305 lines
6.7 KiB
Markdown
305 lines
6.7 KiB
Markdown
# 网格删除
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[返回示例目录](index.md)
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以下保留原笔记本的代码和已保存输出；转换过程中未重新执行代码。
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本教程演示球面坐标下的网格删除操作。首先导入所需的库。
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```python
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import meshkernel
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import matplotlib.pyplot as plt
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import numpy as np
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from pathlib import Path
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import datetime as dt
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```
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## 删除简单网格
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创建矩形网格。
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```python
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lon_min, lon_max = -2.5, -1.3
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lat_min, lat_max = 48.4, 49.0
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lon_res, lat_res = 0.01, 0.01
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make_grid_parameters = meshkernel.MakeGridParameters()
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make_grid_parameters.origin_x = lon_min
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make_grid_parameters.origin_y = lat_min
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make_grid_parameters.upper_right_x = lon_max
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make_grid_parameters.upper_right_y = lat_max
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make_grid_parameters.block_size_x = lon_res
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make_grid_parameters.block_size_y = lat_res
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mk2 = meshkernel.MeshKernel(projection=meshkernel.ProjectionType.SPHERICAL)
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mk2.get_projection()
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mk2.curvilinear_compute_rectangular_grid_on_extension(make_grid_parameters)
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mk2.curvilinear_convert_to_mesh2d()
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mesh2d_orig = mk2.mesh2d_get()
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```
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创建用于删除操作的多边形。
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```python
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pol_x = np.array(
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[
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-2.554972,
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-2.475056,
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-2.488361,
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-2.4375,
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-2.418417,
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-2.319139,
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-2.313333,
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-2.28625,
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-2.336694,
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-2.314167,
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-2.246722,
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-2.213361,
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-2.195028,
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-2.182472,
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-2.157944,
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-2.175444,
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-2.152528,
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-2.125889,
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-2.152528,
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-2.04925,
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-2.057944,
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-2.032111,
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-2.034639,
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-1.997083,
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-2.015472,
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-1.975028,
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-1.962972,
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-1.989667,
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-1.957139,
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-2.015056,
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-2.004583,
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-2.033,
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-1.98925,
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-1.992556,
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-1.941667,
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-1.962972,
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-1.935056,
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-1.905028,
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-1.843389,
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-1.837111,
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-1.872111,
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-1.842528,
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-1.771667,
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-1.635028,
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-1.592528,
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-1.511722,
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-1.51,
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-1.470056,
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-1.43,
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-1.3575,
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-1.412889,
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-1.389222,
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-1.447583,
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-1.453361,
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-1.505028,
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-1.530056,
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-1.570444,
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-1.576278,
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-1.615444,
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-1.580417,
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-1.2,
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-1.2,
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-2.6,
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-2.554972,
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]
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)
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pol_y = np.array(
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[
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48.599583,
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48.622889,
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48.64625,
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48.653722,
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48.634556,
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48.690389,
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48.672083,
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48.667444,
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48.620389,
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48.612111,
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48.645444,
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48.57375,
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48.611222,
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48.577889,
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48.587472,
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48.597472,
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48.618722,
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48.604528,
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48.633694,
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48.639583,
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48.625833,
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48.624972,
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48.604944,
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48.578306,
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48.571667,
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48.536222,
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48.549944,
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48.583333,
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48.578306,
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48.598722,
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48.614111,
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48.650806,
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48.668722,
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48.684583,
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48.684583,
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48.689972,
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48.702917,
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48.690417,
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48.712083,
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48.679972,
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48.645806,
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48.616222,
