Measuring distance with iPhone camera

Question

How to implement a way to measure distances in real time (video camera?) on the iPhone, like this app that uses a card to compare the size of the card with the actual distance?<

Answer 1

Another solution may be to use two laser pointers.

Basically you would shine two laser pointers at, say, a wall in parallel. Then, the further back you go, the beams will look closer and closer together in the video, but they will still remain the same distance apart. Then you can easily come up with some formula to measure the distance based on how far apart the dots are in the photo.

See this thread for more details: Possible to measure distance with an iPhone and laser pointer?.