At Bellingcat, a non-profit investigative organization in the Netherlands, we research war crimes, find tiger smugglers, monitor environmental degradation and track extremist hate. To do this, we use "open sources", including public databases, social media posts, and a wide range of geospatial data and tools. The use of these new online sources has dramatically changed investigative journalism and humanitarian accountability research in the past five years, and there remains tremendous potential for further development, especially in the geospatial realm. In this talk, Bellingcat data scientist Logan Williams will present case studies from our research to illustrate how invaluable open source geospatial tools and data are for "open source" investigative research. Some of the most useful tools for investigators are designed for very different purposes, from academic meterology to outdoor recreation. Additionally, some of Bellingcat's own FOSS geospatial tools, based on Open Street Map and Copernicus satellite data, will be showcased. Finally, the talk will discuss opportunities for deepening the connections between the open source geospatial community and the open source investigation community.