Peer-Reviewed Articles
25 New Methodologies for True Orthophoto Generation
Ayman F. Habib, Eui-Myoung Kim, and Chang-Jae Kim
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Orthophoto production aims at the elimination of sensor
tilt and terrain relief effects from captured perspective
imagery. Uniform scale and the absence of relief displacement
in orthophotos make them an important component of
GIS databases, where the user can directly determine geographic
locations, measure distances, compute areas, and
derive other useful information about the area in question.
Differential rectification has been traditionally used for
orthophoto generation. For large scale imagery over urban
areas, differential rectification produces serious artifacts in
the form of double mapped areas at object space locations
with sudden relief variations, e.g., in the vicinity of buildings.
Such artifacts are removed through true orthophoto
generation methodologies which are based on the identification
of occluded portions of the object space in the involved
imagery. Existing methodologies suffer from several problems
such as their sensitivity to the sampling interval of
the digital surface model (DSM) as it relates to the ground
sampling distance (GSD) of the imaging sensor. Moreover,
current methodologies rely on the availability of a digital
building model (DBM), which requires an additional and
expensive pre-processing. This paper presents new methodologies
for true orthophoto generation while circumventing
the problems associated with existing techniques. The
feasibility and performance of the suggested techniques are
verified through experimental results with simulated and
real data.
37 Land-cover Classification Using Radarsat and Landsat Imagery for St. Louis, Missouri
Heng Huang, Justin Legarsky, and Maslina Othman
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This paper presents the potential of integrating radar data
features with optical data to improve automatic land-cover
mapping. For our study area of St. Louis, Missouri, Landsat
ETM™ and Radarsat images are orthorectified and co-registered
to each other. A maximum likelihood classifier is
utilized to determine different land-cover categories. Ground
reference data from sites throughout the study area are
collected for training and validation. The variations in
classification accuracy due to a number of radar imaging
processing techniques are studied. The relationship between
the processing window and the land classification is also
investigated. In addition, the Landsat images are fused with
several combinations of processed radar features. The
classification accuracies from the Landsat and radar feature
combinations are studied. Our research finds that fusion of
multi-sensor data improves the classification accuracy over
a single Landsat sensor, although different processing
techniques on radar images are required to obtain the best
results. In our study, fusion of Landsat images and Radarsat
feature combinations from a 13 x 13 entropy window, 9 x 9
data range widow, and 19 x 19 mean filter window achieves
the highest overall accuracy improvement (10 percent) over
the Landsat images alone.
45 Monitoring Spatio-temporal Dynamics of Photosynthesis with a Portable Hyperspectral Imaging System
Uwe Rascher, Caroline J. Nichol, Christopher Small, and Leif Hendricks
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Photosynthetic efficiency of higher plants dynamically
adapts to changing light intensity and is greatly influenced
by stress, such as water stress. We tested a new portable
hyperspectral imaging system, the SOC-700, manufactured
by Surface Optics, which produces 12-bit reflectance images
between 440 nm and 880 nm with a 4 nm spectral resolution.
We quantified the reflectance properties and photochemical
reflectance index (PRI) during light adaptation of
genetically modified Arabidopsis thaliana (L.) Heynh. plants
lacking or over-expressing the PsbS protein, an essential
component of the mechanism of non-photochemical dissipation.
In a second experiment, PRI images of gradually water
stressed leaves were compared to leaf-level measurements
of reflectance using a second commercially available spectrometer,
and chlorophyll fluorescence to detect dynamic,
photosynthesis correlated changes in reflectance and PRI.
In both experiments PRI measured with the SOC-700 changed, reflecting the biochemical adaptation of the photosynthetic apparatus to high light intensity (dynamic changes within minutes) and the gradual deactivation of photosynthesis during drying (changes within hours). The quantum efficiency of photosystem II (ΔF/Fm') and non-photochemical energy dissipation (NPQ) measured from chlorophyll fluorescence, were strongly correlated with PRI. Leaf area PRI values estimated from individual pixel spectra of the SOC-700 quantified photosynthetic efficiency more thoroughly than PRI values calculated from point measurements using the hand-held GER-1500. The applications, limitations, and potential of the SOC-700 for plant eco-physiology and remote sensing are also discussed.
