CN105825506A - Method for extracting contour line of water body via point cloud data of LiDAR - Google Patents

Abstract

The invention discloses a method for extracting a contour line of a water body via point cloud data of an LiDAR. Via the method, the contour line of the water body can be extracted only via scattered point cloud data of the airborne LiDAR, and the method can be applied to water body edge detection via point cloud data of the airborne LiDAR. The method is simple, easy to realize, and high in execution efficiency, the contour line of the water body can be directly obtained from the point cloud data of the airborne LiDAR needless of other auxiliary data, and the water body is extracted accurately and comprehensively.

Description

A kind of method utilizing LiDAR point cloud data to extract coastal waters line

Technical field

The present invention relates to a kind of method extracting coastal waters line, particularly to a kind of method utilizing LiDAR point cloud data to extract coastal waters line.

Background technology

Water is the essential condition determining wetland living or death, utilizes remote sensing technology to obtain wetland water body area and has important indicative significance to wetland, and remote sensing technology, as a kind of novel earth observation from space technology, has been widely used for dynamic monitoring and the resource investigation of mud wetland.But traditional optical remote sensing technology exists in terms of beach water body investigation that the quality of data is affected seriously by weather conditions, night cannot work and vegetative coverage stronger area optical remote sensing can not penetrate vegetation etc. and affect, thus optical remote sensing technology in wetland is applied by a definite limitation.

Airborne lidar detection system is a kind of active earth observation systems, there is the features such as high reliability, high-resolution and high accuracy, it is used widely at numerous areas, Airborne LiDAR Technology being applied to wetland potential storage capacity detection aspect and has bigger prospect, water body contour line based on scattered point cloud data accurately extracts, and is the committed step obtaining storage capacity.At present, utilize scattered point cloud data extracting directly to go out one of Main Means that boundary point is Boundary extracting algorithm.

Summary of the invention

The technical problem to be solved is to provide a kind of method utilizing LiDAR point cloud data to extract coastal waters line, the method only utilizing airborne LiDAR scattered point cloud data can extract water body contour line, can apply to the detection of airborne LiADR cloud data coastal waters.

The present invention solves above-mentioned technical problem by the following technical solutions:

The present invention provides a kind of method utilizing LiDAR point cloud data to extract coastal waters line, including step in detail below:

Step 1, reads the original airborne LiDAR point cloud data of target area, obtains total number n of original LiDAR point cloud data；

Step 2, determines the step-length of grid partition and determines x direction and number n of y direction grid_xAnd n_y；

Step 3, the n obtained in traversal step 2_x×n_yAccording to the number putting cloud in grid, individual grid, judges that whether grid is grid in water body, and record the position of grid in each water body, thus grid and position thereof in obtaining all water bodys, specifically comprise the following steps that

301: make w=1, v=1；

302: be numbered four summits of w row v row grid, the wherein summit, the lower right corner numbered 1 of this grid, other summits number consecutively counterclockwise is 2,3 and 4, utilizes formula 4 to calculate the coordinate on this grid 1～4 summit

(x_right,y_down)、(x_right,y_up)、(x_left,y_up) and (x_left,y_down):

$\begin{array}{c}{x}_{left}=\min x+(w-1)\×step\\ x_{right}=\min x+w\×step\\ y_{down}=\min y+(v-1)\×step\\ y_{up}=\min y+v\×step\end{array}---\left(4\right)$

303: in calculating current mesh, put number z of cloud, if z >=5, then perform step 304；If z ＜ 5, then current mesh is labeled as grid in water body, proceeds to step 305；

304: make w=w+1, if w≤n_x, then v keeps constant, returns step 302；If w is ＞ n_x, then make w=1, v=v+1, return step 302；

305: record the position of grid in each water body, thus grid and position thereof in obtaining all water bodys；

Step 4, the eight connectivity grid of grid in l the water body that search step 3 obtains one by one, it is thus achieved that all land and water boundary grid in target area, and determine that all land and water boundary grid are positioned at the summit of water body, specifically comprise the following steps that

