Variable `psi` is not used in "data_extract.ipynb"

[fartagaintuxedo]

In the cell 'Calculating Rotation Matrix for vehicle', the variable psi is not used, if it is not necessary maybe that line could be removed.

However if it should be used in the equations below, maybe there has been a typo (phi/psi)?

It is quite important to know because if the case is the latter, then rotation results would be wrong.

Thanks.