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Institute Seminar - Presentations 2017
Felipe Queiroz de Almeida "Multichannel Staggered SAR for High-Resolution Wide-Swath Imaging"
Mittwoch, 13. Dezember 2017
10.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
In the context of state-of-the-art and next-generation spaceborne Synthetic Aperture Radar (SAR) imaging systems, such as the German Tandem-L mission proposal, a short revisit time coupled with high resolution presents itself as a requirement for the observation of numerous Earth dynamic processes in various scientific and environmental applications. This poses contradicting and demanding requirements on system design for whose realization digital beamforming techniques play a crucial role, in order to enable next-generation systems to significantly outperform current state-of-the-art systems and fulfil the increasingly stringent needs of applications. Multichannel SAR systems with digital beamforming in azimuth have been proposed as an option for coping with these challenging requirements in order to achieve high-resolution wide-swath (HRWS) imaging capabilities. These systems tend however to require a very long antenna to image wide swaths. As an alternative, the use of digital beamforming in elevation, in conjunction with a varying pulse repetition interval (PRI) for the SAR system radar pulses (Staggered SAR), has been proposed. The best azimuth resolution in this case is nevertheless limited by the antenna dimensions. The thesis focuses on the development of new SAR techniques and corresponding processing methodologies which allow the combination of the advantages of the multichannel system architectures in azimuth with those of staggered SAR. This introduces new and potentially highly flexible modes of operation, enabling HRWS imaging with a compact antenna and contributing to the new developments in the field of digital beamforming techniques. The thesis includes the proposal of novel algorithms for the resampling of multichannel staggered SAR data and examples of high-performance HRWS systems designed to make use of the technique. In addition, a proof-of-concept with experimental data from a ground-based radar system and a discussion of the possible effects of errors for the implementation of this new class of spaceborne imaging systems are presented.
Hannah Jörg "Multi-Frequency Polarimetric SAR Tomography for the 3-D Characterization and Monitoring of Agricultural Crops"
Montag, 11. Dezember 2017
10.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Monitoring the temporal variation of soil and plant parameters of agricultural crops is of high interest. Since Synthetic Aperture Radar (SAR) measurements are sensitive to dielectric and geometric properties of the observed scattering scenario, they provide key observables for monitoring the temporal variation of biophysical parameters. However, the scattering mechanisms occurring in agricultural vegetation in dependency of biophysical parameters are highly complex and simultaneous dynamics of the soil and the vegetation are difficult to differentiate. By utilizing several horizontally separated SAR acquisitions, SAR Tomography, as demonstrated for forest volumes, is a powerful tool able to estimate vertical profiles of the backscattered power and to resolve and interpret scattering mechanisms along height. The fact that tomographic SAR techniques are, in principle, independent of scattering models makes their application very promising towards a better understanding of the highly dimensional scattering scenarios of agricultural vegetation. Challenges are however the high vertical resolution required in order to be sensitive to the low plant heights, and the possibly present anisotropic propagation effects of the vegetation volume limiting the application of state-of-the art tomographic ground and volume separation algorithms. The Crop Experiment (CROPEX) campaign in 2014, which plays a key role in this PhD thesis, fills the gap in the availability of fully polarimetric multi-frequency and tomographic SAR data over agricultural crops providing high vertical resolution capability and covering different dates of the phenological cycle. The main objective of the campaign is to foster the physical understanding of the influence that changes in soil and plant parameters have on the ground and volume scattering component as a function of crop type, polarization and frequency. The interpretation of changes on the ground and in the volume from vertical backscatter profiles is limited and can only be quantified by separating the ground and volume scattering components. Without posing model assumptions to the vegetation volume, this separation becomes ill-posed. In the thesis, this is addressed by applying a separation algorithm which overcomes this ambiguity by integrating the a priori knowledge of the ground height as a given parameter and is able to provide robust estimates of the multi-baseline volume coherences and the ground and volume powers. The biggest novelty of this work is the quantitative analysis of the distinct ground and volume powers for agricultural scattering scenarios, particularly taking into account their temporal variation as a function of varying soil and plant parameters. The temporal variation of the estimated powers provides an unambiguous quantification of scattering changes on the ground and in the vegetation. Since the center of mass of the vertical backscatter profiles correspond - at least at the first order - to the interferometric phase center that can be estimated by means of only two acquired tracks, its analysis gives an understanding of the potential of a reduced observation scenario. In conjunction with in-situ measured soil and plant parameters, the sensitivity of the tomographic parameters across different frequencies, X-, C- and L-band, to dielectric (e.g. dynamics of the water content) and geometric (e.g. alignments of plant components) changes is demonstrated. The experimental results in this thesis underline the importance of the three-dimensional information. With the separation in height, the conclusions drawn on the changes of the incoherent scattering signature provide a basis for future research including the coherent ground and volume signatures. Scattering models based on the coherent polarimetric signature might provide promising opportunities towards the inversion of biophysical parameters.