401: make I=1；

402；Using grid in i-th water body as seed grid, being numbered the eight connectivity grid of seed grid, wherein lower right corner grid numbered 1, other grid number consecutively counterclockwise is 2～8；

403: calculate some cloud number h in 1～No. 8 grid respectively, if h >=5, be land and water boundary grid by this grid ticks；

404: make I=I+1, if I≤l, return step 402, otherwise terminate iteration, thus all land and water boundary grid in obtaining target area, perform step 405；

405: determine that the land and water boundary grid of labelling in step 403 is positioned at the summit of water body；

Step 5, K the land and water boundary grid that search step 4 obtains one by one, obtain the coastal waters point of each land and water boundary grid, specifically comprise the following steps that

501: make t=1；

502, optional the t land and water boundary grid is positioned at the summit of water body as kind of a son vertex w₁, use the some cloud in K-D tree seed tissue summit and this land and water boundary grid, utilize nearest neighbor algorithm to obtain the nearest neighbor point of kind son vertex, using nearest neighbor point as initial seed point o of water body limit marginal point₁；

503: with initial seed point o₁For starting point, determine initial seed point o₁The coastal waters point of side, specifically comprises the following steps that counterclockwise

50301: use k nearest neighbor algorithm search initial seed point o₁Nearest neighbor point cloud point p in this land and water boundary grid₁,p₂,...,p_q, wherein q is the number of the nearest neighbor point cloud point searched；

50302: utilize formula 5 to calculate initial angle alpha₀:

In formula, a is o₁And w₁Between distance, b is w₁And w₂Between distance, c is o₁And w₂Between distance, w₂For w in this land and water boundary grid₁Anticlockwise next summit；

50303: utilize formula 6 to calculate p_i、w₁And w₂The ∠ p constituted_iw₁w₂The number of degrees, and be designated as α_i:

In formula, i=1,2 ..., q；a_iFor p_iAnd w₁Between distance, b is w₁And w₂Between distance, c_iFor p_iAnd w₂Between distance；

50304: from α₁,α₂,…,α_qMiddle selection is more than initial angle alpha₀Angle, and the nearest neighbor point cloud point of its correspondence is designated as N again₁,…,N_s, wherein s is α₁,α₂,.….,α_qIn more than initial angle alpha₀The number at angle；

50305: utilize formula 7 to calculate ∠ N_jo₁w₁The number of degrees, and be designated as β_j:

In formula, j=1,2 ..., s；A_jFor N_jAnd o₁Between distance, a is o₁And w₁Between distance, C_jFor N_jAnd w₁Between distance；

50306: from β₁,β₂,…,β_sThe angle that the middle selection number of degrees are minimum, nearest neighbor point cloud point corresponding to this angle is coastal waters point；

50307: coastal waters point step 50306 obtained, as new initial seed point, repeats step 50301～50306, continually look for next coastal waters point, until occurring without new coastal waters point；

504: with initial seed point o₁For starting point, determine initial seed point o₁The coastal waters point of side, specifically comprises the following steps that clockwise

50401: utilize formula 8 to calculate initial angle θ₀:

In formula, a is o₁And w₁Between distance, e is w₁And w₃Between distance, f is o₁And w₃Between distance, w₃For w in this land and water boundary grid₁Clockwise next summit；

50402: utilize formula 9 to calculate p_i、w₁And w₃The ∠ p constituted_iw₁w₃The number of degrees, and be designated as θ_i:

In formula, a_iFor p_iAnd w₁Between distance, e is w₁And w₃Between distance, f_iFor p_iAnd w₃Between distance；

50403: from θ₁,θ₂,...,θ_qMiddle selection is more than initial angle θ₀Angle, and the nearest neighbor point cloud point of its correspondence is designated as M again₁,M₂,...,M_d, wherein d is θ₁,θ₂,...,θ_qMore than initial angle θ₀The number at angle；

50404: utilize formula 10 to calculate ∠ M_uo₁w₁The number of degrees, and be designated as ω_u:

In formula, u=1,2 ..., d；D_uFor M_uAnd o₁Between distance, a is o₁And w₁Between distance, F_uFor M_uAnd w₁Between distance；

