def get_grid_corners(latlons, halfgrid=10):
    """Get 4 corners of observation grids

    Parameters
    ----------
    latlons : sequence
        Sequence of (lat, lon) for grid.
    halfgrid : int or float, optional
        Size of half-grid.

    Returns
    -------
    ys : list
        List containing 5-element tuples for latitude of each grid point.
    xs : list
        List containing 5-element tuples for longitude of each grid point.
    """
    ys = []
    xs = []
    for lat, lon in latlons:
        y = tuple([lat - halfgrid, lat - halfgrid, lat + halfgrid, lat +
            halfgrid, lat - halfgrid])
        x = tuple([lon - halfgrid, lon + halfgrid, lon + halfgrid, lon -
            halfgrid, lon - halfgrid])
        ys.append(y)
        xs.append(x)
    return ys, xs
