For data collection, it is a common situation to work with a laptop or a phone offline in the field. Upon returning to the network, the changes need to be synchronized with the master data source, e.g. a PostGIS database. If several persons are working simultaneously on the same datasets, it is difficult to merge the edits by hand, even if people don’t change the same features.
Therefore, Mathias Walker implemented an offline plugin for QGIS. This plugin automates the synchronisation by copying the content of a datasource (usually PostGIS or WFS-T) to a spatialite database and storing the offline edits to dedicated tables. After being connected to the network again, it is possible to apply the offline edits to the master dataset.
To give the plugin a try, unpack the sources, apply the patch ‘qgis_svn.diff’ to a current svn version of QGIS. Then copy the offline_editing folder to $PREFIX/src/plugins and recompile QGIS.
The usage of the plugin is straightforward:
- Open some vector layers, e.g. from a PostGIS or WFS-T datasource
- Save the project
- Press the ‘Convert to offline project’ button and select the layers to save. The content of the layers is saved to spatialite tables.
- Edit the layers offline
- After being connected again, upload the changes with the ‘Synchronize’ button
Presumably, the offline editing plugin will be part of the next QGIS version (1.6)