How do I get the transformed data of a cartopy geodetic plot?

Question

how do I get all the data of the transformed line of the "handle" - Line2D object in the following code:

import cartopy.crs as ccrs
import matplotlib.pyplot as plt

ax = plt.axes(projection=ccrs.PlateCarree())
ax.stock_img()

ny_lon, ny_lat = -75, 43
delhi_lon, delhi_lat = 77.23, 28.61

handle = plt.plot([ny_lon, delhi_lon], [ny_lat, delhi_lat],
         color='blue', linewidth=2, marker='o',
         transform=ccrs.Geodetic(),
         )
plt.show()

To be more clear: I'm not looking for the output of "handle[0].get_data()", since this just prints my original longitude and latitude, but im looking for the the data of the geodetic line drawn on the map.

Answer 1

I found the answer! According to this question , you can access the data of the transformation via the following code snippet:

[handle] = plt.plot([ny_lon, delhi_lon], [ny_lat, delhi_lat], color='blue', linewidth=2, marker='o', transform=ccrs.Geodetic())

t_path = handle._get_transformed_path()

path_in_data_coords, _ = t_path.get_transformed_path_and_affine()
print(path_in_data_coords.vertices)

In the answer to this question there is also a second approach.

Answer 2

Let me do some computation and plot checks on the code provided by the OP.

import cartopy.crs as ccrs
import matplotlib.pyplot as plt

ax = plt.axes(projection=ccrs.PlateCarree())
ax.stock_img()

ny_lon, ny_lat = -75, 43
delhi_lon, delhi_lat = 77.23, 28.61

# Plot geodetic path in thick 'blue' line
handle = plt.plot([ny_lon, delhi_lon], [ny_lat, delhi_lat],
     color='blue', linewidth=10, marker='o',
     transform=ccrs.Geodetic(),
     )

# Get the geodetic path's coordinates to plot on top in 'red'
t_path = handle[0]._get_transformed_path()
path_in_data_coords, _ = t_path.get_transformed_path_and_affine()

ax.plot(path_in_data_coords.vertices[:,0], 
    path_in_data_coords.vertices[:,1],
    color='red', lw=2)

plt.show()

And, the output plot is:

Congratulations to the OP.

(Extension part 1)

Now, let us compute the length of the geodesic path using the coordinates obtained above. My proposed code is:

# (*** Continued from the code above ***)
import cartopy.geodesic as geodesic
import numpy as np

# defining the earth shape on which to make calculations
myGeod = geodesic.Geodesic(6378137.0, 1/298.257223563)

# get (lat,long) lists from (long,lat) of the geodesic path
latlonlists = []
[latlonlists.append([lat,lon]) for lon,lat in zip(path_in_data_coords.vertices[:,0], path_in_data_coords.vertices[:,1])]
#print(latlonlists)

# compute length of the geodesic
geodesic_in_meters = myGeod.geometry_length(np.array(latlonlists))

print(geodesic_in_meters)  # output: 17554975.077432975