Well, there is a little tool which can be very acurate, but it was invented in Romania and never got a chance to exit the country. It doesn't even have a name in english, if you look for radiesthesic rod it doesn't give the right thing. So, go on google images and look for " ansa radiestezica ". It's a little Y shaped thingy made of silver or copper wire. You can make one yourself. And then draw one of those cards and voila ! Precise dowsing