Most of the time we find depth charts from lure companies to be extremely inaccurate.
Knowing your equipment is key as Mr. Dux alludes to. If you read my article however, it will give a very specific scenario in regards to importance of knowing what your equipment will do. Most do not tell you 15 feet down. Instead, they tell you 80 feet back. If you don't know or understand the curve and equipment, you have little clue as to depth.
Walleye are very depth dependent so that is what I am basing off from.
Precision trolling is measured with actual divers in the water so they are not using pathagareum theory or math or best guesses to measure depth. Certain lures will platue out quick so a set back of 140 is very little difference to 170.
Many diving lures are extremely speed dependant. That is also covered with precision trolling. If you don't want the app, you can purchase stick on cards for the specific lures you want.