50405: from ω₁,ω₂,...,ω_dThe angle that the middle selection number of degrees are minimum, nearest neighbor point cloud point corresponding to this angle is coastal waters point；

50406: coastal waters point step 50305 obtained, as new initial seed point, repeats step 50401～50405, continually look for next coastal waters point, until occurring without new coastal waters point；

505: the coastal waters point that integration step 503 and step 504 obtain, obtain all coastal waters points of current land and water boundary grid；

506, make t=t+1, if t≤K, then return step 502, the coastal waters point of the next land and water boundary grid of search；If t is ＞ K, then terminate iteration, perform step 6；Thus obtain the coastal waters point of all land and water boundary grid；

Step 6, the coastal waters point of all land and water boundary grid obtained in integration step 5, thus obtain the edge image of target area water body.

As the further prioritization scheme of the present invention, step 2 determine the step-length of grid partition and determines x direction and the number of y direction grid, specifically comprising the following steps that

201: preset some cloud number m that each grid is expected to comprise；

202: calculate some coordinate minima minx in cloud x direction and maximum maxx, and coordinate minima miny in y direction and maximum maxy；

203: calculate the average density of target area point cloud；

204: calculate the step-length of grid partition；

205: calculate x direction and the number of y direction grid, thus obtain n_yRow n_xThe grid of row.

As the further prioritization scheme of the present invention, utilize the average density of target area point cloud in formula 1 calculation procedure 203, particularly as follows:

$\mathrm{\σ}=\frac{n}{(\max x-\min x)\×(\max y-\min y)}---\left(1\right)$

In formula, σ is the average density of target area point cloud.

As the further prioritization scheme of the present invention, utilize the step-length of grid partition in formula 2 calculation procedure 204, particularly as follows:

$step=\sqrt{\frac{m}{\mathrm{\σ}}}---\left(2\right)$

In formula, step is the step-length of grid partition.

As the further prioritization scheme of the present invention, utilize x direction and the number of y direction grid in formula 3 calculation procedure 205, particularly as follows:

$\begin{array}{c}{n}_x=fix\left(\frac{\max x-\min x}{step}\right)\\ n_y=fix\left(\frac{\max y-\min y}{step}\right)\end{array}---\left(3\right)$

In formula, n_xAnd n_yBeing respectively x direction and the number of y direction grid, fix represents intercepting mantissa function.

As the further prioritization scheme of the present invention, in step 405, land and water boundary grid is positioned at the summit of water body and is: the common vertex of land and water boundary grid and seed grid.

The present invention uses above technical scheme compared with prior art, have following technical effect that the inventive method is simple, execution efficiency is high, does not utilize other assistance datas just directly can obtain water body contour line from airborne LiDAB point cloud, it is possible to the most accurately and comprehensively to extract water body.

Accompanying drawing explanation

Fig. 1 is the method flow diagram of the present invention.

Fig. 2 is grid summit method for numbering serial.

Fig. 3 is the eight connectivity grid method for numbering serial of seed grid.

Fig. 4 is the schematic diagram of search coastal waters point.

Fig. 5 is original airborne LiDAR point cloud image.

Fig. 6 is the coastal waters image extracted.

Detailed description of the invention

Below in conjunction with the accompanying drawings and technical scheme is described in further detail by specific embodiment:

As it is shown in figure 1, a kind of method utilizing LiDAR point cloud data to extract coastal waters line, comprise the following steps:

1, the original airborne LiDAR point cloud image of certain lake region is as it is shown in figure 5, read original airborne LiDAR point cloud data, total number n=1244620 of cloud data.

2, determine the step-length of grid partition and determine x direction and the number of y direction grid, specifically comprising the following steps that

201: preset some cloud number k=100 that each grid is expected to comprise；

202: calculate X-direction minima minx and maximum maxx, and Y-direction minima miny and maximum maxy；

204: utilize formula 1 calculate target area some cloud average density σ:

$\mathrm{\σ}=\frac{n}{(\max x-\min x)\×(\max y-\min y)}---\left(1\right)$

205: utilize formula 2 to calculate step-length step of grid partition:

$step=\sqrt{\frac{m}{\mathrm{\σ}}}---\left(2\right)$

206: utilize formula 3 to calculate x direction and the number of y direction grid, there are n_yRow n_xRow grid.

