Skip to main content
Research preview — APIs may change. GitHub

​
Location Claims

A location claim is an assertion about where and when an event occurred. It’s the “I was here” statement that location stamps provide evidence for or against.

​
What a Location Claim Contains

A location claim extends the Location Protocol v0.2 specification with verification-specific fields: Asserted location. The location being claimed — a GeoJSON geometry with a spatial reference system. This is where the subject claims the event occurred. Spatial uncertainty (radius). How precisely the claim defines the location, in meters. This field is required — you cannot claim presence at an exact point. Both physical measurement and honest reporting involve uncertainty, and pretending otherwise produces misleading verification results. Temporal bounds. A time range (start and end) during which the event is claimed to have occurred. Like spatial uncertainty, temporal bounds acknowledge that events have duration. Subject. Who or what was at the location. This could be a person (identified by an Ethereum address, DID, or other scheme), a device, an asset, or an organization. Event type. What kind of event is being claimed. The event could be:
  • Presence — a person or device was at a location
  • Transaction origin — a transaction originated from a location
  • Asset location — a physical asset was at a location
  • Delivery — a delivery occurred at a location

​
The Uncertainty Tradeoff

Location claims involve a fundamental tension between precision and confidence:
  • “Somewhere in California during 2024” — easy to verify with high confidence, but not very useful for many use cases
  • “Within 10 meters at 14:32:07” — precise and useful, but harder to verify confidently
Broader claims are easier to verify because the evidence just needs to fall anywhere within a larger target. Narrower claims require more precise evidence. Applications decide what precision/confidence balance they need. This tradeoff also has privacy implications. Broader spatial and temporal bounds reveal less about exact location, which can be a feature rather than a limitation for privacy-sensitive applications. Ultimately, spatial and temporal precision, forgery cost, privacy, latency and other factors are application-specific — different combinations of location stamps will be useful in different contexts.

​
Relationship to Location Stamps

A location claim is an assertion. A location stamp is evidence. They use the same Location Protocol format for their location data, but represent different things:
Location claimLocation stamp
LocationAsserted — where the subject claims to have beenObserved — where evidence indicates the subject was
Created byThe claimantA proof-of-location system
PurposeStates what needs to be verifiedProvides evidence for verification
Evaluation compares the two: does the observed location (from location stamps) support the asserted location (from the location claim)?

Next: Composing location proofs

Bundling location stamps with a location claim
See also: