As the missile approaches its target, the final and most accurate guidance system takes over.

Digital Scene Matching Area Correlation (DSMAC) compares what it can see on the ground with a digital rendition of its target.

This technology is complicated and expensive but has been shown to work.

But it is only as good as the intelligence that underpins it. It will never stop a missile hitting a long-abandoned target building or a civilian shelter if the targeting information is not up to date.