GPS coverage is fundamental for many services and safety reasons, yet the signal cannot always reach some confined areas. We all know the difficulties in receiving phone coverage in underground metro systems; this may be an inconvenience to the general public, but to emergency services personnel the operation of vital communications and other equipment in underground locations can be a matter of life or death. As far as communications are concerned, these metro systems will have leaky feeder and other systems in place to make sure there are adequate communications underground, but what about the location of personnel?  GPS and other GNSS signals are very weak and so there is no chance that standard location technologies can be used in underground emergencies. Until now!

It is not hard to imagine a situation where an incident means that emergency services personnel are trying to save lives with zero visibility in a chaotic atmosphere.  This novel technique which is being used throughout the Stockholm Metro, can locate individuals and teams to support them in this fast-changing critical situation; allowing them to be directed to where help is needed most; perhaps making the difference for both their own safety and the safety of those they are there to help.