All posts tagged gps

One of the most common questions we receive about our trail guide apps is whether or not they work when you do not have a cell/mobile phone signal. The answer is a resounding “YES, they do work offline”! All of our apps are designed to work when you are in the middle of the wilderness, nowhere near a cell tower. (Otherwise our apps wouldn’t be very useful, would they?)

So, how does that work?

Searching for signal in a wild place.

Searching for signal in a wild place.

When you first download the app from the App Store or the Google Play Store, the device to which you download the app must have an internet connection. The connection can be a WiFi connection or a cell/mobile connection (though a mobile connection may not be the best idea since unlimited/unthrottled data plans are quickly becoming a thing of the past).  While you have that initial internet connection, the latest waypoint and track files are automatically downloaded to your device, plus you have the option to download photos and offline maps to your phone. You should download a map set so that you have topographic and other information about your surroundings.

When you are offline, the app uses your device’s built-in GPS unit to detect where you are and plots that information on a map. GPS, or “global positioning system”, is truly global, and works anywhere on planet Earth since the information is received from satellites.


  1. Will your app work when there is no cell/mobile service? Yes. So long as your device has a GPS receiver, it will work.
  2. Do I need a service plan on my phone to use your app? No. So long as you can connect to the internet with WiFi and your device has a GPS receiver, our app will work on your device.
  3. Will your app work on my iPod Touch? It can. The iPod Touch does not come with a GPS receiver. The same is true of a lot of tablets. But you can purchase an external GPS unit to plug into your iPod Touch, such as a Bad Elf.
  4. I’m pretty sure that GPS isn’t available in [remote location X]. Will your app work? Yes. GPS is global. So long as you are not deep in a canyon or cave (i.e. your phone cannot receive a GPS signal from space), you will be fine. Even in canyons, deep mountain valleys, and under deep foliage, the signal will usually just take longer to acquire.
  5. Can I send messages to my family using your app when I do not have cell/mobile service? No. The GPS unit in a phone and tablet is a GPS receiver. In order to transmit messages using GPS, you need a GPS transmitter, such as a DeLorme inReach or Spot.
  6. Why can’t I see Google maps when I’m offline? We do not use Google maps for offline use because it is against Google’s terms of service to cache the maps for offline use. Rather, we use topographic maps (the style depends upon trail location) that you can download to your device and which are displayed in the background of the map.

Let us know if we forgot anything and we will add to the FAQs.


Since April I’ve been testing out a new GPS unit from a small company called Bad Elf, their Pro GPS, which has given me great hope for the future of GPS units. My Garmin eTrex has been trusty and reliable for years, but Garmin’s customer service is crap, and their GPS units aren’t nearly as fun to use as the Bad Elf. The Bad Elf isn’t quite perfect yet, I expect that in a year or two I’ll be able to retire my Garmin and never look back.

Bad Elf PRO in the palm of the hand.

Bad Elf PRO in the palm of the hand.

The Pro is very different from Bad Elf’s original GPS unit, which plugged into your iPhone or Android device. The Pro doesn’t plug into your phone, but can connect with it through Bluetooth. This allows you to use the Pro for two different primary functions– either you can keep it the unit connected to your device by Bluetooth while using a GPS app, or you can use the unit as a standalone GPS track logger.

When using the Pro connected with your phone or tablet, you can leave your phone in Airplane Mode with Bluetooth on, which overrides a major failing of the iPhone, in that the iPhone can’t run its GPS without also trying to get a cell signal. The iPhone GPS will function without a cell signal, but it will eat the battery of your phone much faster, and its GPS is less accurate than it is with the aid of cell-tower-triangulation. Using the iPhone in Airplane Mode, connected to the Bad Elf Pro by Bluetooth, you can use apps like Gaia GPS or my own guides without draining the iPhone battery nearly as quickly as you would using its internal GPS.

I’ve been using the Pro as a standalone GPS for the most part, and comparing it to my Garmin eTrex for use in mapping for my apps. Here are the primary areas that I use to compare it.

