Measuring circumference

Refer the attached image,this is i want to do,measuring circumference of large shell.
For calculating this, im going to fix a sensor stationary and rotating shell, in this the sensor points from position say P0,now the shell rotates P0,P1,P2,sensor keeps tracking…After attaining the initial P0,the sensor stops,length is measured is that the circumference.
is this concept possible to implement?
i am new to arduino…kindly help.
is there any other method to calculate circumference of a big size shell?

I noticed you also posted about this on the Arduino forum, and it looks like there is some participation there. The Arduino forum is a much bigger community, so I encourage you follow-up with everyone posting there. Feel free to make a new post on our forum if you have specific questions about our products.

-Jon