7 research outputs found
Phase History Decomposition for Efficient Scatterer Classification in SAR Imagery
A new theory and algorithm for scatterer classification in SAR imagery is presented. The automated classification process is operationally efficient compared to existing image segmentation methods requiring human supervision. The algorithm reconstructs coarse resolution subimages from subdomains of the SAR phase history. It analyzes local peaks in the subimages to determine locations and geometric shapes of scatterers in the scene. Scatterer locations are indicated by the presence of a stable peak in all subimages for a given subaperture, while scatterer shapes are indicated by changes in pixel intensity. A new multi-peak model is developed from physical models of electromagnetic scattering to predict how pixel intensities behave for different scatterer shapes. The algorithm uses a least squares classifier to match observed pixel behavior to the model. Classification accuracy improves with increasing fractional bandwidth and is subject to the high-frequency and wide-aperture approximations of the multi-peak model. For superior computational efficiency, an integrated fast SAR imaging technique is developed to combine the coarse resolution subimages into a final SAR image having fine resolution. Finally, classification results are overlaid on the SAR image so that analysts can deduce the significance of the scatterer shape information within the image context
Characterization of SU(1,1) coherent states in terms of affine group wavelets
The Perelomov coherent states of SU(1,1) are labeled by elements of the
quotient of SU(1,1) by the compact subgroup. Taking advantage of the fact that
this quotient is isomorphic to the affine group of the real line, we are able
to parameterize the coherent states by elements of that group or equivalently
by points in the half-plane. Such a formulation permits to find new properties
of the SU(1,1) coherent states and to relate them to affine wavelets.Comment: 11 pages, latex, to be published in J. Phys. A : Math. Ge
NASA Tech Briefs, September 1997
Topics include: Data Acquisition and Analysis; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Software; Mechanics; Machinery/Automation; Manufacturing/Fabrication; Mathematics and Information Sciences
Airborne Hyperspectral Imaging of Lakes
In a time of rising concern about climate change and pollution, the water quality of large
lakes acts as an indicator of the health of the environment. To study the water quality at a
large scale - up to several hundreds of kilometres - hyperspectral remote sensing is emerging
as the main solution. Indeed, different quantities relevant to water quality, like turbidity
or concentratrion in chlorophyll-a, can be measured using the spectral reflectance of the
water column. Additionally, airborne and spaceborne sensors can cover large areas, thus
allowing to study the water at a much larger scale than when simply taking water samples at
specific points. Airborne hyperspectral imaging, in particular, offers an acceptable ground
resolution - around a metre - which allows to map relevant quantities precisely. However,
few existing projects deliver maps that have both a sufficient ground resolution and a large
coverage. Furthermore, most existing sensors do not offer a fine spectral resolution, which is
for instance crucial when studying the presence of chlorophyll-a, which can only be detected
in a narrow range of the electromagnetic spectrum. This thesis presents our work with a
hyperspectral sensor developed and used by the Geodetic Engineering Laboratory of EPFL
in the Léman-Baïkal project, a cooperative work which aimed at studying both Lake Geneva
(Switzerland) and Lake Baikal (Russia). The project included ultralight plane flights with
an onboard pushbroom scanner, which allowed to collect data over large areas with a fine
spectral resolution. Alongside the use of this sensor came problematics which are at the
centre of this thesis: the georeferencing of the scan lines, their radiometric calibration, their
analysis and the softwaremanagement of this data. In the following, we present a new method
to georeference pushbroom scan lines that uses co-acquired frame images to perform coregistration
and to achieve a georeferencing, which RMSE is up to 20 times smaller than the
direct one. We propose an efficient radiometric self-calibration method to convert the sensor
output to water-leaving reflectance; this method makes use of the visible peaks of atmospheric
absorption to align the spectral bands with those of a reference acquisition, and uses the
near infrared properties of deep water and vegetation to performabsolute calibration. The
last part of the processing - the software management, including data compression - was
solved by developing a software called HYPerspectral Orthorectification Software (HypOS).
This software is the synthesis of our work, including the tools to performgeometric correction,
radiometric calibration and data compression of our hyperspectral data. Two examples of
applications are given: the first one deals with mapping chlorophyll-a in the Rhone Delta of
Lake Geneva; the second, at a larger scale, uses satellite data to monitor ice coverage over large
lakes like Onega or Ladoga (Russia)
Neues Erbe : Aspekte, Perspektiven und Konsequenzen der digitalen Überlieferung
Die zunehmende Digitalisierung von Informationen und ihre ausschließliche Produktion in digitalen Formen führen zu einer sehr hohen Technikabhängigkeit. Das dokumentarische Erbe, das wir zukünftigen Generationen überliefern, wird primär ein digitales Erbe sein, dessen Erhaltung und Überlieferung heutige Gesellschaften vor große und bisher weitestgehend ungelöste Probleme stellt. Der vorliegende Band leistet disziplinübergreifend eine erste Annäherung an das Themenfeld der digitalen Überlieferung
Neues Erbe : Aspekte, Perspektiven und Konsequenzen der digitalen Überlieferung
Die zunehmende Digitalisierung von Informationen und ihre ausschließliche Produktion in digitalen Formen führen zu einer sehr hohen Technikabhängigkeit. Das dokumentarische Erbe, das wir zukünftigen Generationen überliefern, wird primär ein digitales Erbe sein, dessen Erhaltung und Überlieferung heutige Gesellschaften vor große und bisher weitestgehend ungelöste Probleme stellt. Der vorliegende Band leistet disziplinübergreifend eine erste Annäherung an das Themenfeld der digitalen Überlieferung