Development of digital aerial cameras

Digital aerial cameras have replaced analogue aerial cameras in several countries. The development for operational aerial photogrammetry started with the line scan camera ADS40, followed by Z/I Imaging DMC and Vexcel Imaging UltraCam. Recently the line scan camera Jena Optronik JAS-150 was introduced. The capacity of the UltraCam was enlarged by replacing the used CCDs with 9μm pixels over 7.2μm to 6μm for the UltraCamXp, having 196 Mpix. The DMC and the UltraCam are system cameras, reaching the large number of pixels by a combination of 4, respectively 9 CCDs. Even if the large format line scan cameras have demonstrated their geometric potential, the major replacement of analogue cameras came by the digital large frame cameras, while the line scan cameras found their major field with orthoimages. In the meantime digital mid-format cameras, equipped with a single CCD-array, with approximately 39 Mpix took also a share by the replacement of the analogue aerial cameras. Their combination with GPS and inertial measurement units (IMU) compensates partially the disadvantage of handling a high number of images. The mid-format cameras are equipped with Bayer pattern, limited to 3 spectral bands opposite to the 4 spectral bands offered by the large format frame and line scan cameras. This changed by the introduction of mid-format system cameras RMK D from Z/I Imaging and UltraCamL from Vexcel Imaging. In addition now camera systems equipped with 4 mid-format cameras as the IGI Quattro DigiCAM and the Trimble Aerial Camera (TAC) (former Rolleimetric) AIC-x4 are available. These cameras are not offering homogenous virtual images as the DMC and UltraCam. Just recently a new situation came with the development of large format monolithic CCDs by DALSA. Based on this Z/I Imaging introduced now the DMC II 140, having 11712 × 11200 pixels on one CCD with 2 sec frame rate. In the fall the DMC II 230 (230 Mpix) and in the spring 2011 the DMC II 250 with 17216 × 14656 pixels with 1.7 sec frame rate will follow. This corresponds to the dream of photogrammetrists replacing the film just by one CCD. The geometric performance of the large format digital cameras and the mid-format camera TAC and Quattro DigiCAM have been analyzed in a test of the German Society of Photogrammetry and Remote Sensing (DGPF), showing an advantage of the large format digital cameras against scanned analog photos. The monolithic DMC II 140 was analyzed separately, demonstrating an excellent geometric performance better as other cameras before

Problems and limitations of satellite image orientation for determination of height models

The usual satellite image orientation is based on bias corrected rational polynomial coefficients (RPC). The RPC are describing the direct sensor orientation of the satellite images. The locations of the projection centres today are without problems, but an accuracy limit is caused by the attitudes. Very high resolution satellites today are very agile, able to change the pointed area over 200km within 10 to 11 seconds. The corresponding fast attitude acceleration of the satellite may cause a jitter which cannot be expressed by the third order RPC, even if it is recorded by the gyros. Only a correction of the image geometry may help, but usually this will not be done. The first indication of jitter problems is shown by systematic errors of the y-parallaxes (py) for the intersection of corresponding points during the computation of ground coordinates. These y-parallaxes have a limited influence to the ground coordinates, but similar problems can be expected for the x-parallaxes, determining directly the object height. Systematic y-parallaxes are shown for Ziyuan-3 (ZY3), WorldView-2 (WV2), Pleiades, Cartosat-1, IKONOS and GeoEye. Some of them have clear jitter effects. In addition linear trends of py can be seen. Linear trends in py and tilts in of computed height models may be caused by limited accuracy of the attitude registration, but also by bias correction with affinity transformation. The bias correction is based on ground control points (GCPs). The accuracy of the GCPs usually does not cause some limitations but the identification of the GCPs in the images may be difficult. With 2-dimensional bias corrected RPC-orientation by affinity transformation tilts of the generated height models may be caused, but due to large affine image deformations some satellites, as Cartosat-1, have to be handled with bias correction by affinity transformation. Instead of a 2-dimensional RPC-orientation also a 3-dimensional orientation is possible, respecting the object height more as by 2-dimensional orientation. The 3-dimensional orientation showed advantages for orientation based on a limited number of GCPs, but in case of poor GCP distribution it may cause also negative effects. For some of the used satellites the bias correction by affinity transformation showed advantages, but for some other the bias correction by shift was leading to a better levelling of the generated height models, even if the root mean square (RMS) differences at the GCPs were larger as for bias correction by affinity transformation. The generated height models can be analyzed and corrected with reference height models. For the used data sets accurate reference height models are available, but an analysis and correction with the free of charge available SRTM digital surface model (DSM) or ALOS World 3D (AW3D30) is also possible and leads to similar results. The comparison of the generated height models with the reference DSM shows some height undulations, but the major accuracy influence is caused by tilts of the height models. Some height model undulations reach up to 50% of the ground sampling distance (GSD), this is not negligible but it cannot be seen not so much at the standard deviations of the height. In any case an improvement of the generated height models is possible with reference height models. If such corrections are applied it compensates possible negative effects of the type of bias correction or 2-dimensional orientations against 3-dimensional handling