$\begin{array}{c}{n}_x=fix\left(\frac{\max x-\min x}{step}\right)=113\\ n_y=fix\left(\frac{\max y-\min y}{step}\right)=109\end{array}---\left(3\right)$

Step 3, travels through 109 × 113 grid, judges that whether grid is grid in water body according to the number putting cloud in grid, and records the position of grid in each water body, thus grid and position thereof in obtaining all water bodys, specifically comprise the following steps that

301: make w=1, v=1；

302: be numbered four summits of w row v row grid, as in figure 2 it is shown, the summit, the lower right corner numbered 1 of wherein this grid, other summits number consecutively counterclockwise is 2,3 and 4, utilizes formula 4 to calculate the coordinate (x on this grid 1～4 summit_right,y_down)、(x_right,y_up)、(x_left,y_up) and (x_left,y_down):

$\begin{array}{c}{x}_{left}=\min x+(w-1)\×step\\ x_{right}=\min x+w\×step\\ y_{down}=\min y+(v-1)\×step\\ y_{up}=\min y+v\×step\end{array}---\left(4\right)$

303: in calculating current mesh, put number z of cloud, if z >=5, then perform step 304；If z ＜ 5, then current mesh is labeled as grid in water body, proceeds to step 305；

304: make w=w+1, if w≤109, then v keeps constant, returns step 302；If w ＞ 109, then make w=1, v=v+1, return step 302；

305: record the position of grid in each water body, thus grid and position thereof in obtaining all water bodys.

Step 4, the eight connectivity grid of grid in l the water body that search step 3 obtains one by one, it is thus achieved that all land and water boundary grid in target area, and determine that all land and water boundary grid are positioned at the summit of water body, specifically comprise the following steps that

401: make I=1；

402；Using grid in i-th water body as seed grid, being numbered the eight connectivity grid of seed grid, as it is shown on figure 3, wherein lower right corner grid numbered 1, other grid number consecutively counterclockwise is 2～8；

403: calculate some cloud number h in 1～No. 8 grid respectively, if h >=5, be land and water boundary grid by this grid ticks；

404: make I=I+1, if I≤l, return step 402, otherwise iteration terminates, thus all land and water boundary grid in obtaining target area, perform step 405；

405: determine that the land and water boundary grid of labelling in step 403 is positioned at the summit of water body, be the common vertex of land and water boundary grid and seed grid.

Step 5, search step 4 obtains K land and water boundary grid one by one, obtains the coastal waters point of each land and water boundary grid, as shown in Figure 4, specifically comprises the following steps that

501: make t=1；

502, optional the t land and water boundary grid is positioned at the summit of water body as kind of a son vertex w₁, use the some cloud in K-D tree seed tissue summit and this land and water boundary grid, utilize nearest neighbor algorithm to obtain the nearest neighbor point of kind son vertex, using nearest neighbor point as initial seed point o of coastal waters point₁；

503: with initial seed point o₁For starting point, determine initial seed point o₁The coastal waters point of side, specifically comprises the following steps that counterclockwise

50301: use k nearest neighbor algorithm search initial seed point o₁Nearest neighbor point cloud point p in this land and water boundary grid₁,p₂,...,p_q, wherein q is the number of the nearest neighbor point cloud point searched；

50302: utilize formula 5 to calculate initial angle alpha₀:

In formula, a is o₁And w₁Between distance, b is w₁And w₂Between distance, c is o₁And w₂Between distance, w₂For w in this land and water boundary grid₁Anticlockwise next summit；

50303: utilize formula 6 to calculate p_i、w₁And w₂The ∠ p constituted_iw₁w₂The number of degrees, and be designated as α_i:

In formula, i=1,2 ..., q；a_iFor p_iAnd w₁Between distance, b is w₁And w₂Between distance, c_iFor p_iAnd w₂Between distance；

50304: from α₁,α₂,...,α_qMiddle selection is more than initial angle alpha₀Angle, and the nearest neighbor point cloud point of its correspondence is designated as N again₁,...,N_s, wherein s is α₁,α₂,…,α_qMore than initial angle alpha₀The number at angle；

