Triangular Greenness Index (TGI) is calcultated from the area of a triangle that is defined by 3 points for the reflectance pf wavelength (480nm, R480, 550nm, R550 and 670nm, R670, R= Reflectance of wavelength). The formula for TGI is:

TGI = -0.5[190(R670 – R550) – 120(R670 – R480)]

Article: U.S. Department of Agriculture: Agricultural Research
Service, Lincoln, Nebraska at DigitalCommons@University of Nebraska – Lincoln

A visible band index for remote sensing leaf chlorophyll content at the canopy scale