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Landsat
Processing Level
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Landsat data are typically available with
three levels of processing.
Level Ø Reformatted
(ØR, RAW)
Pixels are neither resampled nor are they
geometrically corrected or registered,
i.e. the pixels are not aligned per scan
line. Any radiometric artefacts such as
impulse noise, coherent noise, memory effects,
etc. are still present in any Level 0R
image. This product is for users able to
do all the processing themselves.
Level 1 Radiometrically
Corrected (1R, RADCOR)
The Level 1R product is a radiometrically
corrected ØR product, which corrects
detector artifacts such as coherent noise,
improves cosmetic artifacts such as banding,
striping, and dropped lines or pixels,
and is calibrated to radiance units,
i.e. colour corrected, as integer values.
Radiometric corrections are not reversible.
As for the Level ØR product, pixels
are neither resampled nor are they geometrically
corrected or registered, i.e. the pixels
are not aligned per scan line—see
image below. This product also requires
extensive processing by the user.
Level 1 System
Corrected (1G)
The Level 1G product should be considered
the standard product for most users. It
is radiometrically and geometrically corrected
to user-specified parameters, including
output map projection, image orientation
(defaults are UTM and WGS84), and resampling
algorithm (Nearest Neighbour or Cubic Convolution).
No atmospheric corrections are applied
to the images.
The System Corrected product is free from
distortions related to the sensor (e.g.,
jitter, view angle effect), satellite (e.g.,
attitude deviations from nominal), and
Earth (e.g., rotation, curvature). Residual
error in the systematic 1G product is less
than 250 metres for Landsat 7 (more for
other Landsat missions) in flat areas at
sea level. Absolute location is better
(circa 100 metres) with post-pass processing
using the definitive efemeris.
System Corrected images can be produced
with 2 different orientations: path oriented
(SYSCOR), that displays on the same rows
the satellite acquisition scan lines, or
map oriented (GEOREF—for full scenes
only) with north-up display.
The 1G System Corrected product does not
employ ground control or relief models
to obtain absolute geodetic accuracy. More
accurate processing (up to orthocorrection
with the use of GCPs and DEM) is available
as an additional service.
(left) Level 0R, RADCOR or 1R images
have unaligned scan lines
(right) System Corrected (Level
1G) with aligned, resampled pixels |
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