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Vorträge im Institutsseminar 2015
Tobias Bollian "RFI Filtering for SAR Systems with Digital Beamforming applied on NASA's EcoSAR"
Dienstag, 22. Dezember 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
For SAR systems operating at low frequencies (e.g. L- or P-band) emissions by other signal sources introduce artifacts and lower the signal-to-noise ratio. As a result, radio frequency interference (RFI) can significantly degrade the image quality. While out-of-band RFI can be controlled by the means of simple filters in the receive and processing chain, any in-band interference challenges a clean recovery of the original SAR signal. However, with the recent development of digital beamforming SAR systems, new options for the suppression of RFI become available. This talk gives an overview of NASA's EcoSAR system and it's digital beamforming capabilities. Existing RFI suppression methods are summarized and possible new techniques are proposed. A time schedule for the further approach of this PhD is presented.
Valeria Gracheva "Multichannel Analysis and Suppression of Sea Clutter for Airborne Radar Systems"
Dienstag, 15. Dezember 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Piracy, smuggling and illegal fishery threaten the overall security on oceans and seas. These threats typically arise from small and agile boats and are distributed over large areas. To control them, small maritime targets have to be detected and observed. Maritime airborne radar systems are capable of monitoring large areas and are therefore suitable to accomplish this challenge. The detection of small boats, however, is still a challenging task due to the small radar cross section (RCS) of these boats. Additionally, the RCS of sea clutter rises for high altitude platforms due to the higher grazing angle, hence targets with low signal-to-clutter plus noise ratios (SCNR) have to be detected. In order to investigate the appropriate processing to detect small boats from airborne radars, data from experiments over the North Sea with the multichannel radar system PAMIR and a small cooperative boat is evaluated. This analysis demonstrates on one hand that traditional processing is not sufficient to detect these maritime targets, and on the other hand that with space-time adaptive processing (STAP) superior detection performance is achieved. To apply STAP to a maritime airborne radar system, it is desirable to know its performance in advance. To accomplish this, the multichannel characteristics of sea clutter have to be understood. In this presentation theoretical and simulation multichannel models are derived by analyzing the spectral density matrix and the space-time filter. Different multichannel properties for sea clutter compared to land clutter are demonstrated, which are due to the varying motion of sea echoes and due to different sea scattering types. An important implication of this difference is the broadening of the space-time filter notch in dependence on the sea condition. To confirm the predicted properties, three measurement campaigns with the airborne radar system PAMIR were performed, where real multichannel sea data was acquired for different swell directions, two different grazing angles and significantly varying sea states. In this presentation the reproducibility of sea clutter multichannel characteristics of real data for different sea conditions is demonstrated with the help of calculations and simulations, which are introduced in this analysis.
Stefan Seel "Optical LEO-GEO Data Relays: The in-orbit experience"
Montag, 23. November 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Laser-based data transmission in orbit is available for commercial application, opening a new chapter for satellite communications. Optical LEO-GEO data relay pave the Space Data Highway for Earth Observation Spacecrafts in low Earth Orbit by offering fast access to large quantity of data. The Sentinel-1A / Alphasat TDP1 optical data relay is operational since November 2014. As of September 2015 also the optical Earth observation satellite, Sentinel-2A, of ESA and EU has commissioned the laser link to Alphasat. More than 100 successful links have been performed since, both of nominal as well as experimental character, demonstrating reliable and stable link service with adequate system margins for the implementation of the European Data Relay Satellite System EDRS. The seminar presentation will report key performances and hands-on experience from in-orbit operations of the optical data relay.
