Many variables affect depth while longliniing. Jig weight, line weight and bouyancy, line length, and boat speed are the most important. I mainly adjust my jig weight, boat speed, and line length. Its not a precise method as each rod will vary some what in depth even with all these variables the same. You are trying to cover water and looking for aggressive feeders, so you are mostly targeting a depth zone that may vary up to four feet. Say you are keeping baits from 6-8 foot deep in 15 foot of water. Best thing to do is get out there and practice and find your way. There is not a chart or cheat sheet to go by. Hope this helps.