Peer-Reviewed Articles
49 Non-Differential GPS as an Alternative Source of Planimetric Control
for Rectifying Satellite Imagery
Jay Gao
Abstract
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The objective of this study was to determine the feasibility of using
uncorrected Global Positioning System (GPS) coordinates to accurately
rectify satellite imagery. Sixty GPS positions were logged with a
Trimble Geo-Explorer receiver at an interval of 5 seconds in three
separate sessions for 20 ground control points (GCPs) around Auckland,
New Zealand. The true coordinates of these GCPs were established
by averaging 60 differentially corrected loggings. The coordinates
of these GCPs were also read from large-scale topographic maps. All
of these coordinates were used to rectify Landsat TM, and SPOTpanchromatic
(PAN) and multispectral (XSL) images in a first-order polynomial
transformation. It was found that image rectification accuracy in
meters is inversely related to image pixel size, but positively correlated
with the quantity of GPS loggings. Coarse-resolution imagery can
be rectified to within 1-pixel size accuracy using two thirds of
the selected GCPs based on coordinates averaged from 30 sequential
loggings for TM and SPOT XSL. SPOT PAN imagery is more
difficult to be accurately rectified using uncorrected GPS coordinates.
Its satisfactory rectification requires a minimum of 30 integrated
or 60 sequential loggings. GPS coordinates averaged from as few as
30 sequential loggings can achieve a consistently higher rectification
accuracy than that from 1:20,000-scale map coordinates. It is concluded
that non-differential GPS coordinates can serve as a reliable
alternative to planimetric control for rectifying satellite imagery
of Earth resources.
57 An Edge-Preserving Filter for Imagery Corrupted with Multiplicative
Noise
H.C. North and Q.X. Yu
Abstract
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In the segmentation of natural imagery, differentiation at feature
boundaries is of crucial importance. The high-amplitude, multiplicative
speckle noise present in synthetic aperture radar (SAR) data demands
a high level of filtering, yet this noise must be removed without
destroying the critical feature boundary information. We previously
designed the minimum coefficient of variation (MCV) filter to meet
the twin demands of noise removal and edge preservation in SAR imagery.
MCV-filtered images exhibit clear feature boundaries, but the filter's
strong edge-preserving nature also introduces step edge artifacts
in areas of intensity gradient and texture. We present the modified
MCV filter (MMCV) which is able to significantly reduce the occurrence
of filtering artifacts, while retaining an edge-preserving character.
The MMCV filter is compared to existing filters by operating them
on SAR imagery and deriving edge maps from the filtered imagery.
Though the MMCV-filtered image is not the most visually pleasing,
the linework derived from it is the most useful in terms of clean,
continuous feature boundaries.
65 An Uncertainty-Based Method of Photointerpretation
Benoît Thierry and Kim Lowell
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In the creation of forest type maps, photointerpreters first identify
features that are the most certain, and subsequently identify features
that are less certain in order to complete the map. In the present
study, a method of photointerpretation is proposed in which only
those features that an interpreter believes to be -100 percent certain£ are
identified. This results in interpretations that are not polygonal
and that do not cover an entire photograph but that are instead treated
using spatial interpolation to produce surfaces containing fuzzy
membership values (FMVs) for all map classes at all locations in
the area under study. These FMV surfaces can then be manipulated
to produce thematic maps in which areas have a known certainty. The
method is demonstrated using a synthetic image. It is concluded that
maps resulting from this alternative method of photointerpretation
are no more or less accurate than those produced from conventional
polygon-based photointerpretation procedures. However, the alternative
method provides considerable time savings and also provides an estimate
of the certainty of each area on the final thematic map -- something
that the conventional photointerpretation method does not produce.
73 Spatial Prediction of Fire Ignition Probabilities: Comparing Logistic
Regression and Neural Networks
Maria José Perestrello de Vasconcelos, Sara Silva, Margarida Tomé,
Margarida Alvim, and José Miguel Cardoso Pereira
Abstract
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The objective of this work was to develop and validate models to predict
spatially distributed probabilities of ignition of wildland fires
in central Portugal. The models were constructed by exploring relationships
between ignition location/cause and values of geographical and environmental
variables using logistic regression and neural networks. The conclusions
are that (1) the spatial patterns of fire ignition identified can
be used for prediction, (2) the spatial patterns are different for
the different causes, (3) the logistic models and the neural networks
both reveal acceptable levels of predictive ability but the neural
networks present better accuracy and robustness, (4) the maps produced
by the two methods are similar, and (5) the information contained
in the spatial position of ignition events can be used to gain predictive
capability over an important phenomenon that is difficult to characterize
and, for that reason, has not been included in most of the currently
used fire danger estimation systems.
