1. Method for synthetic three-dimensional conformal representation of a terrain, said method being used in a piloting and navigation assistance system of an aircraft, said assistance system comprising at least a navigation system, a cartographic database, an electronic calculator, and a display system allowing the superimposition of synthetic images on the exterior, wherein said method comprises: calculation for a determined position of the vehicle, of the terrain perceptible through the display system; selection of a part of the said terrain as a function of a distance or of an altitude or of a range of altitudes; calculation of a three-dimensional conformal cartographic representation of the said selected part of the terrain; and display of the said cartographic representation by the display system.