Three physical quantities
Visible light answers surface state: cracks, corrosion, foreign objects, waterlines. Thermal imaging answers radiated-temperature distribution: overheating, evaporative cooling from a leak, abnormal electrical joints. A gas sensor or optical gas imaging answers whether a target molecule is on the sampling path. They can cue each other — a thermal anomaly triggering a gas re-check — but the conclusion must return to the calibrated world of that sensor.
Municipal and industrial sites like “one picture that shows every risk”. Physics does not offer that convenience. Emissivity, reflection, standoff, downwash, sensor response time and cross-sensitivity all let a single picture lie.
Confounds in onboard gas
Academic discussion of onboard gas measurement treats rotor downwash, airspeed, inlet position and sensor response as experimental factors. Pipes also layer: H₂S and methane do not fill a cross-section uniformly. If the inlet sits in the wake, the reading can be stably wrong.
PipeGuardian therefore modularises the gas bay, and writes calibration gas, a fixed reference, response time and cross-sensitivity as part of G3. Higher thermal resolution does not fill that table.
Consequences for public claims
Public copy that says “infrared detects methane” must name the method (for example an optical-gas-imaging spectral channel) and the calibration. A generic thermal module cannot. The evidence page requires sensing claims to be verified separately. That is not copy hygiene. It is how a wrong field decision is avoided.
How to read this back to PipeGuardian
This article is industry education, not a pilot news item. If a vendor, university, funding scheme or standard appears, treat it as a contrast question: what must our own rig answer, and what must public copy forbid. Copying an external figure into a PipeGuardian spec sheet conflicts with the evidence page.
The English site carries the full method set: system architecture, safety bounds, target specifications, the 18-month roadmap and HK–SZ operations. Field work still starts with a permit and a recovery path. Reading an article is not a confined-space permit.