Source: https://guthlabs.ai/docs/instruments/geologic-strain-dip-strike-helper/

instrument / verified-clean

# Geologic Strain/Dip-Strike Helper

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](<https://guthlabs.ai/docs/instruments/geologic-strain-dip-strike-helper/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/geologic-strain-dip-strike-helper/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/geologic-strain-dip-strike-helper/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/geologic-strain-dip-strike-helper/qualification/>)

## 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-5

**Evidence ID**: t5-090

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The specification is not mathematically correct as written. Replace cos with sin for an angle explicitly measured between strike and section, and provide an honest label stating the angle convention, degree units, valid input ranges, and the undefined parallel-to-strike case.

### Formula and scope findings

- The stated formula uses cos(angle between strike and section), but for an angle measured between the section line and strike, the standard relationship is tan(apparent dip) = tan(true dip) · sin(angle). Therefore true dip = atan(tan(apparent dip) / sin(angle)).

- The cosine form would be appropriate only if the angle were measured between the section line and the true dip direction, not between the section line and strike.

- The inversion requires an explicit domain constraint: 0° < angle between section and strike ≤ 90° for nonzero apparent dip, with dip angles interpreted in a stated range.

### Unit assumptions

- All dip and azimuthal angles are assumed to be in degrees at the user interface; trigonometric functions must convert degrees to radians internally.

- The angle is the acute horizontal angle between the section line and strike, ranging from 0° to 90°.

- Apparent dip and true dip are treated as nonnegative magnitudes from 0° up to but excluding 90°.

- The standard corrected formula is tan(true dip) = tan(apparent dip) / sin(section-strike angle).

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

The exact input combination apparent dip 30° and section-strike angle 90° makes the inversion denominator cos(90°) equal to zero, so the true dip is undefined and the instrument must reject the input rather than return a finite number.

## 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": {
    "apparent_dip_deg": 0,
    "angle_section_to_strike_deg": 45
  },
  "expected_outputs": {
    "true_dip_deg": 0
  },
  "working": "tan(0°) = 0; sin(45°) = 0.70710678; tan(true dip) = 0 / 0.70710678 = 0; true dip = atan(0) = 0°."
}
````

## 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-tranche5/tranche5-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`