Falling off the edge of the world: Dealing with the antimeridian...
summary
Converting EPSG:3994 coastal data into WGS84 and then spherical Mercator exposes antimeridian wrap where longitudes jump from +180 to -180; the fix sorts every feature’s X values, finds the largest longitude gap (often ~359°) and adds 360° to the points left of that gap, which yields contiguous polygons for rendering. Works reliably for polygons and tiled web maps but struggles with multilines, multi-part geometries, bounding-box conventions, intersection tests and datasets spanning >180° (e.g., a continent-sized extent).
AI-written summary · about
chapters (12)
- 0:00Introduction
- 0:20What is Coordinates
- 0:54Available data
- 1:48Projections
- 2:36Global Projections
- 5:51Reference System
- 8:32A closer look
- 8:51Anticlockwise
- 9:34Polygons
- 12:57Other problems
- 13:54World geography
- 14:16Northern vs Southern Hemispheres
related talks
30mA front-end dev epic journey into geography
23mWhere the bloody hell are you? GIS in Go
26mEverything you never wanted to know about maps
31mVisualizing Geographic Data With Python
26mWhy are coordinate transformations so confusing?
10mUpstream/Downstream: Discovering and Displaying Watershed Topology!
01h 41mOpenStreetWhat? Mapping The World With Open Data
24mMaps, Data, and Charts - Bound for Great Things!