Abstract : The SPIRAL2 project located at the Grand Accélérateur National d'Ions Lourds (GANIL facility - Caen, France) is now under construction. This project aims at delivering rare (radioactive) isotope beams with intensities not yet available with presently running machines. An important aspect of this project is that it is foreseen to deliver up to five different beams in parallel to the users. This paper is focused mainly on the preliminary geodetic network for the SPIRAL2 process installation. The positioning of the process and by extension of the buildings is subject to an important constraint due to future connection of the radioactive beam line to the existing accelerator complex. To reach the required accelerator performances, a geodetic surface network made up of concrete monuments around the construction is linked to the local network of the existing accelerator . The surface network has been transferred to the slab of the accelerator tunnel at -2 level (-9.50 m) in order to define the underground reference network for the process setup. Final goal of the geodetic network is to allow the alignment of the process accelerator components      according to design within required tolerance. Various tolerances objectives will be given.