How do cruise missiles use map-matching systems for long-range navigation?

Cruise missiles utilize a navigation technique known as Tercom (terrain contour matching) to achieve accurate long-range guidance. Because inertial navigation systems can accumulate inaccuracies over the extended flight times required for strategic missions, they require periodic updates to maintain precision.12

The map-matching process functions by comparing the terrain over which the missile is flying to a series of digital contour maps stored within the system’s computerized memory. By continuously matching the actual ground profile against these pre-loaded maps, the missile can correct its course and navigate toward its target with high accuracy. This self-contained electronic system allows the missile to maintain its path without relying on external radio guidance, which is subject to range limitations and potential interference.12