def get_polygon_area(verts):
    """
    Calculate the area of a closed polygon
    Parameters
    ----------
    verts : numpy.ndarray
        polygon vertices
    Returns
    -------
    area : float
        area of polygon centroid
    """
    nverts = verts.shape[0]
    a = 0.
    for iv in range(nverts - 1):
        x = verts[iv, 0]
        y = verts[iv, 1]
        xp1 = verts[iv + 1, 0]
        yp1 = verts[iv + 1, 1]
        a += (x * yp1 - xp1 * y)
    a = abs(a * 0.5)
    return a