Trolling with lead core line is a way to get down to deep water fishing. Lead core line is marked with ten different colors, each color ten yards in length. It's an inexpensive way to get to the water levels fish are located without using expensive downrigger devices, or weights. Speed and amount of line out are major factors in lure depth while using lead core line. This Application will factor these and other variables to obtain the greatest measure of accuracy of lure depth while using lead core line. Without a doubt has improved my annual catch of Trout and Bass, proving to me a few feet in depth can make a difference.