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SPOT 4,5 Natural Color?   Jakub Sisak Jan 06, 2009
Re: SPOT 4,5 Natural Color?   William Huber Jan 12, 2009
Re: SPOT 4,5 Natural Color?   Jakub Sisak Jan 15, 2009
Re: SPOT 4,5 Natural Color?   William Huber Jan 15, 2009
Re: SPOT 4,5 Natural Color?   Jakub Sisak Jan 16, 2009
Re: SPOT 4,5 Natural Color?   Lou Reed Mar 09, 2009
Re: SPOT 4,5 Natural Color?   William Huber Mar 09, 2009
Re: SPOT 4,5 Natural Color?   philip desmet May 06, 2009
Re: SPOT 4,5 Natural Color?   Jakub Sisak May 26, 2009
Re: SPOT 4,5 Natural Color?   Jakub Sisak May 26, 2009
Re: SPOT 4,5 Natural Color?   William Huber Jun 02, 2009
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Subject SPOT 4,5 Natural Color? 
Author Jakub Sisak 
Date Jan 06, 2009 
Message I downloaded SPOT satellite imagery 4 bands 20m and 1 panchromatic 10m.
I would like to create a natural color image but there is no blue value. I've read the process is not as straight forward as it is with Landsat7 and Quickbird. How can i do this in ArcGIS?

I can easily combine the bands and produce a nice Infra-Red image but there does not seem to be a way to make a Natural Color image.

Bands:
Panchromatic (10m)
B1 Green (20m)
B2 Red (20m)
B3 Near Infrared (20m)
4 Short Wavelength Infrared (20m)

Can someone explain the process to me using ArcGIS?

Thanks
 
  Jakub Sisak
jsisak@dstgroup.com
www.dstgroup.com 
   
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Subject Re: SPOT 4,5 Natural Color? 
Author William Huber 
Date Jan 12, 2009 
Message You can't manufacture data you don't have, Jakub, but you can fake it.

There are several algorithms for "pseudo natural color" around. One that is described clearly appears at http://myweb.facstaff.wwu.edu/wallin/envr442/COB_ColorIR2004_Processing.pdf . (Please ignore the AML code there: it has typos.) Essentially, it estimates what the blue band might look like based on the other bands. You can implement formulae like these with raster calculations. Let the SPOT bands be [B1] (500 - 590 nm), [B2] (610 - 680 nm, same as the "panchromatic" band), and [B3] (780 - 890 nm). (Band B4, 1580 - 1750 nm, is too far from the visible spectrum to be much use normally.) Compute

Blue = 0.85 * [B1] - 0.15 * [B3]
Green = 0.65 * [B1] + 0.35 * [B3]
Red = [B2]

and put them into a three-band "stack."

I mistrust this particular algorithm (the blue will never be intense and can even become negative), but it does show you the flavor of this approach.

More sophisticated methods are referenced at http://ceos.cnes.fr:8100/cdrom-00b/ceos1/science/gdta/ang/a1an/82.htm . The better ones require having true color images on hand for calibrating the estimates using some kind of classification or regression method. I could not find anything on the SPOT site itself that gives any information about their "pseudo natural color" product, even though some of their technical documents refer to it. 
  --Bill Huber
Quantitative Decisions (http://www.quantdec.com )
More GIS Q&A at http://gis.stackexchange.com/q/3083/664 
   
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Subject Re: SPOT 4,5 Natural Color? 
Author Jakub Sisak 
Date Jan 15, 2009 
Message Thanks. Very informative. Very interesting. I am just unclear on how i physically perform the emulation using ArcGIS 9.3. i don't use AML but am fluent in VB and ArcObjects. Or can this be done using the out of the box tools? Is this just a matter of recalculating each of the different rasters prior to assembly? Can you describe the process?
Thank You 
  Jakub Sisak
jsisak@dstgroup.com
www.dstgroup.com 
   
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Subject Re: SPOT 4,5 Natural Color? 
Author William Huber 
Date Jan 15, 2009 
Message You have the right idea, Jakub. Add the image to your map and use the Raster Calculator to create the pseudo color bands: the examples I gave use its syntax. You can also use the command line or scripting; details are available in the help at http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm . For reassembling the results, look for help on "grid stacks." 
  --Bill Huber
Quantitative Decisions (http://www.quantdec.com )
More GIS Q&A at http://gis.stackexchange.com/q/3083/664 
   
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Subject Re: SPOT 4,5 Natural Color? 
Author Jakub Sisak 
Date Jan 16, 2009 
Message Thanks William. I will definitely give this a try as soon as can. 
  Jakub Sisak
jsisak@dstgroup.com
www.dstgroup.com 
   
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Subject Re: SPOT 4,5 Natural Color? 
Author Lou Reed 
Date Mar 09, 2009 
Message Can this be done without the Spatial Analyst extention? 
   
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Subject Re: SPOT 4,5 Natural Color? 
Author William Huber 
Date Mar 09, 2009 
Message Use its equivalent, Lou. Alternatives include image processing software, GRASS, Manifold, Idrisi, etc. 
  --Bill Huber
Quantitative Decisions (http://www.quantdec.com )
More GIS Q&A at http://gis.stackexchange.com/q/3083/664 
   
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Subject Re: SPOT 4,5 Natural Color? 
Author philip desmet 
Date May 06, 2009 
Message An alternative is to use Globalmapper v9 or newer. It has a SPOT display function that basically at the push of a button converts the raw SPOT image to a "natural color" image. This can then be exported as an ECW image and loaded into ArcGIS. 
   
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Subject Re: SPOT 4,5 Natural Color? 
Author Jakub Sisak 
Date May 26, 2009 
Message Hi Philip,
Can you tell me where in Global Mapper can i find this function? i just downloaded v10.02 and am using the trial.
 
  Jakub Sisak
jsisak@dstgroup.com
www.dstgroup.com 
   
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Subject Re: SPOT 4,5 Natural Color? 
Author Jakub Sisak 
Date May 26, 2009 
Message I finally had a chance to try this. In case anyone is curious as to what the result looks like, check out the 2 attachments. I used the simple Raster Calculator technique provided by William.

The one small issue i had was with pan-sharpening the result. The raster calculator produced 32bit signed integer raster, so the outputs were not supported by the tool until converted to a supported format (8bit unsigned integer raster which was the original format).

If i find using more SPOT imagery i will explore the more sophisticated algorithms.

Thanks William 
  Jakub Sisak
jsisak@dstgroup.com
www.dstgroup.com 
  Emulated RGB.jpg (opens in new window)
Original Bands 1,2,3.jpg (opens in new window)
 
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Subject Re: SPOT 4,5 Natural Color? 
Author William Huber 
Date Jun 02, 2009 
Message Thank you for sharing your results, Jakub. 
  --Bill Huber
Quantitative Decisions (http://www.quantdec.com )
More GIS Q&A at http://gis.stackexchange.com/q/3083/664