Peer Reviewed Articles
709 Automatic Reconstruction of Road Centerlines from Mobile Mapping
Image Sequences
Chuang Tao, Rongxing Li, and Michael A. Chapman
Abstract
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An automatic approach to road centerline reconstruction
from stereo image sequences acquired by a mobile mapping
system is introduced, The rood centerline reconstruction is
treated as an inverse problem and solved by global optimization
techniques. The centerlines are described by a physical
curve model, which is composed of an abstract material and
deforms according to external and internal forces applied.
The external forces, generated from the centerline information
extracted from the image sequences, controls the local
characteristics of the model. The internal forces, arising from
a priori knowledge of the road shape, contribute to the global
shape of the model. Unique constraints that exist only in
mobile mapping image sequences are utilized. The developed
system has been used for processing a large number of
mobile mapping image sequences. Road centerlines of the
images under different conditions have been reconstructed
successfully. The research results also make a contribution
to the general field of structure from motion and stereo.
717 Improving Landsat Scene Selection Systems
Kenneth McGwire
Abstract
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With the goal of periodic global coverage, Landsat 7 will create
a wide variety of opportunities for the use of high-resolution
data at regional and global scales. However significant
improvements to the information systems for Landsat scene
selection are necessary to support such wide-area applications.
There may be significant phenological differences to be
captured in such wide-area surveys, and trade-offs between
image timing and quality must be considered on a scene-by-scene
basis. Ancillary environmental information can be integrated
into the scene selection to ensure the most phenologically
consistent image acquisitions. Also, by defining a
weighting function, users can substantially automate the
scene selection process for extensive and complex compilations
of Landsat scenes.
723 Algorithms for the Detection of Sub-Pixel Targets in Multispectral
Imagery
Edward A. Ashton and Alan Schaum
Abstract
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A new sub-pixel target detection algorithm is developed that
integrates a linear mixing model (LMM) with the powerful "RX' anomaly detector of Reed and Yu (1990). RX applied
to mixing model errors instead of to measured radiances, because
they are more nearly multivariate Gaussian. The integrated
method consistently outperforms spectral anomaly
detectors that are based on either RX or an LMM alone. A
novel method of image-based endmember selection is also
presented, and a simple method of computing the fully constrained
LMM residuals is described.
733 Resource Management of Forested Wetlands: Hurricane Impact and
Recovery Mapped by Combining Landsat TM and NOAA AVHRR Data
Elijah W. Ramsey III, Dal K. Chappell, Dennis Jacobs, Sijan K. Sapkota,
and Dan G. Baldwin
Abstract
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A temporal suite of NOAA Advanced Very High Resolution
Radiometer (AVHRR) images, transformed into a vegetation
biomass indicator, was combined with a single-date classification
of Landsat Thematic Mapper (TM) to map the association
between forest type and hurricane effects. Hurricane
effects to the forested wetland included an abrupt decrease
and subsequent increase in biomass. The decrease was associated
with hurricane impact and the increase with an abnormal
bloom in vegetation in the impacted areas. Impact
severity was estimated by differencing the biomass maps before
and immediately (3 days) after the hurricane. Recovery
magnitude was estimated by differencing the biomass maps
from immediately (3 days) after and shortly (1.5 months) after
the hurricane. Regions of dominantly hardwoods suffering
high to moderate impacts and of dominantly cypress-tupelos
suffering low impacts identified in this study corroborated
findings of earlier studies. Conversely, areas not reported in
previous studies as affected were identified, and these areas
showed a reverse relationship, i.e., highly impacted cypress-tupelo
and low or moderately impacted hardwoods. Additionally,
generated proportions of hardwood, cypress-tupelo,
and open (mixed) forests per each 1-km pixel (impact and
recovery maps) suggest that regions containing higher percentages
of cypress-tupelos were more likely to have sustained
higher impacts. Visual examination of the impact
map revealed a spatial covariation between increased impact
magnitudes and river corridors dominated by open forest.
This spatial association was corroborated by examining
changes in the percentage of open forest per 1-km impact
pixel; the percentage of open forest peaked at moderate to
high impacts. The distribution of recovery supported the impact
spatial distribution; however, the magnitudes of the two
indicators of hurricane effects were not always spatially dependent.
Converse to univariate statistics describing all forested
area within the basin, higher recoveries tended to be
related to higher percentages of hardwoods. Lower recoveries,
on the other hand, tended to be related to forests with
nearly equal percentages of hardwoods and cypress-tupelo.
739 Identifying the Effects of the Gulf War on the Geomorphic Features
of Kuwait by Remote Sensing and GIS
Magaly Koch and Farouk El-Baz
Abstract
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Satellite images combined with landform/surface maps are
used to identify and characterize changes in the desert surface
of Kuwait resulting from military activities during and
after the Gulf War of 1991. These changes are producing alterations
to the surface sediment and morphological features
that lead to environmental degradation.
A geographic information system (GIS) is used to integrate
and analyze multi-source and multi-scale data derived
from satellite images, maps. and field observations. The GIS
is used to identify, describe, and characterize changes occurring
in the landform patterns, the nature and extent of land
surface change, and their potential impacts on the environment.
Postwar satellite images are correlated with prewar
field maps, allowing identification of changes in surface sediment
types and geomorphic units, focusing on areas showing
changes in surface dynamics. Such areas are identified and
classified in terms of alterations in the extent of surface sand
(postwar sand encroachment) and the impact of oil pollution
(formation of layers of tarcrete). The GIS analysis shows that
21.6 percent of Kuwait's area has been affected by the Gulf
War, of which 4.4 percent is due to oil pollution and 17.2
percent is due to remobilized sand sheets. These results suggest
that a reclassification of Kuwait's geomorphic features is
needed to take into account these war-related surface
changes.
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