Difference between revisions of "QuickBird"

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m (Pan Sharpening)
m (Overview: "imagery MUST be converted to radiance")
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Panchromatic band (61-72cm pixel res)
 
Panchromatic band (61-72cm pixel res)
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From the whitepaper [http://www.apollomapping.com/wp-content/user_uploads/2011/09/Radiance_Conversion_of_QuickBird_Data.pdf Radiance Conversion of QuickBird Data]:
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<blockquote>QuickBird products are delivered to the customer as radiometrically corrected image pixels (qPixel,Band).
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Radiometric correction includes a dark offset subtraction and a non-uniformity correction (detector-to-detector
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relative gain). Corrected counts are specific to the QuickBird instrument and therefore QuickBird imagery MUST be
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converted to spectral radiance before radiometric/spectral analysis or comparison with imagery from other sensors in
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a radiometric/spectral manner.</blockquote>
  
 
== Import ==
 
== Import ==

Revision as of 05:56, 27 July 2013

Overview

Scenes are 16.5km x 16.5km.

Data is 11-bit integers stored in a 16-bit integer field. Thus band minimum = 0, band maximum = 2047.

Multi-spectral bands (2.44 - 2.88m pixel res)

band 1 = blue
     2 = green
     3 = red
     4 = Near IR

Panchromatic band (61-72cm pixel res)


From the whitepaper Radiance Conversion of QuickBird Data:

QuickBird products are delivered to the customer as radiometrically corrected image pixels (qPixel,Band).

Radiometric correction includes a dark offset subtraction and a non-uniformity correction (detector-to-detector relative gain). Corrected counts are specific to the QuickBird instrument and therefore QuickBird imagery MUST be converted to spectral radiance before radiometric/spectral analysis or comparison with imagery from other sensors in

a radiometric/spectral manner.

Import

Data comes in a GeoTiff file. Use the `gdalinfo` program to check projection settings. You can then set up a location based on this, e.g. UTM zone 23 South.

  • Once in the appropriate location import with the r.in.gdal module

Cleanup

Rename the NIR band

g.rename QBird_Multichrom.4,QBird_Multichrom.NIR

Red and blue bands are swapped, so fix that by renaming them. (see [1])

g.rename QBird_Multichrom.blue,QBird_Multichrom.realred
g.rename QBird_Multichrom.red,QBird_Multichrom.blue
g.rename QBird_Multichrom.realred,QBird_Multichrom.red

No data is set to 0, so convert that to NULL with r.null:

for BAND in red green blue NIR ; do
  r.null QBird_Multichrom.$BAND setnull=0
  echo $BAND:
  r.info -r QBird_Multichrom.$BAND
  echo
done

Set color tables appropriately for 11-bit data:

for BAND in red green blue NIR ; do
  r.colors QBird_Multichrom.$BAND color=rules << EOF
    0 black
    2047 white
EOF
done


It is not necessarily needed, but if you wish to rescale to 8-bit data you can use r.rescale as follows:

for BAND in red green blue NIR ; do
  r.rescale in=QBird_Multichrom.$BAND from=0,2047 \
     out=QBird_Multichrom255.$BAND to=0,255
done


Display the 3-band RGB image:

d.rgb r=QBird_Multichrom.red g=QBird_Multichrom.green b=QBird_Multichrom.blue

If the image is excessively dark you might try using the i.landsat.rgb module to auto-balance the colors and redraw:

i.landsat.rgb r=QBird_Multichrom.red g=QBird_Multichrom.green b=QBird_Multichrom.blue
d.redraw

Pan Sharpening

Use the i.fusion.brovey module.

i.fusion.brovey -q ms1=qbird_green ms2=qbird_nir ms3=qbird_red \
   pan=qbird_pan outputprefix=brov