Comparing the progression of green-up among years has been one of the most powerful uses of NDVI. The image of Kentucky at the top of the page is a 3 km square of horse farms and other agricultural fields near Lexington. Below is the last 11 years of NDVI data for this square from the MODIS sensor on the Terra satellite. These data are from the same 144 pixels recorded at this location every day since 2000 and summarized as 16-day averages. The striking message is that spring is coming very early this year in Kentucky.