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48.603722,
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48.617889,
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48.639611,
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48.621222,
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48.632056,
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48.625417,
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48.643722,
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48.63375,
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48.659139,
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48.67625,
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48.655389,
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48.672083,
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48.687056,
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48.73125,
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48.744167,
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48.821639,
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48.835806,
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48.856639,
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48.9,
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48.3,
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48.3,
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48.599583,
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]
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)
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```
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执行网格删除。由于网格较大，可能需要约一分钟。
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```python
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delete_pol_geom = meshkernel.GeometryList(x_coordinates=pol_x, y_coordinates=pol_y)
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print("Deleting grid with coastlines: ", end="")
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dtstart = dt.datetime.now()
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mk2.mesh2d_delete(
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geometry_list=delete_pol_geom,
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delete_option=meshkernel.DeleteMeshOption.INSIDE_NOT_INTERSECTED,
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invert_deletion=False,
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)
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print(f"{(dt.datetime.now()-dtstart).total_seconds():.2f} sec")
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```
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```text
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Deleting grid with coastlines: 0.02 sec
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```
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绘制删除后的结果。
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```python
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plt.close("all")
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figsize = (8, 4)
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mesh2d = mk2.mesh2d_get()
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fig, ax = plt.subplots(figsize=figsize)
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mesh2d_orig.plot_edges(ax, color="grey")
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mesh2d.plot_edges(ax, color="k")
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ax.plot(pol_x, pol_y, "r", linewidth=1)
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ax.set_ylim(lat_min - 0.11, lat_max)
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```
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```text
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(48.29, 49.0)
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```
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## 使用全球多边形删除网格
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创建矩形网格。
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```python
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lon_min, lon_max = -6, 2
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lat_min, lat_max = 48.5, 51.2
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lon_res, lat_res = 0.2, 0.2
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make_grid_parameters = meshkernel.MakeGridParameters()
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make_grid_parameters.origin_x = lon_min
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make_grid_parameters.origin_y = lat_min
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make_grid_parameters.upper_right_x = lon_max
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make_grid_parameters.upper_right_y = lat_max
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make_grid_parameters.block_size_x = lon_res
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make_grid_parameters.block_size_y = lat_res
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mk = meshkernel.MeshKernel(projection=meshkernel.ProjectionType.SPHERICAL)
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mk.curvilinear_compute_rectangular_grid_on_extension(make_grid_parameters)
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mk.curvilinear_convert_to_mesh2d()
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mesh2d = mk.mesh2d_get()
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mesh2d_orig = mk.mesh2d_get()
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num_faces_before = len(mesh2d.face_x)
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num_columns = int((lat_max - lat_min) / 0.2)
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num_rows = int((lon_max - lon_min) / 0.2)
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print("num_faces_before ", num_faces_before)
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print("num_columns ", num_columns)
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print("num_rows ", num_rows)
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```
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```text
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num_faces_before 1120
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num_columns 13
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num_rows 40
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```
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导入全球海岸线，约包含 130,000 条线段。
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```python
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polygon_file_path = Path().absolute() / "data_examples" / "global_coastline.pol"
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polygon_np = np.loadtxt(polygon_file_path, comments="*", skiprows=2, dtype=np.double)
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pol_x = np.array(polygon_np[:, 0], dtype=np.double)
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pol_y = np.array(polygon_np[:, 1], dtype=np.double)
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```
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```python
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print(">> deleting grid with coastlines: ", end="")
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dtstart = dt.datetime.now()
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delete_pol_geom = meshkernel.GeometryList(x_coordinates=pol_x, y_coordinates=pol_y)
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mk.mesh2d_delete(
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geometry_list=delete_pol_geom,
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delete_option=meshkernel.DeleteMeshOption.INSIDE_NOT_INTERSECTED,
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invert_deletion=False,
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)
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print(f"{(dt.datetime.now()-dtstart).total_seconds():.2f} sec")
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```
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```text
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>> deleting grid with coastlines: 1.36 sec
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```
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```python
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plt.close("all")
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figsize = (8, 4)
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mesh2d = mk.mesh2d_get()
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fig, ax = plt.subplots(figsize=figsize)
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mesh2d_orig.plot_edges(ax, color="grey")
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mesh2d.plot_edges(ax, color="k")
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ax.plot(pol_x, pol_y, "r", linewidth=1)
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ax.set_xlim(lon_min, lon_max)
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ax.set_ylim(lat_min, lat_max)
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num_faces_after = len(mesh2d.face_x)
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print("num_faces_after ", num_faces_before)
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print("deleted faces ", num_faces_before - num_faces_after)
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```
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```text
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num_faces_after 1120
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deleted faces 213
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```
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