Peer-Reviewed Articles
1225 Digital Surface Models from High-Resolution Satellite
Imagery
Joanne Poon, Clive Fraser, and Chunsun Zhang
Abstract Download
Full Article
Automated processes in commercial-off-the-shelf (COTS)
systems are increasingly prevalent as new technology, and
new knowledge is fused to enhance accessibility to spatial
information. Automated terrain extraction is becoming a
standard capability implemented into photogrammetric
software. This paper focuses on digital surface model (DSM)
generation from high-resolution satellite imagery (HRSI) using
three COTS systems, SOCET SET®, Z/I Imaging, and Imagine®
OrthoBASE, which each have their own image matching
strategy. By generating DSMs of a test field diverse in land-cover, we assess the performance of the COTS terrain extraction methodologies. In checkpoints favorable to image
matching, accuracy to a few meters in height can be achieved
from COTS generated DSMs, however the isolated points are
unlikely to be representative of the entire scene. Therefore,
we look to alternative sources of control, such as the newly
available DLR- and NASA-generated SRTM DEMs. A comparison
to X-band SRTM DEMs demonstrated that height RMSE values
range from 4 to 9 metres, though most of this uncertainty is
attributed to the SRTM data.
1233 Weighting Function Alternatives for a Subpixel
Allocation Model
Yasuyo Makido and Ashton Shortridge
Abstract Download
Full Article
This study investigates the “pixel-swapping” optimization
algorithm proposed by Atkinson for predicting subpixel land-
cover distribution. Two limitations of this method are
assessed: the arbitrary spatial range value and the arbitrary
exponential model for characterizing spatial autocorrelation.
Various alternative weighting functions are evaluated. For this
assessment, two different simulation models are employed to
develop spatially autocorrelated binary class raster maps.
These rasters are then resampled to generate sets of representative medium-resolution class maps. Prior to conducting the
subpixel allocation, the relationship between cell resolution
and spatial autocorrelation, as measured by Moran’s I, is
evaluated. It is discovered that the form of this relationship
depends upon the simulation model. For all tested weighting
functions (Nearest Neighbor, Gaussian, Exponential, and IDW),
the pixel swapping method increased classification accuracy
compared with the initial random allocation of subpixels.
Nearest Neighbor allocation performs as well as the more
complex models of spatial structure.
1241 Comprehensive Analysis of Sensor Modeling
Alternatives for High-Resolution Imaging Satellites
Ayman Habib, Kyungok Kim, Sung-Woong Shin, Changjae
Kim, Ki-In Bang, Eui-Myoung Kim, and Dong-Cheon Lee
Abstract Download
Full Article
High-resolution imaging satellites are a valuable and cost
effective data acquisition tool for a variety of mapping and
GIS applications such as topographic mapping, map updating, orthophoto generation, environmental monitoring, and
change detection. Sensor modeling that describes the
mathematical relationship between corresponding scene and
object coordinates is a prerequisite procedure prior to
manipulating the acquired imagery from such systems for
mapping purposes. Rigorous and approximate sensor models
are the two alternatives for describing the mathematics of
the involved imaging process. The former explicitly involves
the internal and external characteristics of the imaging
sensor to faithfully represent the geometry of the scene
formation. On the other hand, approximate modeling can be
divided into two categories. The first category simplifies the
rigorous model after making some assumptions about the
system’s trajectory and/or object space. Gupta and Hartley’s
model, parallel projection, self-calibrating direct linear
transformation, and modified parallel projection are examples of this category. Other approximate models are based
on empirical formulation of the scene-to-ground mathematical relationship. This category includes among others, the
well-known Rational Function Model (RFM). This paper
addresses several aspects of sensor modeling. Namely, it
deals with the expected accuracy from rigorous modeling of
imaging satellites as it relates to the number of available
ground control points, comparative analysis of approximate
and rigorous sensor models, robustness of the reconstruction
process against biases in the available sensor characteristics,
and impact of incorporating multi-source imagery in a single
triangulation mechanism. Following a brief theoretical background, these issues will be presented through experimental
results from real datasets captured by satellite and aerial
imaging platforms.
