1. A method of transforming an input stratigraphic grid SGrid which represents a region including one or more geological discontinuities, the method comprising: for at least one target cell that is local to one or more geological discontinuities, the to target cell being selected from the group consisting of: i) a divided cell that is divided by one or more of the geological-discontinuities; and ii) a bordering cell that borders one or more the geological-discontinuities and/or one or more of the divided cells, transforming the target cell by displacing at least one target vertex of the target cell of the input SGrid in a selected direction that: i) is selected to approximate a local tangent of the reference horizon; and ii) is oriented from the target vertex to a representative manifold representing one of the geological discontinuities and/or an intersection between two or more of the geological discontinuities, wherein a magnitude of a displacement by which the target vertex is moved is determined according to a non Euclidian distance between the target vertex of the target cell of the input SGrid and the representative manifold.