# Physical coast data

Actual source: GSHHG 2.3.6 as distributed in basemap-data 2.0.0. License stated in installed package metadata: LGPL-3.0-or-later. The map-geometry subset and derivative geometry retain that provenance; COPYING and COPYING.LESSER are included.

Extraction: Basemap cylindrical projection, intermediate resolution, bounds 117 E / 22 N to 149 E / 51 N. Coast polygons and their type are retained as longitude/latitude pairs. Default intermediate area filtering/generalization applies. Rendering clips the polygons to each map viewport, uses a mean-latitude longitude correction and simplifies by 0.006 degrees. No administrative-boundary data is loaded.

The data are a modern physical location baseline. They are not period-specific shorelines. Approximate manually selected city anchors are checked separately in COORDINATE-CHECKS.json.

Natural Earth was explored but its ZIP was not retrieved; it was not the data actually used.