Mountain river terrain elevation interpolation method based on sparse river section point elevation data

Abstract

The invention discloses a mountain river terrain elevation interpolation method based on sparse river section point elevation data. The method comprises the following steps: step 1, obtaining and preprocessing basic data of a target river; 2, judging the directions of different section lines; 3, creating a new section line and calculating the length and latitude and longitude coordinates of the new section line; 4, dividing a new section line to obtain section points, and performing resampling; step 5, obtaining elevation data of each section point on the new section line; and step 6, obtaining elevation data of the target river channel region. According to the mountain river topography elevation interpolation method based on the sparse river section point elevation data, existing elevation data can be fully utilized, local topography features of a mountain area can be expressed more accurately, high-precision mountain river topography elevation interpolation is realized, and a scientific basis is provided for flood inundation analysis.

Description

Technical Field

[0001] The present invention belongs to the technical field of flood inundation analysis, and in particular relates to a mountain river terrain elevation interpolation method based on sparse river section point elevation data. Background Art

[0002] As the impact of global climate change becomes increasingly significant, extreme weather events are becoming more frequent, with floods in mountainous areas being particularly severe. Flood inundation analysis is crucial for flood risk analysis, loss assessment, and protecting the lives and property of residents in disaster-stricken areas. The accuracy of digital elevation model (DEM) data directly impacts the accuracy of flood inundation analysis results, necessitating the use of more precise elevation data, such as 1-meter resolution. However, existing elevation data typically has a resolution of 30 or 90 meters, which clearly falls short of the requirements for flood inundation analysis.

[0003] Currently, commonly used elevation measurement methods include traditional leveling, trigonometric height measurement, remote sensing satellite height measurement, and drone lidar height measurement. Leveling and trigonometric height measurement are inefficient, labor-intensive, and tedious, and because field surveyors are often underqualified, the measurement results are inaccurate. The accuracy of elevation measurement using remote sensing satellites is lower than that of plane coordinate measurement, and the measured geodetic height must be converted to the commonly used normal height, resulting in relatively high measurement costs. Drone lidar scanning systems, due to the influence of their altitude, scanning angle, and external factors such as wind speed and air pressure, often result in measurement errors. Furthermore, the measurement cost is high, making practical application difficult.

[0004] Currently, commonly used elevation interpolation methods include inverse distance weighted interpolation and kriging interpolation. Their basic principle is to use the elevations of known sampling points within a search radius, assign weights to these interpolation points using different methods, and then calculate the elevation of the interpolated point through weighted averaging. This interpolation method fails to fully utilize existing elevation data and cannot effectively represent the local terrain characteristics of mountainous areas. In particular, when interpolating river sections, the elevation of the river channel becomes homogenized, resulting in low interpolation accuracy. Therefore, achieving high-precision elevation interpolation of river channel terrain in mountainous areas is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of the present invention is to provide a mountain river terrain elevation interpolation method based on sparse river section point elevation data to solve the above technical problems.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention discloses a method for interpolating the elevation of mountain river terrain based on sparse river section point elevation data, the method comprising the following steps:

[0008] Step 1. Obtain basic data of the target river channel and perform preprocessing: First, obtain basic data of the target river channel, including cross-section data and river channel line data; the cross-section data includes cross-section and cross-section line serial numbers, cross-section names, cross-section line starting and ending points, types of cross-section sampling points, latitude and longitude coordinates of cross-section sampling points, distance from the starting point of cross-section sampling points, and elevation; the cross-section and cross-section line serial numbers are arranged in order from upstream to downstream; the types of cross-section sampling points include non-feature points and riverbank dividing points; the river channel line data is the river channel line vector file of the target river channel, and the river channel line is a broken line formed by connecting multiple river channel points, and the direction of the river channel line is the direction of the river, that is, from upstream to downstream;

[0009] Then, the basic data are preprocessed, including converting the longitude and latitude coordinates of each sampling point in the cross section into a unified coordinate system, converting the resolution of the river channel line to the specified resolution using the linear interpolation method, and dividing the river channel line into a series of river channel points with equal intervals according to the specified resolution, recorded as R;

[0010] Step 2: Determine the directions of different section lines: Take the i-th section line as the starting section line and the i+1-th section line as the ending section line, where i=1, 2, ..., n, and n is the total number of river section lines. Determine the directions of the starting section line and the ending section line respectively. If the directions of the starting section line and the ending section line are opposite, flip the direction of the starting section line or the ending section line to make them consistent.