83 Measurement and Monitoring of Urban Sprawl in a Rapidly Growing
Region Using Entropy
Anthony Gar-On Yeh and Xia Li
Abstract
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Rapid urban development and dramatic change of landscape have been
recently witnessed in some developing countries as a result of rapid
economic development. The measurement and monitoring of land-use
changes in these areas are crucial to government officials and planners
who urgently need updated information for planning and management
purposes. This paper examines the use of entropy in the measurement
and monitoring of urban sprawl by the integration of remote sensing
and GIS. The advantages of the entropy method are its simplicity
and easy integration with GIS. The measurement of entropy is devised
based on two locational factors -- distances from town centers and
roads -- to capture and reveal spatial patterns of urban sprawl.
The entropy space can be conveniently used to differentiate various
kinds of urban growth patterns. The application of the method in
the Pearl River Delta, one of the fastest growing regions in China,
has demonstrated that it is very useful and effective for the monitoring
of urban sprawl. It provides a useful tool for the quantitative measurement
that is much needed for rapidly growing regions in identifying the
spatial variations and temporal changes of urban sprawl patterns.
91 An Automatic Method for Vine Detection in Airborne Imagery Using
the Wavelet Transform and Multiresolution Analysis
Thierry Ranchin, Bernard Naert, Michel Albuisson, Gilbert Boyer,
and Pär Åstrand
Abstract
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The problem of automatic vine detection from airborne Infrared Color
(IRC) images is addressed. An automatic method was designed, based
on a separate modeling of the textural and spectral information extracted
from the data. A multi-resolution analysis associated with a wavelet
transform allows the separation of spectral and spatial information.
After a description of the vine detection problem, the automatic
method is described. An example application is proposed and a quantitative
evaluation of the results achieved is presented. The analysis of
the results demonstrates the efficiency of the method. The square
system of planting is the main source of errors. But this growing
technique is now nearly abandoned in France due to mechanization.
Thus, this method may help photointerpreters in the updating or definition
of agricultural registers of vineyards as defined by the European
Commission.
99 Integration of Aerial Remote Sensing, Photogrammetry, and
GIS Technologies in Seagrass Mapping
Vanina Pasqualini, Chistine Pergent-Martini, Philippe Clabaut, Hervé Marteel,
and Gérard Pergent
Abstract
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With a view to implementing a sound management of littoral plant formations,
and more particularly that of seagrass beds, it would appear of interest
to test the potentiality of image processing for various types of
photographs (color, infrared, and black and white). The present study
was carried out within the Gulf of St-Florent (Corsica, France) on
a Posidonia oceanica reef platform. Over the last 40 years, no major
diachronic evolution has been observed within this plant formation.
An erosion of the coastline has been noted inland of these seagrass
beds, however, with erosion values of up to 40 m. The use of photogrammetric
techniques, which are new to the marine environment, allows the possibility
of obtaining a numeric model of a given site. The comparison of cartographic
and bathymetric data, brought together in a geographic information
system, allows the spatial distribution of seagrasses to be evaluated
for the first time.
107 CAD-Based Object Reconstruction Using Line Photogrammetry for Direct
Interaction between GEMS and a Vision System
Guoqing Zhou and Deren Li
Abstract
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The paper presents an algorithm for reconstructing Geometric Element
Modeling System (GEMS)-based industrial objects using line photogrammetry
(LP) in order that there can be direct interaction between GEMS and
a vision system. In the GEMS system, each object is constructed by
Boolean set operators of constant solid geometry (CSG) primitives,
each face of which is described by a Boundary presentation (B-pre);
and straight lines, curves, planes, and curved surfaces are described
by parametric equations. Based on this type of data structure and
representation, the geometric elements which describe industrial
objects in GEMS, are taken as unknowns, and are directly solved for
by matching images (2D) and objects (3D). Compared to traditional
photogrammetric DEM products, the advantage of this algorithm is
that the product of reconstruction is parameters describing the industrial
object, which can be directly fed back to the GEMS system. It is
convenient to communicate between GEMS and the vision system without
any transformation. On the other hand, the developed mathematical
model can be used not only for line-to-line correspondences but also
for line-to-surface or surface- to-surface correspondences. A number
of simulations and practical experiments demonstrated that this algorithm
is feasible and reliable in industrial computer vision.
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