Joel Alfredo Amao Oliva "The Short-Time Beltrami Kernel for Despeckling Polarimetric SAR Data"
Donnerstag, 16. November 2017
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
We adapt the Short-time Beltrami (STB) kernel used to smooth manifolds or images painted on manifolds to use the covariance matrices found in polarimetric synthetic aperture (PolSAR) data to reduce speckle noise. The proposed method functions similar to a region growing algorithm finding similar covariance matrices and weighting them accordingly. Preliminary results from the experiments show that the proposed method delivers a good compromise between the preservation of the spatial resolution and smoothing of homogeneous zones.
Ezgi Özis "A semi-analytical approach for microwave transmission and reflection at thin metamaterial sheets"
Dienstag, 07. November 2017
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
In this presentation, an overview about metamaterials, metasheets and their applications to microwave radomes is given. Furthermore, the talk describes a semi-analytical approach to calculate the transmission coefficient of a planar infinite periodic array of small metal circular rings. An equivalent circuit model in combination with a Taylor series expansion is used for calculation of the impedance of the ring. A two-dimensional fit of this approximation to exact numerical results at several values of the ring radii and the frequency is used to obtain the coefficients of the approximation. So far, the equivalent circuit models have been mainly available for right-angled particles such as Jerusalem-crosses or square loops. With the developed approximation, the transmission and reflection coefficients of an array of circular slots in a planar metal screen can be calculated by using the Babinet Principle and the energy conservation. The normally incident plane wave is considered, and frequency range is between 3 GHz and 30 GHz. The presentation describes the progress and recent results of an on-going PhD study.
Tobias Rommel "Implementation of a MIMO-SAR Imaging Mode for NASA’s Next Generation Airborne L-Band SAR"
Montag, 16. Oktober 2017
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
The use of multiple transmit and multiple receive channels (MIMO) turns out to be beneficial for the next generation of Synthetic Aperture Radar (SAR) missions. Apart from an increased flexibility, MIMO-SAR enables for example simultaneous full-polarimetric acquisitions (quad-pol) without any reduction of the swath-width or resolution. By making use of an innovative orthogonal-waveform beamforming technique, a sufficient suppression of cross-correlation interferences from the other channels can be achieved. The talk gives an overview of the work done during a three month stay at the NASA Goddard Space Flight Center (GSFC). It is intended to use the L-band airborne radar sensor DBSAR2 operated by the GSFC to verify the aforementioned MIMO-SAR imaging modes. First test measurements in a laboratory environment have been conducted and a performance analysis for a future flight campaign has shown that the imaging mode will lead to promising results with DBSAR2.
