original fringe image provided by an embodiment of the present invention is shown. Figure 2 As shown, in some embodiments, the method includes:

[0067] S110, controlling the streak tube laser radar to emit a scanning beam toward the target area and scan the area row by row along a direction perpendicular to the flight direction of the aircraft;

[0068] S120, receiving optical signals returned at different times from ground targets within each column of the scanning target area, and converting the optical signals into photoelectron pulses in a streak tube;

[0069] S130 , linearly deflecting the photoelectron pulses generated by the laser echoes so that the photoelectrons at different times are spread out in time sequence on the fluorescent screen, forming an original fringe image for each column of ground targets. Each column of the scanning area may contain multiple ground targets, which will return multiple optical signals. These multiple optical signals are converted into multiple photoelectrons arranged to generate an original echo signal. In other words, each column scanned in the target area generates a scanned image, i.e., an original fringe image.

[0070] Specifically, Figure 3 The detection principle scene diagram of the streak tube laser radar is shown as follows: Figure 3 As shown in the figure, the detection principle includes the following: after the streak tube laser radar emits a laser pulse to the surface of an object, part of the light signal is returned; this part of the light signal is shaped into a linear beam by a slit, and then focused by a focusing lens on the photocathode of the streak tube; the photoelectric effect occurs in the photocathode, converting photons into photoelectrons and amplifying them; then, the photoelectron pulse enters the deflection system, which linearly deflects the photoelectrons returned at different times in a certain dimension, so that the photoelectrons at different times are spread out in time sequence in the dimension on the fluorescent screen, obtaining a stripe image corresponding to each column of concave areas, as shown in the figure. Figures 4a to 4d The original fringe image is shown.

[0071] The target area may be a pre-set ground area, such as a circular, sector-shaped, rectangular or other shaped area, which is scanned in a preset manner with the streak tube lidar as the center. Figure 5 FIG. 4 shows a schematic diagram of a scanning method of a rectangular area by the streak tube laser radar. Figure 5 As shown, in some embodiments, the streak tube lidar is pre-set to scan in a direction perpendicular to the flight direction of the aircraft, thereby achieving column-by-column scanning of the ground area and obtaining the original streak image corresponding to the column. The multiple original streak images include the original streak image obtained by scanning each column. The mapping width is determined by the scanning angle of the laser beam, and wide-area mapping can be achieved.

[0072] S200, filtering out non-ground stripes from each of the original stripe images to generate a first processed image, wherein only ground stripes are retained in the first processed image;

[0073] Based on the working principle of the streak tube laser radar, the collected original echo signals are original streak images with pixels of, for example, 500*1000. Different brightness information represents different echo signal intensities. The specific shape of the streak actually represents the cross section of the object being measured, which has obvious geometric shape characteristics. Figure 4a and 4b The image shown is an original stripe image containing only ground stripes, such as flat land and hills. Its stripes truly reflect that the cross section of the scanned area is a single connected domain; Figure 4c and 4d The figure shows an original fringe image containing non-ground information, such as buildings and trees. From this fringe image, we can observe that the cross-sectional morphology of ground objects all contains multiple connected domains. Different ground objects have distinct morphological characteristics, and there are significant differences between classes. Therefore, by determining the morphological information of the fringe image and combining it with the number of connected domains, we can design non-ground fringe filtering algorithms and ground fringe repair algorithms. The following embodiments of the present invention are described using a series of original fringe images as an example.

[0074] In some embodiments, based on the connected domain of the original fringe image, non-ground fringe signals in the original fringe image are determined and filtered out to obtain a first processed image. The connected domain of the original fringe image includes an image region consisting of adjacent pixels having the same pixel value. Figure 6 FIG. 1 shows a flow chart of a method for determining and filtering out non-ground fringe signals in the original fringe image based on the connected domain of the original fringe image to obtain a first processed image according to an embodiment of the present invention. Figure 6 As shown, in some embodiments, the method includes:

[0075] S210, reading the connected domain of the original fringe image;

[0076] In some embodiments, the connected domains of the original stripe image may be marked in sequence in advance, for example, in natural number order or alphabetical order. For example, Figure 4a and 4b The connected domains of the fringe graphs shown are all 1; Figure 4c The connected domain of the fringe graph is 3, marked as 1, 2, and 3 from top to bottom; Figure 4d The connected domain of the fringe graph is 4, which are marked as 1, 2, 3, and 4 from top to bottom.

