Peer Reviewed Articles
387 The Assessment of Sediment Transport Rates by Automated Digital
Photogrammetry
M. Stojic, J. Chandler, P. Ashmore, and J. Luce
Abstract
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Automated DEM acquisition methods are used to generate
dense elevation models of a controlled experimental flume
used to simulate sediment transport in a braided stream. A
Pentax 645 non-metric camera was used to acquire all imagery,
and uncertainties concerning the interior orientation
of the camera were overcome using a self-calibrating bundle
adjustment. The ERDAS IMAGINE OrthoMAX software package
was used to derive all DEMS, and derived elevation models
were used in a variety of ways to provide data of geomorphological significance, A study of the quality of derived data
suggests that reliable estimates of sediment transport can
theoretically be derived from the detection of morphological
change alone, but it is very difficult to achieve in practice.
397 Co-Registered Aerial Stereopairs from Low-Flying Aircraft
for the Analysis of Long-Term Tropical Rainforest Canopy Dynamics
Stanley R. Herwitz, Robert E. Slye, and Stephen M. Turton
Abstract
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Ground-based censusing of tagged trees in permanent plots
has been the standard research method far monitoring the
long-term dynamics of tropical rainforest tree populations.
This paper describes a method for quantifying the turnover
and crown growth rates of tropical rainforest canopy trees
over an 18-year period using a temporal sequence of largescale
aerial stereopairs. The stereopairs were co-registered
using an array of control points that consisted of surveyed
aerial targets and primary branch bifurcation points(BIPs)
having the same persistent geometry and spatial coordinates
in the crowns of selected canopy trees.
Six crown size classes were distinguished, and critical
late stages in the life history of mature canopy trees were
identified. The smallest crown size classes (<20 and 20 to 40
m²) experienced more than 75 percent of the canopy tree
mortality over the 18-year period. Of the canopy trees that
survived, the mid-range 60- to 80-m² crown size class was
identified as a critical late stage, having both the highest
mean crown growth rate (2.42 m²/yr) among those trees
that exhibited positive growth as well as the highest proportion
of trees (47 percent) experiencing a reduction in crown
size. The results demonstrate that high resolution, aerial stereophotography
from low-flying aircraft serve as a valuable
tool for demographic research in tropical rainforest
ecosystems.
407 Effects of Emergent Grass on Mid-Infrared Laser Reflectance
of Soil
Ram M. Narayanan and Brian D. Guenther
Abstract
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Mid infrared laser reflectances of soils containing specific
minerals show diagnostic features in the 9- to 11 -µm wavelength
range, and are thus useful for remote sensing of terrestrial
lithology. However, the presence of actively growing
vegetation can obscure these diagnostic features to such an
extent as to make mineral identification virtually impossible.
The effects of emergent grass on the mid-infrared laser reflectance
of bare soil were studied experimentally. Speckleaveraged
reflectance data were collected at various wavelengths,
incidence angles, and polarization combinations
from a large movable soil container. Initial measurements
were made on bare soil under various wetness and surface
roughness conditions. Grass was then grown on the soil, and
three different grass densities were used in different sub-plots
of the container. Reflectance data were gathered from each
sub-plot as the grass-blade height increased. Reflectance ratios
(indicative of diagnostic features) were plotted as a
function of grass-blade height for different grass densities.
There appeared a grass-blade height value at which the diagnostic
ratios level off to a value of 1.0, thereby masking the
underlying soil reflectance features. These results should be
useful for identifying optimal conditions under which soil
mineralogy can be identified under overlying vegetation using
mid-infrared laser spectroscopy.
415 Towards Development of a Snow Water Equivalence (SWE) Algorithm
Using Microwave Radiometry Over Snow Covered First-Year Sea Ice
Sheldon D. Drobot and David G. Barber
Abstract
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In this paper we investigate snow geophysical and microwave
radiometric sensor characteristics (frequency, incidence,
and polarization) as they pertain to the development
of a snow water equivalence (SWE) algorithm for first-year sea
ice. Physical and electrical snow properties and in situ microwave
radiometry (19,37,and 85 GHz; V and H polarization)
data were collected during a 36-day period in early
1996 under the Collaborative-Interdisciplinary Cryospheric
Experiment (C-ICE).
Density, liquid water content, and salinity varied significantly over the snow volume vertical dimension. Diurnal sampling indicated a difference in liquid water content. Corresponding changes in salinity and density were not detected. Within the framework of this case study, 37-GHz H polarization was the most precise single frequency for SWE estimation. Multiple regression techniques show promise as an effective avenue to pursue the development of SWE algorithms.
425 Repeat-Pass Dual-Antenna Synthetic Aperture Radar Interferometric
Change-Detection Post-Processing
David A. Yocky and Benjamin F. Johnson
Abstract
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Synthetic aperture radar (SAR) inteferometric change-detection
(ICD) maps are highly sensitive to both macro and micro
temporal changes in SAR surface reflectivity. This change is
detected as decorrelations in the complex cross-correlation
between two SAR complex images collected at different times.
However, in many instances, numerous detected decorrelations
are not due to changes during the elapsed time, but
due to other decorrelating effects. Using information from a
repeat-pass, dual-antenna interferometric SAR (IFSAR) change
pair, we were able to identify over 70 percent of the ICD correlations
less than 0.80 as non-temporal changes. or false
changes. The remaining temporal changes coincided well
with controlled changes made in the scene. Our post-processing
results show the IFSAR coherence maps to be the
most informative SAR data component for such false temporal
change analysis.
431 The Use of Census Data in Urban Image Classification
Victor Mesev
Abstract
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A supervised classification strategy containing a suite of
techniques that allow the linking of urban land cover from
remotely sensed data with urban functional characteristics
from population census data is outlined and demonstrated.
For a stronger link, census tract data are also interpolated
into more disaggregated and more precise raster-based surfaces
using GIS. Census data in tabular and surface format
are then used to modify maximum-likelihood classifications
through stratified class a priori probabilities, and in terms of
assisting the selection of training samples and contextual
post-classification sorting. The strategy is applied to the classification
of housing density of four settlements in the United
Kingdom. The results show high site-specific accuracy, and
improvements in class area estimates.
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