Which instrument measures slant range distance to an object?

The instrument that measures slant range distance to an object is the Distance Measuring Equipment (DME). DME operates by calculating the distance between the aircraft and a ground station by measuring the time it takes for a signal to traverse from the aircraft to the station and back. This distance is indicated in nautical miles and is crucial for pilots to determine their position relative to the facility or to navigate efficiently, especially during approaches and departures.

Other instruments like the altimeter are used primarily for measuring altitude, the VOR (VHF Omnidirectional Range) serves to provide directional guidance from a ground station, and the heading indicator is used to show the aircraft's current heading. These instruments play important roles in navigation and flight safety, but they do not measure slant range distance like the DME does.