Ground-directed bombing (GDB) is a military tactic for airstrikes by ground-attack aircraft, strategic bombers, and other equipped air vehicles under command guidance from aviation ground support equipment and/or ground personnel (e.g., ground observers). Often used in poor weather and at night (75% of all Vietnam War bombings "were done with GDB"), the tactic was superseded by an airborne computer predicting unguided bomb impact from data provided by precision avionics (e.g., GPS, GPS/INS, etc.) Equipment for radar GDB generally included a combination ground radar/computer/communication system ("Q" system) and aircraft avionics for processing radioed commands.