IPhotoMeasure is a program that can convert a photo of a building, room or other location into a series of high-accuracy measurements. You print out a sheet of known dimensions and put it in the frame of the photo and from that sheet, the program figures out the relative size of everything else in the shot.
First off, the "secret sauce" of the solution is called a "DigiTarget". The DigiTarget gives everything in your photo a frame of reference; it's a single sheet of paper with a 7.5 x 7.5-inch square on it. A 15-inch square version is also available for outdoor measurements. Simply print off a free DigiTarget, affix it to something in your photo scene and snap a pic. The iPhotoMEASURE software uses the DigiTarget to compute the measurements of items in your photo and the company claims that any distance in the picture can be measured with up to 99.5% accuracy. Conceptually, it makes sense since the software has that 7.5- or 15-inch frame of reference.
(via /.)
