pymap3d 1.7.0

pure Python coordinate conversions, following convention of several popular Matlab routines.

Python / Matlab / Fortran 3-D coordinate conversions

3-D geographic coordinate conversions, with API similar to popular $1000 Matlab Mapping Toolbox routines for:

• Python
• Matlab, GNU Octave
• modern Fortran 2008 standard (“elemental” functions and subroutines for massively parallel computation)

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

API docs:	https://www.scivision.co/pymap3d

For those not having AstroPy: lower accuracy fallback functions are automatically used.

Why not PyProj?

• PyMap3D does not require anything beyond pure Python.
• 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 for 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.

Contents

• Python / Matlab / Fortran 3-D coordinate conversions
  • Prerequisites
  • Install
  • Usage
    • Python
    • Matlab / GNU Octave
    • Fortran
    • Functions
    • Caveats
  • Matlab / Octave

Prerequisites

• Python PyMap3D: Python >= 3.6
  • AstroPy (optional): If not present, ECI coordinate conversions are not available.
• Matlab / GNU Octave: under matlab/
• Fortran MapTran: under fortran/: Fortran 2008 compliant compiler (tested with gfortran)

Install

The three separate packages are independent, they don’t rely on each other.

• Python PyMap3D:

  pip install pymap3d
  

  or for the latest development code:

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

  One can verify Python functionality after installation by:

  pip install -e .[tests]
  pytest -v
  

• Fortran MapTran:

  cd bin
  cmake ..
  make
  

  verify Fortran (as well as Python and Matlab/Octave) functionality after compiling by:

  make test
  

• Matlab/Octave: from within Matlab/Octave:

  addpath('pymap3d/matlab')
  

  One can verify Matlab code functionality by running:

  tests/Test.m
  

Usage

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

Python

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).

Matlab / GNU Octave

The syntax is reasonably compatible with the $1000 Matlab Mapping Toolbox. Under the matlab/ directory:

x,y,z = geodetic2ecef([],lat,lon,alt)

az,el,range = geodetic2aer(lat, lon, alt, observer_lat, observer_lon, observer_alt)

Fortran

The Fortran API under fortran/ directory is simple like PyMap3D. Modern Fortran “elemental” procedures throughout enable seamless support of scalar or array coordinate inputs. Default precision is real64, set at the top of fortran/maptran.f90.

use maptran

call geodetic2ecef(lat,lon,alt, x,y,z)
call geodetic2aer(lat,lon,alt, observer_lat, observer_lon, observer_alt)

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
enu2aer  enu2ecef   enu2geodetic
geodetic2aer  geodetic2ecef  geodetic2enu  geodetic2ned
ned2aer  ned2ecef   ned2geodetic
azel2radec radec2azel
vreckon vdist

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.

Matlab / Octave

The matlab/ directory contains a subset of the Python conversion functions, usable from Matlab or GNU Octave. Mathworks currently charges $1000 for the Matlab Mapping Toolbox that provides these functions.

• The full set of Python conversions can be accessed from Matlab >= R2014b by commands like:

  lla = py.pymap3d.geodetic2ecef(x,y,z)
  

• Matlab documentation generated by m2html.