Peer-Reviewed Articles
1375 SAR Interferometry: Software, Data Format, and Data Quality
Rüdiger Gens
Abstract
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SAR interferometry (InSAR) is on the way to becoming operational.
The main hurdles of SAR interferometric processing
have already been solved. However, solutions for sophisticated
processing steps such as phase unwrapping, etc., are still being
investigated. Furthermore , research on the potentials and limitations
of various applications has been carried out. Nevertheless,
Some aspects of InSAR software packages such as a
common data format and quantitative quality measures for
interformetric products are still widely neglected and are the
focus of this paper. Basic information about technical specifications
of available commercial and non-commercial software
packages was collected. A general format for SAR interferometric
data is proposed. The importance of the data quality
and suitable quality measures for InSAR data is discussed.
1379 Alternative Criteria for Defining Fuzzy Boundaries Based
on Fuzzy Classification of Aerial Photographs and Satellite Images
Jingxiong Zhang and Roger P. Kirby
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Results from an empirical test, using aerial photographs and
satellite images of an Edinburgh suburb, show that fuzzy
boundaries of land caver can be derived by using the three
criteria of maximum fuzzy membership values, confusion
index, and measure of entropy, with only small differences,
and that slicing based on the maximum fuzzy membership
values provides the easiest and most straightforward solution.
This result demonstrates the suitability of using both a crisp
classification and its underlying uncertainty map for deriving
fuzzy boundaries at different thresholds; together, they provide
flexible and compact management of categorical map data.
Distinctions between fuzzy boundaries and probabilistic
boundaries (such as epsilon error bands) are highlighted, thus
providing useful insights to exploring heterogeneous spatial
data of the real world.
1389 Probabilistic Prediction Models for Landslide Hazard
Mapping
Chang-Jo F. Chung and Andrea G. Fabbri
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A joint conditional probability model is proposed to represent
a measure of a future landslide hazard, and five estimation
procedures for the model are presented. The distribution of
past landslides was divided into two groups with respect to a
fixed time. A mining set consisting of the earlier landslides
and the geographical information system-based multi-layer
spatial data in the study area was used to construct the prediction
maps. The predictions were then cross-validated by
comparing them with the remaining later landslides. When the
database falls short of providing sufficient support for the
prediction, the model allows the introduction of the expert's
knowledge to modify the observed frequencies of the landslides
with respect to the spatial data. The additional information
should improve the prediction results. A case study
from the Rio Chincina region in Colombia was used to illustrate
the methodologies.
1401 An Application of Remotely Derived Climatological Fields
for Risk Assessment of Vector-Borne Diseases: A Spatial Study of
Filariasis Prevalence in the Nile Delta, Egypt
M.K. Crombie, R.R. Gillies, R.E. Arvidson, P. Brookmeyer, G.J. Weil,
M. Sultan, and M. Harb
Abstract
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This paper applies a relatively straightforward remote sensing
method that is commonly used to derive climatological variables.
Measurements of surface reflectance and surface radiant
temperature derived from Landsat Thematic Mapper data were
used to create maps of fractional vegetation and surface soil
moisture availability for the southern Nile delta in Egypt. These
climatological variables were subsequently used to investigate
the spatial distribution of the vector borne disease Bancroftian
filariasis in the Nile delta where it is focally endemic and a
growing problem. Averaged surface soil moisture values, computed
for a 5-km border area around affected villages, were
compared to filariasis prevalence rates. Prevalence rates were
found to be negligible below a critical soil moisture value of 0.2,
presumably because of a lack of appropriate breeding sites for
the Culex Pipiens mosquito species.
With appropriate modifications to account for local conditions and vector species, this approach should be useful as a means to map, predict, and control insect vector-borne diseases that critically depend on wet areas for propagation. This type of analysis may help governments and health agencies that are involved in filariasis control to better focus limited resources to identifiable "high-risk" areas.
1411 Measuring Land-Surface Directional Reflectance with the
Along-Track Scanning Radiometer
F.M. Danson, N.A. Higgins, and N.M. Trodd
Abstract
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The Along-Track Scanning Radiometer (ATSR) was she first
satellite-based instrument designed to routinely observe the
Earth's surface at two different view zenith angles. ATSR-1,
launched on ERS-1, was aimed specifically at measuring sea-surface temperature at high levels of precision; ATSR-2,
launched on ERS-2, continued this mission but included three
new channels in the visible and near infrared region which
provided an opportunity to examine land-surface reflectance
properties from nadir and near-coincident data from a sensor-view zenith angle of 55°. This paper examines the spectral
and directional reflectance information in ATSR-1 and ATSR-2
data of a test site in southeastern Spain. Spectral variation is
shown to account for approximately 76 percent of the total
variance in the image data sets, with approximately 18 percent
attributed to differences between the nadir and forward view
images. Data quality issues are highlighted and issues
concerned with collocation of the dual-view imagery are
discussed.
1419 Accuracy of Road Density Estimates Derived from USGS
DLG Data for Use in Environmental Applications
Timothy G. Wade, James D. Wickham, and David F. Bradford
Abstract
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Collection and analysis of information on accuracy of spatial
date is a growing and active field of research, but has tended
to emphasize land cover. Roads are another spatial data set
that is widely used in environmental studies, but information
on its accuracy is generally lacking. There are several sources
of road data, but all are based on U.S. Geological Survey
(USGS) Digital Line Graph (DLG) data. A three-part weight-of-evidence
approach is used to evaluate accuracy of road density
estimates based on 1:100,000-scale USGS DLG data at
different spatial scales. The first two components use population
to estimate accuracy of road density, because roads
are built to improve human access. The third part compares
USGS DLG roads with roads derived from digital orthophotoquads.
The results suggest that estimates of road density
using USGS DLG road data are of adequate accuracy for use in
habitat fragmentation or other studies requiring road density
data. Commercially available road data would not likely
provide significantly improved estimates of density,
1427 Query Optimization for a Distributed Geographic Information
System
Fangju Wang
Abstract
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Distributed geographic information systems (GESs) have advantages
in data sharing, reliability, efficiency, and system growth.
Query optimization substantially affects the performance of a
distributed GIS. In developing a system, query optimization is
one of the technical issues that must first be addressed. A
distributed GIS is different from a non-spatial distributed
database and requires special techniques for query optimization.
In this paper, a set of query optimization techniques are
presented that were developed in building a distributed GIS.
Two new definitions of spatial operations are introduced that
enable us to apply the well-developed operation-ordering
approach for strategy generation. A Petri net-based strategy-modeling method is described that is aimed at facilitating
strategy generation and cost estimation. A query optimization
algorithm is presented. Cost functions and selectivity functions
for spatial operations are described as well.
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