# Improve polarimetry and merge the two radar_model implementrations into one

List of changes from Paco's message on Slack:

- Generating the bistatic NRCS and Doppler using the monostatic to bistatic conversion that is documented somewhere in the ATBD (not for the Doppler).
- Generating the off-diagonal elements of the covariances.
- I changed how we group the data to make it somewhat consistent with the definition in the Product Specification Document, like this:

```
nrcsd = {"S1": {}, "HA": {}, "HB": {}}
dopd = {"S1": {}, "HA": {}, "HB": {}}
covd = {"S1": numpy.zeros(SHP, dtype=complex), "HA": numpy.zeros(SHP, dtype=complex), "HB": numpy.zeros(SHP, dtype=complex)}
for key in nrcsd.keys():
if key == "S1":
# Here for now I chose to use H/V for S1, but we could also just stay with I (=H) and O (=V)
nrcsd[key] = {"H" : numpy.zeros(SHP), "V" : numpy.zeros(SHP)}
dopd[key] = {"H" : numpy.zeros(SHP), "V" : numpy.zeros(SHP)}
else:
nrcsd[key] = {"I" : numpy.zeros(SHP), "O" : numpy.zeros(SHP)}
dopd[key] = {"I" : numpy.zeros(SHP), "O" : numpy.zeros(SHP)}
```

- I try to follow the drama/stereoid convention (agreed with Andreas some time ago) that all angles should be in radians except angles in parameter files. For backwards compatibility I made some of the classes and functions work with either degrees or radians.
- I changed where some calculations are done. For example, the sum of the components is done in backscatter_doppler, and also the conversion from velocity to Doppler.