Hello all! I am running a non-profit aimed at building an open-source "3D Wikipedia" of historic buildings around the world. We teach high school kids how to build 3D models of buildings in their hometown (using SketchUp, Blender, and other tools), then combine those into an VR-ready Unity project for each town. Users can then explore their community as it appeared throughout history. Google Maps and Google Earth are vital tools for us as they provide the location and dimensional data required for existing buildings.
Ideally, we could someday upload our buildings into Google Earth/Maps itself so that users could "time-travel" back before StreetView photos were being taken.
As of summer 2019, we have pilot projects underway in Vancouver, BC and Mill Valley, CA. We are now at work on a reconstruction of the 1906 San Francisco earthquake.