50305: utilize formula 7 to calculate ∠ N_jo₁w₁The number of degrees, and be designated as β_j:

In formula, j=1,2 ..., s；A_jFor N_jAnd o₁Between distance, a is o₁And w₁Between distance, C_jFor N_jAnd w₁Between distance；

50306: from β₁,β₂,...,β_sThe angle that the middle selection number of degrees are minimum, nearest neighbor point cloud point corresponding to this angle is coastal waters point；

50307: coastal waters point step 50306 obtained, as new initial seed point, repeats step 50301～50306, continually look for next coastal waters point, until occurring without new coastal waters point；

504: with initial seed point o₁For starting point, determine initial seed point o₁The coastal waters point of side, specifically comprises the following steps that clockwise

50401: utilize formula 5 to calculate initial angle θ₀:

In formula, a is o₁And w₁Between distance, e is w₁And w₃Between distance, f is o₁And w₃Between distance, w₃For w in this land and water boundary grid₁Clockwise next summit；

50402: utilize formula 6 to calculate p_i、w₁And w₃The ∠ p constituted_iw₁w₃The number of degrees, and be designated as θ_i:

In formula, a_iFor p_iAnd w₁Between distance, e is w₁And w₃Between distance, f_iFor p_iAnd w₃Between distance；

50403: from θ₁,θ₂,…,θ_qMiddle selection is more than initial angle θ₀Angle, and the nearest neighbor point cloud point of its correspondence is designated as M again₁,M₂,…,M_d, wherein d is θ₁,θ₂,…,θ_qMore than initial angle θ₀The number at angle；

50404: utilize formula 7 to calculate ∠ M_uo₁w₁The number of degrees, and be designated as ω_u:

In formula, u=1,2 ..., d；D_uFor M_uAnd o₁Between distance, a is o₁And w₁Between distance, F_uFor M_uAnd w₁Between distance；

50405: from ω₁,ω₂,...,ω_dThe angle that the middle selection number of degrees are minimum, nearest neighbor point cloud point corresponding to this angle is coastal waters point；

50406: coastal waters point step 50305 obtained, as new initial seed point, repeats step 50401～50405, continually look for next coastal waters point, until occurring without new coastal waters point；

505: the coastal waters point that integration step 503 and step 504 obtain, obtain all coastal waters points of current land and water boundary grid；

506, make t=t+1, if t≤K, then return step 502, the coastal waters point of the next land and water boundary grid of search；If t is ＞ K, then terminates performing, perform step 6；Thus obtain the coastal waters point of all land and water boundary grid.

Step 6, the coastal waters point of all land and water boundary grid obtained in integration step 5, thus obtain the edge image of target area water body, as shown in Figure 6.

Can be seen that from Fig. 5 and Fig. 6, in the case of not utilizing other assistance datas, the present invention just directly can get the profile cloud data of water body from original airborne LiDAR point cloud image, and the point cloud chart picture extracted can the profile of the most accurately and comprehensively body display water body.

The above; it is only the detailed description of the invention in the present invention; but protection scope of the present invention is not limited thereto; any it is familiar with the people of this technology in the technical scope that disclosed herein; it is appreciated that the conversion or replacement expected; all should contain within the scope of the comprising of the present invention, therefore, protection scope of the present invention should be as the criterion with the protection domain of claims.

Claims (6)

1. one kind utilizes the method that LiDAR point cloud data extract coastal waters line, it is characterised in that include step in detail below:

Step 1, reads the original airborne LiDAR point cloud data of target area, obtains total number n of original LiDAR point cloud data；

Step 2, determines the step-length of grid partition and determines x direction and number n of y direction grid_xAnd n_y；

Step 3, the n obtained in traversal step 2_x×n_yAccording to the number putting cloud in grid, individual grid, judges that whether grid is grid in water body, and record the position of grid in each water body, thus grid and position thereof in obtaining all water bodys, specifically comprise the following steps that

