A method for rasterizing depth information of non-uniformly distributed nautical charts

Abstract

The present invention relates to a method for rasterizing depth information of non-uniformly distributed sea charts, and belongs to the field of marine intelligent technology. The method includes four algorithms: rasterizing original depth data, processing blank row or blank column elements, processing individual blank elements, and processing island range depth. The original sea depth data is uniformly rasterized by mathematical interpolation and image processing methods, and finally the rasterized depth data is uniform, safe, and reliable, and can be directly applied to practical engineering problems such as path planning or path navigation.

Description

Technical Field

[0001] The present invention relates to the field of marine intelligence technology, and in particular to a method for rasterizing depth information of non-uniformly distributed nautical charts. Background Art

[0002] The ocean is the cradle of life, covering nearly 3 / 4 of the Earth's total area. It provides numerous resources and services for human development, and all living things on Earth are closely related to the ocean. The new era is an era of ocean exploration. Whoever can understand the deep sea, go into the deep sea, and explore the deep sea will have the right to speak in the era.

[0003] Ocean depth information is the foundation for the development of ocean research. The path planning, detection and search of spacecraft are inseparable from ocean depth information. Due to the complexity of the ocean environment, it is particularly important to obtain ocean depth information in advance for ocean operations.

[0004] When we plan the path of a spacecraft, we need to grid the longitude and latitude of the target sea area according to a certain step length, and plan the path with the best energy consumption or the best distance according to the sea depth information at each grid. However, when the survey ship actually detects the sea depth, it is obviously not realistic to measure the depth with the same step length. Most of the sea depth information obtained by the survey is unevenly distributed and cannot be directly used for tasks such as spacecraft path planning. Summary of the invention

[0005] Technical issues to be solved

[0006] In order to solve the problem that the step accuracy of raw sea depth data is unevenly distributed and cannot meet the needs of actual engineering applications, the present invention provides a rasterization method for non-uniformly distributed sea chart depth information.

[0007] Technical Solution

[0008] A method for rasterizing depth information of non-uniformly distributed nautical charts, characterized by including four algorithms: rasterizing original depth data, processing blank row or blank column elements, processing individual blank elements, and processing island range depth;

[0009] The original depth data rasterization algorithm described above: read the longitude, latitude, and depth data of the obtained original depth data one by one, and initialize the number of grid rows and columns according to the longitude and latitude range and step accuracy; then fill the corresponding depth into the grid one by one when the longitude and latitude coordinate point falls into a certain grid longitude and latitude range, and when multiple longitude and latitude coordinate points fall into the same grid range, the absolute minimum depth value is selected to fill in the corresponding grid from the perspective of navigation safety, and the filled grid map is obtained;

[0010] The blank row or blank column element processing algorithm described above is as follows: first, the filled grid is traversed row by row, and when the first non-blank value of each row is encountered, all depth values ​​before the row are assigned the value, and when the last non-blank value of each row is encountered, all depth values ​​after the row are assigned the value; when a blank value is encountered between the first non-blank value and the last non-blank value of the row, it is interpolated with the previous valid depth according to the same step length, and the interpolated depth grid obtained after the row traversal is completed is recorded as map_x; then the filled grid map is retraversed column by column, and the interpolated grid map_y is obtained in the same way; then the map_x and map_y grids are added element by element to obtain the average value, and map_average=map_x+map_y is obtained;

[0011] The individual blank element processing algorithm described is as follows: first, traverse the map_average grid, and when the blank value encountered is located at the upper left corner, upper right corner, lower left corner, and lower right corner of the grid, fill it in with the average depth value of the three adjacent grids; when the blank value is located in the first row, first column, last row, and last column of the grid, fill it in with the average depth value of the five adjacent grids; when the blank value is located at other positions of the grid, fill it in with the average depth value of the eight adjacent grids, and finally obtain the map_reaverage grid;

[0012] The island range depth processing algorithm described above: firstly, the nautical chart corresponding to the latitude and longitude range is output as a picture with a pixel value equal to the number of grid rows and columns for subsequent processing; secondly, the island range depth processing algorithm is used to convert the sea Figure 2 Value conversion. Since the color depth of the islands and the oceans in the nautical chart is different, the islands will be processed as white and the oceans will be processed as black. Finally, the algorithm is used to extract the positions of white pixels, and special values ​​are assigned to the corresponding positions in the map_reaverage grid to complete the depth processing of the island range and obtain the map_result grid.

[0013] A computer system, characterized in that it comprises: one or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned method.

[0014] A computer-readable storage medium, characterized in that it stores computer-executable instructions, which are used to implement the above method when executed.

[0015] Beneficial Effects

[0016] The present invention proposes a method for rasterizing non-uniformly distributed nautical chart depth information, which uniformly rasterizes the original ocean depth data through mathematical interpolation and image processing methods, and ultimately makes the rasterized depth data uniform, safe and reliable, and can be directly applied to practical engineering problems such as path planning or path navigation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0018] Figure 1 This is the block diagram of the algorithm for rasterizing raw depth data;

[0019] Figure 2 Block diagram of algorithm for processing blank row or blank column elements;

[0020] Figure 3 Processing algorithm block diagram for individual blank elements;

[0021] Figure 4 This is the block diagram of the island range depth processing algorithm. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] The present invention provides a method for rasterizing depth of non-uniformly distributed nautical charts, which includes four algorithms: rasterization of original depth data, processing of blank row or blank column elements, processing of individual blank elements, and processing of island range depth. The method is based on interpolation processing and image processing technology. The chaotic depth data is first inserted into the corresponding grid through the original depth data rasterization algorithm, and then the blank values ​​in the grid are interpolated and valued using the blank row or blank column element processing algorithm and the individual blank element processing algorithm. Finally, the island range depth processing algorithm is used to fill special values ​​into the depth data within the island longitude and latitude range, ensuring that the rasterized depth data is safe and reliable, and can be directly applied to work tasks such as aircraft path planning.

[0024] A method for rasterizing depth of non-uniformly distributed nautical charts includes four algorithms: rasterizing original depth data, processing blank row or blank column elements, processing individual blank elements, and processing island range depth.

[0025] like Figure 1As shown, the original depth data rasterization algorithm reads the longitude, latitude, and depth data of the original depth data one by one, and initializes the number of grid rows and columns according to the latitude and longitude range and step accuracy. Then, one by one, when the longitude and latitude coordinate point falls into a certain grid longitude and latitude range, the corresponding depth is filled into the grid. When multiple longitude and latitude coordinate points fall into the same grid range, the absolute minimum depth value is selected to fill in the corresponding grid from the perspective of navigation safety, and the filled grid map is obtained.

[0026] like Figure 2 As shown, after the original data fills the grid, the step accuracy of the blank row or blank column element processing algorithm may be much smaller than the original data accuracy, or the original depth data may be distributed in a messy and uneven manner, resulting in a large number of blank rows and blank columns in the grid. First, traverse the filled grid row by row. When the first non-blank value of each row is encountered, all depth values ​​before the row are assigned this value. When the last non-blank value of each row is encountered, all depth values ​​after the row are assigned this value. When a blank value is encountered between the first non-blank value and the last non-blank value of the row, it is interpolated with the previous valid depth at an equal step size. After the row traversal is completed, the interpolated depth grid obtained is recorded as map_x. Then re-traverse the filled grid map by column, and use the same method to obtain the interpolated grid map_y. Then add the map_x and map_y rasters element by element and take the average value to obtain

[0027] map_average=map_x+map_y.

