“NASA would like you to take a picture of a tree, please. The space agency’s ICESat-2 satellite estimates the height of trees from space, and NASA has created a new tool for citizen scientists that can help check those measurements from the ground. All it takes is a smartphone, the app, an optional tape measure, and a tree.”

https://www.theverge.com/2019/4/15/18308044/nasa-app-point-smartphone-trees-picture-height-satellite-why