Yea, when you know what you are trying to model it's extremely easy to write a model that represents a traditional linear Kalman filter. But there are many way

Yea, when you know what you are trying to model it's extremely easy to write a model that represents a traditional linear Kalman filter. But there are many ways to write a Kalman filter; depending on where you start non-linear transformation becomes extremely cumbersome to get right.