A method of locating a moving element by determining a reference position and at least one overall protection limit from data from a group of satellites in a constellation of satellites, the overall protection limit calculation comprising the step of calculating protection limits as a function of probabilities for the absence of failure in the constellation of satellites, and of failure in the constellation of satellites, the method comprising the steps of: • from data from the group of satellites, selecting data from a subgroup comprising at least five satellites; • calculating a main position from the data from the group of satellites; • calculating secondary positions from the data from the subgroup of satellites by excluding data from one of the satellites when calculating each secondary position; • calculating protection limits corresponding to the main and secondary positions while distinguishing whether the failure in the constellation does or does not affect the satellites taken into consideration; and • calculating the overall protection limit from the reference position, the main position, the secondary positions, and the protection limits corresponding to the main and secondary positions; • for failure of a data-supplying satellite of the group but not of the subgroup, the corresponding protection limit is calculated on one of the secondary positions; • for failure of one data-supplying satellite of the subgroup, a corresponding protection limit is calculated on each secondary position; • for failure of two data-providing satellites of the group but not of the subgroup, the protection limit is calculated on one of the secondary positions; and • for failure of a data-supplying satellite of the group but not of the subgroup, and of a data-supplying satellite of the subgroup, a corresponding protection limit is calculated on each secondary position; • failure of two data-supplying satellites of the subgroup is made negligible. • from data from the group of satellites, selecting data from a subgroup comprising at least five satellites; • calculating a main position from the data from the group of satellites; • calculating secondary positions from the data from the subgroup of satellites by excluding data from one of the satellites when calculating each secondary position; • calculating protection limits corresponding to the main and secondary positions while distinguishing whether the failure in the constellation does or does not affect the satellites taken into consideration; and • calculating the overall protection limit from the reference position, the main position, the secondary positions, and the protection limits corresponding to the main and secondary positions; • for failure of a data-supplying satellite of the group but not of the subgroup, the corresponding protection limit is calculated on one of the secondary positions; • for failure of one data-supplying satellite of the subgroup, a corresponding protection limit is calculated on each secondary position; • for failure of two data-providing satellites of the group but not of the subgroup, the protection limit is calculated on one of the secondary positions; and • for failure of a data-supplying satellite of the group but not of the subgroup, and of a data-supplying satellite of the subgroup, a corresponding protection limit is calculated on each secondary position; • failure of two data-supplying satellites of the subgroup is made negligible.