为绘图排序多边形坐标

Question

我有一个由许多单元组成的模型网格，我想在matplotlib basemap上绘制阴影多边形。

使用pyproj，我首先使用shapely.geometry的{​​{1}}类创建多边形，然后从中提取网格的外部坐标。然后我将它们还原为WGS84，以便传递给我的绘图功能：

Polygon

然后，使用grid_x_mesh, grid_y_mesh = pyproj.transform(wgs84, nplaea, grid_lons, grid_lats) grid_x = grid_x_mesh.ravel() grid_y = grid_y_mesh.ravel() grid_poly = Polygon(zip(grid_x, grid_y)) grid_x, grid_y = grid_poly.exterior.coords.xy grid_plons, grid_plats = pyproj.transform(nplaea, wgs84, grid_x, grid_y) 方法，我将WSG84坐标投影到地图投影（在本例中为nplaea）和

matplotlib.basemap

当试图这样做时，我得到了一个十字交叉的图案，我假设它必须对我提供给多边形函数的坐标进行排序。

我认为这与我如何提取外部坐标有关，或者只是在我创建最终多边形时绘制坐标列表的顺序。

如果这是问题，是否有一种巧妙的方式来正确订购这些？

绘制多边形

关闭式

Answer 1

Soooo ......显然shapely.geometry.Polygon方法正在绘制具有所有内部网格坐标的多边形，我意识到由于grid_plons和grid_plats具有与{{np.ravel()相同的长度1}}'网格坐标数组。

我最后只是从网格坐标数组中手动​​提取外部坐标，然后将它们传递给Polygon方法（见下文）。虽然，我想可能有一种更漂亮，更通用的方法。

手动提取方法：

grid_x_mesh, grid_y_mesh = pyproj.transform(wgs84, nplaea, grid_lons, grid_lats)

# The coordinates must be ordered in the order they are to be drawn
[grid_x.append(i) for i in grid_x_mesh[0,:]]
[grid_x.append(i) for i in grid_x_mesh[1:-1,-1]]
# Note that these two sides of the polygon are appended in reverse
[grid_x.append(i) for i in (grid_x_mesh[-1,:])[::-1]]
[grid_x.append(i) for i in (grid_x_mesh[1:-1,0])[::-1]]

[grid_y.append(i) for i in grid_y_mesh[0,:]]
[grid_y.append(i) for i in grid_y_mesh[1:-1,-1]]
[grid_y.append(i) for i in (grid_y_mesh[-1,:])[::-1]]
[grid_y.append(i) for i in (grid_y_mesh[1:-1,0])[::-1]]

grid_poly = Polygon(zip(grid_x, grid_y))