57 Mapping Urban Land Cover Using Quickbird NDVI and GIS Spatial Modeling for Runoff Coefficient Determination
Pravara Thanapura, Dennis L. Helder, Suzette Burckhard, Eric Warmath, Mary O’ Neill, and Dwight Galster
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This research presents an integration of remote sensing and GIS
for determining the runoff coefficient (C) recommended by the
American Society of Civil Engineers and the Water Pollution
Control Federation in 1969. The C is a runoff index used as an
input parameter in the most commonly used procedure: the
rational method for storm-water runoff calculation in small
urban watersheds for storm drainage design and analysis. The
objective of this study was to evaluate 8-bit and 16-bit Quick-Bird (QB) NDVI satellite imagery using an unsupervised classification
and the ISODATA algorithm to map impervious area and
open space used for the determination of C in GIS spatial
modeling. The research hypothesis was that mapping impervious
area and open space using high spatial resolution NDVI
satellite imagery, generated using the ISODATA algorithm, was
an efficient and effective information extraction approach for
accurately estimating spatial representative C values. The
overall classification accuracies of the six QB NDVI thematic
maps produced were similar, about 92 percent. In order to
assess the utility of high spatial resolution satellite imagery
and to validate the composite runoff index geographic model
developed by Thanapura in 2005 and 2006, the C values were
calculated in GIS spatial modeling and compared to the
industry standard C. Finally, the hypothesis was accepted that
the finer resolution image and mapping approach used in this
study allowed for better discrimination of land-cover and thus
a more accurate representative C estimation.
67 Investigating the Effects of DEM Error in Scaling Analysis
Timothy D. James, Patrice E. Carbonneau, and Stuart N. Lane
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Digital elevation models (DEMs) are prone to error that,
as they can never be entirely eliminated, must be managed
effectively. Thus, it is important to understand the nature
of error and their sources, especially in the context of the
intended use of a DEM. This paper investigates the effects
that can be expected when common DEM errors propagate
through a scaling analysis. The errors investigated include
those associated with perturbation of camera exterior
orientation parameters, focal length, and DEM image coordinates,
which were simulated numerically. The role of
detrending was also investigated. Scaling analysis, by way
of the fractal dimension, using a new two-dimensional
approach was carried out on a variety of surfaces before
and after the introduction of error and the application of
detrending. The results reveal some serious procedural
implications on scaling analysis and cast doubt on the
authenticity of some scaling analysis results in the absence
of robust quality assessment and of independent supporting
evidence.
79 An Enhanced Spatio-spectral Template for Automatic Small Recreational Vessel Detection
Kevin Pegler, David Colemen, Ronald Pelot, and C. Peter Keller
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This paper investigates the performance of a spatio-spectral
template on Ikonos imagery to automatically detect small
recreational boats. The spatio-spectral template is employed
which is then enhanced through use of a weighted Euclidean
distance metric adapted from the Mahalanobis distance
metric. The purpose is to assist the Canadian Coast Guard
in gathering data on recreational boating for the modeling of
search and rescue incidence risk.
To test the detection accuracy of the enhanced spatiospectral template, a dataset was created by gathering position and attribute data for 53 recreation vessel targets purposely moored for this research within Cadboro Bay, British Columbia, Canada. The Cadboro Bay study site containing the targets was imaged using Ikonos.
The overall detection accuracy was 77 percent. The targets were broken down into two categories: Category A-less than 6 m in length, and Category B-greater than 6 m long. The detection rate for the Category B targets was 100 percent, while the detection rate for the Category A targets was 61 percent. It is important to note that some Category A targets were purposely selected for their small size to specifically test the detection limits of the enhanced spatiospectral template. The smallest target detected was 2.2 meters long and 1.1 meters wide. The analysis also revealed that the ability to detect targets between 2.2 meters and 6 meters long was diminished if the target was a dark color.
89 Performance Analysis of Integrated Sensor Orientation
Alain Ip, Naser El-Sheimy, and Mohamed Mostafa
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Integrated multi-sensor systems, with their major progress
in terms of sensor resolution, data rate and operational
flexibility, have become a very attractive mapping tool over
the last decade. In aerial mapping application, for example,
Exterior Orientation (EO) parameters for the imaging sensors
are required. Using the integrated Differential Global
Positioning System (DGPS) with Inertial Measurement Units
(IMU), direct determination of the EO parameters can be
obtained from the integrated system navigation solution.
This process is referred to as Direct Georeferening (DG). DG
provides substantial benefits over the indirect determination
method of estimating the EO parameters from conventional
Aerial Triangulation (AT) techniques using a block of images
with a sufficient number of known control points. These
benefits include the ability to map remote and inaccessible
regions, and by replacing tie point measurements/matching
and AT, significant cost-savings can be obtained for projects
that do not require stereo models (such as projects with
existing DEM or single image). The accuracy of DG, however,
is limited by the accuracy attainable by the DGPS and any
residual datum calibration errors. These can typically be as
large as 10 cm RMSE, which is not sufficient for some large
scale mapping applications. However, by combining the
direct EO data a traditional block adjustment, AT techniques
can be used to remove the residual errors in the solution.
This technique is known as Integrated Sensor Orientation
(ISO). It has several advantages over traditional AT, primarily
because the stable geometry provided by direct EO can
reduce the number of required GCP and tie-point to a minimum.
At the same time, ISO provides an excellent tool for
Quality Control/Quality Assurance (QC/QA) of the EO derived
from a DG system. This paper examines the factors that
determine the system performance for ISO. In addition,
examples are given to illustrate the expected accuracy of an
aerial mapping project using ISO under different qualities of
DGPS/IMU data.