|
|
|
|
•Each GeoCover mosaic image covers an area
approximately six degrees of latitude by six degrees of longitude.
|
|
•To completely cover a state and the Landsat
scene footprints around a state, multiple GeoCover mosaics are used.
|
|
•The GeoCover handling steps are 1) Imported into Erdas Imagine 2) Reduced to
band two only 3) Resampled from 28.5 to 30 meters 4) Reprojected to one
common UTM zone per state 5) Stitched together with other images to cover the
state footprint 6) Exported to .LAN format.
|
|
•All CDL products are currently processed
entirely by PEDITOR
|
|
•Finalized mosaics are exported to Geotiff
format upon completion.
|
|
•PEDITOR’s Batch program routines process the
scenes in as little as a few hours for the simple mosaics, and can run up to
2/3 a day on a large/complex state with many seams/stitch lines/cloud
problems.
|
|
•The Landsat TM/ETM+ scenes used are
radiometrically and systematically corrected.
There is a need to tie down registration points on a continuing basis
for every scene within each state in the project. Without some image/image registration, the
scene registration tends to float 2-3 pixels in any given direction, for any
given scene.
|
|
•An automated registration method was developed
to co-register each raw scene to an ortho-base image, and then to apply each
raw scene’s correlation coefficients to the categorized scenes.
|
|
•Image recoding is necessary between different
analysis districts, to rectify to a common signature set for a state.
|
|
•Once an Analysis District is categorized, it
possess a unique set of signatures.
These signatures are recoded to a master signature set. For instance, a corn signature or category
may have between 1 and 50 classes for a given Analysis District, and they are
condensed into one class or digital number for the final mosaic. This is done for every cover type in the
project.
|
|
•Clouds pose a big problem when trying to make
acreage estimates, and there are mechanisms within PEDITOR to minimize their
extent, as there are ways to minimize cloud coverage in the mosaic process by
prioritizing scene overlap.
|
|
•Each categorized scene needs to be
geo-registered to an ortho-base image. A block correlation is run between
band two from each raw scene, and band two of the ortho-base image. The
registration of the GeoCover mosaicked scene and the individual raw input
scenes are used to get an approximate correspondence. A correlation procedure is used on the raw
Landsat scenes and the mosaicked scene to get an exact mapping of each pixel
from the input Landsat scenes to the mosaicked scene. The results of the correlation are used to
remap the pixels from the individual input scenes into the coordinate system
of the mosaicked scene.
|
|
•The mosaic process now performs: 1)
Automates image registration/rectification, 2) Converts each categorized image and
associated statistics file to a set standard automatically (recode), 3)
Specifies overlap priority by scene or county, 4) Filters
out clouds when possible
|
|
•Each scene is co-registered to EarthSat's
GeoCover LC imagery (50 meters RMS), and then stitched together using the
priorities previously assigned from the scene observation dates/analysis
districts map.
|
|
•Scenes/analysis districts with better quality
observation dates are assigned a higher priority when stitching the images
together.
|
|
•Clouds are assigned a null value on all scenes,
and scenes of lower priority that are cloud free, take precedence over cloudy
higher priority images.
|
|
•Once cloud cover is established throughout the
mosaic the clouds are assigned a digital value.
|
|
|