Peer-Reviewed Articles
1067 A New Approach to Precision Airborne GPS Positioning for Photogrammetry
Clyde C. Goad and Ming Yang
Abstract
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Precise determination of GPS phase ambiguity integers on the
fly is e key requirement for accurate kinematic positioning. A
fully automatic approach is developed to resolve phase integers
and perform airborne GPS positioning for aerial triangulation
using dual-frequency GPS data. Although always
helpful, static initialization is not required: the problem of
signal interruptions (losses of lock) while an airplane is maneuvering
distant fnom a base station has also been addressed.
Test results show that positions using precise phase
date are reliably determined with this approach.
1079 Aerotriangulation and DEM/Orthophoto Generation from High-Resolution Still-Video
Imagery
Hans-Gerd Maas and Thomas Kersten
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High-resolution solid-state sensor matrix cameras have found
quite some interest among photogrammetrists in the last few
years. The limited resolution of such cameras has so far restricted
their practical use to applications in digital close-range
photogrammetry. Nevertheless, the advantages of the
direct acquisition and processing of digital image data in
combination with the accuracy potential and the increasing
resolution of solid-state sensors have started to make digital
cameras interesting for a number of applications in aerial
photogrammetry.
This paper presents two practical studies on the helicopter-based use of a high-resolution digital still-video camera for digital aerotriangulation and the automatic generation of digital elevation models and orthophotos. Test regions were on alpine village and a landslide area in Switzerland. The current performance and future developments of solid-state matrix sensors are shown. and the advantages and disadvantages of the use of digital cameras in aerial applications are discussed. Using self-calibration techniques, externally verified accuracies of 2 cm for planimetry coordinates and 5 to 6 cm for height coordinates were obtained in digital aerotriangulation using imagery of 1:20,000 scale, and a precision of 0.03 percent of the flying height above ground could be achieved for digital elevation models.
1085 Mobile Mapping: An Emerging Technology for Spatial Data Acquisition
Rongxing Li
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Mobile mapping has been the subject of significant research
and development by several research teams over the past
decade. A mobile mapping system consists mainly of a moving
platform, navigation sensors, and mapping sensors. The
mobile platform may be a land vehicle, a vessel, or an aircraft.
Generally, navigation sensors, such as Global Positioning
System (GPS) receivers, vehicle wheel sensors, and
inertial navigation systems (INS), provide both the track of
the vehicle and position and orientation information of the
mapping sensors. Objects to be surveyed are sensed directly
by mapping sensors, for instance, charge coupled devices
(CCD) cameras, laser rangers, and radar sensors. Because the
orientation parameters of the mapping sensors are estimated
directly by the navigation sensors, complicated computations
such as photogrammetric triangulation are greatly simplified
or avoided, Spatial information of the objects is extracted directly
from the georeferenced mapping sensor data by integrating
navigation sensor data. Mobile mapping technology
has evolved to a stage which allows mapping and GIS industries
to apply it in order to obtain high flexibility in data acquisition,
more information with less time and effort, and
high productivity. In addition, a successful extension of this
technology to helicopter-borne and airborne systems will provide
a powerful tool for large-scale and medium-scale spatial
data acquisition and database updating.
This paper provides a systematic introduction to the use of mobile mapping technology for spatial data acquisition. Issues related to the basic principle, data processing, automation, achievable accuracies, and a break down of errors are given. Application considerations and application examples of the technology in high way and utility mapping are described. Finally, the perspective of the mobile mapping technology is discussed.
1093 Heuristic Reasoning Strategy for Automated Sensor Placement
Scott Mason
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A heuristic reasoning strategy for automating the placement
of sensors in the design of multi-station convergent close range
photogrammetric networks is presented. Optical inspection
of three-dimensional (3D) objects requires acquisition
of a configuration multiple, spatially separated images
about the object. The placement of these sensor stations is
subject to a complex and interrelated set of constraints and
measurement considerations and, therefore, heuristic solutions
are necessary. This strategy exploits the idea of generic
multi-station sensor configurations which comprise an ideal
number and geometry of sensor stations for a class of measurement
problems. A representation , termed the "constraint
sphere," is introduced which accommodates a reasoning
scheme in which these ideal station poses can be efficiently
modified to suit the current object geometry, workspace
restrictions. and measurement criteria. Examples demonstrate the
strategy's potential. This approach is the first to deal
with the menstruation considerations in multi-station sensor
placement.
1103 Hemispherical Photographs Used for Mapping Confined Spaces
Michel Boulianne, Clément Nolette, Jean-Paul Agnard and Martin
Brindamour
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This paper presents two methods for using fisheye photographs
for mapping confined areas. The first approach is intended
for relatively flat objects, observed at very close
range, and consists of producing a rectified view from a fisheye
photograph. After scanning and correcting the spherical
distortions present in the original image, a simple projective
transformation creates a constant scale image from which
two-dfmensional (2D) data can be extracted. The second
method aims at recovering three-dimensional data from two
stereo fisheye photographs. This method also involves the
same image correction for spherical distortions, but the two
resulting perspective images are afterwards analyzed utilizing
stereovision in a digital photogrammetric workstation.
Practical experiments, conducted with a 35-mm camera
equipped with a fisheye lens, demonstrate the applicability
and feasibility of the two softcopy photogrammetry methods
in the context of mapping electric distribution wells.
1111 Constrained FEM Self-Calibration
D.D. Lichti and M.A. Chapman
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Polynomial models have been adapted as standard analytical
tools in imaging metrology for attenuating image distortions
for which corrections are applied to image point
measurements. An alternative correction model, the finite element
approach, stems from the fact that the displacement
of a point in the image plane is projectively equivalent to a
proportional change in the principal distance. By dividing
the image plane into smaller entities, distortions can be
modeled by piecewise principal distance correction using the
finite element method (FEM) of self-calibration. Problems can
arise, however, when a large number of finite elements is
employed. The application of shape function constraints is
proposed to overcame rank defects arising from sparse point
distribution for those cases. The adequacy of this modified
FEM approach is tested relative to on accepted polynomial
model for three different data sets. The evaluation criteria
include the degree of compensation for distortions, object
space precision and accuracy, and parameter correlation.
1121 Relations between the Coefficients in the Projective Transformation Equations
and the Orientation Elements of a Photograph
Kasuo Kobayashi and Chuji Mori
Abstract
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The physical meaning of the 11 coefficients in the projective
transformation (PT) equations between a three-dimensional
(3D) object and the 2D photo plane has already been described.
In this paper, the 2D PT equations which are used for
rectifying a photograph are considered. The relationships between
the eight coefficients of the PT equations and the nine
conventional orientation elements (OEs) are presented, and
the method of computing the nine OEs from the eight PT coefficients
is shown with some numerical examples. It is also
explained that the corresponding coefficients in the 3D and
the 2D PT equations have the identical values.
1129 Accuracy of Plates Calibrated by an Automatic Comparator
Georges Blaha
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In essence, the question addressed in this paper is the following:
Using a master plate free of systematic errors,as previously
calibrated under laboratory conditions, how well can
a specific automatic monocomparator (AM) calibrate a new
series of plates? An extremely simple and intuitively pleasing
answer would be that the coordinate standard error (sigma)
of a new plate lies between the coordinate sigma of the master
plate and the sigma of the AM coordinate determination.
This verbal assessment represents, in fact, the outcome of
the present analysis. The summary section elaborates on this
outcome using the AutoSet monocomparator from Geodetic
Switchers as a concrete example.
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