The increased accuracy allows a TERCOM-equipped missile to fly closer to obstacles and at generally lower altitudes, making it harder to detect by ground radar.
Errors between the two signals drove corrections in the autopilot needed to bring the missile back onto its programmed flight path.
[citation needed] During the cruise portion of the flight to the target, the accuracy of the system has to be enough only to avoid terrain features.
Use of conventional warheads requires further accuracy, which in turn demands additional terminal guidance systems.
[citation needed] The limited data storage and computing systems of the time meant that the entire route had to be pre-planned, including its launch point.
If the missile was launched from an unexpected location or flew too far off-course, it would never fly over the features included in the maps, and would become lost.
The INS system can help, allowing it to fly to the general area of the first patch, but gross errors simply cannot be corrected.
[citation needed] DSMAC was an early form of AI which could guide missiles in real time by using camera inputs to determine location.
The system worked by comparing camera inputs during flight to maps computed from spy satellite images.
Due to its ability to visually identify targets instead of simply attacking estimated coordinates, its accuracy exceeded GPS guided weapons during the first Gulf War.
[1] The massive improvements in memory and processing power from the 1950s, when these scene comparison systems were first invented, to the 1980s, when TERCOM was widely deployed, changed the nature of the problem considerably.
Likewise, the complexity of the live imaging systems has been greatly reduced through the introduction of solid-state technologies like CCDs.
On the other hand, to be ready for a conflict with a technologically advanced adversary, one needs missiles equipped with TAINS and DSMAC.