Gottfried Konecny: The photogrammetric and remote sensing trend setter

PREFACE: There are various publications on the 90th birthday of Gottfried Konecny. His involvement in the International Society for Photogrammetry and Remote Sensing (ISPRS) is particularly described by others. Here, his forward-oriented impulses in research and development at the former Institute for Photogrammetry and Engineering Survey of the (Technical) University of Hannover, today Institute for Photogrammetry and Geoinformation, Leibniz University Hannover, and some of his activities supporting developing and other countries by given short-term courses are highlighted. Gottfried Konecny was always one of the first in pushing new technologies. With the analytical plotter AP/C-3, he introduced analytical photogrammetry in Germany. Based on his experience with this not really operational version, he induced the company Zeiss to develop the first really operational analytical plotter Planicomp, which resulted in the end of analog photogrammetric devices and their limitations. At the invitation of Gilbert Hobrough, a mainly hardware-based image correlator was developed for the AP/C-3 in Hannover which anticipated many of today’s applications. Gottfried Konecny initiated remote sensing in Germany. Based on his proposal with the Metric Camera Flight on Spacelab, the then highest resolution civil stereoscopic space images available were generated. Despite limited computer performance at his institute, a digital stereo plotter was developed, using hardware components from the cooperating Swedish company Context Vision, long before digital stereo workstations with increased and affordable computer capacity were possible. Also, in the area of GIS, he too, pushed development in collaboration with companies and administrations. Shortly before the end of his time as head of the institute, and more so after he became emeritus professor, he started a series of educational workshops, particularly in developing countries, but also other countries, to support the development of photogrammetry, remote sensing and GIS. He promoted the use of space imagery for mapping to improve the situation of poorly updated topographic maps. © 2020 Wuhan University. Published by Informa UK Limited, trading as Taylor & Francis Group

Simulation of Cu-Mg metallic glass: Thermodynamics and Structure

We have obtained effective medium theory (EMT) interatomic potential parameters suitable for studying Cu-Mg metallic glasses. We present thermodynamic and structural results from simulations of such glasses over a range of compositions. We have produced low-temperature configurations by cooling from the melt at as slow a rate as practical, using constant temperature and pressure molecular dynamics. During the cooling process we have carried out thermodynamic analyses based on the temperature dependence of the enthalpy and its derivative, the specific heat, from which the glass transition temperature may be determined. We have also carried out structural analyses using the radial distribution function (RDF) and common neighbor analysis (CNA). Our analysis suggests that the splitting of the second peak, commonly associated with metallic glasses, in fact has little to do with the glass transition itself, but is simply a consequence of the narrowing of peaks associated with structural features present in the liquid state. In fact the splitting temperature for the Cu-Cu RDF is well above $T_g$. The CNA also highlights a strong similarity between the structure of the intermetallic alloys and the amorphous alloys of similar composition. We have also investigated the diffusivity in the supercooled regime. Its temperature dependence indicates fragile-liquid behavior, typical of binary metallic glasses. On the other hand, the relatively low specific heat jump of around $1.5 k_B/\mathrm{at.}$ indicates apparent strong-liquid behavior, but this can be explained by the width of the transition due to the high cooling rates.Comment: 12 pages (revtex, two-column), 12 figures, submitted to Phys. Rev.

