Geospatial Types

Arc provides BSON serializers for types from Cratis.Geospatial. Their writers produce GeoJSON for MongoDB storage and spatial filters. Before using Polygon, read the current Polygon reader limitation: typed reads fail on the coordinate nesting its writer emits.

Supported Types

• Point — Single geographic coordinates (longitude, latitude)
• LineString — Routes and paths (ordered sequences of points)
• Polygon — Geographic areas with optional interior boundaries (holes)

GeoJSON Compatibility

Arc’s BSON serializers write GeoJSON documents. This does not mean the Cratis model types are accepted as geometry arguments by MongoDB driver’s filter builders: use MongoDB.Driver.GeoJsonObjectModel types for those arguments, as the individual guides show. The records and write paths do not validate geometry; the Polygon reader contains some ring checks, not comprehensive validation. Server spatial-index restrictions still apply. Optional geometry also needs an explicit null/omission policy, not just a nullable annotation.

GeoJSON storage enables:

• MongoDB Spatial Queries — Use $near, $geoWithin, and other spatial operators
• Interoperability — Exchange GeoJSON with compatible mapping services and GIS tools
• Standards Compliance — Follow industry-standard GeoJSON specification

Getting Started

Choose the type that matches your use case:

• Use Point for storing single locations (stores, users, events)
• Use LineString for routes, paths, or trajectories
• Use Polygon for service areas, regions, or geographic boundaries

See the individual type documentation for implementation examples and best practices.