Beneath our feet lies one of the least explored environments on Earth. While mountains, rivers, and landscapes are well mapped, the subsurface remains largely hidden. Digital soil field data collection offers an efficient way to shed light on this unseen world. This is particularly important because protecting high-quality soils requires knowing where they are. Despite its importance, only about 13% of agriculturally used soils in Switzerland are covered by detailed soil information, and mapping has traditionally been carried out on paper.

Geodata applications now enable direct digital data collection in the field. In search of an open-source solution, I developed a QField project for practical soil mapping. QField is a powerful mobile app based on QGIS that enables efficient field data collection. This presentation outlines design considerations from the development process built on continuous feedback from field workers.

The overall system architecture is defined by QField, but key decisions such as deployment (local or remote) and data management still need to be designed carefully. The identified best practices will be compared in terms of usability, collaboration, and technical complexity. An important consideration is the choice between local and cloud-based setups, as this affects the optimal project size as well as the handling of databases and layers. For editing layers, either GeoPackages or PostgreSQL can be used. Regarding background layers, it is important to distinguish between online Web Map Service (WMS) and offline raster datasets in order to keep the project lightweight.

Other key design considerations presented include closely replicating paper-based workflows in a digital environment, ensuring near real-time performance, and maintaining a clear overview despite the limited screen size of mobile devices.

In conclusion, careful QGIS project preparation has enabled efficient, robust, and practical digital soil data collection with QField. A major benefit is that observations are now collected and stored digitally. The captured information is no longer in heterogeneous handwritten field notes but instead provides structured data and accessible knowledge. The presented best practices can serve as inspiration for other QGIS users aiming to improve the efficiency and usability of their own QField mobile app projects.