Source: https://guthlabs.ai/docs/instruments/angular-size-physical-size/implementation/

instrument implementation / implementation-contract

# Angular Size ↔ Physical Size implementation

A source-bound implementation contract for Angular Size ↔ Physical Size; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-089

**Effect**: Computation or source lookup only

## Input and validation requirements

A zero-distance input produces an undefined angular size and must be rejected; additionally, an angular-size unit ambiguity can change the computed physical size from approximately 1.74533 m to 100 m.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "physical_size_km": 3474,
    "distance_km": 384400
  },
  "expected_outputs": {
    "angular_size_rad": 0.00903746098
  },
  "working": "θ = size/distance = 3474 km / 384400 km = 0.00903746098 rad."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/angular-size-physical-size/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/angular-size-physical-size/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/angular-size-physical-size/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`