Most GNSS modules out there, designed for recreational use in everyday consumer devices, are GNSS-L1 modules. However, they do not necessarily offer the characteristics needed to establish the precise position of an object on the territory with an accuracy of just a few centimetres.
In many cases, the positions do not always fall at the right place when they are integrated into geographical information systems (GIS). Unfortunately, it is often at this stage that we call on a specialist! The key is in the reference system, also known as datum.