I think you are asking what expression to supply in the Band Math tool? Can you provide more information about how you wish to combine the different RapidEye rule images? Do you want to choose whichever class is most commonly chosen for each pixel, among the different RapidEye classifications at different times? Or would there be some other criteria for assigning the final class value to each pixel, based on the rule images? - Peg

Dear Peg, thanks so much for feedback. Yes, right, i need appropriate expression. Your question about final class value is very good. I think, according to my thesis, the first one with common class value from different images. My issue is: i have 4 multitemporal RapidEye Scenes ( May,Juni, July, August) and i have to classify each of this image by 3 different classifiers (Neural Net, SVM and Maximum Likelyhood) and then assemble these 4 images in final result, so that final result supplies better accuracy assessment. I have in general 6 crop classes as ROIs and to achieve the best goal in classification accuraca for land use map- i have to combine the results from these time-different images in one final result, so that it may be supplies nice result in accuracy to distinguish my crop classes. THANKS in advance!!!

Pleassseee help me.....i need this expression so much!!! Thank you, Dear Peg!!!

Surely you are not going to let Dear Peg do your research for you!

Sorry, I haven't had time to check the forum recently. I had hoped that you'd be looking around in IDL to figure out how to construct your own expression in the meantime, since it sounds like you had figured out exactly what you want it to do. I think you were saying that you need an expression that finds the most common class assigned to each pixel among the classification images from the four dates. I don't have time to write up a full Band Math function for that right now. But basically, I think you'll want to create a Band Math function (which can then have more than one line), that assigns each pixel the Mode (the value that appears most often) of the values from the four classification images. Here's a post in the IDL newsgroup that might help you put together some code to do what you want: https://groups.google.com/forum/?fromgroups=#!searchin/comp.lang.idl-pvwave/%22most$20common$20value%22$20in$20an$20array/comp.lang.idl-pvwave/eSgHgMuwvg4/JQzBSw9kObMJ Peg

Thanks for your reply. Unfortunately i have only ENVI 5 classic and no IDL, with IDL i cannot work. I am sorry to disturb you, but i hadnot in mind to take your time to research anything for me, because i simply though- there is one concret expression for this case in band math in ENVI 5. Actually it should not be so complicated with the expression as it seems like in your post from IDL newsgroup above..