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Equator-Crossing Polygon

vectorGeoJSONPolygonEPSG:4326tinybundled

A simple rectangle straddling the equator in EPSG:4326, spanning latitudes -5 to 5 and longitudes -10 to 10. This exercises hemisphere-boundary logic in spatial operations -- sign changes in latitude, UTM zone selection, and area calculations that cross from the southern to northern hemisphere.

Polygon geometry of equator_polygon, rendered from the case's data
Polygon geometry, rendered from the case's actual geometry. Scale is normalized to the viewport and is not comparable between cases.
Property Value
Case ID equator_polygon
Category vector
Format GeoJSON
Geometry type Polygon
CRS EPSG:4326
Location Equator at the prime meridian (synthetic) — 10.00°W, 5.00°S → 10.00°E, 5.00°N
Test tier unit
Size class tiny
Storage class bundled
Redistributable yes
Loader geopandas
Status validated

Use this case

import pytest


@pytest.mark.geocase_case("equator_polygon")
def test_equator_polygon(geocase_case) -> None:
    data = geocase_case.load()
    assert data is not None

Use GeoCase in your tests

Install the complete set of vector, raster, and NetCDF dependencies:

pip install "geocase[all]"

View GeoCase on PyPI.

What this case checks

Ensure polygon-based utilities handle geometries that straddle the equator without sign errors or incorrect hemisphere assignment.

Risk types covered

Expected behavior

Assertion Expected
expect_loadable yes
expect_valid_geometry yes
expect_crs yes
expected_epsg 4326
expected_geometry_types Polygon

Notes

A GeoJSON Polygon that straddles the equator (latitude 0°).

Purpose

The existing equator_crossing_line case provides a LineString that crosses latitude 0°. A line is one-dimensional, so it doesn't exercise:

  • Area calculations that span hemispheres,
  • Polygon clipping at the equator boundary,
  • UTM zone-letter selection (N vs S bands),
  • Hemisphere-aware containment checks.

This polygon fills that gap with a simple, easy-to-reason-about rectangle.

Geometry

A closed rectangle spanning −10° to 10° longitude and −5° to 5° latitude. The geometry is intentionally small and simple so that distortion from projection choice is minimal but the equator-crossing property is present.

Edge-case value

Concern Detail
Hemisphere boundary Latitude sign changes from negative to positive
UTM zone selection Straddles UTM zones 30/31 and crosses the N/S band line
Area calculation Planar vs geodesic area should agree closely at the equator
Containment Point-in-polygon for (0, 0) — the origin — must return true

Required capabilities

  • load
  • geometry-validation
  • reprojection

Files

Browse this case on GitHub

Source and license

  • Source: geocase-curated
  • License: MIT

Tags

crs edge_case equator geojson polygon vector