TSAVI=(s(NIR-s*Red-a))/(a*NIR+Red-a*s+X*(1+s2))
NIR = pixel values from the near-infrared band
R = pixel values from the red band
s = the soil line slope
a = the soil line intercept
X = an adjustment factor that is set to minimize soil noise
https://pro.arcgis.com/en/pro-app/latest/help/data/imagery/indices-gallery.htm