Source: https://guthlabs.ai/docs/instruments/seawater-density-simplified-eos/
instrument / verified-clean
# Seawater Density (simplified EOS)
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## Ledger state
The current ledger marks this instrument verified clean within the source-bound verification corpus.
**Area**: Earth & Space (astronomy, orbital mechanics, meteorology, geology, geodesy, oceanography)
**Tranche**: tranche-7
**Evidence ID**: t7-110
**Ledger rows**: 1
No ledger note is attached.
## Review findings
The atmospheric-pressure UNESCO EOS-80 polynomial tested here is standard and gives the expected values. The instrument cannot be approved as specified because it advertises optional pressure without defining the pressure-dependent equation, units, range, or whether pressure is gauge or absolute. The honest-label statement is appropriate only if the exact EOS-80 approximation, validity range, and pressure limitation are displayed.
### Formula and scope findings
- The specification does not state the exact UNESCO EOS-80 density equation or its coefficients, so 'simplified linear/UNESCO-80-style polynomial' is not uniquely implementable.
- Pressure is listed as optional, but no pressure correction, pressure range, or pressure unit is specified. The atmospheric-pressure polynomial alone is not valid for nonzero pressure.
- The implementation should explicitly distinguish practical salinity S in PSU from mass-fraction salinity; PSU is dimensionless and should not be treated as g/kg without qualification.
### Unit assumptions
- Temperature is in degrees Celsius on the IPTS-68/ITS-90-compatible EOS-80 temperature scale.
- Salinity is practical salinity S in PSU, numerically dimensionless, with S^(3/2) interpreted as S multiplied by sqrt(S).
- The tested polynomial computes in-situ density at zero gauge pressure, conventionally P=0 dbar; pressure-dependent density requires the UNESCO pressure correction.
- Output density is in kg/m^3.
- The atmospheric EOS-80 polynomial is intended approximately for -2 <= T <= 40 degrees C and 0 <= S <= 42 PSU; these constraints should be enforced or documented.
## Boundary hardening
**BREAK_CLAIMED** · SELF_FLAGGED
The negative-salinity vector produces an undefined real result and must be rejected. The convention probe also exposes a unit-label hazard: interpreting an unlabeled temperature value of 10 as Celsius versus Fahrenheit changes the expected density substantially.
## Errata and corrections
No applied erratum is attached to this unique-name record.
## Inspectable example
4 review vectors are recorded. One source-bound sample is shown below.
````
{
"inputs": {
"temperature_C": 0,
"salinity_PSU": 0,
"pressure_dbar": 0
},
"expected_outputs": {
"density_kg_m3": 999.842594
},
"reference_data": {
"rho_w_coefficients": {
"a0": 999.842594,
"a1": 0.06793952,
"a2": -0.00909529,
"a3": 0.0001001685,
"a4": -0.000001120083,
"a5": 6.536332e-9
},
"source_convention": "Widely tabulated standard value, UNESCO EOS-80/UNESCO Technical Papers in Marine Science 44 atmospheric pure-water density polynomial"
},
"working": "Use rho_w(T)=a0+a1*T+a2*T^2+a3*T^3+a4*T^4+a5*T^5. At T=0: rho_w=999.842594+0.06793952*0-0.00909529*0^2+0.0001001685*0^3-0.000001120083*0^4+0.000000006536332*0^5=999.842594 kg/m^3. At S=0, all salinity terms are zero, so rho=999.842594 kg/m^3."
}
````
## Related workflows
No source-defined multi-instrument workflow membership is recorded.
## Sources and evidence
These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.
- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`
- `evidence-tranche7/tranche7-results.json`
- `BOUNDARY_HAZARD_CATALOG.json`