Sarah Braun "An Integer Linear Programming Approach to Multi-Satellite Mission Planning"
Mittwoch, 18. November 2015
13.30 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Given a set of satellites as well as targets, multi-satellite mission planning is the task to schedule which satellite is designated to capture an image of each target. In doing so, many constraints need to be taken into account, e.g. in order to ensure certain response times. All these constraints cause the problem of mission planning to be very specific and complex which is why it is crucial to have efficient solution algorithms available. For this purpose, one can either create a heuristic or try to find a model of the problem to which already existing algorithms (like the simplex method) can be applied in order to calculate optimal solutions. While the first approach has been conducted by Bastian Calaminus this talk will give an insight into developing a suitable integer linear program modelling the problem of mission planning. Both a short introduction into the theory of integer programming as well as explanations to one of the developed models will be given. Conclusively, the model sizes and running times of various approaches will be presented and compared, leading to a discussion of their pre- and disadvantages and the quality of the heuristic approach.
Giuseppe Parrella "Characterization of Glacier Facies using SAR Polarimetry at Long Wavelengths"
Dienstag, 17. November 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
The introduction of airborne and satellite remote sensing techniques has lead to unprecedented improvements of glaciological observations in terms of spatial coverage as well as temporal and spatial resolution. In this domain, synthetic aperture radars (SAR) represent a powerful tool. At dry conditions, SAR measurements are sensitive to both surface and sub-surface features of glaciers and ice sheets, especially at long-wavelengths (e.g. L- and P-band). This qualifies SAR for the retrieval of a number of glaciological parameters, including glacier facies extent, snow and firn grain size, accumulation rate. In particular, polarimetric SAR (PolSAR) exploits the polarization diversity of electromagnetic waves to gain sensitivity to different scattering mechanisms as well as to geometrical and dielectric properties of the illuminated scene. Nevertheless, such potential remains largely underexploited as a satisfactory physical interpretation of SAR signal from glaciers and ice sheets is still lacking. For instance, the relative contribution of surface and subsurface features as well as its dependence on frequency, imaging geometry and glacier zone is still not understood. The primary objective of this study is to develop a scattering model able to relate PolSAR measurables to physical quantities of glacier subsurface. Both amplitude and phase information contained in the complex signal are taken into account. A newly developed three-component polarimetric model is presented to describe the measured signal as the sum of volume, surface and a novel anisotropic propagation component. The latter is shown to be able to interpret polarimetric phase differences with the presence of anisotropic firn and to provide estimates of physical properties of such medium (e.g. thickness, density and degree of anisotropy). The proposed model is successively used to perform a polarimetric decomposition of L- and P-band PolSAR data acquired by the DLR’s E-SAR sensor over the Austfonna ice cap, Svalbard, during the SVALEX 2005 and ICESAR 2007 campaigns. The focus of the investigation is on the estimation of the thickness of the firn layer and its dependency on frequency and test site. Decomposition results are validated against ground penetrating radar and stratigraphic measurements. The retrieval of this kind of information is valuable to improve glacier facies classification and to characterize their subsurface properties. It will be also shown that the availability of multi-temporal SAR data (2005-2007) opens to novel approaches to monitor variations of glacier subsurface, which determine surface mass balance. Finally, other possible applications of the proposed model will be presented and discussed.
Silvan Leinss "Depths, Anisotropy and Water Equivalent of Snow estimated by Radar Interferometry and Polarimetry"
Dienstag, 20. Oktober 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Radar interferometry is a well established technique and can be used to derive properties of dry and wet snow. In contrast interferometry, the analysis of copolar phase differences for determination of snow properties is a completely new scientific field. Dry snow is almost transparent for microwaves. The refractive index of snow is determined by its microstructure whose spatial symmetry is broken by gravity and a vertical temperature gradient. This causes a specific birefringence. The birefringence can be measured by the phase difference of vertically and horizontally polarized microwaves. The analysis of four years of polarimetric radar measurements allowed the verification an electromagnetic model developed for the determination of the anisotropy of snow. Beyond that, a unique dataset was obtained to develop a thermodynamic model which describes the temporal evolution of the anisotropy. The gained knowledge about the evolution of the anisotropy makes it possible to utilize the copolar phase difference for determination of the depth of fresh fallen snow with space-borne radar sensors like TerraSAR-X. Differential radar interferometry is very sensitive to signal delays. The total signal delay which results from the refractive index of snow can be shown to be proportional to the amount of water stored in the snow pack. This makes differential interferometry a powerful tool to determine the water equivalent of dry snow (SWE). I will show the currently longest time series of successful SWE measurements covering four entire winter seasons. These results rise the hope that future SAR missions operating with repeat passes of several days at low frequencies are good candidates for global SWE monitoring. For snow covered regions, digital elevation models derived from radar interferometry do not corresponds to the snow surface but show an elevation several meters below the surface. In contrast to dry show, where microwaves penetrate many meters into snow, the penetration depth in wet snow is reduced to a few centimeters. The limited penetration depth allows snow depth determination using single-pass Interferometry. I will show that the current TanDEM-X mission cannot be used to determine the depth of dry snow but is indeed capable to determine the depth of seasonal snow during snow melt.
