...the red ocean of Forbidden Siren resources!
This material was available to download from the official Forbidden Siren 2 website. I believe it was promoted as research material by the ingame character Mamoru as part of his magazine job. In fact of course, these were inspirational photos taken by the developers on their research tour through Japan and Gunkanjima island. The Excel sheet at the bottom of the page features several birds eye views and maps of Yamijima Island.