I'm trying to derive from MODIS 8 day composite MOD09Q1.006 product

My formula follows the standard interpretation:

EVI2 = 2.5(NIR-Red)/(NIR + 2.4*Red+1)

I already know that MODIS bands for NIR and Red have a scaling factor applied, and when I say "-1 to 1" I know I'm really expecting values to lie between -10000 and 10000.

My surface reflectance Band 1 and 2 (RED and NIR) values range from -100 to 16000 as they should.

When I perform my calculation for EVI using the previously mentioned formula, I have a wide range of values including roughly fitting between -25,000 to 25,000.

This leads to my question: How am I supposed to expect EVI2 values to fall between -1 and 1? Is there some kind of transformation I should be applying to my band values? With the multiplier of 2.5 in the formula, I see that the the function converges at 2.5 (thus those 25,000 values) as NIR approaches infinity.

  • @Luke you're right, that was my issues! thanks for the correct answer. I'm new here and I'm not seeing how to mark your comment as the answer yet.. can't upvote or anything. – arthur rosales Oct 22 '18 at 16:21
  • I've converted my comment to an answer. You can mark it as accepted using the tick between the voting buttons – user2856 Oct 23 '18 at 9:01

You need to apply the scaling factor so the NIR & Red values are 0-1 reflectance.

2.5(NIR*0.0001-Red*0.0001)/(NIR*0.0001 + 2.4*Red*0.0001+1)
  • I'll also comment that if you're working with standard MOD09Q1 data, sometimes processing that calc in a software like ERDAS is very time consuming with those decimal places. If you want to have the same format as MODIS NDVI, the formula after scaling by 10,000 could be: 2.5(NIR-Red)/(NIR+2.4*Red)+10000 – arthur rosales Oct 23 '18 at 18:16

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.