# Sensors and Measurement Systems for Marine Engineering Applications
###### Abstract  
In recent years, vast developments and applications of sensor technologies have been recorded in various industries, including shipbuilding. Therefore, the employment of novel sensors in marine environments has significantly progressed, as illustrated by some key examples. For example, wireless sensor networks (WSNs) have emerged as an efficient and cost-effective alternative for the real-time monitoring of the marine environment, used for oil spill detection and localization [1], offering significant advantages such as ease of deployment [2]. Optical-fiber-based sensors have attracted considerable attention for environmental applications such as the in situ measurement of seawater salinity [3] and structural health monitoring in marine applications [4; 5] due to their durability under extreme temperature and pressure conditions, high sensitivity, and flexibility. In addition, piezoelectric energy harvesters have been proposed to eliminate batteries from future sensing devices [6; 7], while piezoelectric sensors have already been employed to determine ocean wave height and period, as well as underwater objects [8]. Furthermore, nanofibrous grids utilizing piezoelectric fibers demonstrate high-resolution, self-powered tactile sensing capabilities, suggesting their use in real-time motion tracking and spatial sensing in marine environments [9], whereas monolithic printed sensors pave the way for on-demand, on-site fabrication [10]. These examples underscore the vast technological developments that have been pivotal in addressing the challenges related to marine research and environmental protection.  
Moreover, over the past three decades, the miniaturization of sensors has led to the newly developed field of \"microsensors\"--an emerging field that has grown rapidly, building on the significant advancements of the semiconductor industry. Consequently, the sensors deployed on ships have followed the same trend, taking their role one step further by incorporating semiconductor-based technology into standard marine equipment and measuring systems. Typical types of sensors employed aboard are gas detection sensors, gas/air flow sensors, humidity sensors, temperature/pressure sensors, speed/acceleration sensors, strain sensors, IMUs, etc., which are all essential with regard to vessel safety since the proper operation of all modern vessels relies heavily on the information provided by the onboard measuring devices that quantify critical performance parameters. As a common example, a typical Ro-Ro vessel has four medium-power 4-stroke engines installed onboard, which are required for the operation of the corresponding generator sets [11]. Failure to detect a possible malfunction by the appropriate sensing system in any of the installed engines, even one, can lead to immediate safety compromises, as outlined by the corresponding safety regulations [12], with severe consequences. In addition, modern sensing devices play a vital role in advancing marine technology by enabling the integration of new technologies, such as the Internet of Things (IoT), big data, and cloud computing [13]. These technologies rely heavily on sensing devices for functionality and also contribute to their rapid development.  
This Special Issue encompasses the diversity of nine relevant studies, spanning from the design of novel sensors and energy-harvesting solutions for the maritime industryto advanced engine-monitoring systems. Specifically, it comprises eight articles and one review, which are briefly outlined in the next section. It is important to note that the purpose of this editorial is not to elaborate on each of the papers presented but rather to encourage readers to explore them further.