Checks reference

Every issue geomlint reports has a stable code, used both in the table/JSON output and in config (disabled_checks, severity_overrides).

Geometry validity & topology

Code	Default severity	Applies to	What it means
unparseable-geometry	error	all formats	The feature's geometry couldn't be parsed at all (malformed JSON geometry, or a format the reader couldn't decode).
empty-geometry	error	all formats	The feature has a geometry object, but it's empty (no coordinates).
invalid-geometry	error	all formats	The geometry is topologically invalid per GEOS (self-intersections, collapsed rings, etc.) — shapely's explain_validity() reason is included in the message.
zero-area-polygon	error	Polygon/MultiPolygon	The polygon's area is at or below zero_area_epsilon — almost certainly a collapsed ring, not "just small."
zero-length-line	error	LineString/MultiLineString	The line's start and end coincide with zero length.
duplicate-vertices	warning	all geometry types	Consecutive vertices repeat. Harmless on its own, but a common precursor to self-intersection after the next simplify/reproject.
wrong-ring-orientation	warning	Polygon/MultiPolygon, GeoJSON only	A ring doesn't follow the RFC 7946 right-hand rule (exterior counterclockwise, holes clockwise). Not checked for Shapefile/GPKG, which don't share that convention.
antimeridian-crossing-suspected	warning	all non-point geometry types	The feature's bounding box spans more than 180° of longitude — almost always a feature that crosses ±180° without being split, not a genuinely huge shape.
excessive-coordinate-precision	info	all geometry types	A coordinate carries more decimal places than max_coordinate_precision — usually fake precision from a float round-trip, not real measurement accuracy.

CRS sanity

Code	Default severity	Applies to	What it means
unrecognized-crs	error	all formats	The file declares a CRS that doesn't resolve via pyproj — check the authority code/name.
missing-crs	warning	Shapefile/GPKG only	No CRS was found at all. Not flagged for GeoJSON, since RFC 7946 mandates WGS84 with no CRS member required.
coordinates-out-of-wgs84-range	error or warning	all formats	Coordinates fall outside valid lon/lat bounds — very likely projected data (UTM, state plane, etc.) mislabeled or exported without reprojecting to WGS84. Severity is error when more than out_of_range_error_pct% of features in the file are affected, warning otherwise.
mismatched-crs-across-files	warning	batch-level, across all files in one run	Two or more files in the same run declare different CRSes — an easy way to silently corrupt a spatial join if it's not intentional.

Structural checks

Code	Default severity	Applies to	What it means
duplicate-feature-id	error	GeoJSON, features with an explicit id member	The same user/pipeline-assigned id is used by more than one feature in the file. Not checked for Shapefile/GPKG, where ids are driver-assigned FIDs guaranteed unique by the format.

Not implemented

Positional/GPS-drift detection isn't a check here — on purpose

Telling a real turn from a multipath-induced jump needs a speed/heading-plausibility model, not a distance threshold — see geomlint/checks/drift.py for the full roadmap. Passing --drift on the CLI fails loudly with that explanation rather than silently doing nothing.