fix: use proj4 +over flag to prevent antimeridian longitude wrapping#353
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proj4's `adjust_lon` normalizes longitude to (-π, π], which causes 360° round-trip errors for coordinates at the antimeridian (±180°): - `forward(-180.001°, lat)` wraps to positive easting (wrong sign) - `inverse(-WM_HALF, northing)` returns +180° instead of -180° These errors make the Delatin mesh refinement unconvergeable for tiles touching the antimeridian on global EPSG:4326 COGs (e.g. a 1.4M×600K pixel DEM spanning ±180° longitude). The round-trip error equals the full image width, producing visibly distorted tile meshes at low zoom. Fix: Add `+over` to the target projection definitions for both the 4326 and 3857 converters. The `+over` flag disables `adjust_lon`, allowing coordinates to pass through unwrapped. This is safe for longlat and Mercator projections where the 180° meridian is a straight line. The `+over` flag is supported since proj4js v2.20.0 (PR proj4js#530). Fixes developmentseed#352
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This looks very hacky. I think we need a deeper consideration of how to handle images spanning the antimeridian. |
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kylebarron
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May 27, 2026
…hes to ±85.051° (#574) * docs(specs): add antimeridian crossing-tile (cut-in-two) design Design for rendering imagery crossing ±180° in Web Mercator (issues #171, #366). Splits a crossing tile at the antimeridian into west/east pieces so each reprojects as a normal non-crossing tile — avoiding the proj4-rewrap unwrap that prior attempts (#353/#374/#269) stumbled on. Generalizes the RasterReprojector to accept a delaunator-shaped initial-triangulation seed (subsuming #351 uvBounds / pole clamp), splits in _renderSubLayers into two single-mesh RasterLayers, and uses a two-box bounding volume composing with the merged world-copy traversal (#518). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * docs(specs): refine antimeridian spec — add test fixture, handle slanted cuts - Use the vendored geotiff-test-data antimeridian.tif fixture (42x42 EPSG:4326, crosses -180 at column 24) as the primary deterministic crossing test. - Handle slanted (rotated-geotransform) cuts, not just vertical: any straight cut yields convex pieces delaunator triangulates exactly; error only on curved/concave cuts. createInitialConditions is therefore part of the MVP crossing path. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * feat(raster-reproject): add createInitialConditions (delaunator-backed seed) Add the InitialTriangulation type and a tree-shakeable createInitialConditions helper that builds a Delaunay seed from a UV point set. delaunator is confined to its own module (initial-conditions.ts); delatin.ts does not import it and the package is sideEffects:false, so it tree-shakes out for consumers that don't use it. Foundation for antimeridian cut-in-two and the sub-domain capability in #351. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * refactor(raster-reproject): document delaunator seed pattern, don't ship a wrapper Per review: a one-line delaunator wrapper isn't worth a runtime dependency. Expose only the InitialTriangulation type and show the delaunator one-liner in its docstring. delaunator moves to devDependencies — used by tests to validate winding compatibility, not shipped to consumers. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * docs(specs): drop createInitialConditions wrapper from antimeridian design raster-reproject exposes only the InitialTriangulation type + documents the delaunator one-liner; delaunator is a dev/test dep (winding validation), not shipped. Runtime seed-building for crossing tiles is the deck.gl-raster builder's job (follow-up plan). Mark stage 1 done. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * feat(raster-reproject): seed RasterReprojector from an initial triangulation Generalize the constructor to accept an optional initialTriangulation seed (delaunator's data shape), defaulting to a hardcoded unit-square seed so behavior is unchanged and the package needs no runtime triangulation dep. Refinement only ever splits existing triangles, so a sub-domain seed confines the mesh to that region. Tests build seeds via delaunator (the documented pattern) to validate winding compatibility + sub-domain confinement. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * feat(raster-reproject): add rectangleSeed helper for sub-rectangle seeds Build an axis-aligned 2-triangle rectangle seed for a UV sub-rectangle (no delaunator, runtime-safe). UNIT_SQUARE_SEED is now rectangleSeed(0,0,1,1). Used to clamp a mesh to a UV band — e.g. the valid Web Mercator latitude band (#182 / #351) — and reused by the antimeridian vertical-cut case. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * feat(deck.gl-raster): add webMercatorClampSeed (clamp mesh to ±85.051°) Pure helper that returns a rectangleSeed clamping a north-up geographic tile's reprojection mesh to the Web Mercator latitude band, or undefined when no clamp is needed/possible (rotated/projected tiles, fully-polar tiles). Avoids the degenerate near-pole triangles from #182 / #351. Unit-tested with synthetic corner latitudes. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * feat(deck.gl-raster): clamp Web Mercator meshes to valid latitude band Wire the reprojector seed through the render path: RasterLayer gains an initialTriangulation prop (passed to RasterReprojector, regenerated on change); getTileMetadata computes a per-tile _webMercatorReprojectorSeed via webMercatorClampSeed; _renderSubLayers passes it in the Web Mercator branch only (globe shows the poles, full mesh). Fixes the degenerate near-pole triangles for EPSG:4326 imagery reaching ±90° (#182 / #351). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * refactor(deck.gl-raster): name clamp seed as initialTriangulation Rename webMercatorClampSeed → webMercatorInitialTriangulation and the tile metadata field _webMercatorReprojectorSeed → _webMercatorInitialTriangulation, for consistency with the InitialTriangulation type and the RasterLayer.initialTriangulation prop (drops the ad-hoc 'seed'/'ReprojectorSeed' terms). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * refactor(deck.gl-raster): rename clamp fn to createInitialWebMercatorTriangulation Verb-prefixed name for the builder (was webMercatorInitialTriangulation); the tile metadata field stays _webMercatorInitialTriangulation. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * refactor(raster-reproject): rename rectangleSeed -> triangulateRectangle Active verb name for the helper that triangulates a UV rectangle into an InitialTriangulation; internal UNIT_SQUARE_SEED -> UNIT_SQUARE_TRIANGULATION; test file renamed to match. Updates the deck.gl-raster clamp caller too. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> * refactor: apply triangulateRectangle rename across source + caller Completes the rename (a657eb8 only moved the test file): rectangleSeed -> triangulateRectangle in delatin.ts + index export + the renamed test, and the deck.gl-raster web-mercator-clamp caller. UNIT_SQUARE_SEED -> UNIT_SQUARE_TRIANGULATION. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
+overflag on target projection definitions (EPSG:4326 and EPSG:3857) to disableadjust_lonlongitude normalizationProblem
proj4's
adjust_lonnormalizes longitude to (-π, π], causing:forward(-180.001°, lat)→ positive easting (wrong sign)inverse(-WM_HALF, northing)→ +180° instead of -180°For tiles touching the antimeridian on global EPSG:4326 COGs (e.g. 1.4M×600K pixel DEM), the round-trip error equals the full image width (5625 pixels), producing visibly distorted tile meshes at low zoom levels.
Fix
Add
+overto the target projection definitions:The
+overflag is safe for longlat and Mercator projections where the 180° meridian is a straight line. Supported since proj4js v2.20.0 (proj4js#530).Test plan
Fixes #352