Peer Reviewed Articles
443 The Continuum of Classification Fuzziness in Thematic
Mapping
Giles M. Foody
Abstract
Download
Full Article
Thematic mapping from remotely sensed data is generally
achieved through the application of a supervised image classification.
Although this is one of the moss common applications
of remote sensing, the maps derived are often of insufficient
accuracy for operational use. Consequently, considerable
research effort has been derived at increasing the accuracy
of thematic mapping, particularly through the development
of classification techniques that make fuller use of the information
content of remotely sensed data. One major set of
problems limiting the accuracy of thematic maps derived
from remotely sensed data relates 20 conceptual issues associated
with the use of classification techniques as the tool for
mapping. It is shown that the conventional "hard" classifications
may be less appropriate than fuzzy classifications and
that a continuum of classification fuzziness can be defined.
The potential for classification at any point along this continuum,
from completely crisp to fully fuzzy, is discussed
and may provide a framework for realizing more fully the
potential of remote sensing as a source of thematic map
data. The implications of the continuum on spatial data
standards and reporting are also briefly discussed.
453 Automatic Lineament Detection Using Digital Elevation
Models with Second Derivative Filters
David Wladis
Abstract
Download
Full Article
A grid operator designed for the analysis of potential field
data has been applied to a digital elevation model for the
detection of lineaments. The results obtained have been evaluated
using both an existing lineament map of the area and
a field investigation. The evaluation indicates that the suggested
methodology facilitates lineament detection. The high
degree of consistency between the suggested method and the
existing tectonic map indicates that lineaments in the study
area are largely topographic features. Field validation confirmed
these findings except in a few well-defined situations.
459 Semiautomatic Extraction of Building Outlines from Large-Scale
Aerial Images
Liora Sahar and Amnon Krupnik
Abstract
Download
Full Article
One of the most challenging problems in digital photogrammetry
today is automatic extraction of cartographic features
from large-scale aerial images. Automatic detection of such
features in general, and buildings in particular, will significantly
improve the map compilation process as well as other
tasks, such as DEM and orthophoto generation.
This paper presents a semiautomatic approach for the
extraction of buildings from large-scale images. The main
goal is to recover three-dimensional (3D) outlines of buildings.
The extraction should be sufficiently accurate, reliable,
and efficient in order to comply with the high standards set
by the photogrammetric community. In order to obtain a 3D
description, the approach comprises stereo analysis for extracting
building heights, along with a general knowledge of
building geometry and shadow information.
The paper explains the approach, presents experiments,
and discusses the results.
467 Digital Photogrammetric Change Analysis as Applied to Active Coastal
Dunes in Michigan
Daniel G. Brown and Alan F. Arbogast
Abstract
Download
Full Article
A pilot study was conducted to investigate the applicability
of digital photogrammetric methods to the study and management
of dynamic dune systems. Two sets of panchromatic
stereographic aerial photographs taken over Ludington State
Park, Michigan, one pair each from 1965 (1:20,000-scale) and
1987 (1:15,000-scale), were obtained from historical archives.
Stereo models were constructed for the stereo-pairs, using
post-processed differential GPS ground control points, and digital
elevation models (DEMs) were extracted from each at a
resolution of 3 metres. The analysis involved computing differences
between the two DEMs at each location, and computing
a volume of sediment (sand) flux over the 22-year time
period. Maps of elevation change were then constructed and
interpreted to suggest patterns resulting from eolian processes.
Processes of dune development, movement, and "blowout"
were identifiable and measurable. The project illustrates how
recent developments in photogrammetry have enhanced capabilities
for monitoring geomorphologically sensitive landscapes
such as dune fields.
475 Change Analysis in the United Arab Emirates: An Investigation
of Techniques
Terry L. Sohl
Abstract
Download
Full Article
Much of the landscape of the United Arab Emirates has been
transformed over the past 15 years by massive afforestation,
beautification, and agricultural programs. The "greening" of
the United Arab Emirates has had environmental consequences,
however. including degraded groundwater quality
and possible damage to natural regional ecosystems.
Personnel from the Ground-Water Research project, a
joint effort between the National Drilling Company of the
Abu Dhabi Emirate and the U.S.Geological Survey, were interested
in studying landscape change in the Abu Dhabi
Emirate using Landsat thematic mapper (TM) data. The EROS
Data Center in Sioux Falls, South Dakota was asked to investigate
land-cover change techniques that (1) provided locational,
quantitative, and qualitative information on landcover
change within the Abu Dhabi Emirate; and (2) could
be easily implemented by project personnel who were relatively
inexperienced in remote sensing. A number of products
were created with 1987 and 1996 Landsat TM data using
change-detection techniques, including univariate image differencing,
on "enhanced" image differencing, vegetation index
differencing, post-classification differencing, and change-vector analysis.
The different techniques provided products that varied in levels of adequacy according to the specific application and the ease of implementation and interpretation. Specific quantitative values of change were most accurately and easily provided by the enhanced image-differencing technique, while the change-vector analysis excelled at providing rich qualitative detail about the nature of a change.
485 Remotely Sensed Estimates of Vegetation Structural Characteristics
in Restored Wetlands, Southern California
Stuart R. Phinn, Douglas A. Stow, and David Van Mouwerik
Abstract
Download
Full Article
Traditional field sampling approaches for ecological studies of
restored habitat can only cover small areas in detail, can be
time consuming, and are often invasive and destructive. Spatially
extensive and non-invasive remotely sensed data can
make field sampling more focused and efficient. The objective
of this work was to investigate the feasibility and accuracy of
hand-held and airborne remotely sensed data to estimate vegetation
structural parameters for an indicator plant species in
a restored wetland. High spatial resolution, digital, multispectral
camera images were captured from an aircraft over
Sweetwater Marsh (Sari Diego County, California) during each
growing season between 1992-1996. Field data were collected
concurrently, which included plant heights, proportional
ground cover and canopy architecture type, and spectral radiometer
measurements. Spartina foliosa (Pacific cordgrass) is
the indicator species for the restoration monitoring. A conceptual
model summarizing the controls on the spectral reflectance
properties of Pacific cordgrass was established.Empirical models were developed dating the stem length, density,
and canopy architecture of cordgrass to normalized-diffrence-vegetation-index values. The most promising results were
obtained from empirical estimates of total ground cover using
image data that had been stratified into high, middle, and low
marsh zones. As part of on-going restoration monitoring activities,
this model is being used to provide maps of estimated
vegetation cover.
495 Indications of Relative Drought Stress in Longleaf Pine
from Thematic Mapper Data
John E. Pinder III and Kenneth W. McLeod
Abstract
Download
Full Article
Multitemporal Thematic Mapper data indicated that the ratios
of reflectances of band 5 to band 4 increased as longleaf
pine were subjected to a prolonged drought that began in the
fall of 1989 and continued through the fall of 1990. Mean ratios
increased from 0.42 preceding the drought to 0.55 during
the drought, but the amount of the increase varied from
0.05 to 0.25 among forest stands. Ratios returned to pre-
drought levels once the drought was broken. Tree ring widths
in 1990 were significantly smaller than were those for years
of average rainfall before the drought, and residual drought
stress effects contributed to smaller ring widths in subsequent
years. The degree of reduction in ring widths was correlated
to the degree of increase in the ratio of band 5 to
band 4. The greatest size reductions in ring widths occurred
in those stands with the greatest increase in band ratios.
| Top | Home |