CHARTING TWO FOR ONE

摘要

Someone asked me about a note on the ILS Z or LOC Z Rwy 23 at Wal-terboro, SC (KRBW). The note says: "GPS and DME required." (Emphasis added.) How can that be? GPS can be used in lieu of DME, but it can't be a typo because it would just say "DME required." The note is correct as written—and an IFR GPS alone is fine. Now follow me down a logical rabbit hole to understand why, as well as see how GPS and digital tech in general are changing how we fly IFR.