MIT outlines the process for "re-photography"

In our fast-changing world, it’s easy to forget what once stood at, say, the site of a new skyscraper, or what the neighborhood liked like before that new condo.

However, systems for superimposing a historic photo on a current photo can show just what has changed, providing valuable context — and some cool imaging tech.

At the Massachusetts Institute of Technology, new work in computational re-photography combines a laptop PC, camera, and software to do the superimposition in real time. The “visual homing” software compares the current view from the laptop-connected camera to an historical scene, and instructs how to adjust the camera’s position and zoom to best match the scene.

A historical photograph paired with a well-aligned modern “rephotograph” can serve as a compelling “then and now” visualization of the passage of time, writes one of the MIT researchers behind the technology. “However, the task of rephotography is tedious and often imprecise, because reproducing the viewpoint of the original photograph is challenging. The rephotographer must disambiguate between the six degrees of freedom of 3D translation and rotation, and the confounding similarity between the effects of camera zoom and dolly.”

To overcome those challenges, the MIT team developed “a real-time estimation and visualization technique for rephotography that helps users reach a desired viewpoint during capture. The in- put to our technique is a reference image taken from the desired viewpoint. The user moves through the scene with a camera and follows our visualization to reach the desired viewpoint. We employ computer vision techniques to compute the relative viewpoint difference. We guide 3D movement using two 2D arrows. We demonstrate the success of our technique by rephotographing historical images and conducting user studies.”

Full details are here: http://people.csail.mit.edu/soonmin/rephoto/rephoto.pdf

In Britain, a self-described “social movement” named We Are What We Do received funding from Google to build on Google Maps and Street View and develop “Historypin,” which it describes as “a digital time machine that provides a new way for the world to see and share history.”

Historypin is an online tool enabling people to upload images and ‘pin’ them to a particular location on Google Maps and Street View. Users layer their old images onto modern Street View scenes, revealing a series of windows into the past. “Individuals will be encouraged to include a date and story behind their image, and invite others to share images of similar historical moments to create a narrative,” the group says.

Users can upload, review, comment on and share images. Pictures are dated and geo-tagged before placed atop modern Street View photography. “The result is a fascinating snapshot of the changing face of local streets and well known landmarks… and provides a new perspective on historic moments,” the group says.

The site has ambitions to become the world’s largest user-generated archive of historic images and stories, “providing easy access to digitized history stretching from the invention of the camera to yesterday.”

Historypin launched in London in June, and will spread further “in the next few years.”

We Are What We Do is a not-for-profit founded in 2004.

Pin an historical photo atop its current counterpart.