aTypical Joe: a gay New Yorker living in the rural South

Thursday, March 20, 2008

reCAPTCHA: Digitizing Books one word at a time

Luis von Ahn is an assistant professor at Carnegie Mellon University who developed the CAPTCHA - those squiggly series of letters which help us prove we are human when leaving comments or performing other internet chores that require authentication.

I know this because I listened to him speak with Dr. Moira Gunn in a Tech Nation interview available via IT Conversations. The whole tales worth the telling but the part that merits even more attention is this notion of the reCAPTCHA:

About 60 million CAPTCHAs are solved by humans around the world every day. In each case, roughly ten seconds of human time are being spent.
Individually, that’s not a lot of time, but in aggregate these little puzzles consume more than 150,000 hours of work each day. What if we could make positive use of this human effort? reCAPTCHA does exactly that by channeling the effort spent solving CAPTCHAs online into “reading” books.

To archive human knowledge and to make information more accessible to the world, multiple projects are currently digitizing physical books that were written before the computer age.  The book pages are being photographically scanned, and then, to make them searchable, transformed into text using “Optical Character Recognition” (OCR). The transformation into text is useful because scanning a book produces images, which are difficult tostore on small devices, expensive to download, and cannot be searched. The problem is that OCR is not perfect.

reCAPTCHA improves the process of digitizing books by sending words that cannot be read by computers to the Web in the form ofCAPTCHAs for humans to decipher. More specifically, each word that cannot be read correctly by OCR is placed on an image and used as a CAPTCHA. This is possible because most OCR programs alert you when a word cannot be read correctly.

If you didn’t follow that, he explains it beautifully in the podcast. It’s a brilliant idea. You can add it to your site. I hope to add it to mine. Here’s more from Wikipedia.