comp.lang.idl-pvwave archive: archive » ENVI band math: "b1 gt b2 " , "(b1-b2) gt 0" same or not?

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ENVI band math: "b1 gt b2 " , "(b1-b2) gt 0" same or not? [message #34756]

Thu, 10 April 2003 18:48

cshen
Messages: 6
Registered: April 2003

Junior Member

I have a strange problem. I often used band math to generate mask,
such as "b1 gt 0" will give me 1 to all points which satisfies the
condition. But now I want to find all points that b1>b2, I meet
unexpected result. If I use "b1 gt b2", I get the correct answer. If I
use "(b1 - b2) gt 0", ENVI will also return a result, but I can not
guess what ENVI is doing because the result is weird. Can anyone tell
me what happened? Thanks

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