When downloading cartography in your Navionics mobile app these files are stored in a memory space of your device that may be erased at any point in time by the operating system whenever the available free space in the device is running low. This can happen when using other apps that require memory space for temporary files when viewing videos (YouTube) or programs in streaming and playing games, but also by consuming additional space by adding other files through the installation of new apps, downloading emails, making pictures or storing music/videos. Once the available memory space runs low the system will try to free up as much as possible by removing files allocated in specific areas. System files, pictures, movies and music are not erased as they use specific memory spaces that are not erased automatically.
Please note that this behavior of the device’s operating system is entirely beyond our control and we strongly suggest you keep the total available free memory space under control to avoid a sudden partial or even total loss of cartography.
Another cause for loss of the cartography dataset can be a third party utility that has been installed on the device. Those applications are specifically designed to check and optimize the memory status of your mobile device. They work in background and have the full rights to erase contents from the disk of your device. Examples of such cleaner utilities are PhoneClean, App Cache Cleaner, Clean Master Phone Boost but some other management apps may include the same functionality like the Battery Doctor app using its Junk feature. In case you are experiencing unexpected loss of data we strongly suggest disabling or uninstalling these utilities.
Should you experience the loss of previously downloaded files then these can be downloaded again dependent on the available amount of free space. Note that an internet connection is required to do so which may not always be the case when discovering the issue. If you are using an Android device to access the Boating HD app, you are now able to change the storage location of the app data on your device to your external memory cards. - See Android: Memory and storage management of Navionics app on Android Device