Peer-Reviewed Articles
29 Mapping Spatial Thematic Accuracy with Fuzzy Sets
Liem T. Tran, James Wickham, S. Taylor Jarnagin, and C. Gregory Knight
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Common thematic map accuracy measures (e.g., error
matrix and kappa coefficient) are inadequate for analyzing
the spatial variation of thematic map accuracy. This paper
presents a method of mapping spatial accuracy of thematic
land cover maps using fuzzy sets. First, we define a multilevel
agreement between reference data and corresponding
pixels on the map. Next, we formulate a discrete, multi-level
agreement fuzzy set regarding a particular land-cover type
for each pixel on the map. Then, we construct spatial
accuracy maps based on information from the multi-level
agreement fuzzy sets. We illustrate the method by constructing
accuracy maps of several land cover types for the Mid-Atlantic Region.
Results show that thematic map
accuracy is not spatially homogenous, but varies across a
landscape and different land cover types having different
spatial patterns of accuracy. The method provides valuable
information about thematic map accuracy for both scientists
and decision makers, such as in designing adaptive sampling
schemes, deriving landscape indicators, or thematic
map-based modeling.
37 Configuring an Airborne Laser Scanner for Detecting Airport Obstructions
Christopher E. Parrish, Grady H. Tuell, William E. Carter, and Ramesh L. Shrestha
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To ensure the safety of the national airspace system, the
Federal Aviation Administration (FAA) oversees surveying
programs with the goal of geolocating vertical features that
penetrate 3D Obstruction Identification Surfaces (OIS) around
airfields. These OIS are defined mathematically and are
based on the layout of the runways, the types of electronic
navigation equipment used for each runway, and other
factors. Under a series of interagency agreements, the
National Geodetic Survey (NGS) is tasked with supplying
obstruction survey data to the FAA.
Airport obstruction surveys have traditionally been conducted using a combination of photogrammetry and conventional field survey techniques. In this study, we investigate the use of airborne laser scanning technology for this application. Specifically, we examine the effects of varying the forward look angle, laser footprint, flying height, flying speed, scan angle, scan frequency, transmitted power, and receiver sensitivity, as these parameters relate to the detection and measurement of vertical obstructions. We present results of test flights over the Gainesville Regional Airport (GNV) using fourteen different configurations of an Optech ALTM 2050. The results are compared to field-surveyed obstruction data obtained by NGS. Our analysis shows that certain configurations of the airborne laser scanning system notably improve the detection of obstructions. In this study, the best results were obtained using a 20° forward tilt angle and a 0.2 milliradian beam divergence from a flying height of 750 m. With this configuration, all obstructions were detected and the vertical accuracy (RMSE) was 0.88 m when compared to the field-surveyed obstructions.
47 A Four-Component Efficiency Index for Assessing Land Development Using
Remote Sensing and GIS
Xia Li
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A variety of indices have been proposed to facilitate the
quantitative analysis in remote sensing applications. The
assessment of land development is important for minimizing
development impacts and formulating alternative development
plans. Much attention has been paid to the quantity of land
use changes in general development assessment using remote
sensing. However, additional information can be obtained from
remote sensing and GIS for revealing land use problems more
effectively. This paper presents four indicators, quantity,
quality, location, and morphology to characterize land development
patterns for fast-growing regions. A four-component
efficiency index is further developed for ranking purposes to
reflect economic and environmental considerations. The
implementation of the method has been demonstrated in a
fast-growing region in south China. Efforts have been made to
verify the model with independent empirical data.
59 The Performance of Fuzzy Operators on Fuzzy Classification of Urban Land
Covers
Z. Islam and G. Metternicht
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The research discussed in this paper evaluates the performance
of selected fuzzy operators (e.g., maximum, minimum,
algebraic sum, algebraic product, and gamma operators) for
integrating fuzzy membership values associated with multiple
spectral bands for mapping the complex spatial mixture that
characterises urban land covers. Accordingly, a supervised
classification approach based on the fuzzy c-means algorithm
was implemented to generate fuzzy memberships of selected
bands (1, 3, 4 and 7) of a Landsat-7 ETM image that
provided the highest spectral separability among different
urban land covers (e.g., forest, grassland, urban, and dense
urban) as determined by a transformed divergence analysis.
Maps resulting from the application of each fuzzy operator
were evaluated against field data. The results show that the
fuzzy algebraic product and the fuzzy gamma operators (0.1
to 0.8) are optimal for integrating the fuzzy memberships of
selected urban land covers on multi-band data sets, as they
exhibited a Khat statistic of 75 percent as compared to a Khat
statistic of 59 percent, 64 percent and 71 percent for maximum,
minimum and fuzzy algebraic sum, respectively.