Carlos Henrique Severino "Compact Feeding System for a P-Band Circular Horn Antenna"
Donnerstag, 6. August 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
P-Band remote sensing provides unique capabilities for instance to evaluate the magnitude and distribution of forest biomass and its changes. The pertinent wavelength, however, forces the need for several meters long hardware and imposes challenges for both embedded systems and calibration transponders regarding feasibility and mobility. As part of an effort to acquire competence on reduced size structures for applications at P-Band, a compact high performance corrugated horn antenna was developed in 2014. Such antenna, which came to be known as VeGA (Verkürzte-Gauss-Antenne), still lacks of a proper feeding system that brings together dual linear polarization capabilities, high performance and reduced size. This seminar presents an overview of feed alternatives and introduces some of the first results on a novel compact orthomode transducer (OMT) optimized for VeGA that mostly overcomes the limitations of the current compact transducer designs. The combination of the developed horn antenna and the new proposed device could potentially lead to an overall system that is more compact than the available alternatives.
Prof. Dara Entekhabi "The SMAP Mission : Status and Recent Results"
Mittwoch, 22. Juli 2015
10.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
For information on the Soil Moisture Active Passive Mission (SMAP): http://smap.jpl.nasa.gov/
For information on Prof. Entekhabi : https://cee.mit.edu/entekhabi
Markus Bachmann "Antenna Pattern Modeling and Calibration for Spaceborne SAR Systems"
Montag, 13. Juli 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Synthetic aperture radar (SAR) is used in remote sensing to acquire high-resolution, wide-coverage images of the earth's surface. The growing scientific and commercial interest in SAR data tightens the user demands in terms of resolution, coverage, accuracy and image quality. Modern spaceborne SAR systems treat this with a large variety and flexibility of acquisition modes. One main part of a SAR system is the SAR antenna. Its radiation characteristic, the antenna pattern, is a key quantity for the quality of the SAR images and its knowledge affects the radiometric accuracy of the acquisitions. The antenna patterns have to be compensated during image processing and thus must be known for the thousands of possible beams of a SAR system. This can be achieved using an antenna model that simulates the SAR antenna. The antenna model derives the antenna amplitude patterns as well as phase patterns, which are required in interferometric applications like the derivation of digital elevation models. This seminar emphasizes the main aspects of antenna pattern modeling and improvements on the antenna model approach: First, the calibration and corrections applied on the antenna model, demonstrating the high accuracy of the model are shown, as well as the resulting simplifications for SAR system calibration. Second, the optimization of the antenna patterns in order to improve the image quality is described. A system representation and its effect on image performance is derived and verified. Finally, a novel self-calibration approach is developed to further improve the antenna model accuracy. Nominal acquisitions can be utilized to calibrate the antenna model and monitor its performance, eliminating the necessity of dedicated measurements over reference targets like rain forest. This makes the antenna model a key feature even for future SAR systems.
