The InfraMarker mobile application can work offline. While offline all the features of the application are fully functional, except of course, the sync to the server.
To be able to work offline, the very first time the InfraMarker application is launched, it needs to be online and logged in with a user account. Then the user need to open a project and make sure that sync of the project is finished. During the sync, all the datasets of the project will be synced to the mobile device.
Base-layers won't sync automatically, but there is large enough cache on the mobile device that if user will zoom and pan around the area of interest, the base layer tiles will be cached and available offline.
There are also Offline Areas that can be defined. Most people skip this step, but the reference data may be necessary for some people. The Offline Area is the way to predefine and download base-layer tiles to the mobile device. Here is the article that describes how to setup Offline Areas.
Now the project is ready and available offline. After the project sync is finished, the InfraMarker application can be turned off. Do not logout, just exit the InfraMarker application instead. It will be able to start while offline.
When in the field the InfraMarker application can be launched. If there is absolutely no internet connection the application will automatically switch into offline mode, and will log into the last active user account. The projects that were synced earlier can be opened and data collection will be operational. If the connection is slow or unreliable, the InfraMarker application will try to connect to the server. Depending on the connection, it may take a long time or sometimes fail. For these conditions it is better to switch the InfraMarker application into offline mode in the application Settings as described here. The offline mode is also useful for reducing the data usage over cellular connection. The offline mode will prevent the InfraMarker application from using any data connections.