Axes Setup

For some spatial plots (FOV, Fan, Grid), pyDARN allows users to choose between Polar and Geographic axes using the projs keyword and Projs module. Convection maps do not allow for geographic projections due to lack of interest.

Projs.POLAR

Option	Action
lowlat=(int)	Lower Latitude boundary for the polar plot (degree) (default: 30)
hemisphere=(pydarn.Hemisphere)	Hemisphere of the radar (default: Hemisphere.North)
coastline=(bool)	Uses Cartopy to add outlines to the coastlines below data
nightshade=(int)	Uses the value given to calculate and show where on the plot the Earth is in shadow

This choice will return an ax object and a value of None for the Cartopy ccrs (coordinate reference system).

Projs.GEO

REQUIRES CARTOPY INSTALLATION

Option	Action
lowlat=(int)	Lower Latitude boundary for the polar plot (degree) (default: 30)
hemisphere=(pydarn.Hemisphere)	Hemisphere of the radar (default: Hemisphere.North)
coastline=(bool)	Uses Cartopy to add outlines fo the coastlines below data
grid_lines=(bool)	Uses Cartopy to plot grid lines
nightshade=(int)	Uses the value given to calculate and show where on the plot the Earth is in shadow

This choice will return an ax object and a Cartopy ccrs object (coordinate reference system).

Custom Axes

pyDARN does not currently support use of custom axes to read in and plot on. This means that use of subplots is not supported. There are ways to get around this if a custom axis that has the same setup as either axes above is read into the subplot. For example, a polar and a geographic plots can be positioned using subplots as follows:

import pydarn
import datetime as dt
import numpy as np
import matplotlib.pyplot as plt 
import cartopy.crs as ccrs

# Polar plot
date=dt.datetime(2022, 1, 8, 14, 5)
fig = plt.figure(figsize=(6, 6)) 
ax1 = fig.add_subplot(121, projection='polar')
ax1.set_ylim(90, 30)
ax1.set_yticks(np.arange(30, 90, 10))
ax1.set_xticks([0, np.radians(45), np.radians(90), np.radians(135),
                       np.radians(180), np.radians(225), np.radians(270),
                       np.radians(315)])
ax1.set_xticklabels(['00', '', '06', '', '12', '', '18', ''])
ax1.set_theta_zero_location("S")
pydarn.Fan.plot_fov(stid=65, date=date, ax=ax1)

# Geo plot
deg_from_midnight = (date.hour + date.minute / 60) / 24 * 360
pole_lat = 90
noon = -deg_from_midnight
ylocations = -5
proj = ccrs.Orthographic(noon, pole_lat)
ax2 = fig.add_subplot(122, projection=proj, aspect='auto')
ax2.gridlines(draw_labels=True)
extent = min(45e5,(abs(proj.transform_point(noon, 30, ccrs.PlateCarree())[1])))
ax2.set_extent(extents=(-extent, extent, -extent, extent), crs=proj)
pydarn.Fan.plot_fov(stid=65, date=date, ax=ax2, ccrs=ccrs, coords=pydarn.Coords.GEOGRAPHIC, projs=pydarn.Projs.GEO)
plt.tight_layout()
plt.show()