[0028] like Figure 3 As shown, the individual blank element processing algorithm obtains the map_average grid after interpolating the blank rows and columns in the map grid. However, when the rows and columns where the blank values ​​are located are all 0, there will still be individual blank values ​​that cannot be processed. If ignored, it will pose a great threat to the aircraft path planning. First, traverse the map_average grid. When the blank value encountered is located in the upper left corner, upper right corner, lower left corner, and lower right corner of the grid, take the average depth value of the adjacent 3 grids to fill in. When the blank value is located in the first row, first column, last row, and last column of the grid, take the average depth value of the adjacent 5 grids to fill in. When the blank value is located in other positions of the grid, take the average depth value of the adjacent 8 grids to fill in, and finally get the map_reaverage grid.

[0029] like Figure 4As shown, the island range depth processing algorithm, after the original depth data has been subjected to grid filling, blank value estimation and other operations, has obtained rasterized depth data. However, in the process of estimating and filling the blank values, the above algorithm has no way to distinguish whether the blank values ​​are caused by the step accuracy and uneven distribution of the depth data, or whether the range is an island land and there is no depth value itself. If the depth value of the island range is not processed, there may be a risk of the vehicle running aground during route planning, which is unacceptable. First, the nautical chart corresponding to the longitude and latitude range is output as a picture with a pixel value equal to the number of grid rows and columns for subsequent processing. Secondly, the island range depth processing algorithm is used to convert the sea Figure 2 Value conversion. Since the color depth of the islands and the oceans in the nautical chart is different, the islands will be processed as white and the oceans will be processed as black. Finally, the algorithm is used to extract the positions of white pixels, and special values ​​are assigned to the corresponding positions in the map_reaverage grid to complete the depth processing of the island range and obtain the map_result grid.

[0030] The embodiment of the present invention proposes a method for rasterizing non-uniformly distributed nautical chart depth information, comprising the following steps:

[0031] Step 1: Read the original ocean depth data

[0032] The original sea depth data is generally saved in txt format as three columns, namely longitude data, latitude data, and depth data. Call the importdata function in matlab to read the txt original data into map.mat and save it in standard row and column format;

[0033] Step 2: Determine the grid size

[0034] Read the longitude data in map.mat and save it in the lon_list array. Call the sort function to sort the lon_list array from small to large to determine the longitude range. Read the latitude data in map.mat and save it in the lat_list array. Call the sort function to sort the lat_list array from small to large to determine the latitude range. Call the N=size(lon_list) function to count the number of longitude and latitude points as N. Use the formula x=ceil((lat_list(N)-lat_list(1)) to determine the number of rows of the grid as x, and use the formula y=ceil((lon_list(N)-lon_list(1)) to determine the number of columns of the grid as y, where the ceil() function rounds the calculation result. From this, we can determine that the target grid size should be x rows and y columns;

[0035] Step 3: Rasterize and fill the original data

[0036] The value of the initial grid filled in row m and column n represents the minimum ocean depth value in the longitude range [lon_list(0)+sp*m,lon_list(0)+sp*(m+1)) and the latitude range [lat_list(0)+sp*n,lat_list(0)+sp*(n+1)). Traverse the original ocean depth data one by one, and when its longitude and latitude range falls into the grid range, fill its depth value into the grid. When multiple longitude and latitude fall into the same grid, select the absolute minimum depth value to fill the grid. Until all the original ocean depth data are traversed, the original data rasterization filling is completed;

[0037] Step 4: Processing blank rows and columns in the grid

[0038] First, traverse the grid row by row. When traversing to the first non-blank value element in each row, assign this value to all blank values ​​before the grid in this row. When traversing to the last non-blank value element in each row, assign this value to all blank values ​​after the grid in this row. Interpolate the blank grids between the two traversed non-blank values ​​with equal steps. For example, there are 4 blank grids between 10 and 20. Interpolate 12, 14, 16, and 18 for these 4 blank grids from left to right. Perform the same operation by column traversal, add the interpolated grid obtained by row traversal and take the average value;

