Peer-Reviewed Article Abstracts
1073 Kronos: A Software System for the Processing and Retrieval of
Large-Scale AVHRR Data Sets
Zengyan Zhang, Joseph JáJá, David A. Bader, Satya N.V. Kalluri,
Huiping Song, Nazmi El Saleous, Eric Vermote and John R.G. Townshend
Abstract
Download
Full Article
Raw remotely sensed satellite data have to be processed and mapped
into a standard projection in order to produce a multi-temporal data
set which can then be used for regional or global Earth science studies.
However, traditional methods of processing remotely sensed satellite
data have inherent limitations because they are based on a fixed
processing chain. Different users may need the data in different
forms with possibly different processing steps; hence, additional
transformations may have to be applied to the processed data, resulting
in potentially significant errors. In this paper, we describe a software
system, Kronos, for the generation of custom-tailored products from
the Advanced Very High Resolution Radiometer (AVHRR) sensor. It allows
the generation of a rich set of products that can be easily specified
through a simple interface by scientists wishing to carry out Earth
system modeling or analysis. Kronos is based on a flexible methodology
and consists of four major components: ingest and preprocessing,
indexing and storage, a search and processing engine, and a Java
interface. After geo-location and calibration, every pixel is indexed
and stored using a combination of data structures. Following the
users' queries, data are selectively retrieved and secondary processing
such as atmospheric correction, compositing, and projection are performed
as specified. The processing is divided into two stages, the first
of which involves the geo-location and calibration of the remotely
sensed data and, hence, results in no loss of information. The second
stage involves the retrieval of the appropriate data subsets and
the application of the secondary processing specified by the user.
This scheme allows the indexing and the storage of data from different
sensors without any loss of information and, therefore, allows assimilation
of data from multiple sensors. User specified processing can be applied
later as needed.
1083 Assessing the Quality of the Radiometric and Spectral Calibration
of casi Data and Retrieval of Surface Reflectance Factors
Anne Jacobsen, Kathleen B. Heidebrecht, and Alexander F.H. Goetz
Abstract
Download
Full Article
The spectral and radiometric data quality of the Compact Airborne Spectrographic
Imager (casi) was assessed using atmospheric modeling and fitting the band
center location of the oxygen absorption feature centered around 0.762 ?m.
Atmospheric modeling was used to assess the quality of the radiometric calibration.
A software program that locates the position of the oxygen absorption feature
and performs atmospheric modeling was used to assess the spectral calibration
of the scanner. These methods were adequate to reveal problems with the radiometric
and spectral calibration and spectral alignment. The analyses required image
data with a continuous spectrum and were performed on spectral mode data.
Based on one calibration target, two different methods for retrieving surface reflectance factors were applied to the spectral and spatial mode data, respectively. Atmospheric modeling and normalization to the calibration target were used on the spectral image data because water vapor correction on a pixel-by-pixel basis was possible. Water vapor correction on a pixel-by-pixel basis was not possible on the spatial data, and surface reflectance retrieval was accomplished using modeled path radiance and field spectra from the calibration target.
1093 Extraction and Delineation of Alluvial Fans from Digital Elevation Models
and Landsat Thematic Mapper Images
G. Ch. Miliaresis and D. P. Argialas
Abstract
Download
Full Article
A methodology was designed and computer algorithms were implemented for the
extraction of alluvial fans from digital elevation models and Landsat TM
imagery, and it was demonstrated for the Death Valley region of the southwestern
U.S.A. First, the drainage network was extracted from the digital elevation
model and the outflow points to the basin floor were detected. Then, region
growing of the outflow points was performed on the basis of the gradient
value of the surrounding pixels in the digital elevation model, and a set
of fan polygons was derived. These polygons were then used as seeds to another
region-growing algorithm that extracted each down-fan area using a criterion
that was based on both (1) the gradient and (2) the difference of the spectral
signatures (in the Landsat TM band 1) between the playa deposited in the
basin floor and the down-fan area. The finally extracted fan-polygons were
found to be in accordance with the alluvial fans depicted on the topographic
map and the satellite imagery.
