Table 4 A summary of some chlorophyll (Chl) vegetation indices (VIs) which were used to estimate the Chl content of vegetation in previous studies

(1)

Normalized Difference VI (NDVI)

\(\frac{NIR - R}{NIR + R}\)

[69]

Optimized Soil-adjusted VI (OSAVI)

\(\frac{1.16(NIR - R)}{NIR + R + 0.16}\),

[70]

Enhanced VI (EVI)

\(\frac{2.5(NIR - R)}{{NIR{ + 6} \times R - 7.5 \times B + 1}}\)

[71]

Two-band Enhanced VI (EVI2)

\(\frac{{2.5\left( {NIR - R} \right)}}{R + 2.4 \times R + 1}\)

[72]

(2)

Renormalized Difference VI (RDVI)

\(\frac{NIR - R}{{(NIR{ + }R)^{1/2} }}\)

[73]

Pigment-specific Normalized Difference Index (PSND)

\(\frac{NIR - B}{NIR + B}\)

[20]

Transformed Chlorophyll Absorption Reflectance Index (TCARI)/OSAVI

\(\frac{{ 3 ( ( {\text{NIR}} - {\text{R)}} - 0. 2 ( {\text{NIR - G)(NIR/R))}}}}{{ ( 1 { + 0} . 1 6 ) ( {\text{NIR}} - {\text{R)/(NIR + R + 0}} . 1 6 )}}\)

[55]

(3)

Red-edge Chlorophyll Index (CI(red edge))

\(\frac{RE3}{RE1} - 1\)

[50]

Normalized Difference Red-edge Version 1 (NDRE1)

\(\frac{RE2 - RE1}{RE2 + RE1}\)

[54]

Normalized Difference Red-edge Version 2 (NDRE2)

\(\frac{RE3 - RE 1}{RE3 + RE 1}\)

[57]

Red-edge-based Transformed

Chlorophyll Absorption Reflectance Index/OSAVI (TCARI/OSAVI_RE)

\(\frac{{ 3 ( ( {\text{RE1}} - {\text{R)}} - 0. 2 ( {\text{RE1}} - {\text{G)(RE1/R))}}}}{{ ( 1 { + 0} . 1 6 ) ( {\text{NIR}} - {\text{R)/(NIR + R + 0}} . 1 6 )}}\)

[55]