The simple ratio vegetation index (RVI) is calculated using the following formula: **RVI = NIR / RED** where NIR and RED (or VIS) are the response in the near-infrared and red or visible bands respectively. RVI values for bare soils generally are near 1; as the amount of green vegetation increases in a pixel (picture element), the RVI increases. Note that the RVI is not bounded; its values can increase far beyond 1. Information from http://www.ccpo.odu.edu/SEES/veget/class/Chap_4/4_5.htm