NSR Team Leader, Tim Jones, was on CBC One today – MP3 available soon at this link – http://www.cbc.ca/radio/podcasts/british-columbia/bc-almanac-1/ and one of the callers was asking about using a cell phone’s GPS to provide coordinates.
In our experience these coordinates are not always accurate, so we use a combination of tools to try and determine subject location. One of these tools is to get up in the helicopter and speak to the subject on the phone. The subject can then describe where they are in relation to the helicopter and we then have a much greater chance of finding the actual location of the subject. A number of times we have received coordinates that are inaccurate. So we must verify with descriptions of where the subject went and hopefully a confirmation of “Yes, the helicopter is directly overhead.”
This obviously only works if weather permits flying and it is daylight. So calling early can make a huge difference of a few hour rescue vs. a day long search. As well, battery life is key – so call 911 immediately if you are in trouble and don’t phone friends wasting battery life.
I am sure someone with more cell phone experience can explain it better, but cellphones use a combination of GPS and cell tower information to determine GPS coordinates. If the cell phone is only hitting one cell tower, has intermittent coverage, is in a gully, or it is a heavily treed area, GPS coordinates can be inaccurate.
Again, always tell someone where you are going. It doesn’t hurt to carry a SPOT, or another form of a personal locater beacon like a DeLorme.