Simple Ratio (SR) — formula and who’s credited?
essential vegThe first vegetation index. Divide NIR by Red — see how much more NIR came back. A jungle gives you 30+, a parking lot gives you 1. Simple but the number has no upper limit, so you can’t easily compare scenes against each other.
That’s why NDVI replaced it for most modern work — same idea, but locked between −1 and +1.
SR = NIR / Red. Cohen (1991) identified it as the first true vegetation index. On Landsat TM: Band 4 / Band 3.
Simple Ratio = Simple division. No subtraction, no normalization — just NIR/Red. Unbounded. Cohen 1991 (not Rouse, that's NDVI).