Two complete new chapters have been introduced. The first one, Chapter 16, amplifies the many rich interactions between Geographie Information Systems (GIS) and the Navstar CPS. The words and pietures in this new chapter foeus on the powerful eleetronie mapmaking techniques that rely on Navstar navigation together with the many benefits stemming from the full-eolored "layered" maps now being produeed. Chapter 17, which is also new, deals with Intelligent Vehicle Highway Systems (lVHS). Navstar navigation techniques form the hidden backbone of most of the new electronic teehnologies that are helping to make America's traffic f10w more smoothly. Chapter 17 c10ses with narrative descriptions of three interesting IVHS projects: emergency tow-truck dispatching, optimum ambulance-routing, and the in-car traffie reports now being beamed into family cars cruising along Ameriea's major traffic arteries. Many helpful individuals contributed toward the successful completion of Under- standing the Navstar. My lovely wife, Cyndy, was unquestionably the most beneficial contributor. Her affectionate comments and her broad-ranging support were greatly appreciated. So was her diligent and uncomplaining work in word-process- ing the many drafts of the final manuseript. The artists, Lloyd and lInka Wing and Anthony and Dianne Vega, were also enormously helpful in providing quality figures and tables on schedule. They have become true masters of the Macintosh computer with its many beils and whistles. Preparing a book for publication is a time-consuming, invigorating task. I hope you enjoy reading it as much as I enjoyed putting it together for your use.