Are you using ERDAS model maker? Please look all the connect input to function, formula and output file (float single or unsigned 8-bit etc)

@kabir Uddin: Yes I am using ERDAS model maker.

what si NDMI? do you mean NDVI

@Saif Uddin: NDMI stands for Normalised Difference Moisture Index.

Thanks for explanation how different it is from NDWI and what ratios are you using for it.

Hi,

In order to store your first output as temporary raster to be utilized for performing the second function;

Double click the raster object and then look in the lower left of the dialogue box. There should be an option of "Temporary raster only". Check this box and then run your model. This should work.

Good luck!

Hi, I am not regular user of ERDAS. but for remote senced data processing. Arcgis 10.1 "raster calculator" as part of map algebra function easily do it.

If you are using Landsat images and model in ERDAS imagine just open NDVI model and replace the red (3rd Band) with NIR (4th band) and NIR (4th band) with MIR (5th Band) and don't change any other syntax. Run it and hopfully you can get your desire output.

@Richa Sharma: Thank you Richa. Let me try it out.

@Hammad Gilani: That would be really wonderful if it really works like that. Thanks a lot for the suggestion.

@Paresh Chaudhary: Actually I do not know how to work with the model maker available in Arc GIS. To create the functions and the algorithm we have to first build the model and that part is quite alien to me in Arc GIS. Only after that the raster calculator part will come.

@Saif Uddin: NDMI can easily detect water beneath vegetation cover. It effectively detects moist soil and vegetation. It is used in combination with NDWI for the aforementioned causes. In NDMI ratios of NIR band and SWIR bands are utilised.