Sample GeoJSON file (antimeridian)

Handle it in code

Each snippet below was run against this exact file with Python 3.14.4 and Node 24.15.0 when this page was built, and the output shown is what it printed.

Python

GeoJSON is [longitude, latitude], polygon rings must close, and RFC 7946 (section 3.1.9) asks for lines that cross the 180th meridian to be split, or a map draws them the long way round the world.

import json

def points(c):
    if isinstance(c, list) and c and all(isinstance(v, (int, float)) for v in c):
        yield c
    elif isinstance(c, list):
        for item in c:
            yield from points(item)

def check(geom, n):
    kind, coords = geom.get("type"), geom.get("coordinates") or []
    for p in points(coords):
        if len(p) < 2 or not (-180 <= p[0] <= 180 and -90 <= p[1] <= 90):
            yield f"feature {n}: {p} is not [longitude, latitude] in range"
    if kind == "Polygon":
        for ring in coords:
            if len(ring) < 4 or ring[0] != ring[-1]:
                yield f"feature {n}: polygon ring is not closed (4+ positions, last equal to first)"
    if kind in ("LineString", "Polygon"):
        line = coords if kind == "LineString" else coords[0]
        for a, b in zip(line, line[1:]):
            if abs(a[0] - b[0]) > 180:
                yield f"feature {n}: {a} to {b} crosses the antimeridian; split it"

with open("antimeridian.geojson", encoding="utf-8") as f:
    features = json.load(f)["features"]
found = [p for n, feat in enumerate(features, 1) for p in check(feat.get("geometry") or {}, n)]
print(f"{len(features)} features:", "valid" if not found else f"{len(found)} problem{'s' * (len(found) != 1)}")
for p in found:
    print("  " + p)

Run against this file, it prints: 2 features: 1 problem feature 1: [170, 0] to [-170, 0] crosses the antimeridian; split it