[0011] Step 3. Create a new section line and calculate the length and longitude and latitude coordinates of the new section line: record the series of river points between the starting section line and the ending section line as r; create a new section line for each river point in r, and each new section line contains five elements, namely: the length of the left section line L 左 , right section line length L 右 、Width of the left river channel l 左 、Width of the right river channel l 右 , the direction of the section line, the section line direction is represented by the section line unit direction vector u; the length of the right section line L 右 The length of the starting section line on the right side of the river channel line and the length of the ending section line on the right side of the river channel line are linearly changed, and the same is true for the left side; the width of the river channel on the right side is l 右 It is obtained by linearly changing the length of the right bank dividing point of the starting section line from the river channel line and the length of the right bank dividing point of the ending section line from the river channel line, and the same applies to the left side; the section line direction is the direction of the unit direction vector u from the unit direction vector of the starting section line to the unit direction vector of the ending section line;

[0012] Traverse the river point index in r, take the jth river point in r, j = 1, 2, ..., m, m is the number of river points in r, and calculate the length of the new section line:

[0013] L=L 左 +L 右 (1)

[0014] Where: L is the length of the new section line;

[0015] Assume that points A, B, and C are the starting point of the new section line, the end point of the new section line, and the river point respectively. The formula for calculating the coordinates of the starting point and end point of the new section line is:

[0016] X A =X C -(u*L 右 ) (2)

[0017] Y A =Y C -(u*L 右 ) (3)

[0018] X B =X C +(u*L 左 ) (4)

[0019] Y B =Y C +(u*L 左 ) (5)

[0020] Where: X A 、X B 、X C are the longitude coordinates of points A, B, and C, respectively. A 、Y B 、Y C are the latitude coordinates of points A, B, and C respectively;

[0021] Step 4: Divide the new section line to obtain section points and resample: Based on the start and end coordinates of the created new section line, divide the new section line at the specified resolution to obtain a series of section points, and calculate the number of non-river section points on the right side of the new section line, the number of non-river section points on the left side, and the number of river section points. The calculation process is as follows:

[0022] 1) Calculate the index positions of the right bank dividing point and the left bank dividing point in the new section line coordinate point list:

[0023]

[0024] Where: I 右 , I 左 are the right bank dividing point index and the left bank dividing point index, respectively.max The maximum index of the new section line coordinate point;

[0025] 2) Calculate the number of non-river section points on the right side of the new section line, the number of non-river section points on the left side, and the number of river section points:

[0026] N 右 =I 右 (8)

[0027] N 左 =I max -I 左 (9)

[0028] N 河 =I max -N 左 -N 右 (10)

[0029] Where: N 右 、N 左 、N 河 They are the number of non-river section points on the right side of the new section line, the number of non-river section points on the left side, and the number of river section points;

[0030] 3) According to the number of three types of cross-section points on the right side of the new cross-section line, namely, non-river cross-section points on the left side, and river cross-section points, resample the cross-section points of the corresponding categories of the starting cross-section line and the ending cross-section line to ensure that the number of non-river cross-section points and river cross-section points on the right side and left side of the starting cross-section line, the ending cross-section line, and the new cross-section line are consistent;

[0031] Step 5: Obtain the elevation data of each section point on the new section line: Obtain the elevation of each section point on the new section line through inverse distance weighted interpolation. The calculation formula is:

[0032]

[0033] Where: Z k is the elevation of each section point on the new section line, I 河 is the index of the river point corresponding to the new section line, M is the number of river point indexes, Z Fk 、Z Sk They are the elevations of each section point on the ending section line and the starting section line respectively;

[0034] Step 6: Obtain the elevation data of the target river area: Divide the target river area into grids according to the specified resolution. Some grids contain cross-section points with known elevations, while some grids do not contain elevation data. Use the nearest neighbor interpolation method, that is, the elevation of the grid is equal to the elevation of the nearest grid with elevation data. Finally, the elevation data of the entire target river area with the specified resolution can be obtained.

