28
ERDC TR-05-1
3.2
IKONOS
The primary post-processing step applied to the IKONOS image was to re-
project its coordinates to the NAD27 datum. Additional steps included:
Masking out (i.e., removing) cloud pixels.
Clipping (i.e., removing) the area outside the Lake Okeechobee levee.
Rescaling the 11-bit data to 8-bit data.
3.3
AISA
The reflectance data were provided on a set of nine CDs. Each flightline
included a suite of files including a reflectance calibrated image file (*.dat), an
ENVI formatted header file, a sensor information/calibration file, an instrument
calibration file, and an aircraft navigation file.
3.3.1
Geometric Correction
The raw reflectance data for each flightline were unzipped and individually
displayed to ensure the images were not corrupt. Based on the development of
the flightline diagram (Fig. 7), combined with an assumption of radically differ-
ent vegetation phonologies that would be observed in June as compared to Sep-
tember and October, post-processing of the AISA images was limited to the 7
and 30 June data.
Several test mosaics of a two to three adjacent flightlines, using only a subset
of bands to minimize processing time, were created to evaluate the geometric
fidelity of the AISA imagery. The mosaics showed acceptable georegistration of
the reflectance-calibrated images, with horizontal errors no greater than three to
four pixels. Certainly a higher level of geometric accuracy would be desirable.
However, considering the volume of data acquired and the intended purpose of
the imagery, this level of geometric accuracy was considered to be acceptable.
Figure 17 shows two examples of the typical departure of linear features between
adjacent flightlines.
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