I calculated Topographic Wetness Index (TWI) using SAGA and TauDEM. Overall trend is similar but SAGA returned larger values compared with TauDEM. Sometimes the deviations are as large as 7 or 8. I am using 1 m resolution DEM. I suppose the calculation methods are the same.

What is causing these differences?

  • 1
    What's your basis for supposing the calculation methods are the same? Did you read the technical documentation for each of those tools? The Wikipedia article about TWI says "Methods of computing this index differ primarily in the way the upslope contributing area is calculated," so presumably there are different ways of computing it.
    – csk
    Oct 21, 2019 at 19:26
  • You are, in fact, incorrect. The methods are different. It is up to you to figure out how and in understanding why it may matter. Oct 22, 2019 at 1:45
  • Hi, Thank you for your replies. I originally looked at the algorithm reference papers both applications were listing. But when I was looking at the results today, I realized that probably the catchment calculations were different or some part of either calculation was inverted. I’ll look into them. Thanks!
    – Sumi
    Oct 23, 2019 at 0:15


Your Answer

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

Browse other questions tagged or ask your own question.