Understanding Geospatial Types

Geospatial types represent locations and areas on Earth’s surface. Cratis provides three core types, each suited for different scenarios.

Point

A Point is the simplest geospatial type — a single location defined by longitude and latitude coordinates. Use Points when you need to store or track a discrete location: a warehouse address, a vehicle’s current position, a user’s home location.

Points are always paired: longitude (east-west, -180° to 180°) and latitude (north-south, -90° to 90°).

LineString

A LineString is a path formed by connecting two or more Points in order. Unlike an array of points, a LineString explicitly represents the connections between them, forming a continuous line. Use LineStrings for routes, boundaries, and trajectories: a hiking trail, a river boundary, a vehicle’s movement history.

A LineString must have at least two points. It represents the shortest path (geodesic) between consecutive pairs of points on Earth’s surface.

Polygon

A Polygon encloses an area using one or more closed rings of points. The outer ring is the boundary; optional inner rings define excluded areas (like courtyards or lakes within land). Use Polygons for areas and regions: park boundaries, property parcels, delivery zones, geofences.

A Polygon ring must have at least 4 points, with the first and last points identical to close it.

When to Use Each

Scenario	Type
Store a single location (address, landmark, sensor)	Point
Track position over time	Point (repeated snapshots)
Represent a route or boundary line	LineString
Represent a bounded area or region	Polygon
Geofencing (location triggers)	Polygon
Administrative boundaries	Polygon

JSON Serialization

All types serialize to GeoJSON format — a standard adopted by geographic databases and mapping services. This ensures your data integrates seamlessly with external tools and services.

When you send geospatial types to a server or store them, they automatically convert to GeoJSON. The same conversion happens in reverse when deserializing.

Point example:

{
    "type": "Point",
    "coordinates": [10.5, 20.3]
}

LineString example:

{
    "type": "LineString",
    "coordinates": [[10.5, 20.3], [11.2, 21.1], [12.0, 22.0]]
}

Polygon example:

{
    "type": "Polygon",
    "coordinates": [[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]]
}

Full-Stack Type Safety

Use the same geospatial types on both C# backend and TypeScript frontend. Data round-trips cleanly in GeoJSON format:

// C# backend
public record Location(string Name, Point Position);

// TypeScript frontend
class Location {
    @field(String)
    name!: string;

    @field(Point)
    position!: Point;
}

Both serialize and deserialize to identical GeoJSON, so the type information flows end-to-end.