Standard Atmosphere Lapse Rate Model implementation

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

t7-046

Effect

Computation or source lookup only

Input and validation requirements

• Altitude units are ambiguous in the instrument spec; treating feet as metres would produce materially incorrect results.
• Geometric altitude versus geopotential altitude is not specified. ISA/ICAO layer boundaries conventionally use geopotential altitude.
• Division by zero or invalid results can occur if temperature is zero or nonpositive, especially in an inversion or out-of-range input.
• A zero lapse rate causes division by zero in the power-law barometric formula; the isothermal exponential branch is required.
• Negative altitude, altitude above the supported table range, and exact layer-boundary selection are unspecified.
• Real atmospheric pressure, temperature, and density vary with weather, latitude, season, and composition; the existing idealized-atmosphere honest label is necessary and appropriate.

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": {
    "altitude_m": 0
  },
  "expected_outputs": {
    "temperature_K": 288.15,
    "pressure_Pa": 101325,
    "density_kg_m3": 1.225
  },
  "reference_data": {
    "source_convention": "ICAO Standard Atmosphere 1976 / ISO 2533:1975; widely tabulated standard value",
    "sea_level": {
      "geopotential_altitude_m": 0,
      "temperature_K": 288.15,
      "pressure_Pa": 101325,
      "density_kg_m3": 1.225
    },
    "g0_m_s2": 9.80665,
    "R_dry_air_J_kgK": 287.05287
  },
  "working": "At h=0 m, use the exact sea-level standard row directly: T=288.15 K; p=101325 Pa. Then rho=p/(R·T)=101325/(287.05287·288.15)=101325/82713.5≈1.225 kg/m³. This is the zero-altitude boundary case and the widely memorized ISA sea-level entry."
}

Other records

Sources and evidence

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

• VERIFIED_LEDGER.json
• evidence-tranche7/tranche7-results.json