The described technology is generally directed towards creation of shared overlay maps to support automated, real-time, cross-platform sharing of map information among groups of digital navigational map users, including but not limited to unmanned ground vehicles (UGVs). A central map authority (or other collaborative/federated organizational entity) can receive map overlay information from a mobile subscriber device, such as a UGV. The central map authority can promulgate the map overlay information to a group of multiple mobile subscriber devices according to the techniques described herein. Individual mobile subscriber devices can use received map overlay information, along with their individual digital navigational maps (DNMs) and navigation systems, to plan their individual routes.