NDVI (Normalized Difference Vegetation Index) calculated index is used to monitor crop health and vegetation density. The higher the index value, the greater the crop health and density. A color gradient is applied to mape the image easier to interpret. A commonly used gradient is red to green, with red representing the low values and green the high. Typically, four colors are used, with each accounting for approximately 25% of the field. This is similar to how a yield map represents data.