301: make w=1, v=1；

302: be numbered four summits of w row v row grid, the wherein summit, the lower right corner numbered 1 of this grid, other summits number consecutively counterclockwise is 2,3 and 4, utilizes formula 4 to calculate the coordinate (x on this grid 1～4 summit_right,y_down)、(x_right,y_up)、(x_left,y_up) and (x_left,y_down):

$\begin{array}{c}{x}_{left}=\min x+\left(w-1\right)\×step\\ x_{right}=\min x+w\×step\\ y_{down}=\min y+\left(v-1\right)\×step\\ y_{up}=\min y+v\×step\end{array}---\left(4\right)$

303: in calculating current mesh, put number z of cloud, if z >=5, then perform step 304；If z ＜ 5, then current mesh is labeled as grid in water body, proceeds to step 305；

304: make w=w+1, if w≤n_x, then v keeps constant, returns step 302；If w is ＞ n_x, then make w=1, v=v+1, return step 302；

305: record the position of grid in each water body, thus grid and position thereof in obtaining all water bodys；

Step 4, the eight connectivity grid of grid in l the water body that search step 3 obtains one by one, it is thus achieved that all land and water boundary grid in target area, and determine that all land and water boundary grid are positioned at the summit of water body, specifically comprise the following steps that

401: make I=1；

402；Using grid in i-th water body as seed grid, being numbered the eight connectivity grid of seed grid, wherein lower right corner grid numbered 1, other grid number consecutively counterclockwise is 2～8；

403: calculate some cloud number h in 1～No. 8 grid respectively, if h >=5, be land and water boundary grid by this grid ticks；

404: make I=I+1, if I≤l, return step 402, otherwise terminate iteration, thus all land and water boundary grid in obtaining target area, perform step 405；

405: determine that the land and water boundary grid of labelling in step 403 is positioned at the summit of water body；

Step 5, K the land and water boundary grid that search step 4 obtains one by one, obtain the coastal waters point of each land and water boundary grid, specifically comprise the following steps that

501: make t=1；

502, optional the t land and water boundary grid is positioned at the summit of water body as kind of a son vertex w₁, use the some cloud in K-D tree seed tissue summit and this land and water boundary grid, utilize nearest neighbor algorithm to obtain the nearest neighbor point of kind son vertex, using nearest neighbor point as initial seed point o of coastal waters point₁；

503: with initial seed point o₁For starting point, determine initial seed point o₁The coastal waters point of side, specifically comprises the following steps that counterclockwise

50301: use k nearest neighbor algorithm search initial seed point o₁Nearest neighbor point cloud point p in this land and water boundary grid₁,p₂,...,p_q, wherein q is the number of the nearest neighbor point cloud point searched；

50302: utilize formula 5 to calculate initial angle alpha₀:

In formula, a is o₁And w₁Between distance, b is w₁And w₂Between distance, c is o₁And w₂Between distance, w₂For w in this land and water boundary grid₁Anticlockwise next summit；

50303: utilize formula 6 to calculate p_i、w₁And w₂The ∠ p constituted_iw₁w₂The number of degrees, and be designated as α_i:

In formula, i=1,2 ..., q；a_iFor p_iAnd w₁Between distance, b is w₁And w₂Between distance, c_iFor p_iAnd w₂Between distance；

50304: from α₁,α₂,...,α_qMiddle selection is more than initial angle alpha₀Angle, and the nearest neighbor point cloud point of its correspondence is designated as N again₁,...,N_s, wherein s is α₁,α₂,...,α_qIn more than initial angle alpha₀The number at angle；

50305: utilize formula 7 to calculate ∠ N_jo₁w₁The number of degrees, and be designated as β_j:

In formula, j=1,2 ..., s；A_jFor N_jAnd o₁Between distance, a is o₁And w₁Between distance, C_jFor N_jAnd w₁Between distance；

50306: from β₁,β₂,…,β_sThe angle that the middle selection number of degrees are minimum, nearest neighbor point cloud point corresponding to this angle is coastal waters point；

50307: coastal waters point step 50306 obtained, as new initial seed point, repeats step 50301～50306, continually look for next coastal waters point, until occurring without new coastal waters point；