[0077] S220, determining a connected domain to be processed in the connected domain of the original fringe image according to the area of the connected domain;

[0078] Since some connected domains are small in area and can be ignored, such as point-shaped connected domains, in some embodiments, non-ground filtering may be performed based on only part of the connected domains, thereby improving filtering efficiency.

[0079] The calculation method of the area size of the connected domain includes counting the number of pixels in the connected domain to be processed and at the boundary. Since the target value in the binary image is 1 and the background value is 0, the area size of the connected domain can be calculated by accumulating the image intensity values. The calculation formula (1) is as follows:

[0080]

[0081] In some embodiments, an area threshold is preset, which is a minimum area threshold and can be an empirical value. The area of each connected domain is compared with the area threshold. If the area of the connected domain is greater than the area threshold, the connected domain is determined to be a connected domain to be processed. For example, Figure 4d The connected domains to be processed that can be determined are 1, 2, and 4.

[0082] S230, determining and marking ground-type connected domains and non-ground-type connected domains in the connected domain to be processed according to the position of the centroid of the connected domain to be processed;

[0083] After determining the connected domain to be processed in step S220, non-ground connected domains within the connected domain are further determined and removed. Non-ground connected domains include connected domains of ground objects such as trees and buildings, while ground connected domains include connected domains of ground objects such as plains and hills. The centroid of the connected domain is similar to the concept of the center of gravity of an object. If image pixel values are considered to be points of different masses, the average centroid point can represent the image centroid of the connected domain.

[0084] Figure 7 FIG. 1 shows a flow chart of a method for determining ground-type connected domains and non-ground-type connected domains in a connected domain to be processed according to the position of the centroid of the connected domain to be processed, provided by an embodiment of the present invention. Figure 7 As shown, in some embodiments, the method includes:

[0085] S231, determining a target connected domain with a maximum centroid coordinate X value in the connected domain to be processed, where the centroid coordinate X value includes elevation information of the centroid from the streak tube lidar;

[0086] Specifically, according to Figures 4a to 4d The characteristics of the original fringe image shown in the figure show that the fringe image contains obvious geometric information and target elevation information. In fact, the collected fringe image reflects the cross-sectional information of the object being measured. Figure 4c For example, establish an XOY coordinate system, define the coordinate point in the upper left corner of the image as the origin, the horizontal direction as the horizontal coordinate x-axis, and the vertical direction as the vertical coordinate y-axis. The x-axis direction reflects the elevation information of the object being measured. The smaller the x-coordinate, the higher the actual elevation of the object being measured. The y-axis direction reflects the spatial orientation information of the object being measured. Then, we can conclude that Figure 4c The centroid coordinate X value of connected domain 3 is the largest, that is, connected domain 3 is determined to be the target connected domain. Subsequently, based on the target connected domain, other connected domains to be processed are judged to be ground or non-ground. The elevation information between two connected domains includes the difference between the two connected domains.

[0087] S232, determining whether the X value of the centroid coordinate of the connected domain to be processed is greater than or equal to a critical value, where the critical value includes the sum of the X value of the centroid coordinate of the target connected domain and a preset offset value;

[0088] S233: When the X value of the centroid coordinate of the connected domain to be processed is greater than or equal to a critical value, mark the connected domain to be processed as a non-ground connected domain; or when the X value of the centroid coordinate of the connected domain to be processed is not greater than or equal to the critical value, mark the connected domain to be processed as a ground connected domain.

[0089] Specifically, in an original stripe image with multiple connected domains, since the elevation of non-ground connected domains such as trees and buildings is necessarily higher than the ground, the larger the X value of the centroid coordinate in the above-mentioned coordinate system XOY, the ground connected domain. Other connected domains with centroid coordinates X values greater than the maximum centroid coordinate can be regarded as non-ground connected domains such as buildings and trees. Therefore, whether it is a non-ground connected domain can be determined by judging whether the X value of the centroid coordinate is greater than or equal to the X value of the centroid coordinate of the target connected domain.

[0090] In some embodiments, due to the presence of potholes and other conditions on the ground, multiple ground connected domains may be formed. To account for this, a preset bias value can be introduced into the judgment condition. This preset bias value provides a dynamic adjustment range to avoid deleting some ground connected domains as non-ground connected domains, further ensuring data accuracy. The preset bias value is an empirical value and is not specifically limited.

