Peer-Reviewed Articles
959 Conceptual Framework of a Generalized Roaming Scheme
Toni Schenk and Charles Toth
Abstract
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Roaming is an important system task of softcopy workstations.
The impIementotion of roaming in most of today's
softcopy workstations is an emulation of the same operation
in analytical plotters. The performance is quite inferior to
that which photogrammetrists are accustomed when moving
the measuring mark. Mimicking the analytical plotter imposes
self-inflicting constraints on the soJution which Ore
technologically and procedurally unjustified. We take o fresh
look at roaming and describe in this paper a conceptual
framework that is based on extending the spatial extent from
one model to the entire project. The information in which
roaming is performed is extended from imagery to include
vector data, DEM, databases, and design data. We show that
it is feasible to roam within a project of 300 color images
without ever explicitly identifying models. Lineal features
can be digitized in stereo, across the project. Rapid mouse
movements in navigation mode cause the system to display
imagery monoscopically at the proper resolution. The third
roaming mode resembles the "drive to" feature of analytical
plotters with the distinct difference that any point within the
project can be reached.
965 Automated DEM Extraction and Orthoimage Generation from SPOT Level 1B Imagery
N. Al-Rousan, P. Cheng, G. Petrie, Th.Toutin, and M.J. Valadan Zoej
Abstract
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This paper describes the testing and validation of the photogrammetric
modules of the PCI EASI/PACE system using SPOT
stereo-pairs over a high accuracy test field established in a
desert area in Jordan. The mathematical modeling and analytical
photogrammetric solution used by the system are first
described. This is folJowed by a description of the algorithm
employed in the automatic image matching procedure used
to extract a dense DEM from the SPOT digital image data. The
results of extensive tests of the geometric accuracy of the exterior
orientation and analytical rectification carried out with
the SPOT images using EASI/PACE are given. The DEMs generated
from five SPOT level 1B stereo-pairs have been merged
and validated through a comparison of the resulting contours
with the corresponding contours generated by aerial
photogrammetric methods, the two plots showing an excellent
agreement. The final ortho-images are of a high quality
in radiometric terms, while a check of their geometric accuracy
reveals sub-pixel accuracy. The results of this highly automated
all-digital photogrammetric procedure are of
considerable relevance to those concerned with the topographic
mapping of extensive areas of arid and semi-arid terrain.
975 Image-to-Image Registration by Matching Area Features Using Fourier Descriptors
and Neural Networks
Yi-Hsing Tseng, Jin-John Tzen, Kei-Pay Tang, and Shin-Hung Lin
Abstract
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An automatic method of image-to-image registration, which
may be applied to register overlapped images of a scene
from different views and dates, is presented. The proposed
approach is a feature-based matching with constraints of orientation
consistency and one-to-one match. Area features of
homogeneous regions in gray level are extracted from images
as matching entities. The boundaries of area features are
matched in the frequency domain, ie., matching their Fourier
descriptors. The spatial meaning of the matching is
transforming a feature to fit the other optimally. After the
matching process, this scheme provides not only a quantitative
evaluation of the remaining lock of fitness as an objective
index of shape similarity, but also the solved transformation
parameters to represent the relative orientation between
features. The evaluation of shape similarity is used as
the key information in recognizing conjugate features for
overlapped images. Furthermore, the consistency of relative
orientation between matched pairs is considered as the principal
constraint to dissolve improperly registered features.
The registration procedure is implemented by combining the
factor of shape similarity as well as the constraints of orientation
consistency and one-to-one match into a cost function
and driving the cost function to reach its lowest value by using
an artificial neural network system. The lowest cost represents
the optimal solution of matching conjugate features.
The planar registration of images then can be solved by using
matched conjugate features. Two application examples,
registering a stereo pair of aerial images and mosaicking
overlapped images for automatic aerial triangulation, are
presented to show the success of this method.