504: with initial seed point o₁For starting point, determine initial seed point o₁The coastal waters point of side, specifically comprises the following steps that clockwise

50401: utilize formula 8 to calculate initial angle θ₀:

In formula, a is o₁And w₁Between distance, e is w₁And w₃Between distance, f is o₁And w₃Between distance, w₃For w in this land and water boundary grid₁Clockwise next summit；

50402: utilize formula 9 to calculate p_i、w₁And w₃The ∠ p constituted_iw₁w₃The number of degrees, and be designated as θ_i:

In formula, a_iFor p_iAnd w₁Between distance, e is w₁And w₃Between distance, f_iFor p_iAnd w₃Between distance；

50403: from θ₁,θ₂,...,θ_qMiddle selection is more than initial angle θ₀Angle, and the nearest neighbor point cloud point of its correspondence is designated as M again₁,M₂,...,M_d, wherein d is θ₁,θ₂,...,θ_qMore than initial angle θ₀The number at angle；

50404: utilize formula 10 to calculate ∠ M_uo₁w₁The number of degrees, and be designated as ω_u:

In formula, u=1,2 ..., d；D_uFor M_uAnd o₁Between distance, a is o₁And w₁Between distance, F_uFor M_uAnd w₁Between distance；

50405: from ω₁,ω₂,...,ω_dThe angle that the middle selection number of degrees are minimum, nearest neighbor point cloud point corresponding to this angle is coastal waters point；

50406: coastal waters point step 50305 obtained, as new initial seed point, repeats step 50401～50405, continually look for next coastal waters point, until occurring without new coastal waters point；

505: the coastal waters point that integration step 503 and step 504 obtain, obtain all coastal waters points of current land and water boundary grid；

506, make t=t+1, if t≤K, then return step 502, the coastal waters point of the next land and water boundary grid of search；If t is ＞ K, then terminate iteration, perform step 6；Thus obtain the coastal waters point of all land and water boundary grid；

Step 6, the coastal waters point of all land and water boundary grid obtained in integration step 5, thus obtain the edge image of target area water body.

A kind of method utilizing LiDAR point cloud data to extract coastal waters line the most according to claim 1, it is characterised in that determine the step-length of grid partition in step 2 and determine x direction and the number of y direction grid, specifically comprising the following steps that

201: preset some cloud number m that each grid is expected to comprise；

202: calculate some coordinate minima minx in cloud x direction and maximum maxx, and coordinate minima miny in y direction and maximum maxy；

203: calculate the average density of target area point cloud；

204: calculate the step-length of grid partition；

205: calculate x direction and the number of y direction grid, thus obtain n_yRow n_xThe grid of row.

A kind of method utilizing LiDAR point cloud data to extract coastal waters line the most according to claim 2, it is characterised in that utilize the average density of target area point cloud in formula 1 calculation procedure 203, particularly as follows:

$\mathrm{\σ}=\frac{n}{(\max x-\min x)\×(\max y-\min y)}---\left(1\right)$

In formula, σ is the average density of target area point cloud.

A kind of method utilizing LiDAR point cloud data to extract coastal waters line the most according to claim 3, it is characterised in that utilize the step-length of grid partition in formula 2 calculation procedure 204, particularly as follows:

$step=\sqrt{\frac{m}{\mathrm{\σ}}}---\left(2\right)$

In formula, step is the step-length of grid partition.

A kind of method utilizing LiDAR point cloud data to extract coastal waters line the most according to claim 4, it is characterised in that utilize x direction and the number of y direction grid in formula 3 calculation procedure 205, particularly as follows:

$\begin{array}{c}{n}_x=fix\left(\frac{\max x-\min x}{step}\right)\\ n_y=fix\left(\frac{\max y-\min y}{step}\right)\end{array}---\left(3\right)$

In formula, n_xAnd n_yBeing respectively x direction and the number of y direction grid, fix represents intercepting mantissa function.

A kind of method utilizing LiDAR point cloud data to extract coastal waters line the most according to claim 1, it is characterised in that in step 405, land and water boundary grid is positioned at the summit of water body and is: the common vertex of land and water boundary grid and seed grid.