Cairns have long been welcome sights for hikers and mountaineers — stacks of stones that fellow explorers leave behind to mark trails and help keep others from getting lost. Appropriate name, then, for this new app that marks spots with cellular coverage in the great outdoors, helping lost or injured hikers find places where they can call for help.
Cairn creates a map of cell coverage on hiking and mountain trails that can be filtered by carrier, in case an emergency call needs to be made. Like the stone cairns before them, that map is created with the help of fellow outdoors enthusiasts — the app is community-based, with the coverage map generated through crowdsourced data collection from all of the app’s users. While the app is launching now, beta users have been building up a good base of data since the beginning of the year, which now includes 300,000 data points in 10 states, including a complete map of the Pacific Crest Trail. Cairn should become more comprehensive as more users join in.
Users can also assign emergency contacts, then tell the app when they’ve started on a trek and when they expect to finish. If the user doesn’t check in by the time they’ve indicated, those emergency contacts will be notified and will receive a map of where the trail the user has taken.
Cairn is available for free, but is currently available only on iOS.