pymap3d 1.8.1

pure Python (no prereqs) coordinate conversions, following convention of several popular Matlab routines.

Python 3-D coordinate conversions

Pure Python (no prerequistes beyond Python itself) 3-D geographic coordinate conversions. API similar to popular $1000 Matlab Mapping Toolbox routines for:

• Python
• Matlab, GNU Octave
• modern Fortran

PyMap3D is intended for non-interactive use on massively parallel (HPC) and embedded systems. Includes some relevant Vallado algorithms.

API docs

Prerequisites

Python ≥ 2.6 (full features require Python ≥ 3.5)

or

PyPy3

References to Numpy and AstroPy are optional, algorithms from Vallado and Meeus are used if AstroPy is not present. PyMap3D is regularly tested with Python ≥ 3.5. Limited Python 2.6, 2.7 and 3.4 support is available for systems using MicroPython or other cases where a current Python version isn't available.

Install

pip install pymap3d

or for the latest development code:

git clone https://github.com/scivision/pymap3d
cd pymap3d
pip install -e .

One can verify Python functionality after installation by:

pip install -e .[tests]
pytest -rsv

Usage

Where consistent with the definition of the functions, all arguments may be arbitrarily shaped (scalar, N-D array).

import pymap3d as pm

x,y,z = pm.geodetic2ecef(lat,lon,alt)

az,el,range = pm.geodetic2aer(lat, lon, alt, observer_lat, observer_lon, 0)

Python argument unpacking can be used for compact function arguments with scalars or arbitrarily shaped N-D arrays:

aer = (az,el,slantrange)
obslla = (obs_lat,obs_lon,obs_alt)

lla = pm.aer2geodetic(*aer,*obslla)

where tuple lla is comprised of scalar or N-D arrays (lat,lon,alt).

Example scripts are in the examples directory.

Functions

Popular mapping toolbox functions ported to Python include the following, where the source coordinate system (before the "2") is converted to the desired coordinate system:

aer2ecef  aer2enu  aer2geodetic  aer2ned
ecef2aer  ecef2enu  ecef2enuv  ecef2geodetic  ecef2ned  ecef2nedv
ecef2eci  eci2ecef  eci2aer  aer2eci
enu2aer  enu2ecef   enu2geodetic
geodetic2aer  geodetic2ecef  geodetic2enu  geodetic2ned
ned2aer  ned2ecef   ned2geodetic
azel2radec radec2azel
vreckon vdist
lookAtSpheroid
track2

Additional functions:

loxodrome_inverse: rhumb line distance and azimuth between ellipsoid points (lat,lon) akin to Matlab distance('rh', ...) and azimuth('rh', ...)

Abbreviations:

• AER: Azimuth, Elevation, Range
• ECEF: Earth-centered, Earth-fixed
• ECI: Earth-centered Inertial
• ENU: East North Up
• NED: North East Down
• radec: right ascension, declination

Caveats

• Atmospheric effects neglected in all functions not invoking AstroPy. Would need to update code to add these input parameters (just start a GitHub Issue to request).
• Planetary perturbations and nutation etc. not fully considered.

Notes

As compared to PyProj:

• PyMap3D does not require anything beyond pure Python -- not even Numpy is required for basic functions.
• PyMap3D API is similar to Matlab Mapping Toolbox, while PyProj's interface is quite distinct
• PyMap3D intrinsically handles local coordinate systems such as ENU, while PyProj ENU requires some additional effort.
• PyProj is oriented towards points on the planet surface, while PyMap3D handles points on or above the planet surface equally well, particularly important for airborne vehicles and remote sensing.

AstroPy.Units.Quantity

At this time, AstroPy.Units.Quantity is not supported. Let us know if this is of interest. Impacts on performance would have to be considered before making Quantity a first-class citizen. For now, you can workaround by passing in the .value of the variable.