A method of determining the location of a mobile terminal in a given area, comprising the step of including said mobile terminal both in a satellite-based positioning system and in a cellular communications system, whereby said mobile terminal is adapted to receive satellite signals from said satellite-based system and to be covered by at least one cell of said cellular communication system, the method including the step of providing a geographical data base including data base items associating to a given set of bi-dimensional positioning coordinates (xi, yi)of said mobile terminal in said area corresponding values for said altitude coordinate (zi) the method further including the step of determining at least approximately the coordinates (x, y, z) of said mobile terminal based both on satellite signals received from said satellite-based system and information related to said cellular communication system, wherein said coordinates include an altitude coordinate (z) and a bi-dimensional coordinate (x,y), and wherein said step of determining at least approximately comprises the following phases a), b): a) estimating bi-dimensional coordinates (x, y) and altitude coordinate (z) on the basis of said information related to said cellular communication system, b) repeating at least once the following sequence of operations b1), b2), b3): b1) deriving a search area for said coordinates (x, y, z) based on said satellite signals and said altitude coordinate (z), b2) obtaining a new estimate of bi-dimensional coordinates (x, y) within said search area on the basis of location measurements of said cellular communication system; b3) obtaining a new estimate of altitude coordinate (z) on the basis of said new estimated bi-dimensional coordinates (x, y), by accessing said geographical data base characterized in that said operation b1) of deriving a search area comprises deriving a hyperbolic sector by using said satellite signals and said altitude coordinate. a) estimating bi-dimensional coordinates (x, y) and altitude coordinate (z) on the basis of said information related to said cellular communication system, b) repeating at least once the following sequence of operations b1), b2), b3): b1) deriving a search area for said coordinates (x, y, z) based on said satellite signals and said altitude coordinate (z), b2) obtaining a new estimate of bi-dimensional coordinates (x, y) within said search area on the basis of location measurements of said cellular communication system; b3) obtaining a new estimate of altitude coordinate (z) on the basis of said new estimated bi-dimensional coordinates (x, y), by accessing said geographical data base characterized in that said operation b1) of deriving a search area comprises deriving a hyperbolic sector by using said satellite signals and said altitude coordinate. b1) deriving a search area for said coordinates (x, y, z) based on said satellite signals and said altitude coordinate (z), b2) obtaining a new estimate of bi-dimensional coordinates (x, y) within said search area on the basis of location measurements of said cellular communication system; b3) obtaining a new estimate of altitude coordinate (z) on the basis of said new estimated bi-dimensional coordinates (x, y), by accessing said geographical data base characterized in that said operation b1) of deriving a search area comprises deriving a hyperbolic sector by using said satellite signals and said altitude coordinate.