Peer-Reviewed Articles
909 Single-Photo Resection Using the Modified Hough Transform
Ayman Habib and Devin Kelley
Abstract
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The single-photo resection (SPR) has been a fundamental task in many
photogrammetric, remote sensing, and computer vision applications.
The objective of the SPR is to determine the position of the perspective
center and the orientation of the image coordinate system relative
to the ground coordinate system (i.e., establish the exterior orientation
parameters, or EOP). In traditional photogrammetric techniques, this
problem is solved using 2D image point to 3D object point correspondence.
Recent advances in digital photogrammetry mandate adopting higher
order control features (e.g., linear features). Also, one should
attempt to solve this problem without knowing the correspondence
between the image and object space features. This approach is used
to estimate the parameters of a mathematical model relating the entities
of two data sets when the correspondence of entities is unknown.
As a result of the parameter estimation, the correspondence is implicitly
determined. This technique has been applied to the single-photo resection,
where the collinearity model is used to relate extracted edge (feature)
pixels in a digital image to 3D object space points along linear
features. As a result of this approach, the six exterior orientation
parameters are estimated
and the correspondence between image and object space features is established.
This technique facilitates the fusion of digital imagery with terrestrial mobile
mapping data, GIS data, and line maps. In addition, automated matching facilitates
the detection of changes between object and image space features. It has to
be mentioned that this approach is robust against discrepancies between the
object space control features and the image space extracted features. Only
common features are used for the parameter estimation. On the other hand, non-corresponding
features will not affect the quality of the estimated parameters.
915 Radiometric Corrections for Multispectral Airborne Video Imagery
A. Edirisinghe, G.E. Chapman, and J.P. Louis
Abstract
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Radiometric fidelity of calibrated airborne video imagery is important
if the imagery is to be used for quantitative analysis of target
surfaces. A four-channel Multispectral Airborne Video System (MAVS)
is used at Charles Sturt University (CSU) for a range of environmental
and agricultural monitoring applications. The radiometric distortions
in the MAVS imagery could occur because of lens characteristics in
the form of vignetting effects and optical aberrations. This paper
details the control experiments conducted to detect and quantify
such distortions. The vignetting in particular is shown to be creating
a non-uniform brightness level across the MAVS imagery. The paper
then develops efficient procedures to correct the vignetting in the
MAVS imagery by producing relevant correction coefficients,
templates, and equations. The accuracy of these de-vignetting (correction)
procedures is shown to be comparable to the accuracy of similar corrections
reported elsewhere. An investigation into the effect of spectrum related vignetting
on the MAVS imagery due to spectral filter characteristics found negligible
distortions that did not warrant corrections. This particular type of vignetting
is usually caused by the wavelength shifts in the band-pass window of a filter
at large incident angles.
925 On Preserving Spectral Balance in Image Fusion and Its Advantages
for Geological Image Interpretation
Ernst M. Schetselaar
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The merging of multisource remotely sensed data has become a widely
used technique to take advantage of complementary data sets in image
interpretation. A fundamental problem in its application is how the
transformations between perceptual and display device dependent color
spaces are implemented in addressing the attributes of human color
perception intensity (I), hue (H), and saturation (S) in an optimal
and unambiguous manner. This paper presents a method that preserves
the spectral balance of the multispectral image data and modulates
the IHS
coordinates uniformly. This method takes the limits in the representation of
color of the display device into account, which aids in compromising the amount
and spatial distribution of over-range pixels against contrast in intensity
and saturation. Two processing examples are provided to illustrate the advantages
of this method for geological mapping. In the first example, Landsat TM bands
7, 3, and 1 are integrated with an aerial photograph to map lithological units
in metamorphic basement and its sedimentary cover. In the second example, K,
eTh, and eU gamma-ray spectrometry and Landsat TM data are integrated to map
compositional and structural patterns within a granite batholith.
935 Unveiling the Lithology of Vegetated Terrains in Remotely Sensed
Imagery
Robert E. Crippen and Ronald G. Blom
Abstract
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"
Forced invariance" is a processing method that can subdue the expression
of vegetation and enhance the expression of the underlying lithology
in remotely sensed imagery. Data for each spectral band are altered
in an empirically derived manner so as to produce a refined band that
largely excludes contrasts attributable to variations in vegetation
abundance. This is accomplished by (1) correcting the data for the
effects of additive path radiance, (2) statistically characterizing
the
relationship between the band data and a vegetation index, and (3) multiplying
the band data as a function of the index so that the average band value is
generally invariant across all index values. Comparison of original and processed
color composite displays confirms the method's utility in unveiling rock patterns
consistent with nearby well-exposed bedrock and alluvial patterns downslope,
especially in areas of open canopy vegetation such as in mixed arid and semi-arid
terrains.
947 Integration of Hyperspectral and IFSAR Data
for Improved 3D Urban Profile Reconstruction
P. Gamba and B. Houshmand
Abstract
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In this paper hyperspectral (AVIRIS) and radar (AIRSAR) aerial data
acquired over urban environments are considered. The information
available from each sensor was extracted and merged to improve the
3D profile reconstruction of builtup areas. Two classification schemes
were evaluated for AVIRIS data clustering, while the effect of the
radar view angle was considered in assessing the quality of the associated
digital elevation models. A detailed analysis of what is possible
to
extract and to what extent these data are useful was also produced, considering
precise 2D and 3D ground truth of the UCLA campus.
957 Model-Based Conifer-Crown Surface Reconstruction from High-Resolution
Aerial Images
Yongwei Sheng, P. Gong, and G.S. Biging
Abstract
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Knowledge of tree-crown parameters such as height, shape, and crown
closure is desirable in forest and ecological studies, but those
parameters are difficult to measure on the ground. The stereoscopic
capability of high-resolution aerial images provides a method for
crown-surface reconstruction. However, existing digital photogrammetry
packages, designed to map terrain surfaces, cannot accurately extract
tree-crown surfaces, particularly for conifer-crowns with steep vertical
profiles. In this paper, we integrate crown features derived from
images with stereo matching, and develop a model-based approach for
reconstructing conifer-crown surfaces. The model is based on the
fact that most conifer crowns are a form of solid geometry. We model
a conifer crown as a generalized
hemi-ellipsoid, establish the optimal tree model using a geometric equation,
and apply the optimal tree model to guide a conventional pyramidal image matching
in crown-surface reconstruction. The effectiveness of the approach is illustrated
using an example of a redwood tree on 1:2,400-scale aerial photographs.
967 A Spatio-Temporal GIS Database for
Monitoring Alpine Glacier Change
Jeremy L. Mennis and Andrew G. Fountain
Abstract
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Monitoring alpine glacier change has many practical and scientific
benefits, including yielding information on glacier-fed water supplies,
glacier-associated natural hazards, and climate variability. This
paper describes the design and implementation of a spatio-temporal
GIS database for monitoring glacier geometry and geometric change.
The temporal component of the glacier data is managed through both
a "snap-shot" and time-normalization approach to the relational data
model in which glacier properties are organized according to their
spatial
and temporal dependencies. Because of the integration of diverse historic and
contemporary data sources, metadata play a key role in managing data quality.
For the initial population of the database, historic and contemporary map data
on six glaciers on Mount Rainier, Washington were used to model glacier geometry
and were examined for geometric change over the period 1913-1971.
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