阅读说明：本技术 一种河道断面地形重构方法 (River channel section terrain reconstruction method ) 是由 周建银 王敏 赵瑾琼 宫平 毛冰 龙瑞 邓春艳 元媛 葛华 于 2020-06-04 设计创作，主要内容包括：本发明提供一种河道断面地形的重构方法,包括以下具体步骤：获取初始河道断面地形,辨识水上和水下地形的分界位置；对水上地形进行平滑；对水下地形进行重构,方法是多点外推、距离加权；二者合并,获得完整的重构后的断面地形。本发明可以弥补基于DEM数据插值得到的河道断面地形的不足,提高河道地形的质量。(The invention provides a reconstruction method of river channel section terrain, which comprises the following specific steps: acquiring an initial river channel section terrain, and identifying the boundary position of an overwater terrain and an underwater terrain; smoothing the water terrain; reconstructing underwater terrain by multipoint extrapolation and distance weighting; and combining the two to obtain a complete reconstructed section terrain. The method can make up the defect of the river channel section terrain obtained based on DEM data interpolation, and improve the quality of the river channel terrain.)

1. A reconstruction method of river channel cross-section terrain is characterized by comprising the following specific steps:

s1, acquiring an initial river channel section terrain; the terrain is obtained by performing interpolation calculation along the cross section of the river channel based on a digital elevation model;

s2, identifying the boundary position of the water terrain and the underwater terrain, namely a water edge point;

s3, smoothing the water terrain;

s4, reconstructing underwater terrain;

and S5, combining the water terrain and the underwater terrain to obtain the reconstructed river cross-section terrain.

2. The method of claim 1, wherein the method comprises: the specific implementation steps of step S2 are as follows:

s21, finding out the position of the lowest point of the section;

s22, comparing the terrain points with the lowest point one by one from the lowest point to the left, if the difference between the elevation of the terrain point and the elevation of the lowest point exceeds a preset threshold value, positioning the right adjacent point of the terrain point as a left boundary point of the above-water and underwater terrain, namely a left water edge point L0;

s23, similarly, comparing the landform points with the lowest point one by one from the lowest point to the right, if the difference between the elevation of the landform point and the elevation of the lowest point exceeds the predetermined threshold, positioning the left adjacent point of the landform point as the right boundary point of the above-water and under-water landforms, i.e. the right waterside point R0.

3. The method of claim 1, wherein the method comprises: the specific implementation steps of step S3 are as follows:

s31, for the water topographic point i, taking 1 point to the left and the right respectively by taking the point as the center, adopting a three-point weighted average method to carry out smoothing treatment, wherein the calculation formula is as follows:

in the above formula, Z represents elevation, subscripts i-1, i +1 represent position numbers of topographical points, superscript 0 represents before smoothing, superscript 1 represents after smoothing;

s32, repeating S31 a plurality of times, makes the smoothing effect more sufficient, but the excessive smoothing will reduce the accuracy of the terrain.

4. A method according to claim 2, wherein the method comprises: the specific implementation steps of step S4 are as follows:

s41, optionally taking an underwater topographic point P between L0 and R0, wherein the distances from the underwater topographic point P to L0 and R0 are DL and DR respectively;

s42, reconstructing P point elevations by respectively taking L0 and R0 as anchor points to obtain P point elevations Z_PL、Z_PRThe reconstructed elevation at point P is:

Z_P＝(W_L*Z_PL+W_R*Z_PR)/(W_L+W_R)(2)

in the above formula, W_LAnd W_RRespectively being elevation Z_PL、Z_PRThe calculation method of the consideration weight of (2) is as follows:

in the above formula, x_P、x_L0、x_R0P, L0 and R0 respectively.

5. The method of claim 4, wherein the method comprises: reconstructing the P point elevation by taking the L0 as an anchor point in the step S42 to obtain a P point elevation Z_PLThe specific implementation steps are as follows:

1) and the elevation Z of the point P is obtained by linear extension of the point Li on the left side of the point L0_Li：

In the above formula, β is the underwater gradient adjustment coefficient, and the default value is 0.8, x_L0、Z_L0Starting distance and elevation of L0 point, and the like;

if the left side point Li is found from L0 from near to far to the left for interpolation, the distance D between Li and P_Li>D_maxThen the interpolation based on L0 and Li is still computed normally, but no longer computed to the outlier, where D is_Li＝|x_P-x_Li|，D_maxThe maximum considered distance, which has a value of the distance between L0 and R0;

