Hi Gary, I havn't tried this specific one but have seen such over the years. They're better than nothing if you have the time and patience to stop, hold the thing very level, open and look.
Usually they have to be held within a very few degrees of level so as to allow the card to spin on its needle bearing freely. So, it's of no use trying to follow a course or read whilee moving. If you have any trouble telling where level is, or following a straight course once you've found it, then the thing will probably not help much. Hope this gives you some idea whether it'll fit your needs. Tom Fowle
