Here is a video of the depth gage indicator in action in my test tank.Notice how sensative the indication is ,it seems to be pritty close to mm's .
Depending on when and where the sub is turned on the base starting point of the depth gage starts its readout.

A simple way to display depth,by using the altimiter sensor of the eagletree systems telemitry system.

http://www.youtube.com/watch?feature...;v=aKF096697PE