An automatic method developed for direct access to the virtual heights at chosen range of ionospheric plasma frequencies (digisonde DPS-4, usual cadence is four ionograms per hour) allows us to study the vertical variability of ionospheric layers (e.g., study of gravity or planetary waves), or to give additional information about the type of particular layer for the purpose of Continuous Doppler measurement at stable frequency 3.59 MHz. This method gives us as well rapid overview of ionospheric variability at different plasma frequencies for choosing of time interval of further interest using original digisonde data.