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Detection of aircrafts in satellite images is a challenging problem when the background is strongly reflective clouds with varying transparency. We develop a fast and effective detection algorithm that can find almost all aircrafts above and between clouds in Sentinel-2 multispectral images. It exploits the time delay of a few seconds between the recorded multispectral images such that a moving aircraft is observed at different positions due to parallax effects. The aircraft speed, heading and altitude are also calculated accurately. Analysing images over the English Channel during fall 2020, we obtain a detection accuracy of 80%, where the most of the remaining were covered by clouds. We also analyse images in the 1.38 μm water absorption band, where only 61% of the aircrafts are detected.
Peder Heiselberg; Henning Heiselberg. Aircraft Detection above Clouds by Sentinel-2 MSI Parallax. Remote Sensing 2021, 13, 3016 .
AMA StylePeder Heiselberg, Henning Heiselberg. Aircraft Detection above Clouds by Sentinel-2 MSI Parallax. Remote Sensing. 2021; 13 (15):3016.
Chicago/Turabian StylePeder Heiselberg; Henning Heiselberg. 2021. "Aircraft Detection above Clouds by Sentinel-2 MSI Parallax." Remote Sensing 13, no. 15: 3016.
The Special Issue (SI) "Remote Sensing in Vessel Detection and Navigation" highlighted a variety of topics related to remote sensing with navigational sensors. The sequence of articles included in this Special Issue is in line with the latest scientific trends. The latest developments in science, including artificial intelligence, were used. The 15 papers (from 23 submitted) were published.
Henning Heiselberg; Andrzej Stateczny. Remote Sensing in Vessel Detection and Navigation. 2020, 20, 1 .
AMA StyleHenning Heiselberg, Andrzej Stateczny. Remote Sensing in Vessel Detection and Navigation. . 2020; 20 (20):1.
Chicago/Turabian StyleHenning Heiselberg; Andrzej Stateczny. 2020. "Remote Sensing in Vessel Detection and Navigation." 20, no. 20: 1.
Classification of ships and icebergs in the Arctic in satellite images is an important problem. We study how to train deep neural networks for improving the discrimination of ships and icebergs in multispectral satellite images. We also analyze synthetic-aperture radar (SAR) images for comparison. The annotated datasets of ships and icebergs are collected from multispectral Sentinel-2 data and taken from the C-CORE dataset of Sentinel-1 SAR images. Convolutional Neural Networks with a range of hyperparameters are tested and optimized. Classification accuracies are considerably better for deep neural networks than for support vector machines. Deeper neural nets improve the accuracy per epoch but at the cost of longer processing time. Extending the datasets with semi-supervised data from Greenland improves the accuracy considerably whereas data augmentation by rotating and flipping the images has little effect. The resulting classification accuracies for ships and icebergs are 86% for the SAR data and 96% for the MSI data due to the better resolution and more multispectral bands. The size and quality of the datasets are essential for training the deep neural networks, and methods to improve them are discussed. The reduced false alarm rates and exploitation of multisensory data are important for Arctic search and rescue services.
Henning Heiselberg. Ship-Iceberg Classification in SAR and Multispectral Satellite Images with Neural Networks. Remote Sensing 2020, 12, 2353 .
AMA StyleHenning Heiselberg. Ship-Iceberg Classification in SAR and Multispectral Satellite Images with Neural Networks. Remote Sensing. 2020; 12 (15):2353.
Chicago/Turabian StyleHenning Heiselberg. 2020. "Ship-Iceberg Classification in SAR and Multispectral Satellite Images with Neural Networks." Remote Sensing 12, no. 15: 2353.
The Sentinel-2 satellites in the Copernicus program provide high resolution multispectral images, which are recorded with temporal offsets up to 2.6 s. Moving aircrafts and ships are therefore observed at different positions due to the multispectral band offsets, from which velocities can be determined. We describe an algorithm for detecting aircrafts and ships, and determining their speed, heading, position, length, etc. Aircraft velocities are also affected by the parallax effect and jet streams, and we show how the altitude and the jet stream speed can be determined from the geometry of the aircraft and/or contrail heading. Ship speeds are more difficult to determine as wakes affect the average ship positions differently in the various multispectral bands, and more advanced corrections methods are shown to improve the velocity determination.
Henning Heiselberg. Aircraft and Ship Velocity Determination in Sentinel-2 Multispectral Images. Sensors 2019, 19, 2873 .
AMA StyleHenning Heiselberg. Aircraft and Ship Velocity Determination in Sentinel-2 Multispectral Images. Sensors. 2019; 19 (13):2873.
