# EVI2 values dont' come out -1 to 1? [closed]

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.

## closed as off-topic by PolyGeo♦Mar 13 '18 at 3:39

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• You can share your code to see if an error was made. Probably you're working with DN values instead of reflectance. – aldo_tapia Mar 12 '18 at 17:58
• I am almost certain that is the case! How do I convert DN to reflectance? – Mahavelona Mar 12 '18 at 20:11
• Yo have `ee.Algorithms.Landsat.TOA`. You can also compute it with some math formula (in Sentinel-2 just `DN/10000`). Without the code, I can't help you more – aldo_tapia Mar 12 '18 at 20:17