Duncan Robertson "Millimetre and submillimetre wave radar for applications in environmental monitoring and security"
Mittwoch, 11. Oktober 2017
10.00 h Raum noch nicht bekannt, Gebäude 102
Abstract:
The Millimetre Wave and EPR Group at St Andrews has specialised in instrument development and quasi-optical techniques since it started in the mid 1980s. Currently the group has two major research themes: millimetre wave radar and electron paramagnetic resonance (EPR) spectroscopy. Whilst the applications of these two areas are quite distinct, the hardware underpinning them is very similar and the technology development undertaken by the Group supports both strands of instrumentation. The talk will present an overview of the recent millimetre and submillimetre wave radar research in the Group. Our focus is on applications in environmental remote sensing and security. A major theme in our radar work is real beam imaging (both 2D and 3D) and high speed processing. In the past 15 years we have built 12 different radar systems at frequencies of 24, 38, 94, 220 and 340 GHz, many of which are field deployable. Recent and current projects include terrain mapping for volcano monitoring, real-time sea surface mapping for guiding autonomous boats, detecting drones for perimeter security, and very high resolution 3D imaging for personnel screening.
Roger Appleby "Historical aspects of Passive Millimetre Wave Imaging in the UK and CONSORTIS"
Mittwoch, 11. Oktober 2017
09.30 h Raum noch nicht bekannt, Gebäude 102
Abstract:
This presentation is in two parts, the first describes some of the early history of passive millimetre wave imaging in the UK and the second describes the work that has been done on the FP7 project CONSORTIS (Concealed Object Stand-Off Real-Time Imaging for Security). Historical Passive Millimetre Wave Imaging The equipment’s developed between 1950 and 1992 at the Royal Signals and Radar Establishment in Malvern will be described. In the 1950s the first airborne 35 GHz radiometer was flight tested on a Lincoln bomber. The technology was based on valves and the equipment occupied a large part of the rear of the aircraft. As semiconductor technology matured and gave rise to low noise mixers and amplifiers, new equipment’s were developed. In 1992, MITRE, a 94 GHz data collection system based on super-heterodyne receivers, provided non real time high quality imagery and stimulated interest in both surveillance and security, with images through fog and clothing being demonstrated. CONSORTIS Aviation security is a demanding requirement for modern society: it needs to have a high probability of detection and low false alarm rates to protect people and equipment whilst at the same time it needs to be easy to use for passengers, air crew and security operators. Recognizing these requirements the European Commission through the Seventh Framework Programme (FP7) launched a call for research on sub millimetre wave systems. CONSORTIS was one of the projects selected to conduct this work and began in 2014. CONSORTIS is a stand-off system for the detection of objects concealed on people and operates at frequencies from 200-600 GHz. The system scans people at 10 frames per second as they walk by the sensor. It brings together passive focal plane array of 9000 Kinetic Inductance Detectors (KIDS) operating at 250 and 500GHz and a radar with 16 340 GHz homodyne transceivers as well as a visible Support Sensor and Automatic Anomaly Detection to deliver the necessary performance. The active sensor is positioned above the passive sensor and they have overlapping fields of view.
Prasad Gogineni "Ultra-Wideband Radar Instrumentation for Remote Sensing of Snow, Ice and Soil Moisture"
Donnerstag, 05. Oktober 2017
TBD h Großer Besprechungsraum HR, Gebäude 102
Abstract:
The University of Alabama (UA) established a Remote Sensing Center for supporting a wide range of scientific and operational research on water resources and coastal protections. Two major issues humanity must deal with over the next century are the availability and use of fresh water resources, and the impacts of rising seas. Effective management of water resources is a major adaptation challenge in a warming world for both the USA and other nations. Accurate information on the sources of freshwater, its availability and trends, and methods to reduce consumption while increasing crop productivity are of high importance to the society. Large-scale measurements of polar ice sheets are also critically needed to understand and manage relentlessly expanding coastal inundation due to sea-level rise. Significant progress has been made in determining bed topography mainly for the interior parts of the Greenland ice sheet. However, the lack of fine-resolution bed topography data near the grounding lines of fast-flowing glaciers and the lack of bottom melt rates of ice shelves are major impediments to developing improved models to generate more accurate estimates of sea level rise. UA Remote Sensing Center is developing ultra-wideband radars operating over the frequency range from 1 GHz to 18 GHz to perform surface-based and airborne measurements of snow, soil moisture and ice as well as on rivers. The Center is also developing surface-based and airborne radars operating over the frequency range from about 170 MHz to 550 MHz to sound and image ice in Greenland and Antarctica. The center plans to develop unmanned aircraft systems (UAS) integrated with radars operating to obtain much needed data on fast-flowing glaciers and ice shelves, as well as alpine snow. In this talk, I will provide an overview of the remote sensing center plans and show results from my earlier work on the use of ultra-wideband (UWB) radars on snow and ice. I will also discuss the application of satellite-based radars for sounding and imaging of the Antarctic ice sheet.
