In some situations, you may need greater GPS accuracy and reliability than what you receive via the onboard Android/Apple device GPS. In this case, you should consider purchasing an external GPS receiver to use with your smartphone or tablet.
We've done research to see how GPS receivers can be used with Android and IOS. It appears that you *may* be able to use them without needing any changes to the app side.
For a great summary and 'how to guide' for Android, see this article by Calflora.org. This article outlines the steps for using an external GPS with Android. It says that on IOS, simply pairing the external GPS to your iDevice will do the trick.
We do not officially support external GPS devices due to potential differences in Bluetooth version, operating system versions and device hardware. If you choose to use an external GPS device your mileage may vary in terms of compatibility with our app. If you wish to proceed with using an external GPS device we suggest you purchase one and test it out with the app before purchasing more.
Should you encounter problems, contact our support team and we may be able to help, or look at a project to make the device work with our app.
The Calflora article linked above has been pasted in its entirety below, in case the link is removed in the future.
All copyrights for the content below are attributed to The Calflora Database.
Using an External Bluetooth GPS Receiver with a Smartphone orTablet
Roy West, firstname.lastname@example.org
2014-06-28 (Query about SXBlue GPS receivers in devices section)
Mobile smartphones get their GPS signals from Assisted GPS (AGPS) chips. AGPS is great in populated areas, because is uses cellular networks, Wi-Fi, and other signals and hints to quickly get a rough idea of your location, which in turn helps the chip quickly find and connect with GPS satellites for more precise location data.
Unfortunately, this advantage is lost when you’re in rural areas, particularly if you lose your cell network connection. Then the weakness of the AGPS chips becomes apparent: dedicated GPS devices are much better at getting a precise location from GPS satellites.
Several manufacturers now make GPS receivers, which you can connect to your phone or tablet and get great GPS location data out in the wilderness. The receivers connect to your phone or tablet via Bluetooth (a short-range wireless standard for this kind of purpose). GPS receivers are small, because they have no screen or keypad, and are surprisingly inexpensive ($100 or less is typical). You can use these devices to get great GPS location data for apps that run on your phone or tablet, such as Calflora Observer, Google Maps, Backcountry Pro, My Tracks, and so on. Because they connect wirelessly, you can even put a GPS receiver in a sealed ziplock and store it at the top of your daypack, in your hat, tape it to the top of your backpack frame, and so on, and get great GPS data even in the pouring rain.
I’ve tried several models of GPS receivers with a variety of Android phones and tablets and seen great results (see “Tested GPS Receivers” at the end of this article).
I gather that with iOS devices (Apple iPhones and iPads), you simply pair the iOS device with the GPS device and you’re good to go. I haven’t tried that yet. Connecting a GPS receiver to an Android is another matter.
Connecting an Android Phone or Tablet to a Bluetooth GPS Receiver
Getting a GPS receiver to provide location data to your Android apps requires a bit of fiddling and glue. The exact steps depend on the version of Android you’re running, but these instructions should work for most configurations -- I’d appreciate hearing if these steps don’t work for your particular phone, tablet, or GPS receiver.
As should be obvious, this is something you need to do with a good data connection (preferably Wi-Fi), before you leave for your 3-week wilderness trek: you need to download software from the Google Play Store and if you’re going to use a mapping app that can store maps for use off line, you need to download your maps.
1. Make sure your Android has developer settings.
Recent Android operating systems don't have developer settings available by default, and the location of those settings is in different places on different OS versions.
On older OSs, you can find the developer settings in the Android Settings app, under Applications > Development.
On newer OSs, 'Developer options' are at the top level of Android Settings, but you may need to make them visible. You do that by opening Android Settings > 'About phone' and then scrolling down to find the 'Build number.' Tap the build number about 7 times and you'll see messages that count down until you 'become a developer.'
(If you see Settings / “Developer Options”, then you are already a developer!)
2. Turn on 'Allow mock locations.'
Check the 'Allow mock locations' in Android Settings’ Developer settings. This is required for the Bluetooth GPS app (see step 3) to make the GPS receiver's location data available to your apps, bypassing the built-in GPS.
3. Install the Bluetooth GPS app from the Google Play Store.
This app connects to the GPS receiver and provides a 'mock location' to other apps, such as Calflora Observer.
Here's a link to this app on the web version of the store:
There are a few of these apps. 'Bluetooth GPS' is by a developer named 'GG MobLab' and has worked great for me.
4. Pair and connect your Android to the Bluetooth GPS receiver.
Bluetooth pairing can be easy or infuriating. Each device is different. Read the instructions that come with yours to learn what it wants. The Bluetooth settings are in different locations in Android Settings, depending on the version of Android OS you're running.
If you’re setting up more than one set of phone/receiver pairs, I find it helpful to “name” the GPS receiver in the Bluetooth settings, so I can tell one receiver from another (otherwise they’ll all have the same name, which they broadcast).
One tip if you want to change which mobile device your GPS receiver is connected to: after you “unpair” the receiver and the mobile device, turn the mobile’s Bluetooth off and cycle the power on the receiver, so there’s no chance the receiver can “see” the device it was connected to. Sometimes Bluetooth devices won't connect to a new device if they can still see a device they were paired with before, even if you've 'unpaired' them.
5. Connect the Bluetooth GPS app to the GPS Receiver.
Open the Bluetooth GPS app, check 'Enable Mock GPS Provider,' and then select your GPS receiver in the menu at top-left and click Connect.
If you’re lucky, you'll start seeing live location data on the app's screen (even if you’re indoors and the device can’t get a great satellite fix, the app’s dials will start showing data).
If at first you don't succeed, open the Bluetooth GPS app’s settings (touch the 3 vertical dots top-right on newest Android OSs; press the Menu button on others) and find the 'Connection Problems Related' settings. On my Nexus 7 tablet, I found I had to use all of these, including the delightful 'Other Workaround' setting. (I did not change the 'Channel.')
Once you're connected, apps will start getting their location data from your external Bluetooth GPS receiver.
Be sure to turn most of this stuff off when you're not using them, or you risk draining your battery. For this reason, it's a good idea to keep everything plugged in if you're in a car, for example. There are also portable USB power supplies (basically, large rechargeable 5v batteries with a USB port) that you may want to explore for longer trips.
I needed to go to Settings / Bluetooth to do the pairing. After that, the Bluetooth GPS app worked immediately. JHM (Thanks, John, that’s what worked for me here on step 5 as well. CP)
Tested GPS Receivers
I’ve tested these GPS receivers with Android phones and tablets and they’ve worked great for me. I’m including the Amazon page for each for convenience.
Garmin Portable Bluetooth GPS and GLONASS Receiver
Dual Electronics XGPS150A Universal Bluetooth GPS Receiver
GNS 2000 GPS MFI GLONASS RECEIVER
I ordered a TomTom Mkii Bluetooth GPS Receiver from Amazon:
At $25 it seemed worth a shot. The unit arrived uncharged and the charger delivered no voltage. Returned it. I don’t see this unit on TomTom’s current web site, so I’m not sure what’s up with that.
I would love to hear from anyone who has used a SXBlue GPS receiver from GENEQ Inc.: http://sxbluegps.com/
John from GTrek Ltd writes that these instructions worked to connect a GTrek II GPS receiver and data logger with a Samsung Galaxy S4 running Android 4.4.2.
Copyright 2013-2014 The Calflora Database. All rights reserved.