Source: https://guthlabs.ai/docs/instruments/cloud-base-height-from-spread-quick-field-rule/implementation/

instrument implementation / implementation-contract

# Cloud Base Height from Spread (quick field rule) implementation

A source-bound implementation contract for Cloud Base Height from Spread (quick field rule); 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**: t5-170

**Effect**: Computation or source lookup only

## Input and validation requirements

The formula produces a negative raw height when dew point exceeds temperature and overflows to Infinity for opposite extreme finite inputs. Both cases should be rejected or explicitly flagged rather than silently returned as ordinary estimates.

## 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": {
    "temperature_f": 70,
    "dew_point_f": 60
  },
  "expected_outputs": {
    "estimated_cloud_base_ft_agl": 4000
  },
  "working": "Spread = T − Td = 70 − 60 = 10 °F. Height ≈ 400 × 10 = 4,000 ft AGL."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/cloud-base-height-from-spread-quick-field-rule/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/cloud-base-height-from-spread-quick-field-rule/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/cloud-base-height-from-spread-quick-field-rule/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-tranche5/tranche5-results.json`