Spatial Anchor

A spatial anchor's primary function is to persist digital content in a specific real-world location across multiple user sessions and devices. This is achieved by creating a persistent coordinate system anchored to physical features, allowing users to return to the same spot and find the same digital object. This is analogous to a smart contract address on a blockchain—a persistent, immutable point of reference for digital value.

Spatial anchors use computer vision and sensor fusion (camera, IMU, GPS) to achieve centimeter-level precision. The system recognizes and maps unique environmental features to create a local coordinate frame. This precise oracle-like function—translating real-world data into a digital coordinate—is critical for applications like asset tracking, geofenced NFTs, or AR-based navigation verified on-chain.

Modern spatial anchor systems (e.g., Azure Spatial Anchors, ARKit's Persistent AR) are cloud-hosted. This allows the anchor's spatial data to be shared, discovered, and resolved by multiple users. In a blockchain context, this mirrors decentralized storage and consensus; the cloud service acts as a trusted intermediary that could be replaced by a decentralized protocol for anchor persistence and verification.

A key feature is device and platform agnosticism. An anchor created on an iOS device should be resolvable on an Android or HoloLens device. This interoperability is a core blockchain principle. For Web3, it enables shared metaverse experiences where digital land parcels or objects (as NFTs) have a consistent spatial location regardless of the user's hardware or software stack.

Spatial anchors enable phygital assets—NFTs tied to a physical location. Examples include:

• A digital sculpture only viewable at a specific GPS coordinate.
• A geocaching-style game where users must be at a location to mint or interact with an asset.
• Augmented reality commerce where a virtual storefront is anchored to a real building, accessible via a crypto wallet.

Spatial anchoring is fundamentally a proof of location mechanism. Blockchain projects like FOAM Protocol and XYO Network aim to decentralize this proof, creating a trustless system for verifying real-world location data. A spatial anchor's resolved coordinates could serve as a cryptographic proof for location-based smart contracts, enabling decentralized logistics, insurance, or event verification.

In retail, spatial anchors allow customers to visualize products in their own space with persistent placement. A virtual sofa or artwork can be anchored to a specific wall, remaining in place even after the app is closed and reopened. Key applications include:

• Virtual try-before-you-buy: Seeing how furniture fits and looks over multiple sessions.
• In-store navigation: Anchors can guide customers to specific products or promotions.
• Collaborative design: Multiple users can view and modify a shared virtual layout in a real room.

This is a core use case for creating shared, persistent worlds. A spatial anchor defines a common coordinate system, allowing all players to see and interact with the same virtual objects in the same real-world location. This enables:

• Location-based games: Virtual creatures or items that appear at specific parks or landmarks for all players.
• Persistent world-building: Users can collaboratively build structures that remain for others to discover.
• Social hangouts: Virtual art installations or meeting spots that are permanently tied to a physical venue.

Spatial anchors provide high-precision, persistent landmarks for indoor navigation where GPS is unavailable. By anchoring digital signs or paths to specific doorways or intersections, applications can guide users through complex environments like:

• Airports and hospitals: Providing turn-by-turn directions to gates, clinics, or amenities.
• Warehouses and factories: Guiding workers to specific inventory bins or workstations.
• Museums and campuses: Offering contextual information and guided tours that persist across user sessions.

During the construction phase, spatial anchors are used to align digital Building Information Models (BIM) with the physical construction site. Workers can use AR devices to see where pipes, electrical conduits, or structural elements should be placed before any physical work begins. This facilitates:

• Clash detection: Visualizing potential conflicts between planned systems and existing structures.
• Progress verification: Comparing the as-built structure against the digital model in real-time.
• On-site visualization: Stakeholders can walk through a full-scale, virtual model of the finished building on the empty lot.

Spatial anchors allow for the creation of persistent augmented historical experiences. At archaeological sites or historical landmarks, digital reconstructions, informational plaques, or reenactments can be anchored to specific locations, enriching the visitor experience by:

• Reconstructing ruins: Overlaying a 3D model of an ancient building onto its current foundations.
• Providing contextual stories: Triggering narratives or images when a user points their device at a specific artifact or location.
• Creating layered tours: Different historical periods or narratives can be anchored to the same physical space for exploration.