[0035] Furthermore, the specified resolution is 1m.

[0036] Furthermore, the unified coordinate system in step 1 is specifically a UTM series coordinate system.

[0037] Furthermore, the specific process of determining the directions of the starting section line and the ending section line respectively in step 2 is: take the starting section line and the ending section line as the target section lines respectively, find the river point closest to the target section line from R, take the river point as the starting point and the next river point as the end point, and construct a nearest target river vector; similarly, take the starting point and end point of the target section line as the starting point and end point of the vector respectively, and construct a target section line vector; take the nearest target river vector as the x-axis direction, take the x-axis rotated 90° counterclockwise as the y-axis direction, and take the starting point of the target section line vector as the origin to construct a coordinate system. If the end point of the target section line vector falls in the first or second quadrant, it is positive, and if it falls in the third or fourth quadrant, it is reverse; if it is reverse, the direction of the reverse section line needs to be flipped to ensure that the directions of the starting section line and the ending section line are consistent, that is, both are positive.

[0038] The beneficial effects of the present invention are as follows: the mountain river terrain elevation interpolation method based on sparse river section point elevation data described in the present invention can make full use of existing elevation data, more accurately express the local terrain characteristics of the mountainous area, achieve high-precision mountain river terrain elevation interpolation, and provide a scientific basis for flood inundation analysis.

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the process of the present invention;

[0041] Figure 2 This is a schematic diagram of the process of determining the direction of the river section line;

[0042] Figure 3 Schematic diagram of the process of creating new river section lines. DETAILED DESCRIPTION

[0043] The present invention discloses a mountain river terrain elevation interpolation method based on sparse river section point elevation data. Figure 1 As shown, the method includes the following steps:

[0044] Step 1: Obtain basic data of the target river and perform preprocessing.

[0045] Obtain basic data for the target river, including cross-section data and channel line data. Cross-section data includes the cross-section and cross-section line numbers, cross-section name, cross-section line start and end points, sampling point types, latitude and longitude coordinates, distance from the start point, and elevation. Sampling point types include non-feature points and riverbank demarcation points. In actual measurement, cross-sections correspond one-to-one with cross-section lines, and cross-section and cross-section line numbers are arranged sequentially from upstream to downstream. Select the projection coordinate system to use based on the longitude and latitude of the sampling points and perform a coordinate conversion to a unified coordinate system, most commonly the UTM series. Channel line data refers to the channel line vector file for the target river. Channel lines are polylines formed by connecting multiple channel points, and the channel line direction is the river direction, i.e., from upstream to downstream. Convert the obtained channel line resolution to a specified resolution (1 meter) using linear interpolation. Divide the channel line into a series of channel points with equal spacing, denoted by R, at the specified resolution (1 meter).

[0046] Step 2: Determine the directions of different section lines.

[0047] Take the i-th section line as the starting section line and the i+1-th section line as the ending section line (i=1, 2, ..., n, where n is the total number of river section lines), and determine the directions of the starting section line and the ending section line respectively. The determination process is as follows:

[0048] Take the starting section line and the ending section line as the target section line respectively, find the river point closest to the target section line from R, use this river point as the starting point and the next river point as the end point to construct a nearest target river vector. Similarly, use the starting point and end point of the target section line as the starting point and end point of the vector respectively to construct a target section line vector. Use the nearest target river vector as the x-axis direction, the x-axis rotated 90° counterclockwise as the y-axis direction, and the starting point of the target section line vector as the origin to construct a coordinate system. If the end point of the target section line vector falls in the first or second quadrant, it is positive, and if it falls in the third or fourth quadrant, it is negative. If it is negative, the direction of the negative section line needs to be flipped to ensure that the starting section line and the ending section line are in the same direction, that is, both are positive.

