A technique to generate global maps of ionospheric parameters on an hourly scale is presented. The technique is based on the updating of predicted monthly median maps of ionospheric parameters with hourly observations. The updating procedure is accomplished by computing the differences between the predicted medians and the hourly values of ionospheric parameters that are observed at specific locations on the globe. These differences are extended to areas where data are not available by employing weighting factors that are derived from correlation coefficients determined from past observations. By applying the present technique to observations of the critical frequency of the F2 region, maps representing the daily-hourly structure of the F2 region can be obtained that have accuracies commensurate with the observations used to update the median maps.