A study was conducted to test the effect on airport surface situational awareness of CPS derived position information depicted on a prototypical electronic taxi chart display. The effect of position error and position uncertainty symbology were also tested. Situational awareness was assessed by asking 12 airline pilots a series of probe questions about their Location on the airport surface. The pilots used static 'snapshot' images of a north-up electronic taxi chart as well as a supporting out-the-window view and an aircraft heading display to answer the situational awareness probe questions. Four levels of GPS position error were tested ranging from 4.5 to 90 meters. Two types of position uncertainty symbology were also tested. The variable radius uncertainty circle displayed an estimate of the current GPS position accuracy white the constant radius uncertainty circle displayed a worst-case system accuracy of 100 meters. Situational awareness, as indicated by probe question response accuracy, increased when aircraft position information was displayed on the electronic taxi chart. in addition, response time was also found to improve with the presence of aircraft position information. Response accuracy improved as position error decreased from 90 to 22.5 meters and stayed relatively constant from the 22.5 to 4.5 meter case. Pilots were faster at responding to the probe questions with the variable radius uncertainty symbology. in addition, pilots subjectivity preferred the variable radius uncertainty circle.