Georeferenced transaction data is harvested (“crowd-sourced”) from client devices and sent to a network-based map service. The map service performs cluster analysis on location data points in the harvested data, resulting in one or more clusters representing local densities of transaction occurrences. Data vectors including supplemental data are obtained from one or more vendors. Location data points included in the data vectors are compared to center coordinates of the one or more clusters and the closest matching cluster/vector pair provides a mapping to POI data in a POI database. The mapped POI data is updated with the supplemental data. In some implementations, transaction timestamps in the harvested data are used to estimate the business hours of a business POI.