Close‑Interval Survey (CIS / CIPS): CIS measures pipe‑to‑soil potentials at close spacing along the pipeline to evaluate cathodic protection performance. It highlights areas where protection may be weak or inconsistent and supports early identification of corrosion risks.

Direct Current Voltage Gradient (DCVG): DCVG applies pulsed direct current to locate coating defects and estimate their size. The resulting voltage gradients indicate whether damage is isolated or part of a larger issue and provide insight into corrosion activity at each fault.

Alternating Current Voltage Gradient (ACVG): ACVG uses low‑frequency AC signals to detect coating anomalies along the pipeline. It operates similarly to DCVG but uses alternating current to create measurable voltage gradients that help assess defect severity and guide follow‑up actions.

Electromagnetic (EM) / AC Current Attenuation Survey: EM surveys assess coating condition by measuring how an applied AC signal attenuates along the pipeline. Well‑coated pipe shows gradual signal loss, while damaged areas show sharper attenuation, and the method also provides depth‑of‑cover information.

Four‑Pin (Wenner) Soil Resistivity Method: The Wenner method measures soil resistivity to evaluate how corrosive the environment may be around the pipeline. Lower resistivity indicates more corrosive conditions, and changes between soil types can also increase corrosion risk.