Accuracy aspects of stereo side-looking radar

The geometry of the radar stereo model and factors affecting visual radar stereo perception are reviewed. Limits to the vertical exaggeration factor of stereo radar are defined. Radar stereo model accuracies are analyzed with respect to coordinate errors caused by errors of radar sensor position and of range, and with respect to errors of coordinate differences, i.e., cross-track distances and height differences

Multiple incidence angle SIR-B experiment over Argentina

The Shuttle Imaging Radar (SIR-B), the second synthetic aperture radar (SAR) to fly aboard a shuttle, was launched on October 5, 1984. One of the primary goals of the SIR-B experiment was to use multiple incidence angle radar images to distinguish different terrain types through the use of their characteristic backscatter curves. This goal was accomplished in several locations including the Chubut Province of southern Argentina. Four descending image acquisitions were collected providing a multiple incidence angle image set. The data were first used to assess stereo-radargrammetric techniques. A digital elevation model was produced using the optimum pair of multiple incidence angle images. This model was then used to determine the local incidence angle of each picture element to generate curves of relative brightness vs. incidence angle. Secondary image products were also generated using the multi-angle data. The results of this work indicate that: (1) various forest species and various structures of a single species may be discriminated using multiple incidence angle radar imagery, and (2) it is essential to consider the variation in backscatter due to a variable incidence angle when analyzing and comparing data collected at varying frequencies and polarizations

Effects of Orbit and Pointing Geometry of a Spaceborne Formation for Monostatic-Bistatic Radargrammetry on Terrain Elevation Measurement Accuracy

During the last decade a methodology for the reconstruction of surface relief by Synthetic Aperture Radar (SAR) measurements – SAR interferometry – has become a standard. Different techniques developed before, such as stereo-radargrammetry, have been experienced from space only in very limiting geometries and time series, and, hence, branded as less accurate. However, novel formation flying configurations achievable by modern spacecraft allow fulfillment of SAR missions able to produce pairs of monostatic-bistatic images gathered simultaneously, with programmed looking angles. Hence it is possible to achieve large antenna separations, adequate for exploiting to the utmost the stereoscopic effect, and to make negligible time decorrelation, a strong liming factor for repeat-pass stereo-radargrammetric techniques. This paper reports on design of a monostatic-bistatic mission, in terms of orbit and pointing geometry, and taking into account present generation SAR and technology for accurate relative navigation. Performances of different methods for monostatic-bistatic stereo-radargrammetry are then evaluated, showing the possibility to determine the local surface relief with a metric accuracy over a wide range of Earth latitudes

Die TMS-evozierte N100 im primär motorischen Kortex in Einzel- versus Doppelpulsen

Kurzfassung der Dissertationsschrift Die TMS-evozierte N100 im primär motorischen Kortex im Einzel- versus SICI- Doppelpulsprotokoll von Jana Leberl Aus der Klinik und Poliklinik für Psychiatrie und Psychotherapie des Kindes- und Jugendalters Direktor: Prof. Dr. Stephan Bender Bei der vorliegenden Arbeit handelt es sich um eine Pilotstudie, die zur Planung einer Studie durchgeführt wurde, in der die kortikale Exzitabilität bei Kindern und Jugendlichen mit Angsterkrankungen erforscht werden soll. Hierzu wurden TMS-Pulse über dem primär motorischen Kortex von gesunden, jungen Erwachsenen appliziert. Die durch die Stimulation ausgelösten motorisch evozierten Potentiale (MEP) wurden mittels EMG, die kortikal durch die TMS evozierte Potentiale (TEP) mittels EEG aufgezeichnet. Bei den TMS-Pulsen handelte es sich einerseits um Einzel- und andererseits um inhibierend wirkende Doppelpulse, die sich aus einem konditionierenden Stimulus schwächerer Stimulationsintensität, gefolgt von einem Teststimulus normaler Stimulationsintensität zusammensetzten, zwischen welchen eine Pause von 3 ms lag. Aufgrund der inhibierenden Wirkung, die solch eine Stimulation auf das MEP hat, wird sie „short interval intracortical inhibition“, kurz SICI genannt. Im Gegensatz zu dem bereits bekannten Effekt, den SICI auf das MEP hat, sind die kortikalen Mechanismen, die dieser Doppelpuls auslöst, noch nicht verstanden und deshalb Fragestellung dieser Studie. Aufgrund pharmakologischer Untersuchungen liegt die Vermutung nahe, dass SICI Einfluss auf die Größe der ersten großen Deflektion des TEP, welche ca. 100 ms nach dem TMS Impuls auftritt hat (Premoli et al., 2014). Diese markante Deflektion wird aufgrund ihres zeitlichen Auftretens N100 genannt und gilt als kortikaler Inhibitionsparameter seit in TMS-EEG-Studien beobachtet werden konnte, dass sie bei Vorbereitung auf eine bevorstehende Bewegung kleiner ausfällt (Bender et al., 2005; Jarczok et al., 2016; Nikulin, Kicic, Kahkonen, & Ilmoniemi, 2003). Bei den 17 Probanden dieser Studie wurde untersucht inwiefern sich SICI auf das MEP und auf die N100 auswirkt. Es konnte hierbei ein eindeutiger MEP-SICI-Effekt (Effektstärke: 1,021), aber kein signifikanter Unterschied zwischen der Amplitude und Latenz der TMS-evozierten N100 zwischen Einzel-und SICI- Stimulation detektiert werden, wobei die sehr kleinen Effektstärken bezüglich der Amplitude (0,065) und der Latenz (0,213) darauf hinweisen, dass es tatsächlich keinen Effekt gibt. Die beobachtete Dissoziation zwischen MEP-SICI-Effekt (Reduktion des MEP) und N100-SICI-Effekt (keine signifikante Veränderung der Amplitude und Latenz) weist darauf hin, dass es sich bei SICI und N100 um getrennt ablaufende Prozesse handelt und der inhibierende Doppelpuls SICI bei jungen, gesunden Probanden nur einen untergeordnet zu wertenden Einfluss auf die Größe der N100 hat

