Editing Missile guidance (section)

===Terrestrial guidance===
{{Main|TERCOM|TERCOM#DSMAC}}
[[Tercom|TERCOM]], for "terrain contour matching", uses altitude maps of the strip of land from the launch site to the target, and compares them with information from a [[radar altimeter]] on board. More sophisticated TERCOM systems allow the missile to fly a complex route over a full 3D map, instead of flying directly to the target. TERCOM is the typical system for [[cruise missile]] guidance, but is being supplanted by [[GPS]] systems and by [[DSMAC]], digital scene-matching area correlator, which employs a camera to view an area of land, digitizes the view, and compares it to stored scenes in an onboard computer to guide the missile to its target.

DSMAC is reputed to be so lacking in robustness that destruction of prominent buildings marked in the system's internal map (such as by a preceding cruise missile) upsets its navigation.<ref name="zarc"/>