Gustavo Daniel Martin del Campo Becerra "A Comparative Study of Focusing Methods for SAR Tomography of Forested Areas"
Donnerstag, 09. Juli 2015
11.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
The main purpose of synthetic aperture radar tomography (SARTom) is to retrieve the vertical distribution of the backscattered power within a range-azimuth resolution cell, allowing three dimensional imaging of volumetric targets. For the case of a scene characterized by forest cover, it is common to use longer wavelengths due to their major sensitivity to contributions from the vegetation layer and the surface below. The vertical structure is retrieved from the multibaseline acquisitions of such contributions, whereas the multipolarimetric acquisitions retrieve the electromagnetic properties. Multipolarimetric multibaseline SAR surveys are employed for the analysis of forested areas, since the separation of the ground-only and volume-only scattering mechanisms (SMs) is possible through the use of the sum of kronecker products (SKP) decomposition approach. Thus, different tomographic SAR focusing methods might be applied to the ground and canopy contributions independently. The SARTom vertical distribution estimation problem can be treated within the direction of arrival (DOA) framework, which encompasses parametric and non-parametric techniques. Parametric DOA estimation methods, as multiple signal classification (MUSIC), improve the vertical resolution and mitigate the effect of sidelobes. Nevertheless, these techniques have the main drawback related to the assumption that the scene is composed by a finite number of point-type backscattering sources. On the other hand, the minimum variance distortionless response (MVDR) inspired non-parametric DOA estimation methods, as Capon, are better suited to cope with scenarios characterized by the presence of distributed scatterers. Cross-range profiles over forested terrain follow a simple two-component structure. Their respective power distributions are rather regular, giving rise to sparse representations in the wavelet domain. Therefore, super-resolution compressed sensing (CS) spectral estimators has been introduced recently to tackle with the SARTom vertical distribution estimation problem. SKP decomposition may result in rank-deficient covariance matrices, which restrict the usage of the Capon beamformer due to the involved matrix inversion. Otherwise, the CS approaches imply a considerable computational burden. For this motive, the robust versions of the Capon beamformer are taken into account, being robust with respect to inaccuracies in the track estimation as well as in case of rank deficiencies of the data covariance matrix.
Rayssa Freitas Carvalho "A Posteriori Knowledge based Digital Beamforming Concepts demonstrated with Multi-Channel SAR Data"
Dienstag, 07. Juli 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Future SAR applications such as disaster monitoring or detection of biomass changes on a global scale demand large swath widths and high resolution at the same time. A high azimuth resolution raises the need of a high pulse repetition frequency (PRF) in order to sample the signal adequately and avoid azimuth ambiguities in the SAR imaging process. However, the high PRF limits the swath width. To overcome this limitation, a solution is to split the receiving antenna into multiple sub-apertures and then combine the sub-apertures signals using digital beamforming techniques to suppress the azimuth ambiguities. Since digital beamforming techniques require precise knowledge of the antenna patterns, a first investigation deals with the estimation of the complex azimuth antenna patterns from point target data. These estimated patterns are then applied in an a posteriori beamforming process, meaning that no a priori information in terms of pattern knowledge is required. Here, basically two concepts are presented, the first being an SNR optimizer and the second dedicated to the suppression of azimuth ambiguities. In a second analysis the requirement of no a priori information is dropped insofar that only the so called noise channel covariance matrix is estimated from the data. The beamforming is performed on the basis of the array steering vector, assumed to be known a priori.
Ezgi Özis "Metamaterials for Microwave Radomes: an Overview"
Dienstag, 16. Juni 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
A radome is a cover protecting an antenna from a hostile environment (wind, rain, ice, heat, aerodynamic drag, electromagnetic interference, etc.). In radome applications, metamaterials can enable such features as improved transmission over a broader range of antenna scan angles, reconfigurable pass and reject frequency bands, polarization transformations, one-way transmission and switchability. Metamaterials are artificial structures that involve variously shaped, typically metallic, inclusions placed in a substrate material and organized in periodic arrays. In modern applications it is often desirable to make the radome impenetrable outside the operating frequency band to reduce interference with other antennas that can be maintained on the same platform. This and many other features are hardly possible with conventional materials, but can be achieved with metamaterials. This presentation is an overview of applications of metamaterials to microwave radomes. Relevant applications are shown and illustrated by characteristic examples.