[0091] S240: Filter out the non-ground connected domain to obtain the first processed image.

[0092] Specifically, after determining the non-ground connected domains and the ground connected domains based on the aforementioned critical value, in some embodiments, the non-ground connected domains and the ground connected domains can be distinguished by different labels, and the non-ground connected domains are removed, retaining only the ground connected domains. It should be noted that the column-by-column scanning process generates multiple first processed images, with each column scan corresponding to a corresponding first processed image.

[0093] S300, supplementing ground information in an area adjacent to the first processed image where ground signals are missing, to obtain a second processed image;

[0094] Since only ground-type connected domains are retained in the first processed image obtained in step S240, in some embodiments, a complete ground may be separated by non-ground objects such as buildings, houses, and trees to form multiple ground-type connected domains. Therefore, the first processed image obtained in step S240 can be further processed to supplement the incomplete areas of the two adjacent ground-type connected domains, so that the second processed image is a single ground-type connected domain. Figure 8 FIG. 1 shows a flow chart of a method for supplementing ground information in adjacent ground signal-deficient areas in the first processed image to obtain a second processed image according to an embodiment of the present invention. Figure 8 As shown, the method includes:

[0095] S310, obtaining the number of connected components in the first processed image;

[0096] In this step, since the non-ground connected domains in the first processed image have been filtered out, the number of ground-like connected domains is extracted, for example Figure 4c The number of connected domains after filtering out non-ground connected domains is 2.

[0097] S320, determining whether the number of connected domains is greater than 1. If the number of connected domains is greater than 1, performing pixel supplementation on a first defective region between adjacent ground signals in the first processed image to obtain an intermediate image.

[0098] Specifically, the ground connected domain may be separated or not separated in the first processed image. At this time, it is necessary to determine whether the ground connected domain is separated in the current stripe image. If the ground connected domain is separated, its number must be greater than 1. If it is not separated, the ground connected domain is a single connected domain. Therefore, ground information supplementation is only required when the number of ground connected domains is greater than 1.

[0099] In some embodiments, if the first defective region is small, such as a point, then performing opening and closing operations on the first processed image can supplement the ground information in the first defective region between adjacent ground signals to obtain the intermediate image. The opening operation is a morphological operation that first performs an erosion operation and then a dilation operation on the first processed image. This can smooth the contours of objects, break narrow necks, and eliminate slender protrusions. The closing operation is the opposite of the opening operation, first dilating and then eroding the first processed image. This can bridge narrow breaks and slender grooves, eliminate small holes, and fill gaps in contours.

[0100] In some embodiments, the method further includes directly performing point cloud inversion on the multiple first processed images to generate a DEM when the number of connected domains of the multiple first processed images corresponding to all original fringe images is equal to 1, that is, directly jumping to step S400.

[0101] S330, performing pixel supplementation on a second defective area between adjacent ground signals in the intermediate image to obtain a second processed image; wherein the range of the second defective area is larger than the range of the first defective area.

[0102] It can be understood that the first incomplete area is firstly supplemented with flat ground through different numbers of opening and closing operations, and then the second incomplete area is further fitted with ground information. The second incomplete area includes the larger incomplete area between two adjacent ground connected domains. Figure 9 FIG. 1 shows a flow chart of a method for performing pixel supplementation on the second defective area between adjacent ground signals in the intermediate image to obtain the second processed image in an embodiment of the present invention. Figure 9 As shown, the method includes:

[0103] S331, marking a first connected domain and a second connected domain adjacent to the first connected domain in the intermediate image;

[0104] It should be noted that each time, only the pixels of the two adjacent connected domains currently marked are supplemented. If the pixel supplement needs to be repeated multiple times, the first connected domain and the second connected domain in the current image need to be re-marked each time, that is, the first connected domain and the second connected domain marked each time are different.

[0105] S332, obtaining a first feature point of a minimum circumscribed rectangle of the first connected component and a second feature point of a minimum circumscribed rectangle of the second connected component;

[0106] In this step, the minimum bounding rectangle includes the minimum rectangle that can accommodate the first connected domain or the second connected domain. The first feature point can be the coordinates of certain points of the minimum bounding rectangle of the first connected domain close to the second defective region, and the second feature point can be the coordinates of certain points of the minimum bounding rectangle of the second connected domain close to the second defective region, so as to connect the two connected domains through the first feature point and the second feature point. In some embodiments, if the first connected domain and the second connected domain are marked in order from top to bottom in the original stripe image, the first feature point can include the coordinates of the lower left corner of the minimum bounding rectangle of the first connected domain, and the second feature point can include the coordinates of the upper left corner of the minimum bounding rectangle of the second connected domain.

