Hi Arfan, Because what you want to do will take more time to write out than pointing you were to look for information I will go with the latter. So, I would suggest that you have a look at the ENVI Help regarding the 2 areas you need to explore. For band math try the following location: Working with ENVI > ENVI User's Guide > Basic Tools > Band Math For your vegetation index look at: Working with ENVI > ENVI User's Guide >Vegetation Indices and look at the formulae that you need for your index calculations. If you have further questions it would help if you could provide as many details as possible about the data you are working with and what your goals are. ...Better suggestions can be made with that kind of information. What you could also include is what steps you have tried and where you may have looked for information. That way we know what bases have already been covered. Ciao

Actually I need to calculate soil index because in one of image I have a feature to whom I am confuse whether it is flooded water or some other feature because both the features having very similar appearance and I dont have any reference data to identify clear cut what that feature is? And I wish to calculate NDWI to delineate only the water in the image. I am trying to identify vulnerable landuse pattern along the coast line using the Landsat TM and ETM images. I already tried (spear tools-----> vegetation delineation) and (spear tools----->vegetation analysis----->vegetation calculator). from both functions I have been able to calculate NDVI, But did not able to find how to calculate NDWI and NDSI in ENVI. then I was only left to use Band math operation where I got stuck because I have no programming skills. Now kindly suggest me some solution, I have gone through your suggested material. arfan

From the ENVI main menu try the following: Spectral > Vegetation Analysis > Vegetation Index Calculator Make sure that your images contain the wavelengths needed to carry out your calculations. If you don't have the right wavelengths available you won't be able to chose from the list. This list will only show you what is available given the wavelengths you have in your image. Ciao

Why we use ENVI software to obtain NDSI images......Why not to prefer ERDAS Imagine......

Hi, I was just wondering the same thing. I explored a bit in ENVI 5 and found that the tools: Band Ratio > Band Math worked. for the NDSI (but in my case this was Normalised Difference SNOW Index), Landsat TM, I wrote in the "Enter an expression field:" (b2 - b5) / (b2 + b5), pressed Add to List, then clicked on the newly added expression, then clicked OK. The next dialog window asked me to define b2 and b5, and that was it!The same principle should work for water. As it was already proposed, ENVI Help is always useful, as long as one knows what to type in the search bar :) All the best!