Tracking is much more restrictive, and the dog is on leash and in a harness so the "scene" is MUCH different.

My dogs have all been able to differentiate between the two easily. In upland work they are off leash, a bit farther out from you and are quartering and, you are carrying a gun (in hunting).

In upland work to teach trailing, you can introduce it by using your tracking training and having them follow a FRESH trail laid by dragging a fresh-killed duck along the ground. This kind of trailing is VERY easy for a dog to learn, especially if they have done any tracking training. Once they have the idea let them trail off leash. If you really want to see some good upland work go out with some advanced spaniel people! Things to teach the upland dog include quartering within shotgun range, taking quartering casts, and sit to flush (as well as the forced retrieve, of course).