An automated method for the non-destructive testing of a woven preform for the manufacture of a turbine engine part and including a plurality of first marker threads intertwined with second marker threads, the first and second threads having light-reflecting properties that are different from those of the threads of the preform and being woven with the threads of the preform so as to form a surface grid on a given area of the preform. The method includes determining, with a plurality of consecutive steps, the spatial coordinates of the intersections between the first and second marker threads.