The Swiss National Forest Inventory (NFI) is based upon three main raw data sources: the aerial-photo interpretation, the terrestrial inventory and the interview survey. Once the aerial images have been analysed, all forest sample plots, excluding inaccessible forests, are visited terrestrially. As soon as a forest district is completed, an interview survey is conducted with the responsible forester. The software application MAIRA has been developed for the terrestrial inventory and SILVIS for the interview survey. In the following, we present these two field applications, with special emphasis on the applied data model, the data flow between these two applications and the database, as well as the main tasks of the software during the assessment. We also describe the software architecture and our software engineering approach, and we discuss software quality and data quality considerations.