This Special Issue is devoted to recent developments in instrumentation and measurement techniques applied to the marine field. ¶The sea is the medium that has allowed people to travel from one continent to another using vessels, even today despite the use of aircraft. It has also been acting as a great reservoir and source of food for all living beings. However, for many generations, it served as a landfill for depositing conventional and nuclear wastes, especially in its deep seabeds, and we are assisting in a race to exploit minerals and resources, different from foods, encompassed in it. Its health is a great challenge for the survival of all humanity since it is one of the most important environmental components targeted by global warming. ¶ As everyone may know, measuring is a step that generates substantial knowledge about a phenomenon or an asset, which is the basis for proposing correct solutions and making proper decisions. However, measurements in the sea environment pose unique difficulties and opportunities, which is made clear from the research results presented in this Special Issue.

This book is devoted to recent developments of instrumentation and measurement techniques applied to the aerospace field. It includes 23 selected papers from the 2019 IEEE International Workshop on Metrology for AeroSpace. Measurements are essential for obtaining a deeper knowledge of a phenomenon or an asset, as well as for making proper decisions and proposing new and efficient solutions, and this is especially true in environments as complex as aerospace. The research contributions included in the book can raise the interest of a wide group of researchers, operators and decision-makers from metrology and aerospace fields by presenting the most innovative solutions in this field from the scientific and technological points of view.

This book constitutes the refereed proceedings of the First International Workshop in memory of Prof. Raffaele Santamaria on R3 in Geomatics: Research, Results and Review, R3GEO 2019, held in Naples, Italy*, in October 2019. The 27 full papers along with the 2 short papers presented were carefully reviewed and selected from 39 submissions. The papers are organized in topical sections on: GNSS and geodesy; photogrammetry and laser scanning; GIS and remote sensing.

Syngnathids are a large and diverse group of fishes, including seahorses, pipefishes, seadragons and pipehorses, These iconic and vulnerable fishes are distributed worldwide in warm temperate to tropical environments, usually in coastal shallow water. Most species are marine and strongly associated with vegetal communities or coral reefs, which provide shelter and the necessary dietary resources. Syngnathids have a unique reproductive mode with parental care, diverse brooding structures and other special characteristics that make them highly vulnerable. These iconic fishes are facing several threats, namely environmental disturbances and habitat regression. However, many of their biological, ecological and physiological characteristics have been poorly investigated and limited to a few species. Despite their vulnerability, to date, a large number of species are listed as Data Deficient (meaning they could potentially be threatened) by IUCN due to inadequate or insufficient information, mainly on distribution and/or population status. Due to the progressive regression of wild populations, long-term monitoring programs are necessary to evaluate population dynamics, fisheries, and habitat quality. On the other hand, these charismatic fishes, especially seahorses, are excellent flagship species for marine biodiversity conservation. Unfortunately, illegal harvesting and traffic of seahorses and other syngnathids is a fact, despite CITES controls. Hence, the development of new tools for fish traceability and updated policies are also necessary to reduce the threats to these fishes.

Industry 4.0 refers to fourth generation of industrial activity characterized by smart systems and internet-based solutions. This book describes the fourth revolution based on instrumented, interconnected and intelligent assets. The different book chapters provide a perspective on technologies and methodologies developed and deployed leading to this concept. With an aim to increase performance, productivity and flexibility, major application area of maintenance through smart system has been discussed in detail. Applicability of 4.0 in transportation, energy and infrastructure is explored, with effects on technology, organisation and operations from a systems perspective.