1103 Accuracy Evaluation of Ground Points from IKONOS High-Resolution Satellite
Imagery1
Guoqing Zhou and Ron Li
Abstract
Download
Full Article
To evaluate the geometric accuracy of ground points from integrated Global
Positioning System (GPS), inertial navigation system (INS), and high-resolution
linear array CCD sensor data, this paper presents the mathematical model
of the bundle adjustment and the experimental results on the attainable accuracy
of ground points versus number and distribution of ground control points
(GCPs), versus the image measurement error of GCPs and checkpoints, and versus
the order of the polynomial fit to the orbital path. A geodetic control network
established in Madison County in central Ohio, which is used for testing
the 3D accuracy of the simulated new generation IKONOS high-resolution satellite
imagery, will be introduced. Based on the airborne High Resolution Stereo
Camera (HRSC) system and simulated IKONOS imagery (SpaceImaging, Inc.), various
experimental schemes involving geometric strength with various configurations
of stereo models, the influence of the number and distribution of GCPs, and
the influence of the image measurement errors of GCPs and checkpoints were
performed. Some recommendations and suggestions for improving the geometric
accuracy of ground points were finally drawn up from this experimental research.
1113 Effects of Various Factors on the Accuracy of DEMs: An Intensive Experimental
Investigation
Jianya Gong, Zhilin Li, Qing Zhu, Haigang Sui, and Yi Zhou
Abstract
Download
Full Article
A series of tests on the accuracy of DEMs is described. The effects of four
factors on DEM accuracy have been tested, i.e., the accuracy, the density
of source data, the characteristics of the terrain surface, and the modeling
approaches. A large area covered by two 1:10,000-scale maps was selected
for testing. The terrain types range from flat to hilly to mountainous. Various
sources (photographs and contour maps) were used and various measurement
methods were employed.
From test results, the following has been found: (1) source data measured manually with analytical plotters are the most reliable because automated measurement using image matching techniques could generate systematic errors; (2) the accuracy of DEMs decreases (or the RMSE becomes larger) with an increase in sampling interval, and the relationship is linear; (3) the inclusion of feature points and break lines improves the accuracy of DEMs significantly, especially when the terrain is rough; (4) generally speaking, the accuracy of DEMs decreases with an increase in relief; however, this is not always the case, and the best results may be obtained in hilly areas; and (5) direct modeling from originally measured data to form a triangular network will yield better results than indirect modeling using a random-to-grid interpolation to form a grid network. The difference could be significant if the terrain is rough.
From these conclusions, some advice on DEM production could be made as follows: (1) when using automated photogrammetric systems for data acquisition, editing by experienced operators should be considered; (2) in hilly areas, photogrammetric contouring can be the most efficient method for DEM data acquisition if analytical plotters are used; (3) feature points should always be measured and kept in order to reduce the data volume while retaining the fidelity of the DEM; and (4) when the terrain surface is rough, triangulation-based methods are recommended.
1119 A Stereo Matching Algorithm for Urban Digital Elevation Models
C. Baillard and O. Dissard
Abstract
Download
Full Article
A stereo matching algorithm dedicated to complex urban scenes is described.
It relies on successive complementary matching steps, based on dynamic programming.
First, intensity edges of both images are matched, which produces piecewise
continuous 3D chains. This provides a description of the scene structure
containing the highest elevation of most height discontinuities. Then the
interval pairs defined by the matched edges are matched in a hierarchical
way, by a radio-metrically constrained process followed by a geometrically
constrained one.
The novelty of the approach lies in the use of several successive steps appropriate to different kinds of pixels. It provides dense disparity maps with less noise, while preserving discontinuities, which are a characteristic of urban digital elevation models. The method has proved reliable (producing few noisy and altimetrically accurate 3D data) and fast, and is robust to image variability. Perspectives within an industrial production context are discussed.
1129 Classifying Hills and Valleys in Digitized Terrain
Terrence Cronin
Abstract
Download
Full Article
A technique is presented to differentiate hills from valleys, using a contour
map. Unlike previous classification techniques based on a gridded representation
of terrain, the new method is based on the containment relationship of nested
contours. The primary contribution of this paper is an innovation to accommodate
contours that leave the edge of the map.Because these contours are ambiguous
with respect to interior and exterior, they warrant special treatment during
containment testing operations. Their proper interpretation results in a
more comprehensive classification product. Hills are constructed from the
top down, by starting with a summit contour and incrementally annexing contours
at lower elevations that contain the summit. Conversely, valleys are built
from the bottom up, by annexing contours at high elevations that contain
the basin contour. Construction of hills and valleys terminates when containing
contours cease to exist.