geo3d 0.3.0: exact where it matters

An accuracy release. Your code keeps compiling: no public type, method or signature has changed.
Some results are now more accurate, as listed below.

🎯 More accurate

• Distance along the ground now works for every pair of points
  (#3). geodesic_inverse and geodesic_direct
  now use Karney's algorithm, the one GeographicLib uses, instead of Vincenty's.
  • It is accurate to about 15 nm, up from about 0.5 mm.
  • geodesic_inverse used to return None for points on nearly opposite sides of the Earth. Now
    it only returns None for NaN or infinite input, or a latitude beyond ±90°.
  • It matches geographiclib-rs to within 4 nm on 25 000 test pairs.
  • The code is ported from GeographicLib and geographiclib-rs, which are both MIT-licensed. See
    NOTICE.
• Four precision fixes (#5). Each has a test
  that failed before the fix:
  • Elevation near straight up. It used to round to exactly 90°, up to 0.6 m out at
    geostationary range. This affects every look angle.
  • Great-circle distance. It was up to 0.9 m short near the far side of the Earth. It is now
    accurate to about a nanometre everywhere.
  • Vec3::angle_to. Tiny angles used to come out as 0.
  • Ray–ground intersections. These lost precision when starting close to the surface. This
    affects ray_intersect, ground_strike and line_of_sight.

📖 Clearer docs

• The README and the docs.rs front page were rewritten in plain language. They now have recipes, a
  "find what you need" table, an accuracy table, a glossary, and a lookup table for MATLAB, pymap3d
  and map_3d users.
• There is a new comparison against five other Rust crates, with charts.
  It covers accuracy, tricky cases, features and speed, including the places where geo3d is
  slower.
• There is a new contributing guide.
• A correction: the eci frame is TEME, the one SGP4 satellite models use. It is not J2000, which
  differs by about 0.4°. Treating UTC as UT1 can add up to 400 m. The old docs promised "tens of
  metres", which wasn't true.
• docs.rs now shows the optional features. Searching for familiar names like geodetic2aer,
  vdist or haversine now finds the matching geo3d function.

⚡ Speed

• geodesic_direct is a little faster than before, and about 13 % faster than geographiclib-rs.
• geodesic_inverse takes about twice as long as before (about 0.86 µs per call). That extra work
  is what makes it exact everywhere. It is within 4 % of geographiclib-rs.
• Look angles and great-circle distance are 15–20 ns slower per call, because of the precision
  fixes.

🧹 Housekeeping

• The code is split into one module per topic.
• The crates.io description is simpler. The no-std::no-alloc category was removed, because geo3d
  needs std today (#12 will change that).
• CI now checks that every code change comes with a CHANGELOG line.

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📦 crates.io · 📖 docs.rs · 📊 How it compares