What does "glide slope" refer to in aviation?

The term "glide slope" specifically refers to an electronic guidance system that provides vertical navigation assistance to pilots during an aircraft's approach to landing. It is part of the Instrument Landing System (ILS) and helps ensure that an aircraft descends at the correct angle toward the runway, typically around three degrees. By utilizing a glide slope, pilots can maintain a safe descent path, which is crucial for successful landings, especially in low visibility conditions.

The other options do not accurately define the concept of glide slope in aviation. For instance, a method for calculating fuel consumption does not relate to vertical navigation, a type of navigation chart typically offers horizontal guidance rather than vertical, and a measure of aircraft speed during descent focuses on the aircraft’s speed rather than its vertical guidance path.