The net effect was various alarms and a loss of GPS input to the ship's surface search radar, gyro units and ECDIS, resulting in no GPS data for position fixing, radar over ground speed inputs, gyro speed input and loss of collision avoidance capabilities on the radar display. Fortunately, the vessels were able to safely continue theirvoyage using radar in heads up display, magnetic compass and terrestrial navigation. Approximately six nautical miles later, the vessels' GPS units resumed operation. Although the vessels had back-up systems to allow a safe transit, the consequences could have been severe, warns the Coast Guard. Full content of the alert appears below. Global Navigation Satellite Systems – Trust, But Verify Report Disruptions Immediately Do you know what equipment relies upon the U.S. Global Positioning System (GPS) signal? How would you respond if you lost the signal?