985 Semi-Automatic Linear Feature Extraction by Dynamic Programming and LSB-Snakes
Armin Gruen and Haihong Li
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This paper deals with semi-automatic linear feature extraction
from digital images for GIS data capture, where the identification
task is performed manually on a single image,
while a special automatic digital module performs the high
precision feature tracking in two-dimensional (2-D) image
space or even three-dimensional (3-D) object space. A human
operator identifies the object from an on-screen display of a
digital image, selects the particular class this object belongs
to, and provides a very few coarsely distributed seed points.
Subsequently, with these seed points as an approximation of
the position and shape, the linear feature will be extracted
automatically by either a dynamic programming approach or
by LSB-Snakes (Least-Squares B-spline Snakes). With dynamic
programming, the optimization problem is set up as a discrete
multistage decision process and is solved by a "time delayed"
algorithm. It ensures global optimality
numerically stable, and allows for hard constraints to be enforced
on the solution. In the least-squares approach, we
combine three types of observation equations, one radiometric,
formulating the matching of a generic object model with
image data, and two that express the internal geometric constraints
of a curve and the location of operator-given seed
points. The solution is obtained by solving a pair of independent
normal equations to estimate the parameters of the
spline curve. Both techniques can be used in a monoplotting
mode, which combines one image with its underlying DTM.
The LSB-snakes approach is also implemented in a multi-image
mode, which uses multiple images simultaneously and
provides for a robust and mathematically sound full 3D approach,
These techniques ore not restricted to aerial images.
They can be applied to satellite and close-range images as
well. The issues related to the mathematical modeling of the
proposed methods are discussed end experimental results
are shown in this paper too.
997 Evaluating the Potential of the Forthcoming Commercial U.S. High-Resolution
Satellite Sensor Imagery at the Ordnance Survey®
Helen M. Ridley, Peter M. Atkinson, Paul Aplin, Jan-Peter Muller, and
Ian Dowman
Abstract
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As the NationaI Mapping Agency of Great Britain, the Ordnance
Survey® (OS) is driven by a need to reduce costs and
commercialize operations, and as such has been investigating
photogmmmetric methods to improve existing products.
streamline existing production, and increase the current
portfolio of products. Over the last 18 months, the OS has
been involved in a major research project to tackle these issues
through on evaluation of the forthcoming comrnercial
U.S. high spatia1 resolution satellite sensors which are offering
1-m panchromatic and 4-m multispectral spatial resolutions.
Work has focused on improving the existing National
Height Dataset (NHD), reducing the cost of photogrammmetric
survey, automatic topographic feature change detection, production
of DEMs; three-dimensional (3D) urban models, and
land-use classification. Results from the project using
simulated imagery indicate that if would have potential
within the 0S in all areas evaluated. The work now needs to
be followed up when real high spatial resolution satellite imagery
becomes commercially available.
1007 Automatic Interior Orientation of Digital Aerial Images
Thomas Kersten and Sivio Haering
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A fully operationl automatic interim orientetion (AUTO_IO)
for digital aerial images based on a modified Hough Transform
for rough localization of fiducial marks and leastsquares
matching for precise measurement is introduced in
this paper. For cameras with fiducial mark identification
symbols, e.g., as used in Leica RC30 cameras, the program is
capable of determining the orientation of the photos. Results
are presented using images taken by Leica and Zeiss cameras,
which were scanned on different scanners in various
resolutions to demonstrate the potential and robustness of
the automatic IO procedure.AUTO_IO is implemented on a
Helava/Leica DPW770 Digital Photogrammetric Workstation
and is used in a digital production environment at Swissair
Photo+Surveys Ltd., Switzerland.
1013 The Architecture of a Softcopy Photogrammetry System
Lewis N. Graham, Jr., Kyle Ellison, Jr., and C. Steven Riddell
Abstract
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An overview of the design and development of a digital image
processing and photogrmmmetric software platform based
on the Windows NT'" operating system is presented. The
principle challenge in this work was the movement of processor
intensive algorithms from proprietary dedicated hardware
to the open architecture provided by the symmetric
multiprocessing (SMP) kernel of NT. Photogrammmetry offers a
unique challenge in design in that imagery must be displayed
with very high geometric accuracy at all times, includind
the already processor intensive operation of dynamic
roam.