Alan2,
I use my GPS while hunting for Chukar. These birds are found in canyons up to 800 feet deep. Sometimes I hear them on the other side of the canyon, but there is no way to get there except to drive the long way around. I project a way point to the area the birds are in. Later when I make a hunt to the other side I can go to the projected way points. Since the birds move a lot it doesn't really matter that I am off.
In my Work as a Fish and Game reservist I also use projected way points.
In the spring I go out to catch Sage grouse and we put Radio collars on them. We study them to find out nesting areas and brood raising areas.
A lot of times I see birds fly away from the road and land out in the sage. I project a waypoint to that area so we can have a place to start looking for it later, without going out and bothering the bird right then. Ron