Implementation of geodesic routines in modern Fortran.

Description

This is a library to solve geodesic problems on a planetary body (e.g., the Earth).

Documentation

Some of the algorithms in this library:

Procedure	Body Shape	Description	Reference
cartesian_to_geodetic_triaxial	Triaxial	Cartesian to geodetic	Panou & Korakitis (2022)
cartesian_to_geodetic_triaxial_2	Triaxial	Cartesian to geodetic	Bektas (2015)
heikkinen	Biaxial	Cartesian to geodetic	Heikkinen (1982)
olson	Biaxial	Cartesian to geodetic	Olson (1996)
direct	Biaxial	Direct geodesic problem	Karney (2013)
direct_vincenty	Biaxial	Direct geodesic problem	Vincenty (1975)
inverse	Biaxial	Inverse geodesic problem	Karney (2013)
inverse_vincenty	Biaxial	Inverse geodesic problem	Vincenty (1975)
great_circle_distance	Sphere	Great circle distance	Vincenty (1975)

See the latest API documentation for the full list. This was generated from the source code using FORD (i.e. by running ford ford.md).

Compiling

A fpm.toml file is provided for compiling geodesic-fortran with the Fortran Package Manager. For example, to build:

fpm build --profile release

By default, the library is built with double precision (real64) real values. Explicitly specifying the real kind can be done using the following processor flags:

Preprocessor flag	Kind	Number of bytes
REAL32	real(kind=real32)	4
REAL64	real(kind=real64)	8
REAL128	real(kind=real128)	16

For example, to build a single precision version of the library, use:

fpm build --profile release --flag "-DREAL32"

To run the unit tests:

fpm test --profile release

To use geodesic-fortran within your fpm project, add the following to your fpm.toml file:

[dependencies]
geodesic-fortran = { git="https://github.com/jacobwilliams/geodesic-fortran.git" }

or, to use a specific version:

[dependencies]
geodesic-fortran = { git="https://github.com/jacobwilliams/geodesic-fortran.git", tag = "1.0.0"  }

License

• This library is licensed under a permissive MIT/X11/BSD license.

References

• T. Vincenty, "Direct and Inverse Solutions of Geodesics on the Ellipsoid with Application of Nested Equations", Survey Review XXII. 176, April 1975.
• C. F. F. Karney, Algorithms for geodesics, J. Geodesy 87(1), 43–55 (2013); Addenda.
• G. Panou and R. Korakitis, "Cartesian to geodetic coordinates conversion on an ellipsoid using the bisection method". Journal of Geodesy volume 96, Article number: 66 (2022).
• Gema Maria Diaz-Toca, Leandro Marin, Ioana Necula, "Direct transformation from Cartesian into geodetic coordinates on a triaxial ellipsoid", Computers & Geosciences, Volume 142, September 2020, 104551.

Other links:

• Geographiclib documentation and git repository
• Fortran Astrodynamics Toolkit
• FORWARD and INVERSE from the NGS