Spatially resolved quantum plasmon modes in metallic nano-films from first principles

Electron energy loss spectroscopy (EELS) can be used to probe plasmon excitations in nanostructured materials with atomic-scale spatial resolution. For structures smaller than a few nanometers quantum effects are expected to be important, limiting the validity of widely used semi-classical response models. Here we present a method to identify and compute spatially resolved plasmon modes from first principles based on a spectral analysis of the dynamical dielectric function. As an example we calculate the plasmon modes of 0.5-4 nm thick Na films and find that they can be classified as (conventional) surface modes, sub-surface modes, and a discrete set of bulk modes resembling standing waves across the film. We find clear effects of both quantum confinement and non-local response. The quantum plasmon modes provide an intuitive picture of collective excitations of confined electron systems and offer a clear interpretation of spatially resolved EELS spectra.Comment: 7 pages, 7 figure

Plasmons on the edge of MoS2 nanostructures

Using ab initio calculations we predict the existence of one-dimensional (1D), atomically confined plasmons at the edges of a zigzag MoS2 nanoribbon. The strongest plasmon originates from a metallic edge state localized on the sulfur dimers decorating the Mo edge of the ribbon. A detailed analysis of the dielectric function reveals that the observed deviations from the ideal 1D plasmon behavior result from single-particle transitions between the metallic edge state and the valence and conduction bands of the MoS2 sheet. The Mo and S edges of the ribbon are clearly distinguishable in calculated spatially resolved electron energy loss spectrum owing to the different plasmonic properties of the two edges. The edge plasmons could potentially be utilized for tuning the photocatalytic activity of MoS2 nanoparticles

ASE, GPAW, CMR, and that kind of tools

During the last decades we have developed several, mostly Python-based, tools for setting up, controlling/steering, storing, analyzing, and sharing simulations at the atomic and electronic scale. In particular, we have developed the Atomic Simulation Environment which has become a fairly widely used scripting tool for setting up and controlling simulations with either an interatomic potential code or an electronic structure code as “backends” for the force and energy calculations. More recently, we have developed a real-space density-functional-theory and many-body-perturbation-theory code, GPAW, and most recently the Computational Materials Repository for storing, sharing, and retrieving atomic-scale data. In the discussion, I shall present some of the experiences we have gained through these developments and show some examples of their recent to the problem of finding new materials for efficient solar energy conversion into electricity or fuels

Rich Ground State Chemical Ordering in Nanoparticles: Exact Solution of a Model for Ag-Au Clusters

We show that nanoparticles can have very rich ground state chemical order. This is illustrated by determining the chemical ordering of Ag-Au 309-atom Mackay icosahedral nanoparticles. The energy of the nanoparticles is described using a cluster expansion model, and a Mixed Integer Programming (MIP) approach is used to find the exact ground state configurations for all stoichiometries. The chemical ordering varies widely between the different stoichiometries, and display a rich zoo of structures with non-trivial ordering.Comment: Revised version. New figure added, discussion expanded, some material moved into supplementary fil

Neural Message Passing with Edge Updates for Predicting Properties of Molecules and Materials

Neural message passing on molecular graphs is one of the most promising methods for predicting formation energy and other properties of molecules and materials. In this work we extend the neural message passing model with an edge update network which allows the information exchanged between atoms to depend on the hidden state of the receiving atom. We benchmark the proposed model on three publicly available datasets (QM9, The Materials Project and OQMD) and show that the proposed model yields superior prediction of formation energies and other properties on all three datasets in comparison with the best published results. Furthermore we investigate different methods for constructing the graph used to represent crystalline structures and we find that using a graph based on K-nearest neighbors achieves better prediction accuracy than using maximum distance cutoff or the Voronoi tessellation graph