Spherical Polygons (ligo.skymap.plot.poly)

Plotting tools for drawing polygons.

ligo.skymap.plot.poly.cut_dateline(vertices)

Cut a polygon across the dateline, possibly splitting it into multiple polygons. Vertices consist of (longitude, latitude) pairs where longitude is always given in terms of a reference angle (between -π and π).

This routine is not meant to cover all possible cases; it will only work for convex polygons that extend over less than a hemisphere.

Examples

>>> cut_dateline(np.asarray([[3, 0.1],
...                          [4, 0.1],
...                          [4, -0.1],
...                          [3, -0.1],
...                          [3, 0.1]]))
[array([[-2.28318531,  0.1       ],
        [-2.28318531, -0.1       ],
        [-3.14159265, -0.1       ],
        [-3.14159265,  0.1       ],
        [-2.28318531,  0.1       ]]),
 array([[ 3.14159265,  0.1       ],
        [ 3.14159265, -0.1       ],
        [ 3.        , -0.1       ],
        [ 3.        ,  0.1       ],
        [ 3.14159265,  0.1       ]])]

ligo.skymap.plot.poly.cut_prime_meridian(vertices)

Cut a polygon across the prime meridian, possibly splitting it into multiple polygons. Vertices consist of (longitude, latitude) pairs where longitude is always given in terms of a wrapped angle (between 0 and 2π).

This routine is not meant to cover all possible cases; it will only work for convex polygons that extend over less than a hemisphere.

Examples

>>> cut_prime_meridian(np.asarray([[6, 0.1],
...                                [7, 0.1],
...                                [7, -0.1],
...                                [6, -0.1],
...                                [6, 0.1]]))
[array([[ 0.71681469,  0.1       ],
        [ 0.71681469, -0.1       ],
        [ 0.        , -0.1       ],
        [ 0.        ,  0.1       ],
        [ 0.71681469,  0.1       ]]),
 array([[ 6.28318531,  0.1       ],
        [ 6.28318531, -0.1       ],
        [ 6.        , -0.1       ],
        [ 6.        ,  0.1       ],
        [ 6.28318531,  0.1       ]])]

ligo.skymap.plot.poly.make_rect_poly(width, height, theta, phi, subdivisions=10)

Create a Polygon patch representing a rectangle with half-angles width and height rotated from the north pole to (theta, phi).

ligo.skymap.plot.poly.subdivide_vertices(vertices, subdivisions)

Subdivide a list of vertices by inserting subdivisions additional vertices between each original pair of vertices using linear interpolation.