A method includes: taking a topographical survey of a plurality of geographical points near a structure to be built, the position of each point being determined in an absolute frame of reference XYZ; installing a plurality of reflectors, each reflector being placed at a geographical point of the topographical survey; measuring distances between reflectors and optical devices, using at least three optical devices fixed on a moving arm of an insertion device that bears an element to be inserted; computing, by trilateration, the absolute position of the arm of the insertion device from the measured distances and from the known position of each optical reflector; and moving the arm of the insertion device based on the computed absolute position, so as to bring the element to be inserted into a predetermined implantation position.