A Python wrapper for Apex coordinates

## Overview

This is a Python wrapper for the Apex fortran library by Emmert et al. [2010] [1], which allows converting between geodetic, modified apex, and quasi-dipole coordinates as well as getting modified apex and quasi-dipole base vectors (Richmond [1995] [2]). The geodetic system used here is WGS84. MLT calculations are also included. The package is free software (MIT license).

### Quick start

Install from PyPI using pip:

pip install apexpy

This assumes that the same version of libgfortran is installed in the same location as when the pip wheel was built (if a wheel was used). If not, you may have trouble importing apexpy. If you run into trouble, try the command:

pip install --no-binary :apexpy: apexpy

which requires both libgfortran and gfortran to be installed on your system. More detailed installation instructions (and troubleshooting) is available in the documentation.

Conversion is done by creating an Apex object and using its methods to perform the desired calculations. Some simple examples:

from apexpy import Apex
import datetime as dt
atime = dt.datetime(2015, 2, 10, 18, 0, 0)
apex15 = Apex(date=2015.3)  # dt.date and dt.datetime objects also work

# Geodetic to apex, scalar input
mlat, mlon = apex15.convert(60, 15, 'geo', 'apex', height=300)
print("{:.12f}, {:.12f}".format(mlat, mlon))
57.477310180664, 93.590156555176

# Apex to geodetic, array input
glat, glon = apex15.convert([90, -90], 0, 'apex', 'geo', height=0)
print(["{:.12f}, {:.12f}".format(ll, glon[i]) for i,ll in enumerate(glat)])
['83.103820800781, -84.526657104492', '-74.388252258301, 125.736274719238']

# Geodetic to magnetic local time
mlat, mlt = apex15.convert(60, 15, 'geo', 'mlt', datetime=atime)
print("{:.12f}, {:.12f}".format(mlat, mlt))
56.598316192627, 19.107861709595

# can also convert magnetic longitude to mlt
mlt = apex15.mlon2mlt(120, atime)
print("{:.2f}".format(mlt))
20.90

If you don’t know or use Python, you can also use the command line. See details in the full documentation (link in the section below).

## Project details

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