[0049] Figure 2 The diagram below shows the direction of the river section line. (a) is the forward direction and (b) is the reverse direction. A and B are the starting point and end point of the river section line respectively. are the nearest target river channel vector and target section line vector respectively. Figure 2 In (a), the end point of the target section line vector falls in the second quadrant, so it is positive; Figure 2 In (b), the end point of the target section line vector falls in the third quadrant, so it is in the reverse direction.

[0050] Step 3: Create a new section line and calculate the length and longitude and latitude coordinates of the new section line.

[0051] The series of river points between the start and end section lines of R is recorded as r; a new section line is created for each river point in r, and each new section line contains five elements, namely: the length of the left section line L 左 , right section line length L 右 、Width of the left river channel l 左 、Width of the right river channel l 右 , the direction of the cross section (expressed by the cross section unit direction vector u), the above left and right directions are based on the river line. Among them, the length of the right cross section line L 右 The width of the right river channel is obtained by linearly changing the length of the starting section line on the right side of the river channel and the length of the ending section line on the right side of the river channel. The same is true for the left side. 右 The direction of the cross section is the direction of the unit direction vector u, which is the transition from the unit direction vector of the starting cross section to the unit direction vector of the ending cross section.

[0052] Traverse the river point index in r, take the jth river point in r, j = 1, 2, ..., m, m is the number of river points in r, and calculate the length of the new section line:

[0053] L=L 左 +L 右 (1)

[0054] Where: L is the length of the new section line.

[0055] Assume that points A, B, and C are the starting point of the new section line, the end point of the new section line, and the river point, respectively. The coordinates of the starting point and end point of the new section line are calculated as follows:

[0056] X A =X C -(u*L 右 ) (2)

[0057] Y A =Y C -(u*L 右 ) (3)

[0058] X B =X C +(u*L 左 ) (4)

[0059] Y B =Y C +(u*L 左 ) (5)

[0060] Where: X A 、XB 、X C are the longitude coordinates of points A, B, and C, respectively. A 、Y B 、Y C These are the latitude coordinates of points A, B, and C respectively.

[0061] like Figure 3 As shown in the figure, it is a schematic diagram for creating a new river section line. Find the series of river points R between the starting section line and the ending section line, record it as r; create a new section line for each river point in r. In the figure, A and B are the starting and ending points of the river section line, E and F are the left and right river bank dividing points of the river section line, subscript S represents the starting section line, subscript F represents the ending section line, and subscript j represents the section line created by the jth river point between the starting section line and the ending section line. That is: A S 、E S 、F S 、B S They represent the starting point of the section line, the left bank dividing point, the right bank dividing point, and the end point, respectively. j 、E j 、F j 、B j They represent the starting point, left bank dividing point, right bank dividing point and end point of the cross section line created by the j-th river point, respectively. F 、E F 、F F 、B F They represent the starting point of the end section line, the left river bank dividing point, the right river bank dividing point, and the end point respectively.

[0062] Step 4: Divide the new section line to obtain section points and resample.

[0063] Based on the start and end coordinates of the new section line created in the previous step, divide the new section line at the specified resolution (1m) to obtain a series of section points. Calculate the number of non-river section points on the right side of the new section line, the number of non-river section points on the left side, and the number of river section points. The calculation method is as follows:

[0064] 1) Calculate the index positions of the right bank dividing point and the left bank dividing point in the new section line coordinate point list:

[0065]

[0066] Where: I 右 , I 左 are the right bank dividing point index and the left bank dividing point index, respectively. max The maximum index of the new section line coordinate point.

[0067] 2) Calculate the number of non-river section points on the right side of the new section line, the number of non-river section points on the left side, and the number of river section points:

[0068] N 右 =I 右 (8)

[0069] N 左 =I max -I 左 (9)

[0070] N 河 =I max -N 左 -N 右 (10)

[0071] Where: N 右 、N 左 、N 河 They are the number of non-river section points on the right side of the new section line, the number of non-river section points on the left side, and the number of river section points.

