Once you've download a map area that area will simply be available, even when your phone is out of range or in airplane mode. You don't need to do anything special, just use the app as if you had service. You will see a box indicating the map areas that you've successfully downloaded. To delete downloaded maps from your phone, go to your profile, then tap on the gear icon, and then tap on Map Downloads. From here you can manage your downloaded maps. 

Any tips for extending my phone's battery?

1. Put your phone into low battery mode. This offers significant battery savings without interfering with GPS functionality and location tracking. To do this, go to your iPhone Settings app, choose Battery, then turn on Low Power Mode (or just ask Siri!).  

2. Turn off wifi and bluetooth. You're unlikely to use these in the backcountry. You may also consider putting your phone in airplane mode.  

3. Set how often Cairn updates your location for your contacts. Note that Cairn only does this only if you've asked us to  update your contacts. Use the menu in the lower right to access this setting.

4. Consider carrying a small battery pack. We do, especially on multi-day trips.

5. Use the stat tracking feature only when you're moving. Tracking the stats for your trip is more battery intensive because we're collecting lots of granular data. 

6. Turn off your phone at night. Many people like to use their phone to take photos during the day. But at night, there's no reason to keep your phone on. 

7. Keep your phone warm. A cold phone uses more battery. Who knew? 

How do I add my own destination to the app? 

Tap and hold anywhere on the map to drop your own custom pin. If it’s on a trail, you’ll be able to get all kinds of interesting information about that spot. 

How does the free trial work?

Currently we automatically offer a 60-day free trial of our premium features. At the end of the trial period there is no need to cancel anything; simply sign up for Premium membership if you'd like to continue using those features, Premium features include:

  • Sharing your real-time location with your safety contacts

  • Downloading maps from anywhere in the world for offline use

  • Recording and saving your trail & trip stats

  • Accessing driving directions to the trailhead

If you do subscribe, you can cancel your premium membership through your phone's Settings app. After the trial period you will still be able to see cell coverage on maps and view trail info such as distance, elevation, and estimated time of arrival.

What is the difference between the blue and gray dots?

Blue dots indicate a spot cell coverage was detected by Cairn users. Gray dots indicate that no coverage was found. Tap on the dot to see which carrier(s) did or didn't have coverage at that spot.   

Will Cairn work if I lose cell reception?

Yes! It is designed to work offline, but it really helps if you download the map for the area you'll be exploring before you lose reception. We recommend doing this at home over wifi. Our safety notification feature only works if you set it up before you're out of range. But rest easy knowing that your safety contacts will be alerted if you're overdue regardless of your phone's status.  


Yes, you can tap on a point to see which carriers have coverage (or not) at that point. We don't have data for every carrier (or every point, for that matter) as this data is crowdsourced by other adventurers who use Cairn. 

Can I make emergency calls via other carriers?

Yes! You may be able to make an emergency call (to 911, for example) even if your carrier doesn't have coverage. Your phone just needs to operate on the same frequency band as a carrier that does have coverage. Always try to call 911 in an emergency, even if it doesn't look like you'll get through.


Once you've started a Cairn, you'll see an I'm OK button that makes it easy to send all your emergency contacts a message along with a map of your current location. Choose from one of our pre-filled messages (e.g. Made it to the top!). or write your own. If you don't have coverage (and this is the best part), the app will send your message/location as soon as it notices that you have coverage again. We think it's a pretty handy feature. Once you end your Cairn, we let your contacts know you're safe.


Yes! We're happy to report that after you send a notification to your contacts, you'll see the points of cell coverage that you've collected. It's a nice way to see your own trail without using your phone's GPS constantly. And you can see where your phone did and didn't have coverage along the way. You can also track your stats, which also shows you distance covered, elevation gain/loss and an estimated time of arrival (ETA).

What happens when I put my phone in airplane mode?

Unfortunately we can't tell the difference between airplane mode and no service. So any data you collect when in airplane mode will be recorded as no coverage. However, we know that using airplane mode in the backcountry saves your battery. And so we take this into account in our coverage aggregation algorithm for an area. Please use airplane mode as you normally would, but know that it will be recorded as no coverage. 


Absolutely. And the rest of the ten essentials as well! Cairn is just another tool to throw in your cache of safety gear. We are not advocating that you use your phone at every opportunity, and we get that you probably want some peace and quiet when you're out. But the vast majority of modern day wilderness rescue operations are initiated by cell phones. We'll know Cairn is a success when it helps save a life.  


Phone batteries don't like the cold and your phone will shut itself off even if it still has charge. Some people keep their phones in their inside jacket pockets, or slip in a hand-warmer to keep their phone batteries warm.

HOW can i help gather more data for the coverage map of the wilderness?

The best way is to get more people using Cairn. You can invite people via Twitter or Facebook using our handy links. If you're a member of a Facebook or Yahoo outdoor group, share this website there. We can use all the help spreading the word that we can get. 

My question isn’t answered here. Now What?

Please email us at adventure@cairnme.com. We’re anxious to help.