GeographicLib 2.7 (released 2025-11-06)

Charles Karney — Thu, 06 Nov 2025 14:09:21 -0000

Changes between 2.7 (released 2025-11-06) and 2.6 versions:

Fix two bugs in classes for triaxial ellipsoids:
- Triaxial::Geodesic3::Inverse sometimes threw an exception when
  both endpoints were on the major principal ellipse for very
  eccentric ellipsoids a > 2 c.
- Triaxial::Cartesian3::carttocart2 sometimes returned the wrong
  result in the interior of the ellipsoid with Z = 0.
Cite the paper covering some of the triaxial classes Jacobi's
solution for geodesics on a triaxial ellipsoid.
Minor documentation fixes.

GeographicLib 2.6 (released 2025-09-30)

Charles Karney — Tue, 30 Sep 2025 17:53:33 -0000

Changes between 2.6 (released 2025-09-30) and 2.5.2 versions:

Support for triaxial ellipsoids. This is all placed in the
GeographicLib::Triaxial namespace with the header files in the
GeographicLib/Triaxial directory. This provides
- Triaxial::Ellipsoid3 supports basic conversions of ellipsoidal
  coordinates.
- Triaxial::GeodesicLine3 and Triaxial::Geodesic3 solve the direct
  and inverse geodesic problems on a triaxial ellipsoid. This
  implements Jacobi's solution for the direct problem. The inverse
  problem extends the method for solving the inverse problem on a
  biaxial ellipsoid.
- Triaxial::Cartesian3 performs conversions between different
  systems of triaxial coordinates.
- Triaxial::Conformal3 implements Jacobi's conformal projection for
  a triaxial ellipsoid. This allow a triaxial ellipsoid to be
  conformally mapped to a sphere or to any other ellipsoid.
- Geod3Solve is a command-line utility offering access to
  Triaxial::Geodesic3.
- Cart3Convert is a command-line utility offering access to
  Triaxial::Cartesian3.
- Conformal3Proj is a command-line utility offering access to
  Triaxial::Conformal3.
- Constants::Triaxial_Earth_a, Constants::Triaxial_Earth_b,
  Constants::Triaxial_Earth_c, and Constants::Triaxial_Earth_lon0
  specify a simple triaxial model for the Earth.
- experimental::TriaxialGeodesicODE is provided to illustrate the
  solution of the direct geodesic problem by integrating the
  ordinary differential equations for the geodesic. Because this
  depends on Boost, this is not part of the GeographicLib library.
- experimental/Geod3ODE.cpp a utility for doing direct geodesic
  calculations using experimental::TriaxialGeodesicODE.
To support the triaxial routines, the following classes have been
added:
- AngleT provides an accurate representation of angles of any
  magnitude. This might replace AuxAngle at some point.
- Trigfun supports representing periodic functions as Fourier
  series with automatic selection of the number of terms to
  use. This offers a tiny subset of the functionality of the trig
  series in Chebfun. This might replace DST at some point.
C++17 is now required. Minimum version of Visual Studio supported
is Visual Studio 15 2017.
Add Math::clamp.
Because experimental::TriaxialGeodesicODE depends on Boost, the
CMake option USE_BOOST_FOR_EXAMPLES has been renamed
USE_BOOST. This will cause find_package(Boost) to be called, but
does not affect how the library or the tools are built.

GeographicLib 2.5.2 (released 2025-08-22)

Charles Karney — Fri, 22 Aug 2025 11:07:08 -0000

Changes between 2.5.2 (released 2025-08-22) and 2.5.1 versions:

Fix potential buffer overflow in DMS. Upgrading from earlier
versions is strongly recommended. If upgrading is not possible,
avoid processing untrusted or malformed inputs and run programs
linked to the library with restricted privileges. Thanks to
Rosario Matteo Grammatico for finding this vulnerability.