[0072] 3) According to the number of three types of section points, namely, non-river section points on the right side, non-river section points on the left side, and river section points of the new section line, the section points of the corresponding categories of the starting section line and the ending section line are resampled to ensure that the starting section line, the ending section line, and the new section line are consistent in the number of non-river section points and river section points on the right side and left side.

[0073] Step 5: Obtain the elevation data of each section point on the new section line: Obtain the elevation of each section point on the new section line through inverse distance weighted interpolation. The calculation formula is:

[0074]

[0075] Where: Z k is the elevation of each section point on the new section line, I 河 is the index of the river point corresponding to the new section line, M is the number of river point indexes, Z Fk , Z Sk They are the elevations of each section point on the ending section line and the starting section line respectively.

[0076] Step 6: Obtain the elevation data of the target river area.

[0077] The target river area elevation data is obtained using the nearest neighbor interpolation method. This method, also known as the natural neighbor interpolation method, selects the nearest known elevation to the point to be interpolated as the interpolated result. While simple to use, it is only suitable for situations where known elevation points are densely packed, as distortion can easily occur. After the above steps, a sufficient number of cross-section lines and cross-section point elevations have been obtained, making it suitable for interpolation using the nearest neighbor method.

[0078] The target river channel area is divided into grids with a side length of 1m according to the specified resolution (1m). Some grids contain cross-section points with known elevations, while some grids do not contain elevation data. The nearest neighbor interpolation method is used, that is, the elevation of the grid is equal to the elevation of the nearest grid with elevation data. Finally, the elevation data of the entire target river channel area with a resolution of the specified resolution (1m) can be obtained.