2) solving for Z_LiCorresponding initial weight

3) Normalizing the weights to ensurew_LiMeter (2)Is calculated as

4) Through weighting calculation, the P point elevation Z is obtained by reconstructing the P point elevation by taking the L0 as an anchor point_PL：

6. The method of claim 4, wherein the method comprises: reconstructing the P point elevation by taking the R0 as an anchor point in the step S42 to obtain a P point elevation Z_PRThe specific implementation steps are as follows:

1) and the elevation Z of the point P is obtained by linear continuation of the point R0 and the right Ri thereof_Ri：

In the above formula, β is the underwater gradient adjustment coefficient, and the default value is 0.8, x_R0、Z_R0The starting point distance and the elevation of the R0 point, and the like;

if the right side point Ri is searched from R0 from near to far to the right for interpolation, the distance D between Ri and P_Ri>D_maxThen the interpolation based on R0 and Ri points is still calculated normally, but no longer to the outlier, where D is_Ri＝|x_P-x_Ri|，D_maxThe maximum considered distance, which has a value of the distance between L0 and R0;

2) solving for Z_RiCorresponding initial weight

3) Normalizing the weights to ensurew_RiIs calculated as

4) Through weighting calculation, the P point elevation Z is obtained by reconstructing the P point elevation by taking R0 as an anchor point_PR：

Technical Field

The invention relates to the field of river numerical simulation, in particular to a reconstruction method of river channel section terrain.

Background

River terrain data is the basis for river numerical simulation. The quality of the terrain data directly influences the quality of river numerical simulation results. When the numerical simulation of the mountainous river is carried out, actually measured river terrain is often lacked, so that the required river terrain needs to be extracted from DEM (digital elevation model) based on satellite data. However, DEM terrain suffers from two problems: firstly, the extracted river terrain is stepped due to low precision; secondly, the lack of underwater topography.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a reconstruction method of a river channel section terrain, which can improve the quality of the section terrain.

The technical scheme of the invention is as follows: a reconstruction method of river channel section terrain comprises the following specific steps:

s1, acquiring an initial river channel section terrain; the terrain is generally obtained by performing interpolation calculation along a river channel section based on a digital elevation model;

s2, identifying the boundary position of the water terrain and the underwater terrain, namely a water edge point;

s3, smoothing the water terrain;

s4, reconstructing underwater terrain;

and S5, combining the water terrain and the underwater terrain to obtain the reconstructed river cross-section terrain.

The specific implementation steps of step S2 are as follows:

s21, finding out the position of the lowest point of the section;

s22, comparing the terrain points with the lowest point one by one from the lowest point to the left, and if the difference between the elevation of the terrain point and the elevation of the lowest point exceeds a preset threshold value, positioning the adjacent point on the right side of the terrain point (namely the terrain point which is compared before) as the left boundary point of the above-water and underwater terrains, namely the left water side point L0;

s23, likewise, comparing the topographic points with the lowest point one by one from the lowest point to the right, if the difference between the topographic point elevation and the lowest point elevation exceeds a predetermined threshold value, locating the adjacent point to the left of the topographic point (i.e. the previous topographic point to be compared) as the right boundary point of the above-water and under-water topography, i.e. the right water boundary point R0.

The specific implementation steps of step S3 are as follows:

s31, for the water topographic point i, taking 1 point to the left and the right respectively by taking the point as the center, adopting a three-point weighted average method to carry out smoothing treatment, wherein the calculation formula is as follows:

in the above formula, Z represents elevation, subscripts i-1, i +1 represent position numbers of topographical points, superscript 0 represents before smoothing, superscript 1 represents after smoothing;

s32, the process of S31 may be repeated as many times as necessary to make the smoothing effect more sufficient, but excessive smoothing will reduce the accuracy of the terrain.

The specific implementation steps of step S4 are as follows:

s41, optionally taking an underwater topographic point P between L0 and R0, wherein the distances from the underwater topographic point P to L0 and R0 are DL and DR respectively;

s42, reconstructing P point elevations by respectively taking L0 and R0 as anchor points to obtain P point elevations Z_PL、Z_PRThe reconstructed elevation at point P is:

Z_P＝(W_L*Z_PL+W_R*Z_PR)/(W_L+W_R) (2)

in the above formula, W_LAnd W_RRespectively being elevation Z_PL、Z_PRThe calculation method of the consideration weight of (2) is as follows:

in the above formula, x_P、x_L0、x_R0P, L0 and R0 respectively.

