Improving Transparency in Guided Wave Testing: Aligning Long-Range Ultrasonic Inspection with Conventional UT Reporting Principles

Guided Wave Testing (GWT) has become a widely used long-range ultrasonic screening technique for pipelines and industrial structures. The method enables inspection of tens of meters from a single probe location and is particularly useful for insulated, buried, or otherwise inaccessible piping systems. Despite its widespread adoption, a significant challenge in current GWT practice is the lack of transparency in inspection reporting. In many field applications, results are presented using highly compressed long- range plots, log-scaled amplitude displays, or Distance Amplitude Correction (DAC) curves without calibrated amplitude scales. These approaches often rely heavily on field interpretation and can obscure defect signals or limit the ability of inspectors to verify indications. Because guided wave testing is fundamentally an ultrasonic inspection method, reliable reporting requires three essential calibrations: distance calibration to accurately locate reflectors, amplitude calibration to express signal strength as reflection coefficient (%), and attenuation calibration to compensate for signal loss over distance. This paper discusses how these three calibrations form the technical foundation for transparent GWT reporting, proposes a methodology that aligns guided wave inspection with conventional ultrasonic testing principles, and demonstrates how Time-Corrected Gain (TCG) plots with calibrated amplitude axes significantly improve the reliability and credibility of guided wave inspection results.