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UTM Zone 56S Polygon (Sydney)

vectorGeoJSONPolygonEPSG:32756tinybundled

A polygon over Sydney recorded in EPSG:32756 -- UTM zone 56 South. Southern-hemisphere UTM adds a 10 000 000 m false northing, so the northings here are around 6.26 million rather than the negative values a consumer that ignores the hemisphere would expect.

Polygon geometry of utm_zone_56s_small, 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 utm_zone_56s_small
Category vector
Format GeoJSON
Geometry type Polygon
CRS EPSG:32756
Location Sydney, Australia (synthetic, UTM 56S) — 150.80°E, 33.90°S → 151.30°E, 33.60°S
Test tier unit
Size class tiny
Storage class bundled
Redistributable yes
Loader geopandas
Status validated

Use this case

import pytest


@pytest.mark.geocase_case("utm_zone_56s_small")
def test_utm_zone_56s_small(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

Confirm that a southern-hemisphere UTM polygon reprojects to a negative latitude, catching a consumer that drops the false northing or assumes the northern zone code.

Risk types covered

Expected behavior

Assertion Expected
expect_loadable yes
expect_valid_geometry yes
expect_crs yes
expected_epsg 32756
expected_geometry_types Polygon

Notes

The false northing

Southern-hemisphere UTM zones carry a 10 000 000 m false northing, so that coordinates stay positive south of the equator. The northings in this file are around 6 260 000 -- meaning roughly 3 740 000 m south of the equator, not 6 260 km north of it.

That single fact is the case's whole point, and it fails in a specific, recognisable way: a consumer that treats EPSG:327xx as EPSG:326xx (or that hard-codes the northern variant when deriving a zone code from a longitude) places this polygon in Siberia rather than New South Wales. The error is thousands of kilometres and the wrong hemisphere, but the numbers stay plausible-looking throughout, so nothing crashes.

Why it was missing

Every UTM case in the bundled catalog previously resolved to zone 33N. There was no southern-hemisphere fixture at all, which meant the false northing -- the single most common UTM mistake -- was untested by construction.

What to assert

Reproject to EPSG:4326 and check the latitude is negative and near -33.7. See also utm_zone_1n_small (zone edge) and utm_zone_boundary_straddle (cross-zone).

Required capabilities

  • load
  • bounds-check
  • reprojection

Files

Browse this case on GitHub

Source and license

  • Source: geocase-curated
  • License: MIT

Tags

crs polygon southern_hemisphere utm valid vector