Thomas Weiss "Polarimetric Analysis of SAR-Data to estimate Plant Moisture in Agriculture"
Montag, 08. Juni 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Plant moisture is an important parameter in agriculture, forestry and hydrology, as it controls plant vitality, plant growth and transpiration capabilities. Compared to other environmental key parameters e.g. soil moisture or biomass only few studies for a SAR-based retrieval exist up to now. Therefore a case study, pursued within a master thesis framework, wants to investigate with SAR polarimetry, if it is possible to retrieve plant moisture with the detailed analysis of dihedral scattering at L-band. A model based, polarimetric decomposition technique was developed and applied to isolate the dihedral scattering component from a mixed agricultural scattering scenario. In a second step a methodology was implemented to invert the dihedral scattering component for the plant dielectric constant. In a last step a transfer-function was established to convert the pant dielectric constant into gravimetric plant moisture. The analyses are based on fully polarimetric L-band data, which were acquired during the Wallerfing campaign in 2014 by the F-SAR sensor of DLR. Due to the acquisition period from May to August, a time series including different phenological stages of the agricultural plants was available for thorough investigations. Simultaneously to the SAR acquisitions, plant parameters, like biomass and plant moisture, were measured with in situ measurements in collaboration with the LMU Munich and the ETH Zürich. In this way, the agricultural case study is able to reveal, which limitations or potentials are inherent to this approach. The research results serve as a proof of concept for plant moisture retrieval with polarimetric SAR decompositions. They indicate that if a distinct dihedral scattering signal is present, it is possible to retrieve the plant dielectric constant and eventually plant moisture. The quality of the inversion results can be improved through different algorithm adaptions within the polarimetric decomposition and inversion. The validation of the inversion results with the in situ measurements was challenging because of the low number of in situ sample points and the fact that the fields with sample points were by chance in unfavorable incidence angle ranges for the used approach. Besides these weak points, the retrieval concept was proven and plant moisture was estimated for several corn fields within the 20% deviation interval.
Eduardo Makhoul Varona "Ground Moving Target Indication with Synthetic Aperture Radars for Maritime Surveillance"
Dienstag, 2. Juni 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
The explosive growth of shipping traffic all over the World, with around three quarters of the total trade goods and crude oil transported by sea, has raised newly emerging concerns (economical, ecological, social and geopolitical). Geo-information (location and speed) of ocean-going vessels is crucial in the maritime framework, playing a key role in the related environmental monitoring, fisheries management and maritime/coastal security. In this scenario space-based synthetic aperture radar (SAR) remote sensing is a potential tool for globally monitoring the oceans and seas, providing two-dimensional high-resolution imaging capabilities in all-day and all-weather conditions. The combination of ground moving target indication (GMTI) modes with multichannel spaceborne SAR systems represents a powerful apparatus for surveillance of maritime activities. The level of readiness of such a technology for road traffic monitoring is still low, and for the marine scenario is even less mature. Some of the current space-based SAR missions include an experimental GMTI mode with reduced detection capabilities, especially for small and slow moving targets. This doctoral dissertation focuses on the study and analysis of the GMTI limitations of current state-of-the-art SAR missions when operating over maritime scenarios and the proposal of novel and optimal multichannel SAR-GMTI architectures, providing subclutter visibility of small (reduced reflectivity) slow moving vessels. This doctoral activity carries out a transversal analysis embracing system-architecture proposal and optimization, processing strategies assessment, performance evaluation, sea/ocean clutter characterization and adequate calibration methodologies suggestion.
Prof. Werner Wiesbeck "Unmanned Aerial Vehicles – UAV, Drones – Detection, Tracking, Control"
Dienstag, 26. Mai 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Content of the presentation: Application of UAVs and Drones, Security - problems and tasks, Approaches for UAV localization (control by Radar network, transponder localization, optical localization, state of the art systems), UAV/Drone control.