Chicago/Turabian StyleHenning Heiselberg. 2019. "Aircraft and Ship Velocity Determination in Sentinel-2 Multispectral Images." Sensors 19, no. 13: 2873.
The European Space Agency Sentinel-2 satellites provide multispectral images with pixel sizes down to 10 m. This high resolution allows for fast and frequent detection, classification and discrimination of various objects in the sea, which is relevant in general and specifically for the vast Arctic environment. We analyze several sets of multispectral image data from Denmark and Greenland fall and winter, and describe a supervised search and classification algorithm based on physical parameters that successfully finds and classifies all objects in the sea with reflectance above a threshold. It discriminates between objects like ships, islands, wakes, and icebergs, ice floes, and clouds with accuracy better than 90%. Pan-sharpening the infrared bands leads to classification and discrimination of ice floes and clouds better than 95%. For complex images with abundant ice floes or clouds, however, the false alarm rate dominates for small non-sailing boats.
Peder Heiselberg; Henning Heiselberg. Ship-Iceberg Discrimination in Sentinel-2 Multispectral Imagery by Supervised Classification. Remote Sensing 2017, 9, 1156 .
AMA StylePeder Heiselberg, Henning Heiselberg. Ship-Iceberg Discrimination in Sentinel-2 Multispectral Imagery by Supervised Classification. Remote Sensing. 2017; 9 (11):1156.
Chicago/Turabian StylePeder Heiselberg; Henning Heiselberg. 2017. "Ship-Iceberg Discrimination in Sentinel-2 Multispectral Imagery by Supervised Classification." Remote Sensing 9, no. 11: 1156.
The European Space Agency satellite Sentinel-2 provides multispectral images with pixel sizes down to 10 m. This high resolution allows for ship detection and recognition by determining a number of important ship parameters. We are able to show how a ship position, its heading, length and breadth can be determined down to a subpixel resolution. If the ship is moving, its velocity can also be determined from its Kelvin waves. The 13 spectrally different visual and infrared images taken using multispectral imagery (MSI) are “fingerprints” that allow for the recognition and identification of ships. Furthermore, the multispectral image profiles along the ship allow for discrimination between the ship, its turbulent wakes, and the Kelvin waves, such that the ship’s length and breadth can be determined more accurately even when sailing. The ship’s parameters are determined by using satellite imagery taken from several ships, which are then compared to known values from the automatic identification system. The agreement is on the order of the pixel resolution or better.
Henning Heiselberg. A Direct and Fast Methodology for Ship Recognition in Sentinel-2 Multispectral Imagery. Remote Sensing 2016, 8, 1033 .
AMA StyleHenning Heiselberg. A Direct and Fast Methodology for Ship Recognition in Sentinel-2 Multispectral Imagery. Remote Sensing. 2016; 8 (12):1033.
Chicago/Turabian StyleHenning Heiselberg. 2016. "A Direct and Fast Methodology for Ship Recognition in Sentinel-2 Multispectral Imagery." Remote Sensing 8, no. 12: 1033.
The spin diffusion and damped oscillations are studied in the collision of two spin polarized clouds of cold atoms with resonant interactions. The strong density dependence of the diffusion coefficient leads to inhomogeneous spin diffusion that changes from central to surface spin flow as the temperature increases. The inhomogeneity and the smaller finite trap size significantly reduce the spin diffusion rate at low temperatures. The resulting spin diffusion rates and spin drag at longer time scales are compatible with measurements at low to high temperatures for resonant attractive interactions but are incompatible with a metastable ferromagnetic phase. This does not exclude that the colliding clouds can evolve into a repulsive initial state which subsequently decays during the bounce and the initial damped oscillations.
H. Heiselberg. Inhomogeneous Spin Diffusion in Traps with Cold Atoms. Physical Review Letters 2012, 108, 1 .
AMA StyleH. Heiselberg. Inhomogeneous Spin Diffusion in Traps with Cold Atoms. Physical Review Letters. 2012; 108 (24):1.
Chicago/Turabian StyleH. Heiselberg. 2012. "Inhomogeneous Spin Diffusion in Traps with Cold Atoms." Physical Review Letters 108, no. 24: 1.
DOI: http://dx.doi.org/10.1103/PhysRevLett.108.249904 © 2012 American Physical Society
H. Heiselberg. Erratum: Collective Modes of Trapped Gases at the BEC-BCS Crossover [Phys. Rev. Lett. 93 , 040402 (2004)]. Physical Review Letters 2012, 108, 1 .
