Efficient Interactive Visualization of Very Large Geospatial Query Results

We present a web mapping application that offers interactive visualization of query results with hundreds of millions of geospatial objects. This is in contrast to existing applications, which are slow or unresponsive when the number of objects in the result is large. We describe a general technique, which works for any database engine that represents each geospatial object with a unique IDs and that can return a query result either with the objects or with the IDs. We have implemented a web mapping application using this technique and with the QLever SPARQL engine as backend. We evaluate it on queries on the complete OpenStreetMap (OSM) data, with result sizes ranging from small to very large. We compare it against the map interfaces of Overpass, PostGIS, and OSCAR.