Working with HTML5 Canvas object? For example Speedometer

In some test cases I need to verify the speed shown in the speedometer(varying for a particular period of time) is equal to the speed updated in any table(may be a DB).

Take the object attached in this question. The Speedometer needle moves from 0 to 140, Now the data updated in the table will be 140(take it as Milles or Kmph). I need to verify the needle position in the 140 and the table value as same. I mapped the object as a whole, But i didn't get the properties of the moving needle. I need to the meep the needle also as a value. So how to automate it?