To write a json detector file, first we start with the channels, each one
having an antenna. The mandatory parameters for a channel are:

- channel_id, the ID that will be used interally in NuRadioMC and NuRadioReco
- station_id, the ID of the station the channel belongs to
- adc_sampling_frequency, the sampling frequency for the analog-to-digital converter,
which can be used for resampling traces.
- ant_type, the antenna type. For instance, 'bicone_v8' or 'createLPDA_100MHz'
- ant_position_x, the x coordinate of the antenna in metres
- ant_position_y, the y coordinate of the antenna in metres
- ant_position_z, the z coordinate of the antenna in metres
These positions are referred to the altitude, northing, and easting of the
associated station.
- ant_orientation_theta. For dipoles, this theta marks the zenith of the direction
along which the axis is placed. For LPDAs, it marks the boresight, the direction of
maximum gain. All angles are in degrees.
- ant_orientation_phi. The same as ant_orientation_theta, but for azimuth.
- ant_rotation_theta. The zenith angle of the direction of the tines of the antenna,
that must be perpendicular to the direction defined by ant_orientation_theta and
ant_orientation_phi.
- ant_rotation_phi. The same as ant_rotation_theta, but for azimuth.

For instance, a vertical dipole would have ant_orientation_theta: 0 and any
ant_orientation_phi. ant_rotation_theta and ant_rotation_phi can be any direction
perpendicular to the orientation, for instance ant_rotation_theta: 90 and
ant_rotation_phi: 90

Another example: a 45-degree downward-pointing LPDA antenna with the tines on the XZ plane
would have ant_orientation_theta: 135, ant_orientation_phi: 0, ant_rotation_theta: 45,
ant_rotation_phi: 0

The rest of the parametres are either not used yet (they're here for future modules)
or they are used by modules not needed for the present example.

After the channels, the stations must be defined. The mandatory parameters for a
station are:

- pos_altitude, the altitude of the station in metres
- pos_easting, the easting of the station in metres
- pos_northing, the northing of the station in metres
- station_id, the ID of the station that will be used internally by NuRadioMC and NuRadioReco

One of the advantages of the default_detector_station option given by NuRadioReco
is that, if we want to create another station 102 that has a channel setup identical
to station 101, we can just define station 102 without any channel associated and then
run our simulation using default_detector_station=101. The channels from station 101
will be copied to station 102, and their coordinates will be read as relative to the
easting, northing, and altitude of station 102.
