Abstract
Twenty three centuries ago, Eratosthenes estimated the circumference of the earth, with an error of less than 10%, measuring a surface distance based on camel traveling time. At the end of the 19th century, astronomers were measuring φ and λ with an accuracy of 1 arcsec which is equivalent to 30 meters. Current day Global Navigational Satellite Systems (GNSS) like GPS, Galileo, GLONASS, have reached accuracies better than 1mm in 3D, including the height above the mean sea level. Repeated positioning estimations reveal the 3D displacements, due to complex tectonic motions. Therefore, from the era of determining φ,λ at epoch t, we have reached today a 13-component group which should be assigned to any point: X,Y,Z,σX,σY,σΖ,vX,vY,vZ,σvX,σvY,σvZ, at a selected epoch t. Many international or regional agencies (like EUREF/EPN) and a number of national mapping and cadastral agencies (civil, military, public or private) operate CORS (continuously operated reference stations), like the Hellenic HEPOS providing high accuracy positional services to the general public. In areas of significant tectonic motion, these networks offer valuable geodata to all sciences, under a unique scientific umbrella since the end of 2017. GIS, cartography, cadastral, navigation, construction engineering, as-built databases, transportation, internet of things, and most interdisciplinary applications, have a lot to benefit from cheap and accurate satellite positioning.