Spatial anchors enable shared AR/VR environments where multiple users can see and interact with the same digital objects in a real-world location. This is foundational for:

• Collaborative design reviews in architecture and engineering.
• Social applications where users leave persistent notes or art in physical spaces.
• Location-based games that maintain game state across different player sessions.

In industrial settings, spatial anchors are used to lock procedural guidance and 3D schematics to specific machinery or workspaces. Technicians wearing AR headsets can access:

• Step-by-step holographic instructions overlaid on equipment.
• Remote expert assistance, where an off-site guide can annotate the worker's live view.
• Persistent data tags displaying historical performance or maintenance logs for a machine.

Spatial anchors power indoor navigation and contextual commerce by tethering digital information to store layouts. Applications include:

• In-store AR navigation to products on shelves.
• Virtual try-on stations for furniture or clothing that stays anchored in a showroom.
• Persistent promotional displays or information kiosks that customers can revisit.

Spatial anchors act as registration points between the physical world and its digital twin. This enables:

• Infrastructure monitoring with sensor data visually anchored to bridges, pipes, or power lines.
• Urban planning visualizations where proposed buildings are persistently viewed at the actual construction site.
• Public AR experiences, such as historical tours where information is anchored to landmarks.

Deploying spatial anchors involves solving key technical challenges:

• Precise localization using visual features, GPS, and sensor fusion for accurate placement.
• Cloud synchronization to store and share anchor poses across devices and sessions (e.g., Azure Spatial Anchors, ARCore Cloud Anchors).
• Environmental drift, where changes in the physical space can degrade anchor accuracy over time, requiring update mechanisms.

A World Lock is a method of anchoring digital content to a fixed location in the physical world's coordinate system (e.g., GPS coordinates). Unlike a Spatial Anchor, which uses visual features for precise local positioning, a world lock provides a coarse, global location that is less resistant to drift but useful for large-scale AR experiences.

• Key Use: Geospatial AR, outdoor navigation, and location-based games.
• Example: Placing a virtual landmark at a specific latitude and longitude.

A Point Cloud is a set of data points in a 3D coordinate system, representing the external surface of objects in an environment. These points are the raw spatial data that a Spatial Anchor system uses to recognize and re-localize a position.

• How it Works: Created by depth-sensing cameras or LiDAR scanners.
• Function: Serves as the 'map' or spatial fingerprint for anchor persistence.

SLAM is the computational technique that allows a device to construct a map of an unknown environment while simultaneously tracking its own location within it. This is the foundational technology that enables the creation and recall of Spatial Anchors.

• Core Process: Uses sensor data (camera, IMU) to model surroundings in real-time.
• Direct Relationship: A Spatial Anchor is a saved, persistent location within a SLAM-generated map.

6DoF refers to the freedom of movement in three-dimensional space: translation along the X, Y, and Z axes (moving forward/back, left/right, up/down) and rotation around those axes (pitch, yaw, roll). Spatial Anchors require 6DoF tracking to place and maintain content with full positional and rotational accuracy relative to the real world.

• Contrast with 3DoF: 3DoF only tracks rotation (like a VR headset without positional tracking).

A Persistent Coordinate Frame is a shared, stable coordinate system that multiple devices can align to, allowing for collaborative AR experiences. In platforms like Microsoft's Mixed Reality, a Spatial Anchor creates a PCF, enabling different users to see and interact with the same virtual object in the same physical location.

• Key Feature: Enables multi-user persistence and shared spatial understanding.

VIO is a sensor fusion technique that combines data from a camera (visual odometry) and an inertial measurement unit (IMU—accelerometer, gyroscope) to accurately track a device's position and orientation. It is a critical component of mobile SLAM systems and is essential for the high-precision, drift-free tracking required by Spatial Anchors.

• Advantage: Compensates for the weaknesses of either sensor used alone.