A method for determination of a radio coverage and a method for positional determination of a mobile terminal in a multi-cellular mobile radio system in which the actual received field strength for several or all base stations is measured at a number of measuring points in differing locations. The measured values for the actual received field strengths are entered in a databank as actual local values. Interpolated values are calculated from the actual received field strengths for virtual measuring points lying between the measuring points and the base stations and entered in the databank. Substitute values for the received field strengths are calculated for geographical positions at which neither measured nor interpolated values for the received field strengths are available, the substitute values being calculated from the relevant transmitter power, the distance from the relevant base station to said geographical point and a propagation model and entered in the databank.