AMA StyleH. Heiselberg. Erratum: Collective Modes of Trapped Gases at the BEC-BCS Crossover [Phys. Rev. Lett. 93 , 040402 (2004)]. Physical Review Letters. 2012; 108 (24):1.
Chicago/Turabian StyleH. Heiselberg. 2012. "Erratum: Collective Modes of Trapped Gases at the BEC-BCS Crossover [Phys. Rev. Lett. 93 , 040402 (2004)]." Physical Review Letters 108, no. 24: 1.
Universality and crossover is described for attractive and repulsive interactions where, respectively, the BCS-BEC crossover takes place and a ferromagnetic phase transition is claimed. Crossovers are also described for optical lattices and multicomponent systems. The crossovers, universal parameters and phase transitions are described within the Leggett and NSR models and calculated in detail within the Jastrow-Slater approximation. The physics of ultracold Fermi atoms is applied to neutron, nuclear and quark matter, nuclei and electrons in solids whenever possible. Specifically, the differences between optical lattices and cuprates is discussed w.r.t. antiferromagnetic, d-wave superfluid phases and phase separation.Comment: 50 pages, 15 figures. Contribution to Lecture Notes in Physics "BCS-BEC crossover and the Unitary Fermi Gas" edited by W. Zwerge
Henning Heiselberg. Crossovers in Unitary Fermi Systems. String Field Theory 2011, 49 -97.
AMA StyleHenning Heiselberg. Crossovers in Unitary Fermi Systems. String Field Theory. 2011; ():49-97.
Chicago/Turabian StyleHenning Heiselberg. 2011. "Crossovers in Unitary Fermi Systems." String Field Theory , no. : 49-97.
Itinerant ferromagnetism in cold Fermi gases with repulsive interactions is studied applying the Jastrow-Slater approximation generalized to finite polarization and temperature. For two components at zero temperature, a second-order transition is found at akF$\simeq${}0.90 compatible with results of quantum-Monte-Carlo (QMC) calculations. Thermodynamic functions and observables, such as the compressibility and spin susceptibility and the resulting fluctuations in number and spin, are calculated. For trapped gases, the resulting cloud radii and kinetic energies are calculated and compared to recent experiments. Spin-polarized systems are recommended for effective separation of large ferromagnetic domains. Collective modes are predicted and tricritical points are calculated for multicomponent systems.
H. Heiselberg. Itinerant ferromagnetism in ultracold Fermi gases. Physical Review A 2011, 83, 1 .
AMA StyleH. Heiselberg. Itinerant ferromagnetism in ultracold Fermi gases. Physical Review A. 2011; 83 (5):1.
Chicago/Turabian StyleH. Heiselberg. 2011. "Itinerant ferromagnetism in ultracold Fermi gases." Physical Review A 83, no. 5: 1.
We perform angle- and frequency-resolved radar cross section (RCS) measurements on objects at terahertz frequencies. Our RCS measurements are performed on a scale model aircraft of size 5-10 cm in polar and azimuthal configurations, and correspond closely to RCS measurements with conventional radar on full-size objects. The measurements are performed in a terahertz time-domain system with freely propagating terahertz pulses generated by tilted pulse front excitation of lithium niobate crystals and measured with sub-picosecond time resolution. The application of a time domain system provides ranging information and also allows for identification of scattering points such as weaponry attached to the aircraft. The shapes of the models and positions of reflecting parts are retrieved by the filtered back projection algorithm.
Krzysztof Iwaszczuk; Henning Heiselberg; Peter Uhd Jepsen. Terahertz radar cross section measurements. Optics Express 2010, 18, 26399 -26408.
AMA StyleKrzysztof Iwaszczuk, Henning Heiselberg, Peter Uhd Jepsen. Terahertz radar cross section measurements. Optics Express. 2010; 18 (25):26399-26408.
Chicago/Turabian StyleKrzysztof Iwaszczuk; Henning Heiselberg; Peter Uhd Jepsen. 2010. "Terahertz radar cross section measurements." Optics Express 18, no. 25: 26399-26408.
We present the result of terahertz radar cross section measurements on various objects including models of aircraft fighters. Application of a time domain system provides both values of radar cross section and ranging information.
Krzysztof Iwaszczuk; Henning Heiselberg; Peter Uhd Jepsen. Terahertz radar cross section measurements. 35th International Conference on Infrared, Millimeter, and Terahertz Waves 2010, 1 -3.
AMA StyleKrzysztof Iwaszczuk, Henning Heiselberg, Peter Uhd Jepsen. Terahertz radar cross section measurements. 35th International Conference on Infrared, Millimeter, and Terahertz Waves. 2010; ():1-3.
