feat(coords): TWD97 (Taiwan) grid + Go to Coordinate entry#52
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Add TWD97 / TM2 zone 121 (EPSG:3826) coordinate support so Taiwan users can read and enter local grid coordinates. - TWD97Converter: Transverse Mercator on GRS80 (lon0=121, k0=0.9999, FE=250000, FN=0). TWD97 is GRS80/ITRF-referenced (towgs84=0) so no datum shift is needed. Redfearn forward/inverse, verified to 0.004 m against the yychen/twd97 reference; central-meridian E=250000 exact. - Two digit-input modes: full7 (7+7 absolute, the Taiwan 二度分帶 standard) and grid5 (5+5 truncated local grid, MGRS-style; parsing recovers the 100 km cell from the current map centre). - New "Go to Coordinate" sheet (TWD97 / MGRS / Lat-Lon) with the 7+7 vs 5+5 toggle, live lat/lon + 7+7/5+5 readback, and a drop-marker toggle. OmniTAK had no manual coordinate entry before. - Wire .twd97 into the display-format enums + Settings picker; jump the map (both engines) via a new .goToCoordinate notification, handled on a sibling view to stay under the type-checker ceiling. - en + zh-Hant localization for all new strings. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Why
A Taiwanese contributor (who did the zh-Hant localization) asked for TWD97 / TM2 (Taiwan) grid support and specifically wants to compare two digit-entry modes — 7+7 vs 5+5. OmniTAK previously had no way to type a coordinate at all (display-only / tap-to-place), so this also adds a general "Go to Coordinate" entry point.
What
TWD97Converter— TWD97 / TM2 zone 121 (EPSG:3826). Transverse Mercator on GRS80 (lon0=121°, k0=0.9999, FE=250000, FN=0). TWD97 is GRS80/ITRF-referenced (towgs84=0) so no datum shift is needed. Redfearn forward/inverse.full7— 7+7 absolute metres (the Taiwan 二度分帶 standard; unambiguous).grid5— 5+5 truncated local grid (MGRS-style; shorter, but parsing recovers the 100 km cell from the current map centre)..twd97added to the coordinate-format enums and the Settings format picker (full 7+7 readout)..goToCoordinatenotification centres both the 2D (MapLibre) and 3D (Cesium) engines and optionally drops a marker. Handled on a siblingEmptyView(via.background) to keepMapViewController.bodyunder the Swift type-checker ceiling.Verification
yychen/twd97reference: forward off by 0.004 m, inverse by ~2e-8°, central-meridian easting = 250000 exact, Taiwan round-trips < 1 mm.xcodebuild(Debug, iOS Simulator) BUILD SUCCEEDED.0306966 / 2769659→25.033971, 121.564504.🤖 Generated with Claude Code