GPS Receivers In Emergency Vehicles

The flight crew of a medevac helicopter has just received a request for a medevac resulting from a serious motor vehicle accident at the intersection of two major state highways. In less than five minutes, the helicopter is airborne with an estimated time of arrival of 12 minutes.

Once aloft, the crew programs the aircraft's navigation computer with the latitude and longitude coordinates of the landing zone fire apparatus' vehicle Global Positioning System (GPS) receiver, passed via the dispatch center. The helicopter flies directly to the landing zone, a field near the accident scene. Within 25 minutes of the request, the patient is en route to a trauma center.

Photo by Bill Green
GPS-equipped units are helping to cut response times.

That scenario already is a reality in some parts of the country. This article is intended to educate members of the fire and rescue service of the value of equipping emergency vehicles with GPS receivers so that whenever a rescue helicopter is needed, the aircraft will quickly and accurately find the landing zone or search location by using vehicle GPS-derived latitude and longitude coordinates.

A language barrier exists between helicopter flight crews and ground emergency response personnel. A flight crew is trained to locate accident scenes, landing zones or search areas by many means, including "dead reckoning," course and heading, roadmaps and charts, crew familiarity and electronic navigation. The most time-saving and most accurate method is navigation in terms of latitude and longitude derived from GPS. Ground personnel locate accident scenes and landing zones by geographic location and street address. It is impossible for the helicopter crew from 1,500 feet above the ground the aircraft's minimum cruise altitude due to Federal Aviation Administration (FAA) regulations and noise abatement rules to read a street address on a mailbox or building. When a flight crew interpolates from a roadmap, an error of one inch can put the aircraft more than 10 miles from the landing zone.

The following actual incident illustrates the language problem between flight crews and ground personnel.

My flight paramedic and I were dispatched to a daytime medevac in Howard County, MD. The patient, a deer hunter, had fallen out of a tree stand about 25 feet above the ground. He had sustained broken ribs, a collapsed lung and a punctured lung. The paramedic and I were unfamiliar with the landing zone. When we were about five minutes from the landing zone, we established radio communications with the landing zone fire apparatus personnel. The latitude and longitude coordinates derived from a roadmap put us within three miles of the landing zone.

As soon as the fire personnel saw the helicopter, they gave me directions to the landing zone. I noted the time when we flew over the roadmap-derived coordinates. It took us seven minutes time taken from the patient's "golden hour" to find the actual landing zone and touch down. It didn't help that the fire engine and ambulance were parked under trees in fall foliage. When you add seven minutes to the ground emergency response time, initial medical evaluation time, helicopter dispatch and flight times, flight paramedic's medical evaluation time and flight time to the trauma center, the "golden hour" can be exceeded easily.

Emergency vehicles equipped with GPS receivers let a helicopter crew and ground personnel speak the same language, resulting in the helicopter responding more quickly by flying directly to the landing zone.

Using roadmaps to provide latitude and longitude coordinates to a helicopter crew provides highly inaccurate information. Vehicles equipped with GPS receivers provide the flight crew with much more accurate landing zone coordinates (within 100 feet), which greatly lessens the helicopter's response time. Also, vehicle GPS receivers will eliminate the confusion associated with finding an unfamiliar landing zone that manifests itself in the form of a radio exchange between the flight crew and landing zone fire personnel in the following form: The helicopter crew asks the fire personnel if they see the helicopter. The fire personnel responses can include, "yes, turn right" or "we are off your left side near a white house." The flight crew members spend valuable time visually searching for the unfamiliar landing zone when they need to be looking for obstacles such as towers, wires and other aircraft.

Although not obvious to the ground personnel, the flight crew may see 20 or 30 white houses off the left side of the helicopter. With trees blocking the ground equipment from the aircraft, it can be difficult for the flight crew to pick out the correct white house. This type of radio exchange is distracting to the flight crew when it is preparing to land the helicopter, one of the most critical and dangerous aspects of the flight.

GPS consists of a constellation of 24 satellites in earth orbit. The system was developed and placed into orbit by the U.S. Air Force. At all times, a minimum of six satellites above the horizon transmit signals that provide highly accurate latitude and longitude coordinates as well as time and elevation information. During the Persian Gulf War, GPS navigation information let U.S. aircraft to drop ordnance with unprecedented accuracy. Since then, the use of GPS navigation information by emergency services agencies as well as civilian companies has skyrocketed.

Thanks to mass production, vehicle GPS receivers are inexpensive, costing from $100 to $450, depending on the features offered. A vehicle GPS receiver should:

  • Have an external antenna to allow quicker acquisition of the satellites.
  • Be rugged and have a vehicle mounting bracket with a power supply cable so that the unit can be powered in the same manner as the vehicle's radios.
  • Be simple to operate.

Most vehicle GPS receivers require only the pushing of the "on" button to be operational. When the satellites are acquired, the display indicates the present position in latitude and longitude of the vehicle, whether moving or stationary.

When a fire apparatus or ambulance equipped with a vehicle GPS receiver responds to an incident, the driver needs only to turn on the GPS receiver when leaving the station. The GPS receiver will acquire the satellites within two minutes and continually display the position of the fire apparatus or ambulance in latitude and longitude as it travels to the scene. When the vehicle stops at the landing zone, the driver contacts the helicopter crew and passes the location of the landing zone in latitude and longitude "North 3838. 45 West 7721. 35." The flight crew programs the landing zone coordinates into the helicopter navigation computer and the site is found quickly.

Initial and recurrent training is important with any new piece of equipment. If your company installs a vehicle GPS receiver, contact a flight crew from a helicopter that serves your area and schedule a drill. A drill with one helicopter and several fire companies would be best. It's suggested that the drill consist of actual dispatches of the helicopter with vehicle-derived GPS latitude and longitude coordinates transmitted by the fire personnel to the helicopter, with the helicopter then flying over the vehicle's precise location.

David C. Delisio is a civilian pilot flying the SA 365 Dauphin 2 helicopter for the Aviation Division of the Maryland State Police, assigned to Trooper 3 in Frederick. He has been flying helicopters for 18 years and has extensive experience flying medevac and search-and-rescue helicopters in the U.S. Air Force, U.S. Coast Guard, U.S. Army National Guard and Maryland State Police.