How do VOR and DME work together for navigation?

VOR (VHF Omnidirectional Range) provides bearing to/from a ground station; DME (Distance Measuring Equipment) provides distance (slant range). VOR operation: Transmits 30 Hz variable signal rotating in azimuth plus reference signal; aircraft receiver compares phase difference to determine bearing. DME operation: Aircraft transmits interrogation pulses; ground station replies; aircraft measures round-trip time to calculate distance. Together they provide rho-theta position fix. Limitations: VOR only provides bearing (2D), DME is slant range (not ground distance), and Line-of-sight range. VOR accuracy ~2 degrees, DME ~0.2 nm. Being replaced by GPS-based navigation but remains backup. TACAN provides military equivalent with bearing and range.