Hanna Jörg "Application of Polarimetric SAR Tomography on Agricultural Vegetation"
Dienstag, 28. April 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
The interpretation of scattering mechanisms occurring in agricultural vegetation is rather difficult, at (almost) all frequencies and for most of the crop types, due to the complexity of wave propagation and scattering trough and within the vegetation layer and the interaction with the underlying ground. The very different architecture of the different crop types and the individual phenological cycle and plant development make the propagation and scattering properties spatial and time dependent, increasing the complexity of the problem. As a result, not only the inversion of parameters becomes difficult but also the definition of the optimum observation space required for a certain (quantitative) application is not straightforward. In order to contribute to the interpretation of propagation and scattering in agricultural vegetation we explore polarimetric SAR tomographic data at different frequencies. (Polarimetric) SAR Tomography enables to resolve the scattering processes in the vertical dimension and therefore to assess the differences in the 3-D scattering distribution with respect to species and development stage at different polarisations or frequencies. Our analysis is based on experimental SAR data acquired by DLR’s airborne sensor F-SAR in 2014 over an agricultural area near Wallerfing. The fully polarimetric multi-baseline SAR acquisitions at X-, C- and L-band cover different stages of the phenological cycle from May to August with an almost weekly sampling. The baseline planning was adapted to the requirements for the small vegetation heights, ensuring a high vertical resolution and at the same time a sufficient number of tracks for an accurate inversion. We investigate different spectral analysis methodologies with respect to their suitability for agricultural vegetation applications. One main problem is that even with a suitable baseline planning, the Rayleigh resolution is still in the order of the vegetation heights. Nevertheless, it is possible to detect changes in a spatial and temporal context. The trade-off between the benefit of a large observation space vs. the information content which can actually be assessed due to the unreliability of the estimation procedure is discussed.
Ronny Hänsch "Generic Object Categorization in PolSAR Images - and beyond"
Dienstag, 31. März 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Generic object categorization refers to the task of detecting instances of object classes within images. The standard processing chains to tackle this problem usually consist of preprocessing, feature extraction, classification, and post-processing steps. These individual modules commonly involve task-dependent knowledge (e.g. which features are descriptive), that leads to expert systems, which cannot easily be transferred to other tasks (e.g. other classes or data sources). In this talk it is assumed that the final categorization problem is not known during the design of the classification framework. Consequently, any kind of category-specific optimization, such as sophisticated feature design or manual selection, top-down processing, or task-specific choice of the classifier, is not possible. By using polarimetric synthetic aperture radar (PolSAR) images as an example, the talk will discuss a two-stage classification system based on random forests that automatically derives high-level semantic information from general low-level features. It will be shown, that this system is able to solve different categorization problems based on different data sources and furthermore provides deeper insights into the given classification tasks.
Guiseppe Parrella "Linking polarimetric phase difference in SAR images to the subsurface layers of glaciers"
Dienstag, 24. März 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Glaciers and ice sheets are primary components of the Earth’s cryosphere. They represent a key source of fresh water and as such, they can profoundly affect the global water cycle, the ocean circulation and the sea level, with implications onnatural resources management as well as on economic and socialaspects of our society. In the last decades, the introduction of airborne and satellite remote sensing has drastically improved glaciological observations in terms of spatial coverage as well as temporal and spatial resolution. However, large uncertainties remain in the quantification of glacier dynamics. In this sense, synthetic aperture radars (SARs) represent a powerful tool due to their capability to sense surface as well as subsurface layers. In fact, at dry snow conditions, SAR signal easily penetrates the shallow snow-cover and interacts with buried features, especially at long-wavelengths (e.g. L-band). This gives SARs the unequalled potential to deliver information about a number of glaciological parameters, including snow and firn density, grain size, accumulation rate, etc. Nevertheless, such exceptional potential remains largely underexploited. So far, the complexity of the involved scattering scenarios and the scarcity of distributed validation data have severely hindered the development of models able to provide a physical-based interpretation of SAR backscattering. Focussing on polarimetric measurements, the interpretation of polarization phase differences, often observed over glaciated areas, likely represents the main open issue. In this seminar, a newly-developed physical model is presented to relate co-polarization HH-VV phase difference (co-pol phase) to structural properties of glacier subsurface. In particular, it will be shown that co-pol phase can be the result of differential propagation effects due to the anisotropic microstructure of snow and firn which characterize the near-surface layers. The results of a sensitivity analysis of the model with respect to the most relevant parameters will be illustrated to assess its potential and limitations. Successively, the model is applied on experimental SAR data to invert physical parameters, such as firn depth. The employed data were acquired at L-band, in fully-polarimetric mode, by the DLR’s E-SAR system over the Austfonna ice-cap, in Svalbard, during the SVALEX2005 and ICESAR2007 campaigns. A set of ground measurements, including GPR and stratigraphic data, is exploited to properly set up the model and to validate the results. The availability of multi-temporal SAR acquisitions will also allow assessing the potential of the proposed technique to track temporal dynamics of Austfonna over the period 2005-2007, supported by existing literature. Finally, further possible applications of the model will be discussed.
