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Reference ellipsoids for geodesy and geophysics

Project description


Reference ellipsoids for geodesy and geophysics

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Part of the Fatiando a Terra project

Latest version on PyPI Latest version on conda-forge Test coverage status Compatible Python versions. DOI used to cite Boule


Boule is Python library for representing reference ellipsoids, calculating their gravity fields, and performing some global coordinate conversions. "Boule" is also French for "ball" as well as a traditional shape of bread resembling a squashed ball.

Some examples of where Boule can be applied:

  • Storing and manipulating ellipsoid parameters for spherical harmonic analysis.
  • Calculating normal gravity for generating gravity anomalies and disturbances.
  • Modelling in spherical coordinates, which requires geodetic to geocentric spherical coordinate conversions.

Project goals

  • Provide a representation of ellipsoid parameters and derived quantities, including units and citations.
  • Convert between geodetic coordinates and geocentric spherical, topocentric, etc.
  • Calculate the gravity, gravitational, and centrifugal potential (and its derivatives) of ellipsoids in closed form.
  • Include a range ellipsoids for the Earth and other planetary bodies.

Project status

Boule is ready for use but still changing. This means that we sometimes break backwards compatibility as we try to improve the software based on user experience, new ideas, better design decisions, etc. Please keep that in mind before you update Boule to a newer version.

We welcome feedback and ideas! This is a great time to bring new ideas on how we can improve the project. Join the conversation or submit issues on GitHub.

Getting involved

🗨️ Contact us: Find out more about how to reach us at

👩🏾‍💻 Contributing to project development: Please read our Contributing Guide to see how you can help and give feedback.

🧑🏾‍🤝‍🧑🏼 Code of conduct: This project is released with a Code of Conduct. By participating in this project you agree to abide by its terms.

Imposter syndrome disclaimer: We want your help. No, really. There may be a little voice inside your head that is telling you that you're not ready, that you aren't skilled enough to contribute. We assure you that the little voice in your head is wrong. Most importantly, there are many valuable ways to contribute besides writing code.

This disclaimer was adapted from the MetPy project.


This is free software: you can redistribute it and/or modify it under the terms of the BSD 3-clause License. A copy of this license is provided in LICENSE.txt.

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