Peer-Reviewed Article Abstracts
47-55 Automatic Relative Orientation of Aerial Images
Tang Liang and Christian Heipke
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An approach is described for automatic relative orientation of a stereopair
of digital aerial images. Features-based image matching using point features
extracted with a modified version of the Moravec operator and a coarse-to-fine
strategy are incorporated into the approach. In higher image pyramid levels,
where images are small in size and of low resolution, the entire model area
is searched for interest points. In lower levels, window tracking is carried
out in order to speed up the entire procedure and to stabilize the final
results. In all levels, matching is based on geometric as well as radiometric
constraints. The approach was developed as one of the automation-oriented
software components of a digital photogrammetric workstation.
57-66 A Recursive Approach to Space Resection Using
Straight Line
Antonio Maria Garcia Tommaselli and Clsio Luis Tozzi
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An approach using straight lines as features to solve the photogrammetric space
restriction problem is presented. An explicit mathematical model relating
straight lines, in both object and image space, is used. Based on this model,
Kalman Filtering is applied to solve the space resection problem. The recursive
property of the filter is used in an iterative process which uses the sequentially
estimated camera location parameters to feedback to the feature extraction
process in the image. This feedback process leads to a gradual reduction
of the image space for feature searching and consequently eliminates the
bottleneck due to the high computational cost of the image segmentation phase.
It also enables feature extraction and the determination of feature correspondence
in image and object space in an automatic way, ie without operator interference.
67-72 Precision Rectification of SPOT Imagery Using
the Direct Linear Transformation Model
Yasser El-Manadili and Kurt Novak
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A simple rigorous method for the geometric processing of SPOT images is formulated
and evaluated. This method is based on the Direct Linear Transformation (DLT)
model, which is employed after correcting the image coordinates for systematic
distortions caused by Earth rotation and cell size variations due to off-nadir
viewing. Corrections for other types of systematic errors are considered
through the adjustment. Several experiments are presented using synthetic
and real data to evaluate the new method. Simulated data are generated from
a general model that imitates the SPOT orbit using the Eulerian parameters,
satellite deviations, and velocity vectors, as well as sensor attitude angles
as functions of time. The results show that sub-pixel accuracy can be achieved
with as few as six control points, if control point errors are kept small.
73-77 Relative Accuracy of Rectifications Using Coordinates
Deter mined from Maps and the Global Positioning System
Allen E. Cook and John E. Pinder III
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Global positioning systems (GPS) that use code phase receivers have the potential
for providing more accurate coordinates for ground control points (GCPs)
than do 7.5-minute quadrangle maps. To evaluate the effect of the greater
accuracy of GPS in determining coordinates for satellite images, GCP coordinates
were measured on maps and by GPS techniques and were then used to rectify
Landsat Thematic Mapper, SPOT multispectral, and SPOT panchromatic images
from the same area. There were major differences between rectifications using
map and GPS coordinates. The improvements in accuracy when using the GPS
data were substantial for even the relatively large Thematic Mapper pixels
and warrant the use of GPS where position accuracy is essential.
79-83 Initial Approximations for the Three-Dimensional
Conformal Coordinate Transformation
Bon A. Dewitt
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The three-dimensional conformal coordinate transformation has many applications.
In terrestrial photogrammetry it can be used to transform artibtary stereomodel
coordinates to object space systems. Determination of initial approximations
in such situations is typically not as straightforwad as in the aerial case.
A method is presented which allows a direct solution of initial approximations
given any arbitrary angular orientation and three-dimensional control.
85-88 Design and Implementation of a Photogrammetric
Geo-Calculator in a Windows Environment
Rongxing Li
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The design and implementation aspects of a Geo-Calculator developed in a windows
environment are described. Using this 'soft' calculator, geometric entities
such as coordinates, distances, differences of elevation, azimuths, areas,
and profiles can be calculated through the measurement of objects appearing
in stereo images. The Geo-Calculator is implemented as an individual system
to provide convenient geo-functions. Thus, it can be adapted as a separate
component for softcopy photogrammetry, digital mapping, and geographic information
systems. Because the graphic user interface is designed to be user-friendly,
no specific photogrammetric background is required when using the calculator.
89-92 A Photogrammetric Simulator for Close-Range
Applications
Tian-Yuan Shih
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Simulation is an important process for project design. An algorithm specifically
designed for close-range applications is described in this study. This algorithm,
based on human behaviour, simulates the hand-held camera situation. The algorithm
and a numerical example are presented. An implementation into a CAD system
has been attempted, in which the initial results are rather encouraging.
93-99 Shape Reconstruction from Multiple Images of the Ocean
Surface
Howard Schultz
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To analyze the fine scale structure of the ocean surface, a new technique (known
as Specular Surface Stereo) is proposed that makes use of the unique optical
properties of water. In this method, the surface shape is recovered by solving
the inverse problem of finding a surface shape (defined by an elevation and
gradient map) that results in a set of synthetic (computer generated) images
that closely match a set of observed images. To accomplish this, the algorithm
requires an image of the illumination source, three images of the water surface,
a few initial elevation estimates, and an image synthesis model that predicts
the appearance of an image of the surface. Based on these numerical results,
it is shown that the Specular Surface Stereo technique can potentially recover
both surface elevations and gradients over a wide range of wavenumbers.