def METHOD_NAME(self, table):
    fov_lon, fov_lat = horizontal_to_telescope(
        alt=table["true_alt"],
        az=table["true_az"],
        pointing_alt=table["subarray_pointing_lat"],
        pointing_az=table["subarray_pointing_lon"],
    )
    # numpy's trigonometric functions need radians
    psi = table["hillas_psi"].quantity.to_value(u.rad)
    cog_lon = table["hillas_fov_lon"].quantity
    cog_lat = table["hillas_fov_lat"].quantity
    delta_lon = fov_lon - cog_lon
    delta_lat = fov_lat - cog_lat
    true_disp = np.cos(psi) * delta_lon + np.sin(psi) * delta_lat
    true_sign = np.sign(true_disp)
    if self.project_disp:
        true_norm = np.abs(true_disp)
    else:
        true_norm = np.sqrt((fov_lon - cog_lon) ** 2 + (fov_lat - cog_lat) ** 2)
    return true_norm * true_sign