Manuel Bertoluzza "Monitoring Forest Height Dynamics by Means of L-band Multi-baseline PolInSAR data"
Donnerstag, 26. Februar 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Forest height is one of the most important parameters for forest characterization, since it is closely related to forest biomass, disturbance regime and logging activities. Beyond absolute height measurements, the knowledge of forest height changes is of extreme importance in the characterization of dynamic forest processes. Polarimetric SAR interferometry (PolInSAR) represents a very promising alternative tool to LIDAR for estimating forest height from space and its dynamics as it can provide large continuous coverage and high spatial and temporal resolution. PolInSAR combines the inherent sensitivity of the interferometric coherence to the vertical structure of volume scatterers with the potential of SAR polarimetry to characterise scattering mechanisms. Exploiting this combination, forest height PolInSAR products have reached in the last decade accuracy in the order of 10% or better. In this seminar, a qualitative and quantitative analysis of the capability of PolInSAR height maps for monitoring forest dynamics will be presented. The study is based on a multibaseline-multitemporal PolInSAR L-band airborne dataset acquired over the temperate forest site of Traunstein (South of Germany) covering more than ten years by the DLR’s E- and F-SAR radar platforms. For each acquisition date, a multibaseline PolInSAR inversion has been carried out using tracks characterized by short temporal baseline (of the order of one hour). Accordingly, a time series of accurately estimated forest heights has been obtained without disturbances due to long-term temporal decorrelation. For each campaign, each single baseline has been inverted by means of the Random Volume over Ground (RVoG) model. In order to obtain a single height map, different methodologies can be employed combining the single-baseline results. The related height estimation accuracies have been quantified and critically compared. Next, an experimental analysis has been carried out in order to characterize the effects of different sources on height estimation, like weather condition (i.e. rain event), seasonal cycles, disturbances and management activities. Extensive results of this analysis will be presented, and the capability of distinguishing between different sources of PolInSAR height changes will be discussed together with their potentials for identifying and monitoring ecosystem changes.
Carolina Lautz "Das DLR-Fortbildungsprogramm 2015 – neue und bewährte Qualifizierungsangebote für eine gezielte fachliche und persönliche Weiterentwicklung"
Dienstag, 20. Januar 2015
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Ihre Personalentwicklerin am Standort Oberpfaffenhofen stellt das DLR-Fortbildungsprogramm 2015 für Mitarbeiterinnen und Mitarbeiter vor. Orientiert an den systematisch erhobenen Qualifizierungsbedarfen der Institute und Einrichtungen ist das Fortbildungsangebot weiterentwickelt und erweitert worden. Was ist neu? Welche Angebote haben sich bewährt? Sie erhalten einen Überblick über das vielfältige Angebot und haben die Möglichkeit, Ihre Fragen zu klären sowie Anregungen einzubringen.
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