【正文】 based on different technologies (optical, mechanical, electromagic, etc.). These systems are more or less adequate, depending on measuring conditions, user’s experience and skill, cost, accuracy, portability, etc. In general formeasuring medium–largesize objects, portable systems can be preferred to fixed ones. Transferring the measuring system to the measured object place is often more practical than the viceversa [1]. This paper analyzes the Mobile Spatial coordinate Measuring System (MScMS), which has been developed at the industrial metrology and quality engineering laboratory of DISPEA – Politeicodi Torino [6]. MScMS is a wirelesssensorwork based system, designed to perform dimensional measurements ofmedium–largesize objects(for example, longerons of railway vehicles, airplane wings, fuselages,etc.). These objects can hardly be measured by traditional coordinatemeasurement systems, such as, for example, Coordinate Measurement Machines (CMMs) because of their limited working volume [7,1]. MScMS working principle is very similar to that of wellknown NAVSTAR GPS (NAVigation Satellite Timing And Ranging Global Positioning System) [8]. The main difference is that MScMS is based on ultrasound (US) technology to evaluate spatial distances, instead of radiofrequency (RF).MScMSis easily adaptable to different measuring environments and does not require plex procedures for installation, startup or calibration [6]. The aim of this paper is to describe the online diagnostics tools implemented in the system in order to continuously monitor measurement reliability. 2. The concept of “reliability of a measurement” If we refer to the field of CMMs, the concept of “online metrological performance verification” is strictly related to the notion of “online selfdiagnostics” [5,9]. In a same sense, this approach is “plementary” to that of uncertainty evaluation [10–15]. In general, the online measurement verification is a guarantee for the preservation of a measurement system characteristics (including accuracy, repeatability, and reproducibility) [16,17]. The effect of a measuring system degradation is the production of “nonreliable measurements”. In general, we can define the concept of “reliability of a measurement” as follows. 3. MScMS technological and operating features MScMS prototype is made up of three main ponents (see Fig. 1) [6]: a constellation (work) of wireless devices (Crickets), opportunely arranged around the working area。 2021. ISBN: 9783540732112.