mõõtjale tähelepandamatu hälve, ebanormaalsus, ebajärjepidevus, ebamäärasus vms mõõteprotseduuris või suuruse mõõtmisel, its automated inspection and data acquisition and processing systems detect hidden flaws such as corrosion, porosity and cracking, detection of factory defects, especially hidden flaws is rather difficult for surveyor and requires professional skill and top carefulness