**2.4 Vegetation fraction estimation**

To estimate the plant fraction above soil, nine vegetation indices were evaluated, reported in recent literature as the most appropriate in terms of results and adaptation to the type of crop or plant mass mapped. The equations and fonts for each of the selected indexes are shown in **Table 2**.

Operations for calculating indexes, according to the equations listed in **Table 2**, were performed using the Spatial Analysis tools in ArcGIS software. Specifically


**∗ ∗** *The band values are transformed ranging from 0 to 1, according to: Marcial et al. [9]*

**Rn** <sup>¼</sup> *<sup>R</sup> Rmax* **Gn** <sup>¼</sup> *<sup>G</sup> Gmax* **Bn** <sup>¼</sup> *<sup>B</sup> Bmax*

*where Rn, Gn, and Bn are the normalized values of its corresponding bands; R, G, and B are the original values of the red, green and blue, bands, respectively. Rmax = Gmax = Bmax are the maximum values for each band (255 for 24-bit colour images).*

*\*\* Obtaining the normalized spectral r, g, and b components, according to:*

*<sup>r</sup>* <sup>¼</sup> *Rn Rn*þ*Gn*þ*Bn <sup>g</sup>* <sup>¼</sup> *Gn Rn*þ*Gn*þ*Bn <sup>b</sup>* <sup>¼</sup> *Bn Rn*þ*Gn*þ*Bn*

#### **Table 2.**

*Most appropriate RGB indexes for the plant study reported in recent specialized literature.*

**Figure 2.**

*Orthophoto with different coverages and selection of sampling areas.*

worked on the Map Algebra tool, through which Spatial Analyst operators and functions were executed with the Raster Calculator, a simple Map Algebra expression was constructed and executed, using Python syntax in a calculator-like interface, designed for use in the application only as a tool dialog box [16].
