Which of the following helps pilots to manually track their position relative to navigational beacons?

Navigational beacons play a crucial role in helping pilots determine their location relative to the airspace they are navigating. Among the choices provided, a Non-Directional Beacon (NDB) is specifically designed for this purpose. An NDB transmits a continuous radio signal that pilots can receive using their aircraft's Automatic Direction Finder (ADF) system. By tuning into the NDB frequency, pilots can effectively track their position by identifying the direction of the signal, which is essential for navigation, especially in adverse weather conditions or when visual landmarks are not available.

While other options like GPS offer highly accurate position tracking and navigation capabilities, they are not focused on the manual tracking aspect utilizing beacons. ASR (Airport Surveillance Radar) and VORTAC (a combination of VOR and TACAN) serve different functions, such as providing radar information and combining navigation methods for specific uses. However, the straightforward nature of NDBs in providing directional guidance through ground-based signals makes them the most appropriate choice for manually tracking position relative to navigational beacons.