Peer-Reviewed Article Abstracts
829 The Use of Intensity-Hue-Saturation Transformation of Landsat-5
Thematic Mapper Data for Burned Land Mapping
Nikos Koutsias, Michael Karteris, and Emilio Chuvico
Abstract
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Several techniques have been developed to detect and map burned areas
using Landsat Thematic Mapper data, ranging from simple ones, such
as visual analysis, to more complex, such as spectral mixture analysis.
However, the Intensity-Hue-Saturation transformation, a method mainly
used for merging multiresolution and multispectral data and for contrast-stretching
applications, has never been applied. In this study, a method is
presented by which transforming the RGB values of a three-channel
composite to IHS values, the mapping of areas affected by forest
fires can be easily achieved. Specifically, the hue component of
two RGB color composites, consisting of TM7-TM4-TM1 and TM4-TM7-TM1,
respectively, proved to be very useful in mapping of burned areas.
841 A Comparison of Canonical Discriminant Analysis and Principal Component
Analysis for Spectral Transformation
Gukang Zhao and Ann L. Maclean
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A study was conducted in Michigan's Upper Peninsula to test the strength and
weakness of canonical discriminant analysis (CDA) as a spectral transformation
technique to separate ground scene classes which have close spectral signatures.
Classification accuracies using CDA transformed images were compared to those
using principal component analysis (PCA) transformed images. Results showed
that Kappa accuracies using CDA images were significantly higher than
those derived using PCA at a = 0.05. Comparison of CDA and PCA eigen
structure matrices indicated that there is no distinct pattern in terms of
source variable contributions and load signs between the canonical discriminant
functions and the principal components.
849
LandScan: A Global Population Database for Estimating Populations at Risk
Jerome E. Dobson, Edward A. Bright, Phillip R. Coleman, Richard C. Durfee,
and Brian A. Worley
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The LandScan Global Population Project produced a world-wide 1998 population
database at a 30- by 30-second resolution for estimating ambient populations
at risk. Best available census counts were distributed to cells based on
probability coefficients which, in turn, were based on road proximity, slope,
land cover, and nighttime lights. LandScan 1998 has been completed for the
entire world. Verification and validation (V&V) studies were conducted
routinely for all regions and more extensively for Israel, Germany, and the
southwestern United States. Geographic information systems (GIS) were
essential for conflation of diverse input variables, computation of probability
coefficients, allocation of population to cells, and reconciliation of cell
totals with aggregate (usually province) control totals. Remote sensing was
an essential source of two input variables-land cover and nighttime lights-and
one ancillary database-high-resolution panchromatic imagery-used in V&V
of the population model and resulting LandScan database.
859 Remote Estimation of Grey Seal Length, Width, and Body Mass from
Aerial Photography
Sean D. Twiss, Paddy P. Pomeroy, Christopher J. Thomas, and Jon P.
Mills
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High-resolution images of two UK grey seal breeding colonies were derived
from multi-temporal aerial photography and geo-referenced in a GIS using
ground control points obtained in the field with sub-meter DGPS. Lengths and
widths of seals were digitized from these images. Elevations at seal locations
were determined using sub-meter DEMs, allowing measurements to be adjusted
for proximity to the camera. Mass estimates of seals were computed from these
measures using models developed from direct field measurements. Comparisons
of estimates derived from the images and actual masses of seals measured in
the field indicate that this method provides a consistent index of relative
body size. Seasonal patterns of changes in remotely determined size and mass
estimates and inter-colony comparisons mirrored patterns observed from direct
field measurements. Our work permits the remote estimation of seal body size
for any sample of seals without the intrusive complications and sample limitations
of direct field measurements.
867 Mapping of Urban Areas: A Multiresolution Modeling Approach for Semi-Automatic
Extraction of Streets
Isabelle Couloigner and Thierry Ranchin
Absract
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A new method to hierarchically extract urban road networks from very high spatial
resolution space-borne imagery (spatial resolution of 2 m and higher) is
presented. An explicit and generic model of "streets" was developed according
to a multiresolution analysis of images associated with a wavelet transform.
The method consists of two processing steps the multiresolution extraction
of edges of streets, and, if existing, the multiresolution extraction of
strips of streets. The extraction of sides is achieved by the use of a multiscale
representation of images, and the extraction of strips is done by a modeling
of distinct substructures of streets at different characteristic scales achieved
by the application of the associated wavelet transform. The method would
help cartographers in their cartographic works in urban areas by a partial
automation of tasks.
875 Accuracy Assessment Curves for Satellite-Based Change Detection
Jeffrey T. Morisette and Siamak Khorram
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The concept of "accuracy assessment curves" as they relate to image-based change
detection is developed. These curves are a graphical representation of the
relationship between typical accuracy assessment figures and a binary change
detection threshold level. After an introduction to accuracy assessment curves,
an example is presented. The relationship between typical accuracy assessment
parameters and the location of the binary change threshold level is first shown
with a series of error matrices. This relationship is then expanded across
a range of thresholds and shown as accuracy assessment curves. These curves
show how accuracy figures are dependent on the change metric's threshold level.
This dependency indicates some limitations of binary change maps. These limitations
provide the impetus for a continuous change product. We describe how a continuous
Probability-of-change (POC) image, derived from statistical models, can be
incorporated with the accuracy assessment curves to produce a more meaningful
and informative change detection product.
881 Exploring the Capability of Some GIS Surface Interpolators for
DEM Gap Fill
Peter Doucette and Kate Beard
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Scene occlusions in aerial or satellite imagery are at times an unavoidable
occurrence resulting from natural or mechanical effects. At their most severe,
occlusions can render terrain modeling and feature extraction tasks incomplete
or impossible in affected regions of an image, creating gaps of missing information
in the extracted data sets. In lieu of alternative sources, a simple solution
for gap fill of digital elevation data may be to perform interpolation, provided
the gap is not impracticably large. The expediency that interpolation offers
must be appropriately justified vis-a-vis the potential for substantial uncertainty
in the estimates. This study evaluates the gap fill capabilities of four
ESRI Arc/Info offered surface interpolator functions: (1) kriging, (2) splining,
(3) inverse distance weighting, and (4) surface trend analysis. Using a simple
error assessment approach with different terrain textures, the evaluation
tends to favor the use of the splining function when interpolating for the
kind of gaps and sample configurations considered.
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