Measurements play a crucial role in modern science, but without them everyday life is unthinkable. For example, without measurements, it is impossible to know what is near us and what is far away. If we make a list of all the measurements that we take during the day, we will be surprised at how long it will be. Over its history, humanity has developed various measurement methods. With their help, we were able to determine the size of our planet, the length of interstellar space and even measure time. This issue will discuss the mathematical methods on which astronomical, geodetic, calendar and metrological measurements are built.