## 1 Introduction  
Since the 1970s, the evolution of electronic and computer technology, with the increasing miniaturisation of components, has influenced the construction of surveying instruments and techniques, and, on the other hand, scientific software developments have provided new surveying methodologies taking advantage of automatic calculation tools. As a consequence, geomatics surveying methodologies have undergone an unexpected development. In a few decades, for topographic surveying, we have witnessed a transition from optical-mechanical instruments, such as theodolites and tilting levels (associated with meta-grad rods) [1], to integrated electronic theodolites and Total Stations, able to measure both angles and distances, as well as perform calculations, with the possibility of remote monitoring. In the 1990s, the development of a _Global Positioning System_ (GPS), an innovative integrated US system that uses, for the first time in modern history, a constellation of artificial satellites for topographic and geodetic surveying, was a true innovation in the field of geomatics. This system, originally made for military purposes of assisting navigation, has expanded its applications and, by enabling the determination of the position of points on the earth's surface with sufficient accuracy for geodetic surveys, has attracted the interest of topographers, who have contributed to developing new positioning solutions. As a further development of satellite navigation systems, the _Global Navigation Satellite System_ (GNSS) was simplified to set up suitable infrastructures for wide-ranging Earthmonitoring for scientists all over the world. As widely known, four satellite navigation systems will be fully operational in 2023, e.g., the American Navstar GPS [2], the European Galileo system [3], the Russian GLONASS system [4], and last but not least, the Chinese BeiDou Navigation Satellite System (BDS) [5]. In the next few years, other three GNSS systems will be available: those defined as Regional Navigation Satellite Systems (RNSS), including the Japanese Quasi-Zenith Satellite System (QZSS) [6], the Regional South Korean Positioning System (KPS) [7], and the Indian Regional Navigation Satellite System IRNSS/NavIC [8]. The large amount of data provided by GNSS systems contributed to the development of hardware and software such as those of Continuously Operating Reference Stations (CORS), which allows research bodies and technicians to acquire free data at global, national, and regional scales. Moreover, according to the upcoming CORS upgrades to four constellations currently operational (GPS, Galileo, GLONASS, and Beidou), these systems can provide enormous full-scale potential for both scientific and technical augmentations [9]. According to [PERSON] et al. [10], CORS are crucial in the creation, characterization, and functionality of the National Spatial Reference System (NSRS). Nations' future positioning-related endeavours rely on the correct application of CORS technology. Consequently, the national geodetic survey (NGS) is tasked with ensuring that the national CORS system is resilient, sustainable, and capable of catering to the diverse needs of the geospatial user community. Site monumentation is a critical component of CORS, requiring both significant positional stability and a minimal environmental impact on GNSS signals. The deployment of the national CORS network necessitates collaboration among numerous organizations. Hence, monument materials should be easily obtainable, installation procedures should be uncomplicated, and overall costs should be economical. The importance of CORS is not only related to geodetic and topographic applications.