I read your third post about the hard sand so it makes me change my post a bit. Normally in soft sand you can discriminate by depth. Gold Platinum rarely stays on top 2/3 inches. but in you case that's out the window. You can use the PP on the 3030 to determine depth accuracy. That is you can sweep in normal mode and get a depth reading.Then in PP and if your consistent in your sweep the PP will truly show the items depth! In discriminate foils and can slaw with show upwards of 4/6 inches but when you PP it wit show 2, and lack the strength in tone as compared to a solid target.
Numbers aren't your first choice to discriminate with tone and numbers and passed practices come into play.
BCNJ