What are some good implementation of efforts to digitise an analog dial?

Question

For example,

• the dial of a watch is analog,

  

• in my machine of interest, there is a similar dial which gives the reading for Force.

  http://www.materialtestingmachine.in/full-images/analogue-universal-testing-machine-771364.jpg

I want to install a camera in front of the dial and from the received images, extract the information like time in watch or Force from UTM.

This data extraction has to happen in Real-time and continuously. So, for example, the program output should be "the time" read from the watch which updates say, every second.

Answer 1

First, I would put 4 markers around the dial to help automatic registration and perspective transform:

Now undo the measured perspective distortion and perfectly crop the dial around its center point:

Apply a polar to rectangular transform:

Select the colors of the pointers:

If you are lucky, you can cut out a horizontal strip of the above image, and easily find out the positions of the pointers, first the red one, because that's the front one, then the blue one, considering that it might be (partially) covered by the red one:

Disclaimer: I never did anything similar in real life, so this is just some self-entertainment for me :)