A method for determining at least one geometric parameter of a railroad track with two rows of rails, in which: - a vehicle carrying an inertial unit, a piece of equipment for measuring at least one relative orientation component of at least one of the two rows of rails with respect to the inertial unit, and one or more odometers is made to travel over the railroad track, - successive values of at least one absolute orientation component of the inertial unit in a geostationary reference frame are determined on the basis of at least signals produced by the inertial unit, - for at least one observed row of rails from the two rows of rails, and preferably for each of the two rows of rails taken as an observed row of rails, i) successive curved-abscissa values of the vehicle on the observed row of rails are determined on the basis of at least signals produced by the odometer(s), ii) successive values of at least one relative orientation component of the observed row of rails with respect to the inertial unit are determined on the basis of at least signals produced by the measuring equipment, iii) successive values of at least one absolute orientation or absolute positioning component of the observed row of rails are calculated on the basis of at least the successive values of the absolute orientation component of the inertial unit and the successive values of the relative orientation component of the observed row of rails with respect to the inertial unit, characterized in that: iv) a function s → G ( s) is constructed which links at least some of the successive curved-abscissa values to concomitant values from the successive values of the absolute orientation or absolute positioning component of the row of rails observed in space, v) a high-pass or band-pass linear filter is applied to the function s → G ( s) so as to construct a filtered function s → F ( s), vi) for a succession of current curved-abscissa values l from the curved-abscissa values, an integral I(l) is estimated, over a given curved-abscissa interval bounded by a reference curved-abscissa value l 0 and by the current curved-abscissa value l, from the filtered function I l = ∫ s = l o s = l F s ds - a vehicle carrying an inertial unit, a piece of equipment for measuring at least one relative orientation component of at least one of the two rows of rails with respect to the inertial unit, and one or more odometers is made to travel over the railroad track, - successive values of at least one absolute orientation component of the inertial unit in a geostationary reference frame are determined on the basis of at least signals produced by the inertial unit, - for at least one observed row of rails from the two rows of rails, and preferably for each of the two rows of rails taken as an observed row of rails, i) successive curved-abscissa values of the vehicle on the observed row of rails are determined on the basis of at least signals produced by the odometer(s), ii) successive values of at least one relative orientation component of the observed row of rails with respect to the inertial unit are determined on the basis of at least signals produced by the measuring equipment, iii) successive values of at least one absolute orientation or absolute positioning component of the observed row of rails are calculated on the basis of at least the successive values of the absolute orientation component of the inertial unit and the successive values of the relative orientation component of the observed row of rails with respect to the inertial unit, i) successive curved-abscissa values of the vehicle on the observed row of rails are determined on the basis of at least signals produced by the odometer(s), ii) successive values of at least one relative orientation component of the observed row of rails with respect to the inertial unit are determined on the basis of at least signals produced by the measuring equipment, iii) successive values of at least one absolute orientation or absolute positioning component of the observed row of rails are calculated on the basis of at least the successive values of the absolute orientation component of the inertial unit and the successive values of the relative orientation component of the observed row of rails with respect to the inertial unit, iv) a function s → G ( s) is constructed which links at least some of the successive curved-abscissa values to concomitant values from the successive values of the absolute orientation or absolute positioning component of the row of rails observed in space, v) a high-pass or band-pass linear filter is applied to the function s → G ( s) so as to construct a filtered function s → F ( s), vi) for a succession of current curved-abscissa values l from the curved-abscissa values, an integral I(l) is estimated, over a given curved-abscissa interval bounded by a reference curved-abscissa value l 0 and by the current curved-abscissa value l, from the filtered function I l = ∫ s = l o s = l F s ds