69 Augmenting Grid-Based Contours to Improve Thin-Plate DEM Generation
Michael B. Gousie and Wm. Randolph Franklin
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We present two new pre-processing techniques that improve
thin plate Digital Elevation Model (DEM) approximations
from grid-based contour data. One method computes
gradients from an initial interpolated or approximated
surface. The aspects are used to create gradient paths that
are interpolated using Catmull-Rom splines. The computed
elevations are added to the initial contour data set. Thin
plate methods are applied to all of the data. The splines
allow information to flow across contours, improving the
final surface. The second method successively computes
new, intermediate contours in between existing isolines,
which provide additional data for subsequent thin plate
processing. Both methods alleviate artifacts visible in
previous thin plate methods. The surfaces are tested with
published methods to show qualitative and quantitative
improvements over previous methods.
81 Automated Quality Control for Orthoimages and DEMs
Joachim K. Höhle and Markéta Potucková
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The checking of the geometric accuracy of orthoimages and
digital elevation models (DEMS) is discussed. As a reference,
an existing orthoimage and a second orthoimage derived
from an overlapping aerial image, are used. The proposed
automated procedures for checking the orthoimages and
DEMs are based on matching of corresponding image
patches. Existing topographic databases are additionally
used in order to select time-invariant objects as checkpoints.
In order to avoid blunders in the correlation, thresholds for
similarity measures are applied. Detailed studies show that a
combination of thresholds for the maximum correlation
coefficient, the average mutual information, and distance can
reduce the number of blunders in the automated measurements
considerably and should therefore be applied. The
calculation of DEM errors is carried out by an improved
formula. The new methods and procedures are applied to
two practical examples, and the results are presented.
89 Statistical Ratio Rank Ordered Differences Filter for SeaWiFS Impulse
Noise Removal
Zhengjun Liu, Changyao Wang, Aixia Liu, and Xiangming Xiao
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Due to the 10-bit design of SEAWIFS instrument and the signal
transmission, many SEAWIFS satellite images are expected to
have lower digitization noise and corrupted impulse noise. In
this paper, we first analyze the characteristics of impulse
noise and propose a new rank-ordered filter based on the
difference of sequence for mean/standard, which is named as
Statistical Ratio Rank Ordered Differences (SRROD) filter.
Second, we describe the impulse noise detection and removal
algorithm in detail. Compared with the median filter and
other existing filters, the SRROD filter could effectively remove
impulse noises while preserving other valid pixels without, or
only with minor, modification. Through adjusting the lower
and upper threshold values, different filter performance
could be achieved. We also discuss the blind parameters
optimization for non-recursive implementation. Based on the
assessment of the distribution map of performance estimator according to different
lower and upper threshold pairs, a
nearly optimal threshold could be obtained. Finally, some
concluding remarks are also presented in this paper.
97 Photogrammetric Analysis of the Mars Global Surveyor Mapping Data
Jie Shan, Jong-suk Yoon, D. Scott Lee, Randolph L. Kirk, Gregory A. Neumann,
and Charles H. Acton
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This paper studies the photogrammetric mapping properties
and capabilities of the Mars Global Surveyor (MGS) mapping
data. Starting from the raw MGS data, we decompress the
MOC narrow angle images, extract, and calculate their exterior
orientation from the SPICE kernels, and calculate the 3D
coordinates of MOLA footprints from MOLA PEDR files. A
new approach is proposed that registers a MOLA profile to
stereo MOC images over the same area with robust and faster
convergence. Intersection is conducted to determine the 3D
positions of image points measured on MOC stereo pairs. It
is shown that there is a nearly constant uncertainty of one
MOLA ground spacing distance (approximately 325 m) along
the flight direction in MOC and MOLA registration. This is
caused by the uncertainties in SPICE kernels, MOLA points,
and the determination of time tags for MOC scan lines, which
possibly constitutes the dominant error source for the registration.
Intersection calculation reaches an optimal balance by
distributing the uncertainty evenly in the two images of a
stereo pair. As for the photogrammetric mapping capabilities,
an uncertainty of 180.8 m in planimetric distance and 30.8 m
in elevation difference is estimated. A number of numerical
and graphic results over three of the selected candidate landing
sites for the Mars Exploration Rover mission are presented
for analysis and illustration.