1. Altitude determination method in a cellular communication system comprising the steps of: providing a set of points in a first node in said cellular communication system; said set of points comprising at least three points located at or near a border of a first cell associated with said first node; said at least three points each comprising two coordinates of a horizontal plane and an altitude parameter; transferring a data amount representing said set of points over an interface between said first node and a second node of said cellular communication system; and processing, in said second node, said data amount to obtain an estimated altitude of any first point belonging to said first cell using coordinates of a horizontal plane of said any first point as input arguments.