Chicago/Turabian StyleKrzysztof Iwaszczuk; Henning Heiselberg; Peter Uhd Jepsen. 2010. "Terahertz radar cross section measurements." 35th International Conference on Infrared, Millimeter, and Terahertz Waves , no. : 1-3.
Antiferromagnetic, Mott-insulator, -wave, and gossamer superfluid phases are calculated for two-dimensional (2D) square lattices from the extended Hubbard model using the Gutzwiller projection method and renormalized mean-field theory. The phase separation between antiferromagnetic and -wave superfluid phases is found near half filling when the on-site repulsion exceeds and coincides with a first-order transition in the double occupancy. The phase separation is thus predicted for 2D optical lattices with ultracold Fermi atoms whereas it is inhibited in cuprates by Coulomb frustration which instead may lead to stripes. In a confined optical lattice the resulting density distribution is discontinuous and with extended Mott plateau which enhances the antiferromagnetic phase but suppresses the superfluid phase. Observation of Mott-insulator, antiferromagnetic, stripe, and superfluid phases in density and momentum distributions and correlations is discussed.
H. Heiselberg. Hubbard-model calculations of phase separation in optical lattices. Physical Review A 2009, 79, 063611 .
AMA StyleH. Heiselberg. Hubbard-model calculations of phase separation in optical lattices. Physical Review A. 2009; 79 (6):063611.
Chicago/Turabian StyleH. Heiselberg. 2009. "Hubbard-model calculations of phase separation in optical lattices." Physical Review A 79, no. 6: 063611.
We calculate level densities and pairing gaps for an ultracold dilute gas of fermionic atoms in harmonic traps under the influence of mean field and anharmonic quartic trap potentials. Supershell nodes, which were found in Hartree-Fock calculations, are calculated analytically within periodic orbit theory as well as from WKB calculations. For attractive interactions, the underlying level densities are crucial for pairing and supershell structures in gaps are predicted.
Magnus Ögren; Henning Heiselberg. Supershell structures and pairing in ultracold trapped Fermi gases. Physical Review A 2007, 76, 021601 .
AMA StyleMagnus Ögren, Henning Heiselberg. Supershell structures and pairing in ultracold trapped Fermi gases. Physical Review A. 2007; 76 (2):021601.
Chicago/Turabian StyleMagnus Ögren; Henning Heiselberg. 2007. "Supershell structures and pairing in ultracold trapped Fermi gases." Physical Review A 76, no. 2: 021601.
Phases of Bose or Fermi atoms in optical lattices confined in harmonic traps are studied within the Thomas-Fermi approximation. Critical radii and particle numbers for the onset of Mott insulator states are calculated and phase diagrams are shown in one dimension, and estimated for two and three dimensions. Methods to observe these and phases such as d-wave superconductivity are discussed. Specifically, the collective modes are calculated.
H. Heiselberg. Phases of bosons or fermions in confined optical lattices. Physical Review A 2006, 74, 033608 .
AMA StyleH. Heiselberg. Phases of bosons or fermions in confined optical lattices. Physical Review A. 2006; 74 (3):033608.
Chicago/Turabian StyleH. Heiselberg. 2006. "Phases of bosons or fermions in confined optical lattices." Physical Review A 74, no. 3: 033608.
Raman scattering in single-mode optical fibers is exploited to generate multispectral light from a green nanolaser with high pulse repetition rate. Each pulse triggers a picosecond camera and measures the distance by time-of-flight in each of the 0.5 Mpixels. Three-dimensional images are then constructed with submillimeter accuracy for all visible colors. The generation of a series of Stokes peaks by Raman scattering in a Si fiber is discussed in detail and the laser radar technique is demonstrated. The data recording takes only a few seconds, and the high accuracy 3D color imaging works at ranges up to approximately 200 m. Applications for optical tomography in highly scattering media such as water and human tissue are mentioned.
Joachim F. Andersen; Jens Busck; Henning Heiselberg. Pulsed Raman fiber laser and multispectral imaging in three dimensions. Applied Optics 2006, 45, 6198 -6204.
AMA StyleJoachim F. Andersen, Jens Busck, Henning Heiselberg. Pulsed Raman fiber laser and multispectral imaging in three dimensions. Applied Optics. 2006; 45 (24):6198-6204.
Chicago/Turabian StyleJoachim F. Andersen; Jens Busck; Henning Heiselberg. 2006. "Pulsed Raman fiber laser and multispectral imaging in three dimensions." Applied Optics 45, no. 24: 6198-6204.
