I am trying to standardise Standard Precipitation Index data and Vegetation Health Index data over time on a 0 to 1 scale. I was previously using the fuzzy membership function to standardise the data over space, but this was not reflecting the raw data appropriately, especially as the Standard Precipitation Index data has negative values which are of higher preference to larger, positive values.

I have tried the reclassify and rescaling functions but these have not proven to work either.

  • 1
    There is no ArcGIS Pro 10.8. Do you mean ArcMap 10.8 or ArcGIS Pro 2.7 perhaps?
    – PolyGeo
    Commented Feb 4, 2021 at 11:42

1 Answer 1


I would suggest you create 5 class for both data. Let say with below classification:

  • No drought; VHI >40; SPI > -0.5
  • Mild drought; VHI >30 to 40; SPI -1.0 to -0.5
  • Moderate drought; VHI >20 to 30; SPI -1.5 to -1.0
  • Severe drought; VHI >10 to 20; SPI -2.0 to -1.5
  • Extreme drought; VHI <10; SPI < -2.0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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