Before si units came into being I found them by just doing long days on the water. Then keeping meticulous records and returning to same spots year after year. But all that changed when I started using si sonar. While I have on occasion smelled a bluegill bed that is not a set in stone way to find them. The use of si units just changed everything for me. I could dissect an area in minutes and find them or move on. Even on a new big lake it has not been an issue finding them with si. I know that sounds simple but no other way to put it. For a little over 11 years now that is how I have caught so many shell cracker and bluegill.
Regards