[0107] S333: Perform straight line fitting on the first feature point and the second feature point, and assign a predetermined width value to the straight line to supplement the second incomplete region between the first connected domain and the second connected domain, thereby obtaining the second processed image.

[0108] In this step, a fitted line is obtained within the second defective region by connecting the coordinates of the lower-left corner of the minimum bounding rectangle of the first connected region with the coordinates of the upper-left corner of the minimum bounding rectangle of the second connected region. Because the second defective region has a certain width, the fitted line can be given a predetermined width to ensure the connection between adjacent connected regions. Optionally, the predetermined width is the elevation difference between the first and second connected regions, thereby forming the first and second connected regions into a single connected region.

[0109] In some other embodiments, the first feature point includes the coordinates of the lower left corner and the lower right corner of the minimum circumscribed rectangle of the first connected domain, and the second feature point includes the coordinates of the upper left corner and the upper right corner of the minimum circumscribed rectangle of the second connected domain. The lower left corner and the upper left corner are fitted with a straight line, and the lower right corner and the upper right corner are fitted with a straight line to obtain a fitted rectangle of the second incomplete area. The fitted rectangle is filled in to connect adjacent connected domains.

[0110] In step S333, each time the second incomplete area is supplemented, the number of current ground connected domains in the second processed image needs to be determined. If the current number of ground connected domains is greater than 1, the second incomplete area is supplemented again and steps S331-S333 are re-executed; if the current number of ground connected domains is equal to 1, it means that all the first incomplete areas and the second incomplete areas are supplemented, and the current ground connected domain is a single connected domain, and there is no incompleteness.

[0111] S400: Perform point cloud inversion on a plurality of the second processed images corresponding to all original fringe images to generate a DEM.

[0112] Since each column of original fringe images obtains a second processed image, multiple second processed images are subjected to point cloud inversion to obtain a point cloud inversion image of the entire target area, that is, a DEM image is generated.

[0113] In some embodiments, before acquiring the original stripe image generated by scanning the target area with the stripe tube laser radar, the method further includes: receiving a first folder address input by a user end to store the original stripe image.

[0114] In some embodiments, after filtering out non-ground stripes from the original stripe image to generate a first processed image, and before supplementing ground information in adjacent ground signal-deficient areas in the first processed image to obtain a second processed image, the method further includes: receiving a second folder address for storing the first processed image input by a user terminal; and acquiring the first processed image based on the second folder address.

[0115] Figure 10 shows a scanning effect diagram of the target area in an embodiment of the present invention, Figure 11 Shows the Figure 10 The scanning effect image is an effect image after non-ground stripes are filtered out; Figure 12 Shows the Figure 11 The DEM point cloud image after the ground stripe information is supplemented. Figure 10-11 As shown, in actual application, the streak tube lidar is controlled to scan the target area column by column to obtain multiple original streak images, which are saved in a folder to be processed; the user inputs the address of the folder to be processed into the non-ground streak filtering algorithm for processing, and the processed result is written to the first folder, which stores multiple first processed images; the user inputs the address of the first folder into the ground streak information supplement algorithm for processing, and the processed result is written to the second folder, which stores multiple second processed images; finally, the system performs point cloud inversion on the multiple second processed images in the second folder to generate a DEM.

[0116] The DEM image generation method provided by the present invention starts with the raw echo signals from a streak tube lidar. It first performs non-ground fringe filtering based on the original fringe pattern, then performs a supplementary fitting of ground fringe information, and finally inverts the fringe pattern point cloud to generate DEM point cloud data. This method, based on scanning with a streak tube lidar, can more accurately filter out non-ground target information. Furthermore, the DEM is generated directly from the raw echo signals from the streak tube lidar, eliminating the tedious process of converting all raw echo signals into point cloud data. This allows for rapid and accurate DEM generation. The integrity of the raw echo signals improves the accuracy and precision of the generated DEM.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A DEM image generation method based on streak tube laser radar, characterized in that: include: Acquire a plurality of original streak images generated by scanning the streak tube laser radar; filtering out non-ground stripes from the original stripe image to generate a first processed image, wherein only ground stripes are retained in the first processed image; Supplementing ground information to an area adjacent to the first processed image where ground signals are missing, to obtain a second processed image; Point cloud inversion is performed on the plurality of second processed images corresponding to the plurality of original fringe images to generate a DEM image.

