Coverage planning and optimization is one of the most crucial tasks for a radio network operator. Efficient coverage optimization requires accurate coverage estimation which relies on geo-located field measurements. These measurements are gathered today during highly expensive drive tests and will be reported in the near future by users equipments thanks to the 3GPP MDT feature (still costly in terms of battery consumption and signaling overhead). In both cases, predicting the coverage on a location where no measurements are available remains a key and challenging task. This paper describes a powerful tool that gives an accurate coverage prediction on the whole area of interest, i.e. a coverage map, by spatially interpolating geo-located measurements using Kriging technique. The paper focuses on the reduction of the computational complexity of the kriging algorithm by applying Fixed Rank Kriging (FRK). The performance evaluation of the FRK algorithm both on simulated measurements and real field measurements shows a good trade-off between prediction efficiency and computational complexity. In order to go a step further towards operational application of the proposed algorithm, a scenario with multiple cells is studied. Simulation results show a good performance in terms of coverage prediction and detection of best serving cell.