A: Think of a measuring tape. The tape starts at zero. You don't record the zero, but it is the origin of your length measurements. Note that the plotted value for the extra depth is always zero. If your inclinometer installation is 12m deep, and you take readings at half-meter intervals, you will take 23 readings. Your bottom reading is taken at 11.5 meters, but the origin of that interval is at 12 meters. When DigiPro draws the plot, it establishes a zero at 12 meters.