2. The DEM image generation method according to claim 1, characterized in that: The step of filtering out non-ground stripes from the original stripe image to generate a first processed image includes: According to the connected domain of the original fringe image, non-ground fringe signals in the original fringe image are determined and filtered out to obtain a first processed image.

3. The DEM image generation method according to claim 2, characterized in that: Determining non-ground fringe signals in the original fringe image according to the connected domain of the original fringe image and filtering them out to obtain a first processed image includes: Reading the connected domain of the original fringe image; Determining a connected domain to be processed in the connected domain of the original fringe image according to the area of the connected domain; According to the position of the centroid of the connected domain to be processed, determining the ground connected domain and the non-ground connected domain in the connected domain to be processed and marking them; The non-ground connected domain is filtered out to obtain the first processed image.

4. The DEM image generation method according to claim 3, characterized in that: The step of determining the ground-type connected domain and the non-ground-type connected domain in the connected domain to be processed according to the position of the centroid of the connected domain to be processed includes: Determine a target connected domain with the largest centroid coordinate X value in the connected domain to be processed, wherein the centroid coordinate X value includes elevation information of the centroid from the streak tube laser radar; Determine whether the X value of the centroid coordinate of the connected domain to be processed is greater than or equal to a critical value, where the critical value includes the sum of the X value of the centroid coordinate of the target connected domain and a preset offset value; When the X value of the centroid coordinate of the connected domain to be processed is greater than or equal to a critical value, the connected domain to be processed is marked as a non-ground connected domain; or When the X value of the centroid coordinate of the connected domain to be processed is not greater than or equal to a critical value, the connected domain to be processed is marked as a ground-type connected domain.

5. The DEM image generation method according to any one of claims 1 to 4, characterized in that: The step of supplementing the ground information of the adjacent ground signal-deficient region in the first processed image to obtain the second processed image includes: Obtaining the number of connected components in the first processed image; determining whether the number of connected domains is greater than 1, and when the number of connected domains is greater than 1, performing pixel supplementation on a first defective region between adjacent ground signals in the first processed image to obtain an intermediate image; Pixels of a second defective area between adjacent ground signals in the intermediate image are supplemented to obtain the second processed image; wherein the range of the second defective area is larger than the range of the first defective area.

6. The DEM image generation method according to claim 5, characterized in that: The step of supplementing pixels of a first defective area in an adjacent ground signal in the first processed image to obtain an intermediate image includes: Opening and closing operations are performed on the first processed image to supplement ground information in the first incomplete area between adjacent ground signals to obtain the intermediate image.

7. The DEM image generation method according to claim 5, characterized in that: The step of supplementing pixels in the second defective area between adjacent ground signals in the intermediate image to obtain the second processed image includes: marking a first connected domain and a second connected domain adjacent to the first connected domain in the intermediate image; Obtaining a first feature point of a minimum circumscribed rectangle of the first connected region and a second feature point of a minimum circumscribed rectangle of the second connected region; A straight line is fitted between the first feature point and the second feature point, and a predetermined width value is assigned to the straight line to supplement a second incomplete region between the first connected domain and the second connected domain, thereby obtaining a second processed image.

8. The DEM image generation method according to claim 5, characterized in that: The method further comprises: When the number of connected domains of the first processed image corresponding to each of the original fringe images is equal to 1, point cloud inversion is directly performed on all the first processed images to generate a DEM.

9. The DEM image generation method according to claim 1, characterized in that: Before acquiring a plurality of original streak images generated by scanning the streak tube laser radar, the method further includes: A first folder address storing the plurality of original fringe images is received from a user terminal.

10. The DEM image generation method according to claim 1, characterized in that: The method further comprises: After filtering out non-ground fringes from the original fringe image to generate a first processed image, and before supplementing ground information in adjacent ground signal-deficient regions in the first processed image to obtain a second processed image, the method further includes: receiving a second folder address input by a user terminal for storing a plurality of the first processed images; Based on the second folder address, a plurality of the first processed images are acquired.

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