Felipe Queiroz de Almeida "Multichannel Staggered SAR with Reflector Antennas: Ground-based Demonstrator Proof of Concept"
Mittwoch, 04. Oktober 2017
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
In the context of state-of-the-art and next-generation spaceborne SAR systems, demanding and contradicting requirements on system design arise due to the increasingly important need to cover ultra-wide swaths with high azimuth resolution, as required by numerous applications. To fulfil these demands, different multichannel SAR system concepts have been proposed which employ digital beamforming on receive with planar arrays, and more recently also reflector antennas. The use of multiple elevation beams in combination with SCORE is a promising technique to extend the swath whereas suppressing range-ambiguity by the use of DBF on elevation. It has however the downside that the imaged swath consists of multiple sub-swaths separated by blind ranges. A possibly solution for this issue is staggered SAR, which uses a single azimuth channel and multiple elevation beams together with variable pulse repetition intervals to map a very wide swath with medium resolution. To improve the azimuth resolution of such systems, this PhD Thesis examines the extension of the staggered SAR concept to a system configuration with multiple azimuth channels. For this, a new multichannel azimuth processing technique is introduced that combines staggered SAR interpolation with beamforming for reconstruction of the multichannel SAR signal. The seminar reviews the technique and reports a first proof of concept using SAR data acquired by the experimental ground-based DBF demonstrator system developed at the HR Institute. A reflector with a multichannel feed and 8 azimuth channels is used in X-Band to image an example scene consisting of corner reflectors. The data is considerably oversampled in azimuth to allow data-driven calibration and interpolation to arbitrary grids. After calibration, the data are used to simulate an staggered SAR acquisition with a reduced PRF and reconstruction according to the new algorithm (which both regularizes the sampling instants and increases the sample rate) is performed. The parameters are chosen so that the original data at the highly sampled regular grid can be directly compared to the reconstructed images, in order to evaluate the quality of the outputs and thus the degree of success of the reconstruction.
Olaf Eisen "Peering into ice sheets: the use of AWI’s new radar magnifying glass"
Montag, 31. Juli 2017
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
The large Ice sheets, Greenland and Antartica, are two key players for understanding the future effects of climate change when it comes to sea level rise. A considerable uncertainty is their dynamic response to changing boundary conditions, e.g. increased melting at the surface percolating to their base or warmer ocean water temperatures underneath ice shelves. To decipher ongoing processes and reveal their development, glaciologists often turn to the observation of internal structures in and basal conditions of ice sheets using radio-echo sounding (RES) techniques. Over the last twenty years the radar techniques employed for these observation have seen a considerable improvement, such that today’s ice-penetrating radar has little in common with the former RES techniques, where data were still stored on photographic films. The newest of such systems, in operation since 2016, is AWI’s ultrawideband radar, operating in the radio (150-600 MHz) and microwave frequency range, an advancement from the original MCoRDS/I system developed by the Center for Remote Sensing of Ice Sheets (CReSIS). With 24 elements in use for the AWI UWB, the lateral and vertical resolution for imaging the interior of ice sheets at kilometers depth has been brought to the range of the sub-meter scale. This talk introduces the scientific objectives motivating the development of this system, presents its technical aspects, including data recording and processing, and finally shows first results from the last Greenland and Antarctic field seasons.
