This project uses an inexpensive sign and some code to make a crowd-sourced time lapse image station that can go anywhere one can install a sign. We (Nerds for Nature) built this for use on Mount Diablo State Park, east of San Francisco, California. Our goal is to enlist hikers in documenting landscape changes after a wildfire in fall 2013.
Creating the signs and monitoring processes can be a bit tricky. We lucked out with the right combo of carpenters, coders, designers, and land managers. Repeating exactly what we did would require at least some carpentry and coding skills. We're publishing all our methods, designs, and code in case anyone wants to try this themselves, but your approach will almost certainly be different based on local conditions and the kinds of collaborators you can recruit (unless you're some kind of magical coding carpenter-designer who owns private land visited by lots of people with smartphones.) We've tried to describe some alternative solutions to some parts, but they generally involve substituting technical expertise with labor.
With that in mind, onward!
Summer 2016 note: Due to changes in Instagram's API, it is no longer possible to harvest images by hashtag from Instagram. So this project will work only with Flickr and Twitter.