Size comparison with the Garmin eTrex Vista HCx

Size comparison with the Garmin eTrex Vista HCx

Weight (draw)

The Bad Elf Pro weighs 3.2 ounces. The Garmin eTrex Vista HCx with lithium AA batteries weighs 5.0 ounces. That’s not the full story, though. The Bad Elf’s USB cord weighs 1 ounce, and a standard block charger is about 0.8 ounce. An Anker Astro 6000 mAh battery (which can charge the phone and the Bad Elf) with its USB cord weighs 5.3 ounces. A pair of Lithium AA batteries (for the Garmin) weighs 1.0 ounce. You can do the math yourself, but I’ve found that the weight is very much a function of how often you need to use the GPS, and how often you’ll be near a wall outlet.

Longevity (draw)

I’ve used the Garmin for several  years with the lithium batteries, mainly just as a track logger. I don’t have WAAS enabled, and I’ve regularly had 30 to 40 hours of run time before the batteries die. With the Bad Elf, the only difference in use is that I keep WAAS enabled, and I’ve also had 30 to 40 hours of run time from its internal battery. The Garmin’s battery monitor does seem a little more accurate, though, which gives it a slight edge.

Waterproofing (Garmin wins)

The Garmin is fully waterproof, and I’ve submerged it several times while in use. I’ve walked days in heavy rain with no problems. The Bad Elf claims IPx4 water resistance, but I haven’t had much luck with it in the rain, which gets behind the screen and causes errors with the buttons. Keeping the GPS somewhere waterproof takes care of the problem, though.

Accuracy (Garmin wins mostly)

The most important comparison, of course, is GPS accuracy. With the Garmin and the Bad Elf side by side in the top pocket of my backpack last month, the two produced almost exactly the same tracks about 90% of the time. At some sharp turns and in many deep valleys, the Bad Elf lost the track for short lengths and read about 100 feet off. I check the tracks against National Park Service records for the AT, so I can see that the Garmin’s track is about 99.5% accurate. The Bad Elf loses in this case, but for most people, it’s accurate enough.

Much better track accuracy when the Bad Elf is on top of the pack (blue is Bad Elf, red is official NPS track)

Nearly perfect track accuracy when the Bad Elf is on top of the pack (blue is Bad Elf, red is official NPS track)

A bigger problem arises with the Bad Elf when I put it on the side of my pack, either in my shoulder pockets or in any of the side pockets. I don’t know why this should be a problem, but the GPS track is inaccurate about 40% of the time, with variation of up to half a mile. This is unacceptable for me as far as using the GPS for work, but since keeping the unit in the top of my pack seems to work well, I’ll just leave it in the top of my pack for general use.

A typical track error when the Pro was on the side of the pack.

A typical track error when the Pro was on the side of the pack.

User Friendliness (Bad Elf wins)

Garmin’s GPS has many, many features, but after three years of using it I still haven’t bothered with most of them. The instruction manual for it is almost useless, but trying to figure out how to use the GPS without instruction is impossible. Thank goodness for the Internet. The Bad Elf Pro, on the other hand, has an incredibly simple user interface, and is basically invisible if you use it in conjunction with a GPS app on your phone. If you just want to get track data from the Pro, you just download a free app from Bad Elf that allows you to change the GPS’s settings, download the GPS’s data to your phone with a few simple (and well-labeled) button clicks. Once the data is in your phone, you can upload it to Dropbox, send it by email, open it in Gaia GPS, or use it in any other GPS app. Not only is it simpler to use than the Garmin, but you can back up your tracks to the web, send them to friends, and look at them on any kind of map you like.

Conclusion: Garmin for now, Bad Elf for the future

The Garmin wins in terms of two important distinctions, accuracy and water resistance, but I’m willing to give Bad Elf the edge for now. In my dealings with Garmin over the last few years, I’ve found their customer service to be some of the worst I’ve experienced– it seems they are focusing more on their car navigation GPS units than their handheld units. Bad Elf, a tiny company of less than a dozen people, is innovative and young, which gives me hope that the quality of their GPS units will surpass Garmin’s in no time. In the meantime, I’ll just hope my eTrex holds together as it ages.

Disclosure: Bad Elf gave me a discount on the Pro GPS unit as an app developer, but didn’t solicit this review. Garmin gave me no incentives to write this review.