Applications of a laser radar system with depth accuracy down to 0.2 mm for high accuracy 3-D imaging are described. The system is based on a green pulsed laser triggering a picosecond ICCD camera with data recording of only a few seconds. The submillimeter accuracy gradually degrades at ranges above a few hundred meters due to turbulence, vibrations, etc. As a specific example, we show 3-D accuracy for surface tile inspection of a miniature space shuttle and the resolution of cracks and defects is demonstrated, which is relevant for the planned laser radar inspections from the space shuttle boom and the longer range survey from the International Space Station. By coupling the laser light through a Raman fiber we also demonstrate multispectral 3-D imaging.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
J. F. Andersen; J. Busck; H. Heiselberg. Applications of high resolution laser radar for 3-D multispectral imaging. Defense and Security Symposium 2006, 6214, 62140 -62140.
AMA StyleJ. F. Andersen, J. Busck, H. Heiselberg. Applications of high resolution laser radar for 3-D multispectral imaging. Defense and Security Symposium. 2006; 6214 ():62140-62140.
Chicago/Turabian StyleJ. F. Andersen; J. Busck; H. Heiselberg. 2006. "Applications of high resolution laser radar for 3-D multispectral imaging." Defense and Security Symposium 6214, no. : 62140-62140.
The Bose-Hubbard model is extended to include nearest- and far-neighbor interactions and is related to the fractional quantum Hall effect (FQHE). Both models may be studied in optical lattices with quantum gases. The ground state is calculated for the extended Bose-Hubbard model with strong repulsive interactions (weak hopping). Incompressible Mott insulator states are found at rational filling fractions compatible with the principal and secondary FQHE filling fractions of the lowest Landau levels observed experimentally. It is discussed to which extent these states at fractional filling survive or undergoes a Mott insulator transition to a superfluid as hopping terms are included.
H. Heiselberg. Extended Bose-Hubbard model with incompressible states at fractional numbers. Physical Review A 2006, 73, 013628 .
AMA StyleH. Heiselberg. Extended Bose-Hubbard model with incompressible states at fractional numbers. Physical Review A. 2006; 73 (1):013628.
Chicago/Turabian StyleH. Heiselberg. 2006. "Extended Bose-Hubbard model with incompressible states at fractional numbers." Physical Review A 73, no. 1: 013628.
First and second sound speeds are calculated for a uniform superfluid gas of Fermi atoms as a function of temperature, density, and interaction strength. The second sound speed is of particular interest as it is a clear signal of a superfluid component and it determines the critical temperature. The sound modes and their dependence on density, scattering length, and temperature are calculated in the BCS, molecular Bose-Einstein condensate (BEC), and unitarity limits and a smooth crossover is extrapolated. It is found that first and second sounds undergo avoided crossing on the BEC side due to mixing. Consequently, they are detectable at crossover both as density and thermal waves in traps.
H. Heiselberg. Sound modes at the BCS-BEC crossover. Physical Review A 2006, 73, 013607 .
AMA StyleH. Heiselberg. Sound modes at the BCS-BEC crossover. Physical Review A. 2006; 73 (1):013607.
Chicago/Turabian StyleH. Heiselberg. 2006. "Sound modes at the BCS-BEC crossover." Physical Review A 73, no. 1: 013607.
Results from our fast and high accuracy 3-D laser radar are given at distances up to 500 m. The system is based on gated viewing with range accuracy below 1 mm under optimal circumstances. It consists of a high sensitivity, fast, intensified CCD camera, and an Nd:YAG passively Q-switched 32.4 kHz pulsed green laser at 532 nm. The CCD has 752×582 pixels. Camera shutter and delay steps are controlled in steps of 100 ps. Each laser pulse triggers the camera delay and shutter. A 3-D image is constructed from a sequence of 50-100 2-D reflectivity images, where each frame integrates ~700 laser pulses on the CCD. In 50 Hz video mode we record a 2-D sequence in a second and process a 3-D image in a few seconds. We compare 3-D images at short to long distances and quantify the degree of person identification in 3-D. Turbulence, vibrations and system errors are found to limit a successful PID to distances shorter than ~500m for our prototype system.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
J. F. Andersen; J. Busck; H. Heiselberg. Long distance high accuracy 3-D laser radar and person identification. Defense and Security 2005, 5791, 9 -16.
AMA StyleJ. F. Andersen, J. Busck, H. Heiselberg. Long distance high accuracy 3-D laser radar and person identification. Defense and Security. 2005; 5791 ():9-16.
Chicago/Turabian StyleJ. F. Andersen; J. Busck; H. Heiselberg. 2005. "Long distance high accuracy 3-D laser radar and person identification." Defense and Security 5791, no. : 9-16.