Just in reply to Higgins(and thanks for the bump),
the calibration? i don't think it's really an issue once you get used to your kit.
I use the barryvox pulse and Ortovox collar, it reads 0.7 per foot, once i can remember my 7 times tables i know what depth i'm looking at.
The Ortovox sends out it's signal more frequently than the B+F which is fine for quick readings, but if the dog is moving it does gives a rapidly changing signal which can be nevre wracking, until the dog settles.
The marking facility, would only be useful if you have 2 dogs to ground!!! or can't turn a collar off, It i