There's a confusing double meaning for `_0` here, especially when combined as `lon_0`. I suggest you stick with the `self` vs `other` convention you've used earlier. For example:
 - `central_lon_0` -> `self_lon_0`
 - `central_lon_0_offset` -> `lon_0_offset`
 - `lon_lower_bound_1` -> `other_lon_lower_bound`