Fabricio Otoniel Pérez Pérez "Empirical study of the estimation of radial velocities of particles lying over simulated ocean surface realizations via an ATI‐SAR system"
Donnerstag, 27. Juli 2017
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Over the last four decades, there has been an increasing interest in observing the ocean surface via SAR systems. One of the reasons is that such a monitoring technique offers a rather global view of oceanographic processes, which can very useful when combined with traditional in‐situ techniques. On the other hand, an important progress in theoretical and empirical understanding of ocean dynamics is still required, with the aim of proposing methods and models to resemble such a complex physical reality in the most reasonable way. In the framework of ocean surfaces observed by SAR, it is well known that the radial velocity of each particle over a moving ocean surface realization can be estimated via an Along Track Interferometer (ATI) ‐ SAR system. The reason is that this radial velocity is, under very specific conditions, proportional to the absolute interferometric phase of the compressed SAR data that corresponds to that surface realization. The estimation of these radial velocities can be exploited, for example, to understand and interpret oceanic surface current measurements. The talk starts with a brief introduction to ocean waves, which in turn leads to the description of relevant physical mechanisms that establish important connections between the ocean surface and a radar system, such that wave‐like patterns from a SAR image of the ocean surface can be obtained. Then, the ATI‐SAR principle applied to ocean waves is presented. After this theoretical framework, the OCEANSAR simulator - a software tool that has been developed in DLR and which contains a basic ATI processor - is briefly presented. Subsequently, many experiments produced with OCEANSAR to identify good scenarios with respect to this basic interferometric approach are shown. With the purpose of improving the original estimations, several multilooking techniques at the SAR post‐processing stage were applied, whose results are also shown. As a further step, a known ATI‐SAR model for ocean waves is presented, such that it can be possibly implemented, and thus obtain an improvement of the results. Finally, future trends in SAR oceanography are also shown.
Marwan Younis "Exemplification of Multi-Channel Gain in SAR"
Montag, 10. Juli 2017
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Suggestions for future SAR systems show a tendency towards an increased complexity, which is often based on new ideas for the instrument, antenna, operation modes, processing and mission. When dealing with these newer systems, the answer to simple questions, i.e. simple for conventional SAR, turn out to be rather complicated as they involve multiple aspects of the whole. The difficulty is probably related to the way we understand SAR which is often based on frame-thinking involving individual aspects, which are later connected to yield the complete picture. This talk addresses the topic of signal-to-noise ratio gain of a multi-azimuth-channel system. The approach is to try and describe the underlying phenomena in a simple way with the perspective of contributions from the discussion.
Erich Grossman "Submillimeter Wavelength Scattering from Realistic Rough Surfaces"
Montag, 26. Juni 2017
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Scattering is a fundamental process for two of the most important submillimeter-wavelength application areas: active imaging (including imaging radar) and high bandwidth wireless communication. The realistic, everyday surfaces encountered in these applications (common building materials, human skin, clothing, etc.) have roughness levels and autocorrelation lengths comparable to a wavelength in this frequency range, making theoretical treatment challenging. In this presentation, I first briefly review three ab initio surface-scattering theories, the Beckmann-Kirchoff treatment, Generalized Harvey-Shack (GHS) theory, and Fung’s modified Integral Equation Method (IEM-B). Then I describe bistatic scattering measurements on eight reference targets constructed from Al2O3 grit of various sizes embedded in an absorptive epoxy matrix. These samples’ surface topographies were measured using focus-variation microscopy, and their autocorrelation lengths and root-mean-square (RMS) roughness levels extracted. Bistatic scattering measurements were then performed in the principal plane over the 325 – 500 GHz range and at 650 GHz, using either a vector network analyzer or a narrow band source and detector respectively, in both s and p polarizations, and at incidence angles of 25°, 45°, and 65°. The samples’ root-mean-square (RMS) roughness levels cover the range of 36 – 280 μm, corresponding to 0.039 < sigma/lambda < 0.61. Their autocorrelation lengths cover the range of 0.10 < L/lamda < 0.81, generally shorter than the samples in most previous studies. The bidirectional reflectance distribution function (BRDF) measurements include regimes of both diffuse scattering and specular reflectance. The measurements are compared to the GHS and IEM model predictions – in both cases, there are no adjustable free parameters in the comparison. Although there are several individual cases where either the IEM or the GHS theory (or both) provide an excellent match to measurement, their overall agreement with measurement across the entire dataset is poor. In addition, the diffuse BRDF in each bistatic scan has been fit to a Lambertian (constant) dependence on scattering angle, and a purely empirical model has been developed for the dependence of the Lambertian scattering on frequency, roughness, polarization, and incidence angle. Across the entire dataset, this empirical model provides the best match to measurement, and can be used for reliable phenomenology studies of submillimeter imaging or wireless telecommunication. I conclude with some speculations about the reasons for the ab initio models’ shortcomings, and possible approaches for improving on them in the future.
