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Re: ENVI band math: "b1 gt b2 " , "(b1-b2) gt 0" same or not? [message #34755 is a reply to message #34751]

Thu, 10 April 2003 19:19

rmoss4
Messages: 21
Registered: October 2002

Junior Member

It sounds like you might be having a problem because of byte arithmetic.
What is the data type of you imagery?

Robert Moss, PhD

xinhai68 wrote:
> 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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[Message index]

		Re: ENVI band math: "b1 gt b2 " , "(b1-b2) gt 0" same or not? By: rmoss4 on Sat, 12 April 2003 08:25
		Re: ENVI band math: "b1 gt b2 " , "(b1-b2) gt 0" same or not? By: cshen on Sat, 12 April 2003 02:21
		Re: ENVI band math: "b1 gt b2 " , "(b1-b2) gt 0" same or not? By: David Fanning on Fri, 11 April 2003 20:29
		Re: ENVI band math: "b1 gt b2 " , "(b1-b2) gt 0" same or not? By: rmoss4 on Fri, 11 April 2003 20:02
		Re: ENVI band math: "b1 gt b2 " , "(b1-b2) gt 0" same or not? By: rmoss4 on Fri, 11 April 2003 19:59
		Re: ENVI band math: "b1 gt b2 " , "(b1-b2) gt 0" same or not? By: cshen on Fri, 11 April 2003 17:59
		Re: ENVI band math: "b1 gt b2 " , "(b1-b2) gt 0" same or not? By: rmoss4 on Fri, 11 April 2003 07:10
		Re: ENVI band math: "b1 gt b2 " , "(b1-b2) gt 0" same or not? By: cshen on Thu, 10 April 2003 22:48
		Re: ENVI band math: "b1 gt b2 " , "(b1-b2) gt 0" same or not? By: rmoss4 on Thu, 10 April 2003 19:19

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