[0039] Step 5: Processing blank values ​​in the grid

[0040] Traverse the grid obtained after the previous step from left to right and from top to bottom. When the blank value is located in the upper left corner, upper right corner, lower left corner, or lower right corner of the grid, take the blank value as the upper left corner, upper right corner, lower left corner, or lower right corner, and fill in the average depth of the three grids adjacent to it. When the blank value is located in the first row, first column, last row, or last column of the grid, take the blank value as the center, and fill in the average depth of the five grids adjacent to it. When the blank value is located in other positions of the grid, take the blank value as the center, and fill in the average depth of the eight grids adjacent to it, and finally obtain the grid after the blank value processing is completed;

[0041] Step 6: Raster processing within the island and land area

[0042] After the above algorithm is processed, the grids within the island range may also be assigned depth values, so we still need to process these grids. The processing steps are as follows:

[0043] 1) Output the nautical chart corresponding to the latitude and longitude range as an image with the same number of pixels as the number of rows and columns of the grid so as to facilitate the subsequent determination of the location of the island in the grid;

[0044] 2) Call the im2bw function to convert the grayscale of the chart into binary form. The islands will be processed as white and the oceans will be processed as black.

[0045] 3) Extract the position of white pixels, assign special values ​​to the corresponding positions in the grid processed in the previous step, complete the depth processing of the island range, and obtain the final target grid.

[0046] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A method for rasterizing non-uniformly distributed chart depth information, characterized in that It includes four algorithms: rasterization of original depth data, processing of blank row or column elements, processing of individual blank elements, and processing of island range depth. The original depth data rasterization algorithm described above: read the longitude, latitude, and depth data of the obtained original depth data one by one, and initialize the number of grid rows and columns according to the longitude and latitude range and step accuracy; then fill the corresponding depth into the grid one by one when the longitude and latitude coordinate point falls into a certain grid longitude and latitude range, and when multiple longitude and latitude coordinate points fall into the same grid range, the absolute minimum depth value is selected to fill in the corresponding grid from the perspective of navigation safety, and the filled grid map is obtained; The blank row or blank column element processing algorithm described above is as follows: first, the filled grid is traversed row by row, and when the first non-blank value of each row is encountered, all depth values ​​before the row are assigned the value, and when the last non-blank value of each row is encountered, all depth values ​​after the row are assigned the value; when a blank value is encountered between the first non-blank value and the last non-blank value of the row, it is interpolated with the previous valid depth according to the same step length, and the interpolated depth grid obtained after the row traversal is completed is recorded as map_x; then the filled grid map is retraversed column by column, and the interpolated grid map_y is obtained in the same way; then the map_x and map_y grids are added element by element to obtain the average value, and map_average=map_x+map_y is obtained; The individual blank element processing algorithm described is as follows: first, traverse the map_average grid, and when the blank value encountered is located at the upper left corner, upper right corner, lower left corner, and lower right corner of the grid, fill it in with the average depth value of the three adjacent grids; when the blank value is located in the first row, first column, last row, and last column of the grid, fill it in with the average depth value of the five adjacent grids; when the blank value is located at other positions of the grid, fill it in with the average depth value of the eight adjacent grids, and finally obtain the map_reaverage grid; The island range depth processing algorithm described is as follows: first, the nautical chart corresponding to the latitude and longitude range is output as a picture with a pixel value equal to the number of grid rows and columns for subsequent processing; secondly, the nautical chart is binarized using the island range depth processing algorithm. Since the color depths of the islands and the oceans in the nautical chart are different, the islands will be processed as white and the oceans will be processed as black; finally, the algorithm is used to extract the positions of white pixels, and special values ​​are assigned to the corresponding positions in the map_reaverage grid to complete the island range depth processing and obtain the map_result grid.

2. A computer system, characterized in that include: One or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors are enabled to implement the method of claim 1.

3. A computer-readable storage medium, characterized in that Computer executable instructions are stored, and when the instructions are executed, they are used to implement the method of claim 1.

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