GeographicLib 2.5.1 (released 2025-08-20)

Charles Karney — Wed, 20 Aug 2025 16:43:54 -0000

Changes between 2.5.1 (released 2025-08-20) and 2.5 versions:

Fix bug in geodesic inverse problem with very prolate
ellipsoids. For f < −2, a meridional path was incorrectly
returned in some cases for two points on the same meridian. This
affected both the series and exact solutions. (Or course, the
series solution is inaccurate for ellipsoids this eccentric.)
Minor tweak to Math::atan2d to improve accuracy.
Allow GEOGRAPHICLIB_PRECISION > 5 to allow use of mpreal with a
fixed precision.
Document that cmake option -D BINDIR=OFF removes tools from the
default all target for make.
WARNING: C++17 compliant compiler will be required for the next
release. Support for builds with Visual Studio 14 (2015) will
then stop.

GeographicLib 2.5 (released 2024-12-28)

Charles Karney — Sat, 28 Dec 2024 21:16:32 -0000

Changes between 2.5 (released 2024-12-28) and 2.4 versions:

New magnetic models provided
- World Magnetic Model 2025, wmm2025; this covers the period
  2025-2030. This is now the model returned by
  MagneticModel::DefaultMagneticName and is default magnetic
  model for MagneticField (replacing wmm2020 which is only valid
  thru the end of 2024).
- World Magnetic Model High Resolution 2025, wmmhr2025; this is a
  high-resolution version of wmm2025 including terms up to degree
  133 (as opposed to 12 for wmm2025).
- International Geomagnetic Reference Field (14th generation),
  igrf14, which approximates the main magnetic field of the earth
  for the period 1900-2030.
Update CMake's cmake_minimum_required to 3.17.0 (to facilitate
integration with Qt projects).
For GEOGRAPHICLIB_PRECISION > 2, readarray treats doubles as
approximations to exact decimal constants.

GeographicLib 2.4 (released 2023-07-14)

Charles Karney — Sun, 14 Jul 2024 18:34:25 -0000

Changes between 2.4 (released 2024-07-14) and 2.3 versions:

Math::sind, Math::sincosd, etc., now return accurate results for
arguments = 30d, 45d, 60d, ...
Add Math::hypot3.
Add EllipticFunction::am.
Make constructor for AuxAngle explicit.
Include notes for plate carree areas.
C++14 compliant compiler required (this requirement tracks the
Boost Math library).
CMake configuration changes
- update cmake_minimum_required to 3.16.0.
- exclude the tools and doc targets from the default build (make
  all) if these components won't be installed (BINDIR or DOCDIR
  set to OFF).
- testprograms is now excluded from the default build and it now
  depends on tools. Before running the test suite, build
  testprograms, e.g., make testprograms test.
- added a target libs to build only the static and/or shared
  libraries.
- document the use of CMake's FetchContent as an alternative to
  find_package.
- stop requiring that CMAKE_CROSSCOMPILING match with
  find_package(GeographicLib).
Internal code changes
- stop using reserved identifiers (_N in the DST class and _R in
  the Intersect class).
- remove the workaround for the boost-quadmath bug with
  setprecision(0).
- GEOGRAPHICLIB_PANIC(msg) macro now takes a message argument.

GeographicLib 2.3 (released 2023-07-25)

Charles Karney — Tue, 25 Jul 2023 13:05:58 -0000

Changes between 2.3 (released 2023-07-25) and 2.2 versions:

Add the Intersect class and the IntersectTool utility. The
methods are described in "Geodesic intersections",
https://arxiv.org/abs/2308.00495 (2023-08).
Add typedefs Geodesic::LineClass, GeodesicExact::LineClass,
Rhumb::LineClass, GeodesicLine::BaseClass,
GeodesicLineExact::BaseClass, RhumbLine::BaseClass.
Geodesic constructor accepts optional third argument exact, default
false. If true, then the calculations are delegated to
GeodesicExact. GeodSolve and Planimeter now use this simplified
interface.
PolygonAreaExact is deprecated; use PolygonArea instead.
Bug in Planimeter -Q (introduced in version 2.2) has been fixed.
TransverseMercator constructor accepts optional arguments exact
and extendp (default false for both). If exact = true, then the
calculations are delegated to TransverseMercatorExact.
TransverseMercatorProj now uses this simplified interface.
Minor fixes:
- Fix documentation bug for TransverseMercatorProj (incorrectly
  stated that -t for the extended domain was the default).
- Remove unnecessary friend declarations for Ellipsoid in
  AlbersEqualArea and TransverseMercator. (As of version 2.2,
  Ellipsoid uses the AuxLatitude class for this functionality.)
- Small change in EllipticFunction to speed up the default
  contructor.
- Remove workaround for boost 1.76 with enums (not needed for boost
  1.78).
- Remove unused header from NearestNeighbor.

GeographicLib 2.2 (released 2023-03-07)

Charles Karney — Tue, 07 Mar 2023 16:05:33 -0000

Changes between 2.2 (released 2023-03-07) and 2.1.2 versions:

Completely redo Rhumb and RhumbLine classes to yield accurate
results for the course and the area even for very eccentric
ellipsoids:
- these methods are accurate for 1/100 < b/a < 100 (the previous
  methods for the course were limited to 1/4 < b/a < 4 for the
  course and the area calculation was only valid for |f| < 0.01);
- the meaning of the exact flag in the constructor is now more
  straightforward: exact = false (the default) consistently uses
  series expansions valid for |f| < 0.01; exact = true uses exact
  equations for the course of the rhumb line and an accurate DFT
  fit for the area computation;
- the RhumbSolve(1) utiity accepts the -u to unroll the
  longitudes for the results of direct calculations;
- rhumb lines which include a pole as one of the endpoints are
  treated properly (previously point at the pole were moved
  slightly away from the pole);
- this treatment of rhumb areas is described in polygons,
  https://arxiv.org/abs/2303.03219.
The -E option for Planimeter(1) is now a toggle switching on
exact treatment for geodesics (-G option), rhumb lines (-R
option), authlatic lines (-Q option). Previously -E has turned
on the exact treatment for geodesics.
The online version of Planimeter now allows the ellipsoid to be
specified.
The deprecated -l option for GeodSolve and RhumbSolve has been
removed.
Add AuxAngle and AuxLatitude classes to perform accurate
conversions between auxiliary latitudes. The Ellipsoid class has
been mostly reimplimented in terms of the AuxLatitude class. The
DAuxLatitude class computes the divides differences of auxiliary
latitude. and implements additional divided difference formulas
needed by Rhumb.
Created an "experimental" directory + namespace and moved the
JacobiConformal class there. Use the cmake target "experimental"
to build this directory.

GeographicLib 2.1.2 (released 2022-12-13)

Charles Karney — Tue, 13 Dec 2022 15:51:06 -0000

Changes between 2.1.2 (released 2022-12-13) and 2.1.1 versions:

Add MGRS::Decode to break an MGRS string into its components.
Add definite integral overload for DST::integral. This is used in
GeodesicExact.
Add example code examples/AuxLatitude.[hc]pp implementating the
AuxAngle and AuxLatitude classes. These classes implement the
methods documented in the paper "On auxiliary latitudes",
https://arxiv.org/abs/2212.05818. They are not part of
GeographicLib. See Auxiliary latitudes for more details.
Minor cmake issues:
- fix cross-compile build on Windows;
- check cmake version for "cmake rm -rf";
- move cmake_minimum_required to the beginning of the cmake file
  and update minimum version to 3.13.0.

Geodesics on an arbitrary ellipsoid of revolution

Charles Karney — Wed, 03 Aug 2022 13:52:36 -0000

I just posted this on arXiv:

C. F. F. Karney
Geodesics on an arbitrary ellipsoid of revolution
(Aug., 2022)
http://arxiv.org/abs/2208.00492

This documents the algorithms used for the GeodesicExact class and
the -E options for GeodSolve and Planimeter

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