Peer Reviewed Articles
1165 Potential of High-Resolution Satellite Imagery for National
Mapping Products
Rongxing Li
Abstract
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The potential of the upcoming high-resolution (1-m ground
resolution) satellite imagery for national mapping products is
discussed. An analysis of the capabilities of these high-resolution imaging systems and existing satellite imaging systems
for the representation and extraction of elevation information,
such as terrain relief displacement and parallaxes, is
given. In-track and cross-track stereo mapping techniques using
satellite pushbroom CCD linear arrays are described. A
photogrammetric processing model considering such geometry
is introduced. Based on an error estimation and analysis,
it is concluded that, if the strict photogrammetric processing
model and ground control points are employed, high-resolution
satellite imagery can be used for the generation and update
of national mapping products (7.5-minute quadrangles
at a map scale of 1:24,000),including Digital Elevation Models
(DEM], Digital Orthophoto Quadrants (DOQ), Digital Line
Graph (DLG) databases, and Digital Shoreline (DSL) databases.
1171 Wavelets for SAR Image Smoothing
Graham Horgan
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Wavelets are an increasingly widely used tool in many applications
of signal and image processing. This paper reviews
the basic ideas of wavelets for representing the information
in signals such as time series and images, and shows how
wavelet shrinkage may be used to smooth these signals. This
is illustrated by application to a synthetic aperture radar image.
Some guidelines on using wavelet shrinkage are given.
1179 A New Algorithm for Surface Determination Based on Wavelets and
its Practical Application
Jaan-Rong Tsay and Bernhard P. Wrobel
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A new wavelets-based algorithm, FAST Vision (facets stereo vision). is presented for an automatic and simultaneous determination
of an object surface and its ortho image. Two
families of orthogonal and C1 -continuous (continuously differentiable)
object gray-value models, called "S-D-model" and "S-model, " respectively, were developed from the basic
concept of multiresolution spaces. Both models establish two
families of very simple gradient operators and enable FAST
Vision to do a very high resolution representation of an object
surface and a fast solution of a very large system of normal
equations. Test results using digitized aerial images at a
scale of 1 :4000 show that FAST Vision is capable of a fast,
highly resolved, reliable, and precise determination of an object
surface in large windows and with rigorous error computations.
The very high resolution of 2 by 2 pixels per height
facet (0.12 by 0.12 m2 in these tests) was obtained with the
S-model in practical tests. The precision of the determined
object surface was ± 0.02 to 0.06 m, i.e., 0.2 to 0.6 pixels or
0.03 to 0.1% of the flying height above ground, when compared
with the control data measured by an operator on a
Wild AC3 analytical stereoplotter. These figures correspond
well with the natural roughness of the Earth's surface in the
chosen test area.
1189 The Influence of Geographic Sampling Methods on Vegetation Map
Accuracy Evaluation in a Swampy Environment
C.P. Lo and Lee J. Watson
Abstract
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The effectiveness of five sampling methods was evaluated
empirically to determine the thematic accuracy of six-class
vegetation maps of two study areas in the Okefenokee
Swamp produced by computer-assisted supervised classification
of Landsat TM data. An exhaustive survey of the two
study areas permitted estimates of overall, user's, and producer's
accuracies to be made by each sampling method.
The spatial pattern of classification errors also examined
with the aid of spatial autocorrelation analysis. By comparing
Kappa coefficients of agreement among error matrices
generated by the different sampling methods and by applying
Chi-square tests, the stratified random sampling method
was found to perform best for thematic accuracy evaluation
in a swampy environment where vegetation exhibited a mixture
of simple and complex spatial patterns. The higher spatial
resolution of the image data employed to produce the
vegetation map tended to cause stronger positive spatial
autocorrelation in the resultant map error pattern.
1201 Spectral Reflectance and Detection of Iron-Oxide Precipitates
Associated with Acidic Mine Drainage
John E. Anderson and Eleanora I. Robbins
Abstract
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The objective of this study is to develop a repeatable technique
to spectrally discriminate between acid and neutral
streams based on the reflectance characteristics of acid and
neutral iron precipitates. Field spectral measurements were
conducted in situ on iron-oxide precipitates coating bottom
substrates of an acidified stream (pH<4) in the Virginia
Gold-Pyrite Belt. Spectra of two neutral (pH 6 and 7)
streams, one with iron precipitates present, were also measured.
Acid precipitates were found to have higher spectral
reflectance than neutral precipitates in the 650- to 750-nm
region. With regard to water quality, the acid stream possessed
low pH and high specific conductance.
Guided by the field spectral data, a remote sensing technique using bandpass interference filters and a digital multispectral video system was used to detect mine drainage in two Virginia streams. Where acidic discharge was present, false-color composites showed precipitates having high reflectance in both the 650-nm and 750-nm wavebands. In contrast, neutral iron-rich streams were low in reflectance, and streams unimpaired by mine drainage had virtually no detectable reflectance.
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