There is some background information about SD Cards on the following link: Android SD Cards
If you are having issues moving mapping to your SD Card, this is our suggested way to resolve this:
1. Fully uninstall OMN. Please see this link to see how to fully remove OMN from Android:
2. On re-installing OMN3 from Google Play and running for the first time, you should be asked to login with your email/password. If you are NOT asked to login, please return to step 1.
3. OMN should open up, and you should have some mapping on the screen.
4. Press the menu button (three bars bottom right of the screen), and from the menu that comes up, select Manage Maps.
5. Expand the Demo maps product by tapping on it. The product should expand and show you the maps within the product. Tap the button to the right of the map named: "OS 1:50,000 - Demo 20x20". From the menu that pops up tap on Download. Let the map download.
6. When the map has fully downloaded, tap the button to the right of the map again, and this time tap on 'View map'. The map should become visible.
So far we have not touched on the SD Card. What we should have proven if you have reached this part of the instructions is that you have a working OMN Android on your phone/tablet, logged in correctly which can download mapping and run from the internal memory.
7. Tap the menu button (3 lines bottom right on the map), tap on 'Settings' in the menu that comes up, and then tap on 'Data' on the next menu.
You should see something similar to below.
Android file paths aren't very user friendly. In the screenshot below, the maps are stored on /data/user/0/com.anquet.omn3/files/omn3/maps
Basically, we have the 'Current location' where the maps are stored, and a 'Target location' where we will move the maps to. The target in the screenshot below is 'Internal', which is where the maps currently are, and so the 'Move Maps' button is not available.
8. Tap on 'Internal', and up will come a list of possible Targets - places that we can move the maps to.
9. If you select SD Card, you should see something like the screenshot below:
*** Please note, the SD Card file path at no point mentions SD Card in its name! On this device, Android has named the SD Card as /storage/2AE0-0641/Android
10. We now have what we hope is a valid Target. Tap on 'Test Path'. This will try to write a very small test file to the file location, and check it can read it back. If this fails, it is likely OMN does not have read/write privileges to your SD Card.
If the test succeeds, you should get a message like the one below.
11. Tap on Move Maps. Acknowledge the warning message. As we have only downloaded a very small amount of mapping, the move should be very quick. You should now have a screen like below, which indicates 'Move Finished' You will also see that the 'Current Location' is now the SD Card '/storage/2AE0-0641....'
The maps are now on your SD Card. You can now continue to download maps in the normal fashion.