Fig. 1. Predicted ET (FAO 56 and class A pan evaporation) vs. actual ET for the experimental periods. Trend lines and regression equations for each method are displayed. The dotted line represents lysimeter or actual ET.

Image from Applied Turfgrass Science article:
Irrigation Scheduling on Sand-Based Creeping Bentgrass: Evaluating Evapotranspiration Estimation, Capacitance Sensors, and Deficit Irrigation in the Upper Midwest