> ## Documentation Index
> Fetch the complete documentation index at: https://docs.astral.global/llms.txt
> Use this file to discover all available pages before exploring further.

# Location Stamps

> Evidence from a single proof-of-location system about an observed location

<Note>**Research Preview** — APIs may change. [GitHub](https://github.com/AstralProtocol)</Note>

# Location Stamps

A location stamp is a signed piece of evidence from a single [proof-of-location system](/concepts/pol-systems) about an observed location. It's the atomic unit of location evidence in Astral — the building block from which the [location evidence](/concepts/location-proof-structure) component of a location proof is composed.

## Location Stamp Contents

Conceptually, a location stamp carries four things:

**Observed location.** Where the proof-of-location system's evidence indicates the subject was. This uses the same [Location Protocol v0.2](https://github.com/DecentralizedGeo/location-protocol-spec/tree/v0.2-draft) format as location records — a geometry with a spatial reference system.

**Temporal footprint.** When the observation was made. Both location stamps and location claims use time ranges (start and end), not single instants — observations take time, and evidence may span a window.

**Plugin identification.** Which [location proof plugin](/concepts/location-proof-structure#location-proof-plugins) + version was used to create this evidence. This is necessary for verification — the verifier needs to know what kind of evidence to expect and how to evaluate it.

**Signals and signatures.** The raw evidence data (signals) collected by the proof-of-location system, plus cryptographic signatures that bind the evidence to its source. The signals are plugin-specific — each proof-of-location system produces different kinds of raw data (sensor readings, latency measurements, attestation tokens, etc.).

## Independence From Claims

This is a key design decision. A location stamp says "here is evidence about an observed location" — it does not say "this evidence supports a particular claim." The separation matters because:

* The same location stamp could be evaluated against different location claims
* Location stamps can be collected before a location claim is formulated
* Verification can assess each location stamp on its own merits before comparing it to the claim

The connection between location stamps and location claims happens at the [location proof](/concepts/location-proof-structure) level, where they're bundled together. The [evaluation](/concepts/location-proof-evaluation) process then assesses whether the observed evidence (from location stamps) support the asserted location (from the location claim).

## Internal validity

Each location stamp carries enough information to verify its own internal validity — independent of any location claim. Stamp verification checks:

* **Signatures** — Are the cryptographic signatures valid? Do they chain back to a trusted source?
* **Structure** — Does the location stamp conform to the expected format for its plugin?
* **Signal consistency** — Are the raw signals internally consistent? (e.g., do multiple sensor readings agree?)

This is the first phase of [location proof evaluation](/concepts/location-proof-evaluation) — checking each location stamp before assessing how well it supports the claim.

<Card title="Next: Location claims" icon="map-pin" href="/concepts/location-claims">
  Assertions about where and when an event occurred
</Card>

***

**See also:**

* [SDK: Stamps](/sdk/stamps) — collecting, creating, and signing location stamps
* [API: Verify stamp](/api-reference/verify/stamp) — verifying individual location stamps
* [API: Types](/api-reference/types) — LocationStamp type reference