A satellite terminal designed to be installed on board a train and configured to: • store georeferencing data of a railway route of the train; • receive navigation signals from satellites belonging to one or more satellite navigation systems; • extract from the received navigation signals positioning data corresponding to the satellites that have transmitted said navigation signals; and • determine, on the basis of the stored georeferencing data and of the received navigation signals, a position of the train along the railway route and an integrity level associated with said determined position; characterized by being further configured to: • if said satellite terminal receives navigation signals from only two satellites, determine the position of the train along the railway route by computing a train's position bound to the railway route on the basis of the stored georeferencing data and of the positioning data corresponding to said two satellites; and, • if said satellite terminal receives navigation signals from three or more satellites, - compute, for each set of three satellites from which navigation signals are received, a corresponding train's position bound to the railway route on the basis of the stored georeferencing data and of the positioning data corresponding to said three satellites, and a corresponding level of protection on the basis of said corresponding train's position bound to the railway route and of the positioning data corresponding to said three satellites, wherein said corresponding level of protection is indicative of a maximum error associated with said corresponding train's position bound to the railway route, - select a set of three satellites according to a selection criterion based at least on the computed levels of protection, and - determine the position of the train along the railway route and the integrity level associated with said position on the basis, respectively, of the train's position bound to the railway route and of the level of protection computed for the selected set of three satellites. • store georeferencing data of a railway route of the train; • receive navigation signals from satellites belonging to one or more satellite navigation systems; • extract from the received navigation signals positioning data corresponding to the satellites that have transmitted said navigation signals; and • determine, on the basis of the stored georeferencing data and of the received navigation signals, a position of the train along the railway route and an integrity level associated with said determined position; • if said satellite terminal receives navigation signals from only two satellites, determine the position of the train along the railway route by computing a train's position bound to the railway route on the basis of the stored georeferencing data and of the positioning data corresponding to said two satellites; and, • if said satellite terminal receives navigation signals from three or more satellites, - compute, for each set of three satellites from which navigation signals are received, a corresponding train's position bound to the railway route on the basis of the stored georeferencing data and of the positioning data corresponding to said three satellites, and a corresponding level of protection on the basis of said corresponding train's position bound to the railway route and of the positioning data corresponding to said three satellites, wherein said corresponding level of protection is indicative of a maximum error associated with said corresponding train's position bound to the railway route, - select a set of three satellites according to a selection criterion based at least on the computed levels of protection, and - determine the position of the train along the railway route and the integrity level associated with said position on the basis, respectively, of the train's position bound to the railway route and of the level of protection computed for the selected set of three satellites. - compute, for each set of three satellites from which navigation signals are received, a corresponding train's position bound to the railway route on the basis of the stored georeferencing data and of the positioning data corresponding to said three satellites, and a corresponding level of protection on the basis of said corresponding train's position bound to the railway route and of the positioning data corresponding to said three satellites, wherein said corresponding level of protection is indicative of a maximum error associated with said corresponding train's position bound to the railway route, - select a set of three satellites according to a selection criterion based at least on the computed levels of protection, and - determine the position of the train along the railway route and the integrity level associated with said position on the basis, respectively, of the train's position bound to the railway route and of the level of protection computed for the selected set of three satellites.