Upon his retirement from the U.S. Air Force in 1990, David Diggle returned to his alma mater, Ohio University, beginning a doctoral program in electrical engineering and working as a research associate for the Avionics Engineering Center. His area of expertise became real-time precise positioning using the NAVSTAR Global Positioning System (GPS). He received his Ph.D. in electrical and computer engineering in March 1994 and subsequently joined the staff of the center on a full-time basis as research scientist. For his doctoral research, the Radio Technical Commission for Aeronautics honored him in 1994 with its Jackson Memorial Award, given annually for outstanding contribution to the field of avionics. Dave's work continues to center on the application of GPS positioning to aircraft precision approach and landing systems.

He is a member of the Institute of Navigation, Sigma Xi, and the Eta Kappa Nu and Tau Beta Pi engineering honoraries. In addition, he holds a private pilot certificate completed through Ohio University's aviation program.