Images don't forget: Online photogrammetry to find lost graves

The vast amount of public photographic data posted and shared on Facebook, Instragram and other forms of social media offers an unprecedented visual archive of the world. This archive captures events ranging from birthdays, trips, and graduations to lethal conflicts and human rights violations. Because this data is public, it has led to a new genre of journalism, one led by citizens finding, analyzing, and synthesizing data into stories that describe important events. To support this, we have built a set of browser-based tools for the calibration and validation of online images. This paper presents these tools in the context of their use in finding two separate lost burial locations. Often, these locations would have been marked with a headstone or tomb, but for the very poor, the forgotten, or the victims of extremist violence buried in unmarked graves, the geometric cues present in a photograph may contain the most reliable information about the burial location. The tools described in this paper allow individuals without any significant geometry background to utilize those cues to locate these lost graves, or any other outdoor image with sufficient correspondences to the physical world. We highlight the difficulties that arise due to geometric inconsistencies between corresponding points, especially when significant changes have occurred in the physical world since the photo was taken, and visualization features on our browser-based tools that help users address this.