This radar technique helps engineers look for cables and pipes that are just a few metres underground but, for security forces looking for tunnels that can be much deeper, it is ineffective.

• 这种雷达技术可以帮助工程师们寻找地下的电缆和管道，它们通常只有几米深，但是安全保卫部队来寻找这些隧道可能会认为更深一些，效率是不高的。