On GIS projects it is often required to populate certain fields in various layers automatically with data, either from current values, like date and time or user, or fields from other layers, including online and cloud resources. These fields can be populated with some of the processing tools, especially, when a large number of rows need to be updated, or with the expression builder when a new record is added or an existing one updated. Both processes can involve simple calculations, like additions, subtractions, multiplications, divisions or any other mathematical formulas, or complex (spatial) queries of data in other layers or online and cloud resources like digital elevation models or WMS/WMTS, WFS, REST layers hosted on the Internet. While it might be quite easy to automatically update a date field with the integrated “now” function, or a text field with the Plus Code, or a field for the current user with the QGIS variables, it is not a lot more difficult to share data between joined layers, although joins in large QGIS projects could become quite slow. A bit more challenging automated field updates can become between related layers and spatially overlapping or nearby layers, but querying WMS or other online layers can have their own challenges altogether. In some cases database triggers are the most effective way of dealing with field updates, but these need to be configured depending on the database used.

This presentation will provide a short overview of what is possible and demonstrate live field updates directly in QGIS using complex attribute forms and several layers related to each other. The querying of online layers (WMS, WFS and cloud-based DEM) will also be shown and the use of triggers for updating fields explained.