FIX/NEW: plot_center bug fix and new plot_tight option

[carleyjmartin]

Scope

This PR fixes the plot_center option for MAG projections, and includes new plot_tight which will calculate the plot_center and plot_extent to center the FOV in the middle of the plot zoomed in.

Docs amended to include changes. This can be properly formatted during a release.

Note that the plot_center now used MLT when using the magnetic projection, as that it what is plotted so makes more sense.
Plot tight requires information about the FOV so has to be in the fan module to get that information. Tight plotting is only available for FOV and FAN methods for individual radar plots... doesn't make sense to have the option for grid or maps. You can over plot extra fans from other radars, but plot_tight will use whatever radar you have plotted first with that option as True.

issue: to close #430 and #433

Approval

Number of approvals: 2, code review and testing

Test

matplotlib version: 3.10.8
python version: 3.11
Note testers: please indicate what version of matplotlib you are using

• Please test with north and south data, and use various combinations of projections, plot_center and plot_extent.
• The three keywords do not work with the POLAR projection, plot_tight will override any plot_center and plot_extent inputs.
• plot_center uses the plot coordinates, i.e. geographic longitude for GEO proj and MLT for MAG proj

import pydarn
import matplotlib.pyplot as plt
import datetime as dt

# Fitacf data
file1 = '/home/carleyjm/data/fitacf/20250101.0600.00.sas.a.fitacf'
file2 = '/home/carleyjm/data/fitacf/2024/01/20240101.0000.29.rkn.a.fitacf.bz2'
file3 = '/home/carleyjm/data/fitacf/2025/01/20250131.2200.22.lyr.fitacf.bz2'
file4 = '/home/carleyjm/data/fitacf/2026/02/20260201.0000.00.sps.a.fitacf.bz2'


for i, file in enumerate([file1 ,file2 ,file3 , file4]):
    data, _ = pydarn.read_fitacf(file)
    pydarn.Fan.plot_fan(data,scan_index=1,groundscatter=True,coastline=True,
                    projs=pydarn.Projs.MAG, plot_tight=True)
    plt.savefig('/home/carleyjm/projects/plot_tight/fan_mag_' + str(i) + '.png')
    plt.close()


    pydarn.Fan.plot_fan(data,scan_index=1,groundscatter=True,coastline=True, 
                    projs=pydarn.Projs.GEO, coords=pydarn.Coords.GEOGRAPHIC,
                    plot_tight=True)
    plt.savefig('/home/carleyjm/projects/plot_tight/fan_geo_' + str(i) + '.png')
    plt.close()

pydarn.Fan.plot_fov(pydarn.RadarID.INV, dt.datetime(2020,1,1,4,30), plot_tight=True,
                    projs=pydarn.Projs.MAG,coastline=True, fov_color='r')
plt.savefig('/home/carleyjm/projects/plot_tight/fov_mag.png')
plt.close()


pydarn.Fan.plot_fov(pydarn.RadarID.SPS, dt.datetime(2020,1,1,4,30), plot_tight=True,
                    projs=pydarn.Projs.GEO, coords=pydarn.Coords.GEOGRAPHIC,
                    coastline=True, fov_color='b')
plt.savefig('/home/carleyjm/projects/plot_tight/fov_geo.png')
plt.close()

Whole bunch of plots this made for testing: