Key takeaway
Keep cyclic longitude semantics in the geometry and bounding box. West greater than east can identify a valid crossing region rather than a malformed box.
Correct coordinates can still describe the wrong coverage
A receiving validator checks longitude and latitude ranges, then sorts the two longitude limits so the smaller number comes first. The numbers remain plausible and the file passes. For an antimeridian-crossing region, this repair can change a narrow band near ±180° into the broad complementary region around zero. The coordinate reference system can be entirely correct while spatial filtering becomes wrong.
RFC 7946’s GeoJSON guidance recommends cutting antimeridian-crossing geometries into parts that do not cross it. Its bounding-box discussion permits west to be greater than east for a crossing box. OGC API Features likewise describes that case for its longitude/latitude bbox contract. A generic minimum-less-than-maximum rule does not express those particular interfaces.
Preserve one invented twenty-degree rectangle
This hypothetical region extends eastward from longitude 170° to −170° across the antimeridian, between latitude 10° and 20°. All coordinates use the already established GeoJSON longitude/latitude convention. Its bbox is [170,10,−170,20]. The longitude span is (180−170)+(−170−(−180))=20°. This is angular coverage, not a distance or a surface-area calculation.
Sorting the longitude edges produces [−170,10,170,20], whose noncrossing span is 340°. That is the wrong region for this stipulated intent. Keep the producer’s stated coverage and test representative points; the coordinate values alone cannot tell a receiving engineer which of two complementary regions the business intended.
A cut representation uses two polygons inside a MultiPolygon. The completed exterior rings below close at their first point and proceed counterclockwise in this coordinate-plane illustration. The shared ±180° seam is one geographic meridian represented on the two sides. The rings are an original synthetic fixture rather than a real asset boundary or a surveyed area.
| Synthetic component | Complete exterior ring | Coverage |
|---|---|---|
| Eastern component | [170,10], [180,10], [180,20], [170,20], [170,10] | 170° to 180° |
| Western component | [−180,10], [−170,10], [−170,20], [−180,20], [−180,10] | −180° to −170° |
Check inclusion instead of judging the map’s appearance
The hypothetical point [179,15] lies inside the eastern component, and [−179,15] lies inside the western one. The point [0,15] lies outside the intended region. These expected interior results form a small receiving fixture that exposes a sorted-edge complement even if a map projection makes the displayed region hard to inspect. They deliberately avoid exact-boundary predicates at the seam.
For the complement created by sorting, the two near-antimeridian points fall outside while the zero-longitude point falls inside. The file is no longer answering the same spatial question. Retain these three membership expectations together with the region specification and inspect the actual query or geometry engine’s output. No spatial engine was run for this article; the outcomes follow from the stated rectangular interiors.
Match the API’s bbox rule and the geometry representation
OGC API Features specifies a bbox parameter and an intersection-based result condition. Its antimeridian explanation allows the west edge to exceed the east edge. That supports testing this named receiving API behavior; it is not a promise that every mapping SDK, database function or web form accepts a crossing bbox. An unsupported consumer may require a documented decomposition into two queries or another suitable method.
If two queries are used, preserve that decomposition and reconcile overlapping results using the actual feature identity. Do not assume summing two response counts produces a unique-feature count. Features that intersect both queries can appear twice. The antimeridian decision therefore needs the receiving selection rule as well as the delivered geometry and its descriptive extent.
Also preserve holes, multiple components and the declared geometric interpretation during any cut. Replacing a geometry with its bounding box loses shape information even when both bounds are correct. The rectangular fixture avoids that complication; it is a test of the wrap boundary, not a general polygon repair algorithm.
Accept the crossing region with its expected interior points
For the completed illustration, the accepted description remains a 20° longitude band in two components, with the two ±179° points inside and the 0° point outside. The sorted 340° complement is rejected. A receiving record retains the intended region, original geometry, derivative geometry, bbox convention, split method, engine/version and observed membership results when the actual test is performed.
CRS and axis-order checks remain prerequisites; they do not settle cyclic coverage. Bring an unresolved crossing convention to the geospatial owner before using spatial counts or regional coverage claims in an evaluation. The synthetic method does not establish surveying accuracy, parcel authority, navigational fitness or permission to disclose real locations.