Global Positioning System (GPS) tracking units are devices used to determine and track the precise location of the unit at regular defined intervals. These devices rely on the receipt of microwave signals transmitted from satellites in the Global Navigation Satellite System network that define the satellite trajectory and exact time of signal transmission (1,2). With such information from at least three satellites, the location of the GPS tracking unit can be calculated based on the mathematical principle of trilateration. Active GPS tracking units then send the location information to a server via commercial communication satellites or cellular network. Once the server has received the location information, it can then be displayed against a map backdrop in real time.
GPS tracking units are normally used for asset tracking, vehicle tracking, and personal tracking. In terms of personal tracking, law enforcement uses GPS trackers on suspects free on bail and criminals on parole, and athletes use the devices to quantify distance and speed (3). These devices also have been used by parents to monitor the travel patterns and health risks of their children (4,5), in the care of the elderly or vulnerable who may wander (6,7), and for various other appropriate and nefarious surveillance purposes. More recently, GPS tracking has been increasingly used by those participating in wilderness activities and competitions for spectating and safety purposes (8). In this report, we demonstrate how the requirement to carry a GPS tracking unit during a wilderness ultramarathon enabled a successful rescue of a lost runner that likely would have had an adverse outcome if the runner had not been carrying the GPS tracking unit.
The subject was a middle-aged endurance runner with more than 200 ultramarathon finishes, including several 161-km and 217-km events, and two 72-h timed events in which he had covered 328 to 412 km. He had completed a 161-km ultramarathon 5 d before the start of the race in which this incident occurred. The subject provided permission to publish his case, and reviewed and approved the article before submission.
The race was a 332-km point-to-point ultramarathon in the Cascade Mountains of Washington State. The event began at 9 a.m. on August 11, 2017, with a 105-h limit for completion. The course was mostly trails that were well marked. Each competitor was required to carry a GPS tracking device set to transmit location at least at 10-min intervals. The subject was carrying a GPS tracking device with one-way messaging capability (Spot Gen2 Satellite GPS Messenger, Covington, LA) in a pocket near the top of the left shoulder strap of his pack that was set to transmit location at 10-min intervals. To stay warm during the nights with low temperatures of around 4°C, he was carrying a thin windbreaker and large trash bag.
At approximately 2 p.m. on August 14, the subject’s wife reported to the race medical director (author T.N.) who was at the race finish line that the subject had sent her a help message via the messaging function of his GPS tracking unit (Table). Race officials then noted that the subject’s GPS tracks showed he was off course near the 301-km point at 7:32 a.m. on August 14 (70.5 h into the race) (Fig. 1). The last prior location had been at 286 km more than 6 h earlier at 1:19 a.m. (64.3 h into the race). Four subsequent locations were later received between 1 p.m. and 3:14 p.m. showing minimal movement (Fig. 2). At 3:57 p.m. the subject sent an emergency assistance request message via the messaging function of his GPS tracking unit that was forwarded to the local county dispatch, and the county Fire Chief responded to the race headquarters.
The impression was that the subject was lost but not in need of medical intervention, so two rescuers (author C.L. serving as race support staff, and author C.B. the race director) who could be quickly mobilized were sent to locate and retrieve him. Armed with the last GPS coordinates programed into a handheld GPS unit, cell phone, ham radio, and some food and water, the rescuers departed from the 311-km aid station at 4:54 p.m. running the 10 km to the closest point on the course to the last coordinates. They marked this location and recorded the GPS coordinates, and then bushwhacked through dense forest and down a steep incline. Once reaching the last known coordinates, they circled the area while calling for the runner. Within 10 min, a faint response was heard, and he was found pacing back and forth approximately 190 m below and 500 m off the course. Radio contact was then made with the race medical director, who guided a brief assessment. The subject was noted to be without any obvious serious physical injuries and to have normal speech, but he indicated he had been seeing “gang signs on trees” and “burning piles of cell phones” as he pointed to pinecones on the ground. He still had a small amount of fluids with him. It was learned that, after getting off course, he had lost a GPS navigation unit he had been carrying.
