EVI2 values dont' come out -1 to 1?

2018-03-12 20:26:56

I'm very new to remote sensing in general, and aren't sure if I've made an error.

I've calculated EVI2 for a Landsat 8 and Sentinel 2 image. Both Top of Atmosphere. I've used Google Earth Engine to calculate it.

The range of EVI2 has come out as -0.72 to 2.06 for the Sentinel image, and -0.20-0.94 for the Landsat image.

Every paper I've seen which shows EVI2 maps has a scale of -1 to 1. I've tried using ArcMap's stretch tool, with minimum-maximum set to -1 and 1, but the resulting image is mostly a block of white because many of the values are bigger than 1.

I'm confused! Should I present my EVI2 as -0.72 to 2.06, which is a nice image visually?

I have a similar problem with NDVI, although all my NDVI values fall between -1 and 1, the maximums are beneath them.