A trivially-simple UK OS grid reference app for Android, that does not rely on any Google services.
Version 0.1a, August 2023
There are many grid reference apps on the Google Play store, some free. However, I run Lineage OS on my cellphone, with no support for Google infrastructure. Even the free grid reference apps seem to need Google Play services. Partly, I guess, that's so they can connect to Google's advertising infrastructure. However, there is a specific location API that uses Google Play services, and I suppose that's what these apps are using. Google certainly encourages the use of the Google Play location API over the stock Android API. Whatever the explanation, not one of these apps works on my de-googled Samsung phone.
So I wrote my own. It does only one thing, which is to display the GPS location in UK OS grid format. The intention is for me to be able to locate myself on an OS paper map, so the location is only displayed as a six-figure reference. This grid reference provides a spatial resolution of 100m; GPS is usually more precise than that, but the paper maps used by outdoor sports enthusiasts are not.
This app is, and will remain, free and open-source. It does not (indeed, can not) display any kind of advertising. It's never going to be on the Google Play store, because it's designed to run on a de-googled device. Ideally, you'd build it from source, but there is an APK in this repository. If you're running a de-googled device, you'll know how to install an APK. If you're running regular Android, there are plenty of better apps to choose from anyway.
The app has no significant user interface. When started, it will be disabled. Click the 'Active' button to enable it and display the grid reference from GPS. Click 'Active' again to turn GPS updates off. Note that activating this app does not enable location services on the device -- you'll need to do that as well.
This app is designed to return a single reading, which can be referred to a paper map. There's no purpose in leaving GPS updates running in the app -- this will only drain the battery.
The fact that location services are turned off on the device won't stop the app running, but no location will be displayed. The app warns if the Active button is clicked and, in fact, location is turned off.
The time it takes to get a reading depends on many factors. You probably won't get a reading at all if you're indoors, and it will be inaccurate if you're under thick tree cover. The app displays an estimate of the accuracy, along with the time of the last update.
You'll need the Android SDK.
Create a file local.properties that contains a line that indicates where the
Android SDK is installed. For example:
sdk.dir=/home/kevin/lib/android_sdk
Then:
./gradlew clean build
The output is an apk file
./app/build/outputs/apk/release/app-release-unsigned.apk
You can install this in any of the ways that work for installing APK files.
This app was originally designed for Android 6. Although I now build it with a modern version of the Android SDK, it uses no features later than Android 7 (but see 'Permissions issues' below). I no longer have any old devices to test on and, to be frank, I wrote this app specifically for my own purposes. I would expect it to work -- to some extent -- on most Android devices that are still available, but I can't guarantee this.
SimpleOSGrid needs "fine location" permission. In the Android versions this app was originally designed for, the user got prompted to grant permissions when installing an app. With more recent versions, apps are supposed to direct users to the relevant settings page.
So on Android versions 7 and later, SimpleOSGrid will check for permissions, and raise the 'grant permissions' screen if necessary. The user can deny permissions, of course, and that won't stop the app running -- it will just display an error message.
You might need to click the "Active" button again, the first time you grant permissions, because the grant takes a little time.
The app will check permissions every time you click the Active button, because some Android devices quietly withdraw permissions when apps are not used for a while.
So long as the app is not in the 'active' state (and it is displaying 'GPS is stopped'), it should not draw from the battery. From Android 11 (I think) apps need special permissions to use GPS when they are not displayed. SimpleOSGrid does not ask for those permissions, and so it should not use the battery when it is not displayed, whether the app is in the 'active' state or not.
With Android 10 and earlier, apps are allowed to receive background GPS updates even when they are not displayed, and without any additional permissions. Consequently, this app might draw from the battery when it is invisible in these Android versions. That's why it has a prominent 'Active' button -- the app should usually be inactivated when it isn't actually retrieving a grid reference.
With a clear view of the sky, it usually takes about thirty seconds on my device for GPS to reach maximum accuracy. If I've travelled a long way with with the GPS location service turned off, it may take a lot longer than this.
It should, I hope, be obvious that this app won't work outside the UK. It probably does not fail gracefully if the location is outside the range of the UK OS grid system.
SimpleOSGrid is copyright (c)2023 Kevin Boone. It makes use of the JCoord coordinate conversion library, which is (c)2006 Jonathan Stott. Both are released under the terms of the GNU Public Licence. There is, of course, no warranty of any kind.
It should go without saying that you shouldn't be out in the hills with only a cellphone for navigation. Please, please don't rely on this app as your only means of finding your location -- the mountain rescue services are overworked enough already.