Alright, I'll contribute as well. I'd like to expand on cover and angles, specifically changes in cover and how sharp angles forces dogs off line. Lets consider a mark, thrown such that the gunner is aligned with the bottom of the hill and the mark is thrown up the hill such the dog must carry the side hill for more than a short distance. For the sake of argument let's just say ~150 yds on a side hill. Let's also consider that enroute to this mark, there is a change in cover that is a strip of taller, thicker grasses that is at an angle, 45 degrees or less (a very skinny angle), on the line to the mark. The straight line to the mark would be along the side hill, through the strip at a skinny angle. Let's ignore other considerations such as wind, lighting etc......
Do you think the dog would:
1- carry the line to the mark
2- flare the cover and fall off the hill
3- climb the hill and square the cover
Under this scenario you've got a couple of "Factors" the dogs must deal with.
1- running a side hill at a distance is not something most dogs do willingly. I don't blame them, running a side hill is not the most efficient way to get from point A to point B. Most would climb or fall off.
2-Angled cover. I'll use an analogy Ted Shih brought up in an earlier thread I think illustrates this effectively. Consider a spear thrown at a shield at a 90 degree angle. Chances are the spear will have a good chance to penetrate the surface. Now consider a spear thrown at a shield which is held at a 45 degree angle. Chances are good the spear will deflect away from the shield. Consider the dog the spear and the cover the shield. The more severe the angle the likely hood a dog will "flare" away from the cover. Evan brought this definition up earlier in this thread.
Ted Shih had some earlier threads about setting up Derby marks and all age marks. Mind you it isn't the only way to do things, just the way he approaches training to which I concur. Some of these concepts were discussed in greater detail and you might find them helpful.
http://www.retrievertraining.net/for...ad.php?t=80394
http://www.retrievertraining.net/for...ad.php?t=80693