[0079] Finally, it should be noted that the above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Although the present invention has been described in detail with reference to the preferred arrangement scheme, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for interpolating mountain river terrain elevation based on sparse river section point elevation data, characterized in that: The method comprises the following steps: Step 1. Obtain basic data of the target river channel and perform preprocessing: First, obtain basic data of the target river channel, including cross-section data and river channel line data; the cross-section data includes cross-section and cross-section line serial numbers, cross-section names, cross-section line starting and ending points, types of cross-section sampling points, latitude and longitude coordinates of cross-section sampling points, distance from the starting point of cross-section sampling points, and elevation; the cross-section and cross-section line serial numbers are arranged in order from upstream to downstream; the types of cross-section sampling points include non-feature points and riverbank dividing points; the river channel line data is the river channel line vector file of the target river channel, and the river channel line is a broken line formed by connecting multiple river channel points, and the direction of the river channel line is the direction of the river, that is, from upstream to downstream; Then, the basic data are preprocessed, including converting the longitude and latitude coordinates of each sampling point in the cross section into a unified coordinate system, converting the resolution of the river channel line to the specified resolution using the linear interpolation method, and dividing the river channel line into a series of river channel points with equal intervals according to the specified resolution, recorded as R; Step 2: Determine the directions of different section lines: Take the i-th section line as the starting section line and the i+1-th section line as the ending section line, where i=1, 2, ..., n, and n is the total number of river section lines. Determine the directions of the starting section line and the ending section line respectively. If the directions of the starting section line and the ending section line are opposite, flip the direction of the starting section line or the ending section line to make them consistent. Step 3. Create a new section line and calculate the length and longitude and latitude coordinates of the new section line: record the series of river points between the starting section line and the ending section line as r; create a new section line for each river point in r, and each new section line contains five elements, namely: the length of the left section line L 左 , right section line length L 右 、Width of the left river channel l 左 、Width of the right river channel l 右 , the direction of the section line, the section line direction is represented by the section line unit direction vector u; the length of the right section line L 右 The length of the starting section line on the right side of the river channel line and the length of the ending section line on the right side of the river channel line are linearly changed, and the same is true for the left side; the width of the river channel on the right side is l 右 It is obtained by linearly changing the length of the right bank dividing point of the starting section line from the river channel line and the length of the right bank dividing point of the ending section line from the river channel line, and the same applies to the left side; the section line direction is the direction of the unit direction vector u from the unit direction vector of the starting section line to the unit direction vector of the ending section line; Traverse the river point index in r, take the jth river point in r, j = 1, 2, ..., m, m is the number of river points in r, and calculate the length of the new section line: L=L 左 +L 右 (1) Where: L is the length of the new section line; Assume that points A, B, and C are the starting point of the new section line, the end point of the new section line, and the river point respectively. The formula for calculating the coordinates of the starting point and end point of the new section line is: X A =X C -(u*L 右 ) (2) AND A =And C -(u*L 右 ) (3) X B =X C +(u*L 左 ) (4) AND B =And C +(u*L 左 ) (5) Where: X A 、X B 、X C are the longitude coordinates of points A, B, and C, respectively. A 、Y B 、Y C are the latitude coordinates of points A, B, and C respectively; Step 4: Divide the new section line to obtain section points and resample: Based on the start and end coordinates of the created new section line, divide the new section line at the specified resolution to obtain a series of section points, and calculate the number of non-river section points on the right side of the new section line, the number of non-river section points on the left side, and the number of river section points. The calculation process is as follows: 1) Calculate the index positions of the right bank dividing point and the left bank dividing point in the new section line coordinate point list: Where: I 右 , I 左 are the right bank dividing point index and the left bank dividing point index, respectively. max The maximum index of the new section line coordinate point; 2) Calculate the number of non-river section points on the right side of the new section line, the number of non-river section points on the left side, and the number of river section points: N 右 =I 右 (8) N 左 =I max -I 左 (9) N 河 =I max -N 左 -N 右 (10) Where: N 右 、N 左 、N 河 They are the number of non-river section points on the right side of the new section line, the number of non-river section points on the left side, and the number of river section points; 3) According to the number of three types of cross-section points on the right side of the new cross-section line, namely, non-river cross-section points on the left side, and river cross-section points, resample the cross-section points of the corresponding categories of the starting cross-section line and the ending cross-section line to ensure that the number of non-river cross-section points and river cross-section points on the right side and left side of the starting cross-section line, the ending cross-section line, and the new cross-section line are consistent; Step 5: Obtain the elevation data of each section point on the new section line: Obtain the elevation of each section point on the new section line through inverse distance weighted interpolation. The calculation formula is: Where: Z k is the elevation of each section point on the new section line, I 河 is the index of the river point corresponding to the new section line, M is the number of river point indexes, Z Fk , Z Sk They are the elevations of each section point on the ending section line and the starting section line respectively; Step 6: Obtain the elevation data of the target river area: Divide the target river area into grids according to the specified resolution. Some grids contain cross-section points with known elevations, while some grids do not contain elevation data. Use the nearest neighbor interpolation method, that is, the elevation of the grid is equal to the elevation of the nearest grid with elevation data. Finally, the elevation data of the entire target river area with the specified resolution can be obtained.

2. The method for interpolating mountain river terrain elevation based on sparse river section point elevation data according to claim 1 is characterized in that: The specified resolution is 1m.

3. The method for interpolating mountain river terrain elevation based on sparse river section point elevation data according to claim 1 is characterized in that: The unified coordinate system mentioned in step 1 is specifically the UTM series coordinate system.

4. The method for interpolating mountain river terrain elevation based on sparse river section point elevation data according to claim 1 is characterized in that: The specific process of determining the directions of the starting section line and the ending section line in step 2 is as follows: taking the starting section line and the ending section line as the target section line respectively, finding the river point closest to the target section line from R, taking the river point as the starting point and the next river point as the end point, and constructing a closest target river vector; similarly, taking the starting point and end point of the target section line as the starting point and end point of the vector respectively, and constructing a target section line vector; The coordinate system is constructed with the nearest target river channel vector as the x-axis direction, the x-axis rotated 90° counterclockwise as the y-axis direction, and the starting point of the target section line vector as the origin. If the end point of the target section line vector falls in the first or second quadrant, it is positive, and if it falls in the third or fourth quadrant, it is negative. If it is negative, the direction of the reverse section line needs to be flipped to ensure that the direction of the starting section line and the ending section line are consistent, that is, both are positive.

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