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Phase 5 of making the projection system generic. Math: standard Snyder transverse Mercator formulas on the WGS84 ellipsoid, verified independently in Python before porting - the meridian arc against Simpson integration of the meridian radius (<0.5mm divergence) and round trips over 252 points covering all zones and latitudes to 89 degrees (max error 1.06e-08 degrees). - UtmDefinition.swift: UtmHemisphere and UtmDefinition implementing both directions of the projection with a per-zone central meridian, the 0.9996 scale factor, the 500_000 false easting and per-hemisphere false northing. Sector extents follow the EPSG convention (easting 100_000-900_000, northing 0-10_000_000); the world bounding box is the zone sector and no WKT pattern is registered (UTM .prj files would need per-zone parsing). - Projection gains all 120 zone cases (northern 32601-32660, southern 32701-32760) and init?(srid:) accepts the contiguous SRID ranges. wraparoundExtent is nil (zone coordinates never wrap), kind is planar; description now defaults to the EPSG label so it scales with the SRID count. - ProjectionRegistry resolves definitions via an eagerly built dictionary; registration coverage is asserted at runtime by the new UtmDefinitionTests sweep over all UTM SRIDs. Tests: SRID-to-zone/hemisphere mapping for all 120 SRIDs, registry coverage sweep, central meridian math per zone, known forward values (zone-edge equator eastings, scaled meridian arcs, both hemispheres), hemisphere symmetry (equal eastings, exact 10_000_000 northing offset), round trips, boundingBox/contains/distance, antimeridian no-ops in date-line zones, normalize/clamp, WKB round trips and random generation within the zone sector.
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Summary
Phase 5 of making the projection system generic — the UTM family. Stacks on #240 (phase 4: registry-driven WKT matching); merge the chain in order. The API decision from the plan discussion was option 1: 120 dedicated enum cases.
Math
Standard Snyder transverse Mercator on the WGS84 ellipsoid (k₀ = 0.9996, 500_000 m false easting, per-hemisphere false northing). Verified independently before porting:
Coordinate3D.init?(easting:northing:zone:hemisphere:)) already matched the verified math; the new definition adds the long-missing 4326→UTM directionChanges
UtmDefinition.swift:UtmHemisphere+UtmDefinition— both directions of the projection, per-zone central meridian, EPSG sector extents ([100_000–900_000, 0–10_000_000]), world box = zone sector, no WKT patterns (per-zone.prjmatching would need zone-number parsing — left out of scope)Projection: 120 new cases;init?(srid:)accepts the contiguous SRID ranges without enumerating cases;wraparoundExtentisnil(zone coordinates never wrap);descriptiondefaults to theEPSG:label so it scales with SRID countProjectionRegistry: definitions resolve through an eagerly built dictionary (SRID ranges can't drive exhaustive switches); registration coverage is asserted by tests at runtime and viaassertionFailurein debugTesting (+13)
Full suite: 2463 tests in 177 suites, zero warnings.