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

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).

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