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Re: Multi-band sampling strategy [message #72169]

Wed, 18 August 2010 14:11

Maxwell Peck
Messages: 61
Registered: February 2010

Member

On Aug 19, 6:58 am, JessW <jess.wal...@gmail.com> wrote:
> Hi Allard,
>
> Interesting. You are correct; I'm using random pixel locations across
> an entire Landsat scene, so many of the pixels may fall in the same
> slice. I had assumed that since I specify a unique line/column
> address in the ENVI_GET_SLICE command, IDL retrieves only the values
> for that one pixel. But obviously if the command retrieves the entire
> slice prior to defining the column selection, it makes for an
> inefficient process, as you point out.
>
> I've tangled with histograms and reverse indices before; the
> experience left me with a splitting headache, so it may take me some
> time to successfully apply your suggestion to my program. I'll post a
> follow-up message when I have results.
>
> Thanks very much for taking the time to reply!
>
> Jess

Jess,

Allard's approach is certainly better. I was unclear initially if you
were subsetting 'rectangles' or random point locations. As Allard
suggests point ROI's can get slow if you have a lot.. It all really
depends on how many points we're talking.

Max

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[Message index]

		Re: Multi-band sampling strategy By: Maxwell Peck on Wed, 18 August 2010 14:11
		Re: Multi-band sampling strategy By: JessW on Wed, 18 August 2010 13:58
		Re: Multi-band sampling strategy By: wita on Wed, 18 August 2010 12:46
		Re: Multi-band sampling strategy By: penteado on Wed, 18 August 2010 11:09
		Re: Multi-band sampling strategy By: JessW on Wed, 18 August 2010 10:26
		Re: Multi-band sampling strategy By: Maxwell Peck on Tue, 17 August 2010 23:35
		Re: Multi-band sampling strategy By: JessW on Wed, 25 August 2010 11:13
		Re: Multi-band sampling strategy By: wita on Tue, 31 August 2010 02:08

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