Measure items using iphone camera and paper pattern

Hi Guys and Gals, I have written a little iphone app (metoc) to measure things on the floor and vertical heights using just iphone camera. You need a printed paper pattern on the floor to give scale. Not as fancy as the VR apps, but works with still photos. Accuracy typically within 10th inch near the pattern and around 1-2 % further away (but not too far). Website is metoc.xyz