Page 83 - Digital Analysis of Remotely Sensed Imagery

54 Cha pte r T w o

direction for the panchromatic band, and 6892 pixels for each of the
four multispectral bands. The spectral wavelength of both multi-
spectral and panchromatic bands extends from 0.45 to 0.90 μm. The
wavelength of the multispectral bands corresponds to the first four
Landsat 7 ETM bands, and the PAN band is also identical to its
ETM counterpart.
QuickBird imagery closely resembles that of IKONOS in its band
designation. For instance, both sensors contain four multispectral
bands and one panchromatic band that are quantized to 11 bits.
However, QuickBird images have two improvements:

• First, the spatial resolution has been improved from 1 m
and 4 m to 0.61 m in the panchromatic mode and to 2.4 m in
the multispectral mode (Table 2.20), respectively. These
resolutions, however, do vary with the viewing direction.
For instance, they degrade to 0.72 m and 2.8 m, respectively,
at the off-nadir angle of 25°.
• Second, the swath width is increased from 13 to 16.5 km.
QuickBird images can be PAN-sharpened by merging the
fine resolution panchromatic band with multispectral ones to
take advantage of the strengths of both images.

QuickBird data are offered to the public at three accuracy levels:
basic, standard, and georectified. Basic images are radiometrically
corrected and sensor corrected, but not geometrically corrected.
Standard images have been corrected for radiometric, geometric, and
sensor distortions. Georectified data have been projected to a ground
coordinate system. There is a minimum area-of-order restriction, its
actual value varying with imagery type and the nature of the order.
For basic images the unit of purchase is scene. A minimum order
of 25 km is imposed for standard archived images, 64 km for new
2
2
2
collection, and 100 km for orthorectified ones. These figures,
nevertheless, do vary with the urgency of the data order. Data can be
delivered in the GeoTIFF format electronically.
QuickBird imagery is an excellent source of environmental data.
It is useful for detecting changes in land use, agriculture, forest, and
climate. Thanks to its high spatial resolution, QuickBird imagery is
able to identify adequacy of irrigation and soil erosion quickly. It is
also possible to closely monitor and even optimize the use of
pesticides, fertilizer, and other agricultural treatments using QuickBird
data. In forestry, QuickBird satellite imagery can be used to monitor
logging, and assess damage caused by forest fires. Environmental
impacts of logging, such as stream sedimentation associated with
road construction, clear-cut harvesting, and slash-and-burn activities,
can be clearly detected from the imagery. In addition, QuickBird
satellite data can be potentially useful in environmental and hazard
assessment (e.g., damage caused by tsunami in the coastal area). It