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

Project description

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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 (“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.
  • Numpy: without Numpy, scalar inputs are handled with pure Python builtins.

Why not PyProj?

  • PyMap3D does not require anything beyond pure Python.
  • PyMap3D API is virtually identical 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 import for airborne vehicles and remote sensing.

Prerequisites

  • Python PyMap3D: any of Python 2.6, 2.7, 3.4, 3.5, 3.6, but only Python >= 3.5 is tested regularly. * Numpy (optional): if not present, function from math are automatically used, and if Numpy is present, it is automatically used. * AstroPy (optional): If not present, ECI coordinate conversions are not available.
  • Matlab / GNU Octave: under matlab/
  • Fortran MapTran: under fortran/: any Fortran 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 >= 3.5 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:

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.

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