Reconstructing the P point elevation by taking the L0 as an anchor point in the step S42 to obtain a P point elevation Z_PLThe specific implementation steps are as follows:

1) and the elevation Z of the point P is obtained by linear extension of the point Li on the left side of the point L0_Li：

In the above formula, β is the underwater gradient adjustment coefficient, and the default value is 0.8, x_L0、Z_L0Starting distance and elevation of L0 point, and the like;

if the left side point Li is found from L0 from near to far to the left for interpolation, the distance D between Li and P_Li>D_maxThen the interpolation based on L0 and Li is still computed normally, but no longer computed to the outlier, where D is_Li＝|x_P-x_Li|，D_maxThe maximum considered distance is the distance between L0 and R0 (i.e., water width);

2) solving for Z_LiCorresponding initial weightIt is calculated as

3) Normalizing the weights to ensure

w_LiIs calculated as

4) Through weighting calculation, the P point elevation Z is obtained by reconstructing the P point elevation by taking the L0 as an anchor point_PL：

Reconstructing the P point elevation by taking the R0 as an anchor point in the step S42 to obtain a P point elevation Z_PRThe specific implementation steps are as follows:

1) and the elevation Z of the point P is obtained by linear continuation of the point R0 and the right Ri thereof_Ri：

In the above formula, β is the underwater gradient adjustment coefficient, and the default value is 0.8, x_R0、Z_R0The starting point distance and the elevation of the R0 point, and the like;

if the right side point Ri is searched from R0 from near to far to the right for interpolation, the distance D between Ri and P_Ri>D_maxThen the interpolation based on R0 and Ri points is still calculated normally, but no longer to the outlier, where D is_Ri＝|x_P-x_Ri|，D_maxThe maximum considered distance is the distance between L0 and R0 (i.e., water width);

2) solving for Z_RiCorresponding initial weightIt is calculated as

3) Normalizing the weights to ensure

w_RiIs calculated as

4) Through weighting calculation, the P point elevation Z is obtained by reconstructing the P point elevation by taking R0 as an anchor point_PR：

The invention has the technical effects that: through reconstructing the river channel section terrain data extracted from the DEM, a high-quality river channel section terrain is obtained, and the quality of the river channel section terrain data is improved.

Drawings

FIG. 1 is a schematic flow chart of the method of the present invention.

Fig. 2 is an initial channel cross-sectional topographic map of an embodiment of the present invention.

FIG. 3 is a schematic diagram of the positions of feature points according to an embodiment of the present invention.

Fig. 4 is a cross-sectional topographic view of the reconstructed river according to the embodiment of the present invention.

Fig. 5 is a topographic comparison of the initial and reconstructed channel cross-sections for an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, a method for reconstructing a river channel cross-sectional terrain includes the following specific steps:

s1, acquiring an initial river channel section terrain; the terrain is generally obtained by interpolation calculation along a river channel section based on DEM (digital elevation model);

s2, identifying the boundary position of the water terrain and the underwater terrain, namely a water edge point;

s3, smoothing the water terrain;

s4, reconstructing underwater terrain;

and S5, combining the water terrain and the underwater terrain to obtain the reconstructed river cross-section terrain.

The specific implementation steps of step S2 are as follows:

s21, finding out the position of the lowest point of the section;

s22, comparing the terrain points with the lowest point one by one from the lowest point to the left, and if the difference between the elevation of the terrain point and the elevation of the lowest point exceeds a threshold value (given in advance), positioning the adjacent point on the right side of the terrain point (namely the terrain point which is compared before) as the left boundary point of the above-water and underwater terrains, namely the left water side point L0;

s23, similarly, comparing the landform points with the lowest point one by one from the lowest point to the right, if the difference between the elevation of the landform point and the elevation of the lowest point exceeds a threshold value (given in advance), locating the adjacent point to the left of the landform point (i.e. the previous landform point to be compared) as the right boundary point of the above-water and under-water landforms, i.e. the right water edge point R0.

The specific implementation steps of step S3 are as follows:

s31, for the water topographic point i, taking 1 point to the left and the right respectively by taking the point as the center, adopting a three-point weighted average method to carry out smoothing treatment, wherein the calculation formula is as follows:

in the above formula, Z represents elevation, subscripts i-1, i +1 represent position numbers of topographical points, superscript 0 represents before smoothing, superscript 1 represents after smoothing;

s32, the process of S31 may be repeated as many times as necessary to make the smoothing effect more sufficient, but excessive smoothing will reduce the accuracy of the terrain.

