magcoordmap

Adds a grid of constant magnetic latitude and longitude to a cartopy map. This currently only supports Apex coordinates as provided by apexpy.

Installation

This package can be installed with pip after cloning.

git clone https://github.com/ljlamarche/magcoordmap.git
cd magcoordmap
pip install .

Note that some dependencies (apexpy and cartopy) are dependent on correct linking with compiled libraries on your system. If installation is proving problematic, try installing these packages independently following their own installation instructions before installing magcoordmap with pip.

Usage

To add a magnetic coordinate grid to a cartopy map with the axes ax, simpily import magcoordmap and use the add_magnetic_gridlines function.

import magcoordmap as mcm
mcm.add_magnetic_gridlines(ax)

By default, this uses Apex coordinates for the present system date at 0 km altitude. If you would like to customize this, initialize your own Apex object and pass it to the function.

import magcoordmap as mcm
from apexpy import Apex
A = Apex(2015)
mcm.add_magnetic_gridlines(ax, apex=A)

The full list of parameters options for add_magnetic_gridlines are listed in the function's docstring.

ax : :class:`matplotlib.axes.Axes`
    Axes on which to add gridline.  Must have a cartopy projection.
apex : :class:`apexpy.Apex` (optional)
    Apex object that defines coordinate system and conversions.  An 
    Apex object that uses the system's current date will be initialized
    if not provided.
apex_height : float (optional)
    Altitude to use for apex coordinate conversions.  Defaults to 0.
draw_parallels : bool (optional)
    Whether or not to draw parallels (lines of constant MLAT).  Defauts
    to True.
draw_meridians : bool (optional)
    Whether or not to draw meridians (lines of constant MLON).  Defaults
    to True
xlocator : :class:`matplotlib.ticker.Locator` (optional)
    Locator object which will be used to determine the locations of the 
    MLON gridlines.
ylocator : :class:`matplotlib.ticker.Locator` (optional)
    Locator object which will be used to determine the locations of the 
    MLAT gridlines.
**collection_kwargs : (optional)
    :class:`matplotlib.collections.Collection` properties, used to 
    specify properties of the gridline such as linewidth and color.

The following produces the figure shown on this page.

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

# Set up figure
fig = plt.figure()
proj = ccrs.AzimuthalEquidistant(central_longitude=-147, central_latitude=64)
ax = fig.add_subplot(111, projection=proj)

# Set up cartopy map
gl = ax.gridlines(draw_labels=True, zorder=1)
gl.right_labels = False
gl.top_labels = False
ax.set_extent([-170., -135., 52., 72.], crs=ccrs.PlateCarree())
ax.coastlines()
ax.gridlines()

# Add magnetic field lines
mcm.add_magnetic_gridlines(ax)

plt.show()