Add degrees and decimal minutes tick formatting mode - #2740

import matplotlib.pyplot as plt
import cartopy.crs as ccrs
from cartopy.mpl.ticker import LongitudeFormatter, LatitudeFormatter

fig, axes = plt.subplots(1, 3, subplot_kw={'projection': ccrs.PlateCarree()},
                         figsize=(18, 5))

ax = axes[0]
ax.set_extent([-161, -154, 18, 23], crs=ccrs.PlateCarree())
ax.coastlines()
ax.set_xticks([-161, -159.51, -158, -156.3, -155, -154], crs=ccrs.PlateCarree())
ax.set_yticks([18, 19.51, 21, 22.3, 23], crs=ccrs.PlateCarree())
ax.xaxis.set_major_formatter(LongitudeFormatter(dms='dm'))
ax.yaxis.set_major_formatter(LatitudeFormatter(dms='dm'))
ax.set_title("dms='dm' (default format)")

ax = axes[1]
ax.set_extent([-161, -154, 18, 23], crs=ccrs.PlateCarree())
ax.coastlines()
ax.set_xticks([-161, -159.51, -158, -156.3, -155, -154], crs=ccrs.PlateCarree())
ax.set_yticks([18, 19.51, 21, 22.3, 23], crs=ccrs.PlateCarree())
ax.xaxis.set_major_formatter(LongitudeFormatter(dms='dm', minutes_number_format='.1f'))
ax.yaxis.set_major_formatter(LatitudeFormatter(dms='dm', minutes_number_format='.1f'))
ax.set_title("dms='dm' (minutes as .1f)")

ax = axes[2]
ax.set_extent([-161, -154, 18, 23], crs=ccrs.PlateCarree())
ax.coastlines()
ax.set_xticks([-161, -159.51, -158, -156.3, -155, -154], crs=ccrs.PlateCarree())
ax.set_yticks([18, 19.51, 21, 22.3, 23], crs=ccrs.PlateCarree())
ax.xaxis.set_major_formatter(LongitudeFormatter(dms=True))
ax.yaxis.set_major_formatter(LatitudeFormatter(dms=True))
ax.set_title("dms=True (degrees-minutes-seconds)")

plt.tight_layout()
plt.show()