VOR radials and DME can also be used for position fixing. This is done by tuning in two VOR stations and obtaining centered-From CDI readings from each. Plot the two radials on a chart, and your location is where the lines cross. ILSs, localizers, SDFs, and LDAs also operate in the VHF frequency spectrum and provide similar left-right course guidance cues. Tracking with these navaids means making much smaller heading corrections.
ILSs give both lateral and vertical guidance.
NDBs are stations that put out signals in all directions. They operate in the 212 to 415 kHz frequency range. To fly to a station, turn the airplane so as to put the ADF needle on the nose, and fly on. To fly away, turn and put the needle on the airplane's tail. While simple in theory, NDB navigation strikes fear into the hearts of the best pilots because intercepting and tracking a selected NDB bearing can be a daunting task.