Building Façade Separation in Vertical Aerial Images

Three-dimensional models of urban environments have great appeal and offer promises of interesting applications. While initially it was of interest to just have such 3D data, it increasingly becomes evident that one really would like to have interpreted urban objects. To be able to interpret buildings we have to split a visible whole building block into its different single buildings. Usually this is done using cadastral information to divide the single land parcels. The problem in this case is that sometimes the building boundaries derived from the cadastre are insufficiently accurate due to several reasons like old databases with lower accuracies or inaccuracies due to transformation between two coordinate systems. For this reason it can happen that a cadastral boundary coming from an old map is displaced by up to several meters and therefore divides two buildings incorrectly. To overcome such problems we incorporate the information from vertical aerial images. We introduce a façade separation method that is able to find individual building façades using multi view stereo. The purpose is to identify the individual façades and separate them from one another before on proceeds with the analysis of a façade’s details. The source was a set of overlapping, thus “redundant ” vertical aerial images taken by an UltraCam digital aerial camera. Therefore in a first step we determine the building block outlines using the building classification and use the height values from the Digital Surface Model (DSM) to determine approximate “façade quadrilaterals”. We also incorporate height discontinuities using the height profiles along the building outlines to enhance our façade separation. In a next step we detect repeated pattern in these “façade images ” and use them to separate the façades respectively building blocks from one another

Mapping of sea ice and measurement of its drift using aircraft synthetic aperture radar images

Side-looking radar images of Arctic sea ice were obtained as part of the Arctic Ice Dynamics Joint Experiment. Repetitive coverages of a test site in the Arctic were used to measure sea ice drift, employing single images and blocks of overlapping radar image strips; the images were used in conjunction with data from the aircraft inertial navigation and altimeter. Also, independently measured, accurate positions of a number of ground control points were available. Initial tests of the method were carried out with repeated coverages of a land area on the Alaska coast (Prudhoe). Absolute accuracies achieved were essentially limited by the accuracy of the inertial navigation data. Errors of drift measurements were found to be about ±2.5 km. Relative accuracy is higher; its limits are set by the radar image geometry and the definition of identical features in sequential images. The drift of adjacent ice features with respect to one another could be determined with errors of less than ±0.2 km

Venus surface roughness and Magellan stereo data

Presented are results of some studies to develop tools useful for the analysis of Venus surface shape and its roughness. Actual work was focused on Maxwell Montes. The analyses employ data acquired by means of NASA's Magellan satellite. The work is primarily concerned with deriving measurements of the Venusian surface using Magellan stereo SAR. Roughness was considered by means of a theoretical analyses based on digital elevation models (DEM's), on single Magellan radar images combined with radiometer data, and on the use of multiple overlapping Magellan radar images from cycles 1, 2, and 3, again combined with collateral radiometer data