The specific implementation steps of step S4 are as follows:

s41, optionally taking an underwater topographic point P between L0 and R0, wherein the distances from the underwater topographic point P to L0 and R0 are DL and DR respectively;

s42, reconstructing P point elevations by respectively taking L0 and R0 as anchor points to obtain P point elevations Z_PL、 Z_PRThe reconstructed elevation at point P is:

Z_P＝(W_L*Z_PL+W_R*Z_PR)/(W_L+W_R) (2)

in the above formula, W_LAnd W_RRespectively being elevation Z_PL、Z_PRThe calculation method of the consideration weight of (2) is as follows:

in the above formula, x_P、x_L0、x_R0P, L0 and R0 respectively.

Reconstructing the P point elevation by taking the L0 as an anchor point in the step S42 to obtain a P point elevation Z_PLThe specific implementation steps are as follows:

1) and the elevation Z of the point P is obtained by linear extension of the point Li on the left side of the point L0_Li：

In the above formula, β is the underwater gradient adjustment coefficient, and the default value is 0.8, x_L0、Z_L0Starting distance and elevation of L0 point, and the like;

if the left side point Li is found from L0 from near to far to the left for interpolation, the distance D between Li and P_Li>D_maxThen the interpolation based on L0 and Li is still computed normally, but no longer computed to the outlier, where D is_Li＝|x_P-x_Li|，D_maxThe maximum considered distance is the distance between L0 and R0 (i.e., water width);

2) solving for Z_LiCorresponding initial weight

It is calculated as

3) Normalizing the weights to ensure

w_LiIs calculated as

4) Through weighting calculation, the P point elevation Z is obtained by reconstructing the P point elevation by taking the L0 as an anchor point_PL：

Reconstructing the P point elevation by taking the R0 as an anchor point in the step S42 to obtain a P point elevation Z_PRThe specific implementation steps are as follows:

1) and the elevation Z of the point P is obtained by linear continuation of the point R0 and the right Ri thereof_Ri：

In the above formula, β is the underwater gradient adjustment coefficient, and the default value is 0.8, x_R0、Z_R0The starting point distance and the elevation of the R0 point, and the like;

if the right side point Ri is searched from R0 from near to far to the right for interpolation, the distance D between Ri and P_Ri>D_maxThen the interpolation based on R0 and Ri points is still calculated normally, but no longer to the outlier, where D is_Ri＝|x_P-x_Ri|，D_maxThe maximum considered distance is the distance between L0 and R0 (i.e., water width);

2) solving for Z_RiCorresponding initial weightIt is calculated as

3) Normalizing the weights to ensureCertificate (certificate)

w_RiIs calculated as

4) Through weighting calculation, the P point elevation Z is obtained by reconstructing the P point elevation by taking R0 as an anchor point_PR：

The following describes the embodiments of the present invention by way of an example with reference to the accompanying drawings.

Case (2): reconstruction of river cross-sectional terrain

Case introduction: the topographic data of the section of the initial channel is obtained by interpolation calculation of DEM along the section of the channel, as shown in figure 2.

The method for reconstructing the river channel section terrain comprises the following steps:

1) identifying the boundary positions of the above-water terrain and the below-water terrain, namely water edge points L0 and R0, as shown in FIG. 3;

2) the water terrain on the left side of L0 and the right side of R0 is smoothed by a three-point weighted average method which is calculated by the formulaSubscripts i-1, i and i +1 represent position numbers of topographical points, a superscript 0 represents before smoothing, and a superscript 1 represents after smoothing;

3) optionally, an underwater topographic point P between L0 and R0 is selected, the distances between the underwater topographic point P and L0 are DL respectively, and the P point elevation is reconstructed by taking L0 as an anchor point to obtain a P point elevation Z_PL；

4) The distances between the underwater topographic point P and R0 are respectively DR, and the P point elevation is reconstructed by taking R0 as an anchor point to obtain P point elevation Z_PR；

5) P point reconstruction through left-right weighting calculationRear elevation Z_P＝(W_L*Z_PL+W_R*Z_PR)/(W_L+W_R)；

6) And combining the water terrain and the underwater terrain to obtain a reconstructed river channel section terrain, as shown in figure 4.

For visual comparison, the initial cross section is compared with the reconstructed cross section, as shown in fig. 5.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.