Reference
Spatial API Glossary
Plain-language definitions for coordinates, frames, geometry, XR runtimes, scene data, 3D delivery, and spatial queries.
These definitions describe how terms are used throughout SpatialAPI.xyz. Platform documentation may use narrower or vendor-specific meanings.
Anchor
A reference that associates digital content with a location or pose in a tracked, mapped, or geographic space. Runtime anchors may be temporary; product anchors add durable identity and policy.
Bounding box
A rectangular or box-shaped extent used to summarize geometry and filter spatial queries. The coordinate order and intersection semantics must be documented.
Coordinate reference system
A defined system that maps coordinate values to positions, including axes, units, origin, and the model of the underlying space or Earth.
Depth map
An image-like array whose values estimate distance from a camera or viewer. Depth can support occlusion, placement, reconstruction, and measurement.
Entity
A stable domain object such as a building, device, room, vehicle, detected object, annotation, or virtual item. An entity may have one or more spatial representations.
GeoJSON
A JSON-based format for geographic geometry and features. Standard coordinate order is longitude, latitude, with optional elevation.
Geospatial anchor
An anchor associated with geographic coordinates and a localization method that resolves content in the physical world.
glTF
A transmission format for 3D scenes and models, including meshes, materials, textures, animation, and extensible metadata.
Handedness
The convention that determines axis orientation and rotation direction in a coordinate system. Engine and external systems may use different handedness.
Hit test
A query that projects a ray or shape into a scene and returns intersections with surfaces or objects.
Level of detail
Alternative representations selected according to distance, screen size, device capability, or budget to reduce rendering and delivery cost.
OpenXR
A royalty-free native API standard between an XR application or engine and an XR runtime.
Pose
A position and orientation expressed in a reference frame, typically accompanied by time, units, and tracking or accuracy metadata.
Reference frame
The coordinate space relative to which positions and orientations are expressed, such as geographic, facility, local, viewer, stage, or engine world.
Scene graph
A structured representation of entities and spatial relationships, often including parent-child transforms, semantics, and links to geometry or assets.
Spatial index
A data structure that accelerates queries such as intersection, containment, nearest neighbor, visibility, or region lookup.
Spatial query
An operation based on geometry or relationship, such as within, nearest, intersects, contains, visible, reachable, or hit by ray.
Transform
A mapping between coordinate frames that can include translation, rotation, scale, and time-dependent calibration.
Uncertainty
A measure of how precise or reliable a spatial value is, such as an accuracy radius, tracking state, covariance, confidence, or set of alternatives.
WebXR
A web platform API that gives compatible browsers controlled access to immersive sessions, poses, input sources, views, and optional XR features.
World origin
The point treated as zero in a coordinate space. Local tracking origins can reset or shift, while durable application frames should remain explicitly mapped.
3D Tiles
A hierarchical structure for streaming large heterogeneous 3D spatial datasets with level-of-detail selection and feature metadata.