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GPS repeaters improve incident response times from underground police garage

GPS repeater system installed in multi-storey underground police garage ensures vehicle navigation systems never lose GPS lock

The challenge:

Incident and Field Command Systems in police cars parked in a garage extending five levels below ground were experiencing a complete loss of GPS satellite signal.

GPS repeater system in underground police car park

As far as the Command and Control Centre was concerned, each vehicle was “off grid” as soon as it entered the building: location unknown.

More importantly; upon exit from the garage the system in each car could take up to 15 minutes to re-start and regain GPS fix.  Vehicles often had to park up by the side of the road during the satellite acquisition delay before being able to plot a route to an incident.

The solution:

A custom-designed GPS repeater system was installed to provide a live signal throughout the underground garage.

The benefits are many:

  • Vehicles have sky-view at all times while indoors
  • Incident and Command Systems continue to report accurate and up-to-date positional updates.
  • No satellite acquisition delay upon exit.
  • On-board navigation systems now able to plot a route to an incident before exiting the building; location of assets known at all times whether indoors or outdoors.

Equipment in use:

  • 1 x outdoor antenna
  • 6 x splitter 1:5 (S)
  • 4 x amplifier/splitter (A/S)
  • 100m LMR400 trunk cable
  • 4-500m coax feeder cables to repeaters
  • 32 GPS repeaters (R)


The navigation system in a police car ascertains its location from GPS satellite signals.  Periodically the system sends a short message to the regional centre so that controllers can see its location on a command and control screeen.

When the vehicle enters the car park it loses sky view and can not receive GPS signals.

The vehicle’s navigation system continues to transmit location data to the command centre, but it will now give the coordinates of the last known place where it had sky-view – just before it entered the building.

At the beginning of an incident, details are sent to the vehicle’s on-board computer, including, of course, the location of the incident.

Ordinarily, if outdoors, the vehicle immediately plots a route from its current location to the incident location.

When the vehicle reaches the exit ramp of the garage, it regains sky view but has to wait for signals from the satellites to download to get a new positional fix.

The time this takes varies from 5 to 15 minutes; the situation is often worse in a city due to the “canyoning” effect of being in a street where sky view is hindered by tall buildings.

While this download is taking place, police vehicles were having to wait by the side of the road instead of proceeding to the incident.

The GPS repeater system ensures that vehicles never lose sky view and do not experience an excruciating delay when exiting the garage: satellite acquisition delay is no longer a problem.

Applications for GPS repeaters in the emergency services environment

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