Hannah Jörg "Potential of a Fully Polarimetric Tomographic Time Series over Agricultural Crops for Monitoring Bio- and Geophysical Changes"
Dienstag, 13. Juni 2017
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Synthetic Aperture Radar (SAR) Tomography enables to resolve scatterers at different heights within the same resolution cell. The estimated 3-D reflectivity can be used to assess the validity of scattering models. In the case of agricultural crops, to understand better the rather complex scattering processes, this involves for instance the assessment of penetration depth and the identification of the main scattering mechanisms as a function of species and development stage as well as polarization and frequency. The understanding regarding 3-D scattering in this context is still limited and an important step is the separation of ground and volume scattering from each other in order to differentiate between ground and volume dynamics. A filter based separation enables, even in the presence of anisotropic propagation effects through the vegetation volume, the estimation of the multi-baseline (MB) volume only coherences and hence of the volume scattering centers and the powers of the ground and volume component. The analysis of the retrieved parameters shows that, in general, anisotropic propagation effects can be neglected. This allows the application of the Algebraic Synthesis algorithm which is based on the Random Volume over Ground model and yields in addition the ground and volume polarimetric signatures. The latter are analyzed in order to evaluate the possibility of exploiting the polarimetric signature of the ground regarding, for instance, soil moisture.
Son Nghiem "Unraveling the Differences between Arctic and Antarctic Sea Ice Change"
Montag, 29. Mai 2017
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Why has Arctic sea ice decreased drastically and Antarctic sea ice slightly increased as observed in the past several decades? This is a key issue in climate change science considered by scientists as a puzzling and challenging paradox to be resolved. Here, we compare, contrast, and explain the differences between Arctic and Antarctic sea ice change. A regime shift of Arctic sea ice from predominantly perennial sea ice (PSI) to primarily seasonal sea ice (SSI) is examined with the combination of satellite and surface observations over a half century since the late 1950s. Beyond the superficial decrease in the Arctic total sea ice extent (SIE), a profound change in sea ice composition consisting of PSI and SSI has drastically occurred in springtime that is crucial in preconditioning the sea ice cover before the summer melt. We found that the loss of PSI in the 2000s tripled the loss rate in the previous three decades. This drastic change has been accentuated by another record low of SIE in summer 2012. We illustrate the transformative regime shift of Arctic sea ice with sea ice maps and animations derived from satellite data. This shift has profoundly altered the sea ice cover, snow accumulation, melt pond, albedo, and surface heat balance, and has thereby impacted processes governing the atmosphere-sea ice-ocean system. To explain Arctic sea ice change, we consider both dynamic and thermodynamic processes from the seafloor to the sea ice surface and atmospheric effects. Notably, we present an important sea ice loss mechanism, called the Polar Express that forces sea ice loss not only in summer but also in any seasons including winter. Moreover, we show how Arctic sea ice reduction may change Artic halogen processes to lend science support to the Minamata Convention, a global treaty to curb mercury pollution. In contrast, the Antarctic total SIE has been stable with a relatively low rate of change since the late 1970s with a slight increase that has not been nearly as large as the decreasing trend of the SIE in the Arctic and not as widespread geographically. However, Antarctic sea ice change is complicated with regional differences such as the decrease of sea ice with a shortened ice season in the Bellingshausen Sea region in opposite to the late retreat and early advance in the western Ross Sea region. The complexity in Antarctic sea ice change has become further accentuated by successive Antarctic SIE maximum records in 2012, 2013, and 2014 from satellite observations in contrast to record low values of Arctic SIE in March to early June 2015. A record low in Antarctic SIE in the 2016-2017 austral winter also adds more to the puzzle. To address the issue of Antarctic sea ice behavior and its contrast to Arctic sea ice change, an explanation to be considered plausible requires self-consistent answers simultaneously to all of these science questions about Antarctic sea ice: What are the most effective processes for sea ice production pertaining to Antarctic conditions? What are the factors protecting the sea ice cover? What are the factors sustaining sea ice? What are the factors causing regional variability? Is there any discord among these factors? Why do opposite effects occur in Antarctic and Arctic sea ice while both have to obey the same physics? We provide answers to all of the questions using satellite and surface observations of Antarctic sea ice characteristics and factors that impact sea ice change in the Antarctic and how the effects can be different in the Arctic. Finally, we formulate a strategic Antarctic Science Campaign with a coordinated DLR and NASA remote sensing data acquisition together with surface observations to advance the sea ice science.