Using the coordinates of the location where the rescuers had left the course, they found their way up the hill to the trail with the runner managing the climb without assistance. They then walked and ran the 10-km to the 311-km aid station, arriving at approximately 8:30 p.m. There the runner took some fluids and nutrition and his apparent visual hallucinations appeared to have resolved. He transiently considered continuing in the competition, but after he was reminded that his wife had been alerted that he had been lost, he decided to drop out of the event. He was subsequently driven to the finish line and was released with his wife after a medical assessment revealed he had no injuries but appeared moderately disoriented and exhausted.
In discussion with the runner 4 wk later, he was able to recall the incident and indicates he recognized at the time that the things he saw were not actually present. He also indicated that he had only slept about 10 min during the competition. He recalls running in circles to stay warm after he had gotten lost. He completed a 330-km ultramarathon that started 5 wk after this event without incident.
This case demonstrates the value of GPS tracking devices during wilderness ultramarathons, which we have previously suggested as a consideration in these events (8). Without the tracking device, this case would most certainly have had a different outcome. Even with the knowledge that this runner was lost, a formal search might not have been able to deploy until the next morning after the runner would have faced another night of low temperatures with minimal clothing to maintain warmth. Furthermore, since the last known location of the runner would have been at the 286-km aid station, a successful rescue would have required a large search area. Delay in rescue also would have resulted from the search area being dense forest and challenging terrain, and because it would likely not have initially focused as far off the course as where he was located. Without the GPS tracking information, the greatest hope for a successful outcome would have been that the runner regained orientation and managed a self-rescue, but the likelihood of that was diminished by the loss of his GPS navigation unit and the impending sunset. Thus, this case provides rationale for organizers of wilderness endurance events to consider mandating GPS tracking and for governing bodies to examine whether or not GPS tracking should be incorporated into medical and safety guidelines.
Since location determination with GPS relies on line-of-sight signal transmission from at least three satellites to the GPS tracking unit, these units are not always completely reliable in some locations. The orientation of the GPS tracking unit on the subject is another factor that will affect its functionality, with optimal orientation of the receiver and transmitter being toward the sky. These issues are evident in Figure 1 showing a number of missed points, which can occur around mountains, dense forests, and canyons. Stray points also can occur, which could cause some confusion. Nevertheless, even with some shortcomings, data from GPS tracking units can provide invaluable information when correctly interpreted, as was evident with the present case. Of course, it should be acknowledged that other potential issues in the use of GPS tracking units as described herein relate to battery life and the associated expense with their use. It is unknown if their use may alter behavior due to a greater sense of security by the user.
Another interesting aspect of this incident relates to the visual experiences the lost runner reported when he was initially located. Visual hallucinations have been previously described in association with ultramarathon participation (9) and marathon volleyball (10), and it is presumed that these are stimulated by the combination of fatigue and sleep deprivation, as it is known that sleep dysfunction contributes to psychotic experiences (11). The runner had been moving for roughly 70 h with essentially no sleep. He also had traveled more than 300 km and was likely not fully recovered from his completion of another ultramarathon only a few days before the start of this race. Whether or not visual hallucinations played a role in his wayfinding errors is not clear. Regardless, the combination of fatigue and sleep deprivation undoubtedly increased the likelihood of poor attention and cognitive performance (9) which contributed to him getting lost. This provides additional rationale for the use of GPS tracking in wilderness events that extend over multiple days.
In conclusion, this case demonstrates how a GPS tracking system can enable the rescue of lost athletes in the wilderness. Given that the outcome of this case could have been tragic without the GPS data, we suggest that wilderness endurance event organizers consider requiring their participants carry a GPS tracking device, especially when the event extends over multiple days, and that they assure a system is in place to monitor for athletes who are off course.
The authors declare no conflict of interest, but note that Candice Burt is the owner of Destination Trail, the company that organizes the race in which this incident occurred, and Todd Nardi is contracted by Destination Trail to serve as medical director.
This material is the result of work supported with resources and the use of facilities at the VA Northern California Health Care System. The contents reported here do not represent the views of the Department of Veterans Affairs or the United States Government.
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