# M9 Geospatial Edge Cases

Codex must account for these cases early to avoid later rewrites.

## Invalid polygon

Examples:

- self-intersection,
- unclosed ring,
- empty coordinates,
- wrong coordinate nesting.

Required behavior:

- reject with validation error,
- return specific message,
- do not persist.

## MultiPolygon

Required behavior:

- accept for areas and vector features,
- compute total area across all parts,
- display as a single layer.

## CRS mismatch

Scenario:

- reference data is EPSG:31370,
- API uses EPSG:4326,
- raster processing may use native CRS.

Required behavior:

- store original CRS in dataset metadata,
- transform API geometries to EPSG:4326 for frontend,
- use projected CRS for area/length calculations when needed,
- document transformations.

## Very large file

Required behavior:

- reject files above configured limit with clear error,
- do not load huge files into memory at once,
- expose future chunking/tile strategy.

## Raster without georeference

Required behavior:

- accept only as non-georeferenced image if supported,
- mark geospatial operations unavailable,
- do not pretend map alignment exists.

## Feature outside selected area

Required behavior:

- clip if operation requested,
- otherwise keep original and display warning if used for area analysis.

## Geometry collection

Required behavior:

- reject for V1 unless explicitly converted,
- explain supported geometry types.

## Zero-area feature

Required behavior:

- keep for line/point layers,
- reject or ignore for polygon-area metrics,
- record warning in analysis result.

## Duplicate features

Required behavior:

- do not automatically delete without audit trail,
- expose duplicate count in data quality metadata.

## Antimeridian/global edge cases

Not relevant for Kempen V1. Document as out of scope.