Michele Martone "Generation of a global vegetation map from TanDEM-X interferometric data"
Dienstag, 11. April 2017
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Remote sensing data represents a highly valuable source for land classification purposes. In particular, the identification and the monitoring of vegetated areas is critical for a large variety of applications, such as agriculture, forestry, global change research, as well as for regional planning. In this talk we present the first global forest/non-forest classification map generated from the TanDEM-X single-pass interferometric SAR (InSAR) data set. Among the error sources which affect the quality of TanDEM-X InSAR data, the coherence loss caused by volume scattering represents the contribution which is predominantly influenced by the presence of vegetation, and is therefore exploited as input information for a multi-clustering classification algorithm based on fuzzy logic. Since the beginning of the TanDEM-X mission (end of 2010), about half a million of single polarization (HH) bistatic scenes covering all the Earth’s land masses have been acquired and processed. For global classification purposes, we use an averaged and downsampled version of the original full resolution data at a ground independent pixel spacing of 50 m x 50 m (so-called quicklook), which represents a good compromise between final product resolution and resulting computational load. The proposed classification approach and the mosaicking strategy aimed at best combining the multi-temporal, multi-baseline TanDEM-X data set are discussed. Then, the final product is compared and validated with existing vegetation maps and by means of external land cover classification data. Finally, potentials for further applications, such as, e.g., high-resolution mapping as well as forest change detection are introduced as well, verifying the unique capabilities offered by the TanDEM-X mission for a broad range of commercial and scientific applications.
Christopher Wecklich "Height Accuracy and Data Coverage evaluation results for the Global TanDEM-X Final DEM"
Dienstag, 24. Januar 2017
14.00 h Großer Besprechungsraum HR, Gebäude 102
Abstract:
Digital Elevation Models (DEMs) are raster-based digital datasets representing the topography of a planetary body and are of fundamental importance for a wide range of scientific and commercial applications. Within the ±60º latitude band, data from the Shuttle Radar Topography Mission (SRTM) has been the primary source of elevation information. Since 2010 the German Aerospace Center (DLR) has been operating Germany’s first two formation flying Synthetic Aperture Radar (SAR) satellites, TerraSAR-X and TanDEM-X, with the objective to generate an updated global DEM which exceeds the presently available global data sets in terms of resolution, coverage, and quality by orders of magnitude. The primary mission of TanDEM-X is the generation of a world-wide, consistent, current, and high-precision DEM, with a spatial resolution of 0.4 arcseconds (12 m at the equator) and according to the height accuracy and data coverage requirements. This presentation starts with an introduction to TanDEM-X global DEM generation as well as an introduction to the SRTM and ICE-Sat systems. This is followed by a section each dedicated to the evaluation of relative and absolute height accuracy of the global DEM products. Finally we will conclude with an evaluation of the TanDEM-X data coverage or void density.
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