1253 Orthogonal Polynomials Supported by Regional
Growing Segmentation for the Extraction of Terrain
from Lidar Data
Nizar Abo Akel, Sagi Filin, and Yerach Doytsher
Abstract Download
Full Article
Light Detection and Ranging (lidar) systems supply a
massive amount points in 3D space with no semantic
information helping knowing the objects they represent. To
identify points that were reflected from the terrain, numerous algorithms have been developed in recent years. Many
of them apply local operators that tend to face difficulties
with complex scenes while their performance also varies
between landscapes. In this paper, we present a filtering
method that integrates a global approach using orthogonal
polynomials with a local one that is region-based. The
algorithm makes use of only a few parameters, and no
fine-tuning is required between landscapes. Applying the
algorithm over areas with varying topography and objects
such as bridges, tunnels, and complex building, shows an
improved performance compared to results obtained by
others. This improvement is reflected in a lower than
usual rate of misclassification errors for data acquired
over different landscapes.
1267 Line-of-Sight Vector Adjustment Model for
Geopositioning of SPOT-5 Stereo Images
Hyung-Sup Jung, Sang-Wan Kim, Joong-Sun Won, and Dong-Chun Lee
Abstract Download
Full Article
We formulate and present a new geopositioning method for
SPOT-5 High-Resolution Geometric (HRG) stereo images, named
the line-of-sight (LOS) vector adjustment model. It is applicable
to satellites that move along a well-defined close-to-circular
elliptical orbit with a predicted orbit close to true. SPOT-5
satisfies these requirements because it has the improved
capability of providing accurate satellite attitude and a look
angle for each detector. The method’s core idea is that only
the LOS vector was adjusted when correcting the geometric
distortion of SPOT-5 imagery. One advantage of this method is
that it achieves high geopositioning accuracy with a limited
number of ground control points (GCPs). Although a minimum
of three GCPs is needed for processing, a test result satisfied
the accuracy requirement within one pixel of a SPOT-5
panchromatic image even with only three GCPs. The performance in terms of root mean square error (RMSE) improved as
the number of GCPs increased. Five GCPs were found to be the
optimal number in the practical application of the LOS vector
adjustment model. Using five GCPs, the RMSEs were 0.48 m
and 0.64 m in planimetry and height, respectively. The test
results indicate that the proposed method is superior to the
bundle adjustment method for the geopositioning of SPOT-5
HRG stereo images.
1277 Orthophoto Generation from Unorganized Point
Clouds
L. Tournas and M. Tsakiri
Abstract Download
Full Article
The reconstruction of realistic precise surfaces is required in
many different applications. To date, terrestrial laser scanning offers 3D input data which are suitable for surface
generation but are lacking in photo-realistic appearance.
Texture for scanned surfaces can be provided by orthophotos
generated from photographs that are acquired from almost
the same viewpoint as the incident laser beam. However, the
creation of an orthophoto using typical photogrammetric
procedures requires the representation of the scanned surface
with a triangulated mesh which cannot be created automatically in all cases. In this paper, a new method for automatic
orthophoto generation from unorganized point clouds is
presented. In the proposed methodology, the acquisition of
accurate height information is directly derived from the point
cloud without the prior requirement of a triangulated mesh.
Analysis of experimental data with large height variations
demonstrates the success of the algorithm which produces an
orthophoto in near real-time. Issues on the performance of
the method are also discussed.
1285 Fusing Ikonos Images by a Four-band Wavelet
Transformation Method
Wenzhong Shi, Changqing Zhu, and Shulong Zhu
Abstract Download
Full Article
This paper presents a wavelet transformation-based method
for fusing high-resolution satellite images. First, a multi-band wavelet fusion method, specifically the four-band
wavelet method, is proposed for fusing one-meter panchromatic and four-meter multi-spectral Ikonos images. Second,
the fusion experiments are undertaken by using the proposed four-band wavelet method. The results are compared
with fused images from other methods, such as two-band
wavelet and IHS methods. The results are evaluated based
on both visual evaluation and a quantitative analysis, by
using several assessing parameters and a new evaluation
method: the profile intensity curve. Third, as an application
of the fused images, they are applied for recognition and
identification of features in urban area. The quantitative
analysis demonstrates that four-band wavelet transformation
method provides improved fused images.
Color Figures:
[figure 5a.] [figure 5b.] [figure 5c.] [figure 6a.] [figure 6b.] [figure 6c.] [figure 6d] [figure 6e.] [figure 8a.] [figure 8b.] [figure 8c.] [figure 8d.] [figure 8e.]