ECMWF Summer of Weather Code 2019: new dissolve and topological cleaning tool
The European Centre for Medium-Range Weather Forecasts (ECMWF) has finished its second Summer of Weather Code (ESoWC) programme in September 2019. Mundialis has been selected for one of the seven outstanding projects addressing the available challenges: GIS-based dissolve functionalities using GRASS GIS. For this project, two tasks needed to be implemented supporting the maintenance of the European Flood Awareness System (EFAS).
First, an automated method has been developed to combine a new EFAS partner region with existing partner regions, both being defined as polygons. These partner regions needed to be merged into topologically correct new polygons without and overlaps or gaps. Common boundaries between the polygons are dissolved according to the associated EFAS dissemination centre. The challenge here was that these polygons can come from different, inconsistent sources and might need a fair amount of cleaning in order to produce a seamless result.
Second, river basins and hydrological grid points needed to be updated with the IDs of new partner regions. The aim was to provide tools that require little user-intervention and perform all of the processing automatically once input parameters have been set up.
All tools have been implemented as GRASS GIS addons and corresponding QGIS plugins.