2

I am trying to derive Enhanced Vegetation Index (EVI) from Landsat 5 TM data using ERDAS model builder.d I can't seem to get the output I want as it comes out blank.

This is the formula that I used:

2.5 * (("%Band 4%" - "%Band 3%") / ("%Band 4%" + 6 * "%Band 3%" - 7.5 *"%Band 1%" + 1))

can someone assist me with the exact formula I need to type into ERDAS model builder?

Does anyone see something in here that doesn't make sense -- or even better -- a formula I could copy/paste?

  • I can't help you with your formula, but what you are trying to do is impossible. EVI cannot be computed from Landsat 5 TM data. The constants you use are the original values for MODIS data but that has a true blue band (bands 8 and 9 are under 450nm), the TM band 1 is 450-520nm. You need Landsat 8 data to do EVI. – Patrick Mar 24 '14 at 11:58
  • my mistake, I am actually using Landsat 8 and encountered the same problem. I did the same thing in Arcmap and got satisfying results, however implementing the same procedure in ERDAS produced a blank output – Mokhine Motswaledi Mar 24 '14 at 12:08
2

Your problem is likely due to how your model handles bit-depth. EVI, like NDVI, ranges from -1 to 1 and has a practical range of 0 - 1. Therefore, if you try and perform the EVI (or NDVI) calculation and save it as an integer type raster (e.g. signed 8 bit), the output will appear to be black, or all one value. Rather, you need to save the output as a float type, which allows decimals. Alternatively, you can stretch the data to the full range of, for example, an 8-bit unsigned raster (0 - 256).

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.