Research and simulation of images classification algorithm for distributed objects obtained by remote sensing of the Earth's surface

Application of ultra-wideband signals and large apertures makes it possible to obtain a sufficiently detailed radar image of a spatially distributed object at the processing unit output. But the problem of optimal classification of synthetic aperture radar (SAR) data remains relevant due to specific features of radar images. The paper describes solution of the synthesis problem for optimal SAR image classification algorithm. The optimal set of very informative and small dimension features is found and features based on the moments of SAR images are proposed. A comparative analysis of classification algorithms using various features is made, and the ratio is proposed, which can be used as the classification sign that is invariant to object shift and to specific distortions caused by the object rotation. © 2016 Academic Publications, Ltd

Исследование и модификация метода формирования встречного вихревого поля для развертывания фазы

The paper focuses on the problem of the phase unwrapping in spaceborne remote-sensing interferometric synthesized aperture radar (InSAR) systems. Major unwrapping methods and techniques are considered and the modification of the inversed vortex phase field method of phase unwrapping for interferometric data processing of space-borne synthesized aperture radars is proposed. The modification includes the separation and unwrapping of the low-frequency phase only, and obtaining of the residual phase interferogram, which phase range does not exceed 1-2 ambiguity height values. This approach significantly reduces the number of phase residues and increases the processing speed. The other modification implies filter processing of the residual phase without phase unwrapping, which includes iterative separation of the low-frequency using the Gaussian filter and phase subtraction. This approach moves phase fringes to the relief inflection areas, and is similar to the minimum-cost flow unwrapping results. The computational complexity of the algorithm is proportional to the interferogram size and the number of the phase residues of the low-frequency phase interferogram. The accuracy of digital elevation models obtained by the algorithm was estimated using the ALOS PALSAR radar data and the reference altitude data. The results show, that the accuracy is compared with the minimum-cost flow method, but has the less computational complexity. Предложена модификация метода встречного вихревого поля для развертывания фазы при интерферометрической обработке данных космических радиолокаторов с синтезированной апертурой. Модификация включает в себя выделение и развертывание низкочастотной фазы, получение интерферограммы остаточной фазы и ее фильтровую обработку. Произведена оценка точности получаемых при помощи алгоритма цифровых моделей рельефа на примере интерферометрической обработки радиолокационных данных ALOS PALSAR с использованием эталонных высотных данных. Произведено сравнение точности с другими распространенными алгоритмами развертывания фазы.Сосновский А. В. Исследование и модификация метода формирования встречного вихревого поля для развертывания фазы. Ural Radio Engineering Journal. 2021;5(3):239–257. DOI: 10.15826/urej.2021.5.3.003

Ледовая энергетика: перспективы использования искусственных фирново-ледяных массивов для выработки электроэнергии

The problem of the fossil fuel depletion can be solved by means of searching, developing and using of alterna‑ tive energy sources. One of them is the use of thermogradient power plants, which are operating by the tem‑ perature difference of the ocean water near the surface and at great depths. But using of these plants is usu‑ ally limited by technical issues, and energy expenditures on the rise a large volume of water from the ocean depths. These problems can be solved using the natural cold accumulated in the artificial firn-ice massifs on the surface of the Earth. The application of a long jet sprinkler system makes possible for a day to create the firn-ice massifs with a height of over 10 meters. Relatively small number of sprinklers may be sufficient to freeze for the cold period a quantity of the firn-ice masses weighing millions of tons. Daily freezing pro‑ ductivity is approximately 75 tons of ice in recalculation per 1 degree of the air negative temperature. This method provides accumulation of huge reserves of natural cold, which can be stored for a long period of time with the use of thermal insulation. When freezing the firn-ice masses at the air temperature of −15 °С, 1 ton of firn requires energy of 0.5 kW·h, which is 190 times less than it is necessary for melting 1 ton of ice. The use of artificial firn-ice masses will accelerate the development and introduction of thermogradient power plants, and not only in the marine areas.Рассмотрен термоградиентный способ выработки электроэнергии на основе перепада температуры воды на поверхности и в глубине океана, отмечены его недостатки, которые можно устранить с помощью природного холода, аккумулируемого в фирново-ледяных массивах. Дана оценка производительности намораживания и расхода энергии на производство искусственного фирна. Определена эффективность разной теплоизоляции ледяного массива для снижения таяния

Coherence maps application for InSAR data accuracy improving

В работе представлен анализ методов применения карт когерентности для обработки интерферометрических пар изображений радиолокаторов с синтезированной апертурой (РСА). Экспериментально определены размеры окон усреднений, допустимых для решения практических задач. Представлен метод повышения точности цифровых моделей рельефа и карт подвижек рельефа, получаемых при интерферометрической съемке, основанный на маскировании карты когерентности. Показано повышение точности результата по сравнению с классической методикой.The paper presents the analysis of coherence maps application methods for the interferometric SAR images processing. The interferometric coherence is an important indicator of the reliability of the interferograms obtained by the interferometric synthetic aperture radar (InSAR), since the areas with low coherence values are unsuitable for processing the interferometric data. In addition, the coherence is used as a parameter of adaptive phase noise filters, and it can also be used for surface segmentation. The sizes of the averaging windows suitable for the solution of practical problems are experimentally determined. The method of accuracy increasing for the digital elevation maps and displacement maps obtained by InSAR systems based on masking the coherence map is presented. The DEM accuracy improvement in comparison with the classical estimation method is presented

InSAR Data Processing in Digital Elevation Models Creating Tasks: State-of-Art and Issues

Поступила: 10.07.2020. Принята в печать: 30.07.2020.Received: 10.07.2020. Accepted: 30.07.2020.Представлена ретроспектива и обзор современного состояния технологий интерферометрической обработки радиолокационных данных, получаемых космическими радиоэлектронными системами дистанционного зондирования Земли, в задачах построения цифровых моделей рельефа. Рассмотрены вопросы моделирования интерферометрической обработки радиолокационных данных и практических способов ее реализации, а также ошибок способы оценивания точности восстановления абсолютной фазы и рельефа местности.The paper presents a retrospective review and current state-of-art of radar data interferometric processing techniques (InSAR) in space-based radio-electronic systems of the remote sensing of the Earth in the tasks of digital elevation models (DEM) constructing. History of InSAR systems development and trends in the development of data processing methods are considered. It is shown, that InSAR systems take their origin from radio astronomic tasks, related to the Moon and planets’ surface investigations, carried out by the USA and the USSR in 1960th. Since 1980th the InSAR techniques are widely used for the Earth remote sensing tasks (digital elevation models creation, surface displacements detection, recognition of vegetation features, etc.), but the problems of absolute phase restoration inhibit the wide utilization of such systems in the Earth monitoring and mapping tasks, because the accuracy of digital elevation models obtained by such systems remains disputable. The mathematical model and principles of interferometric processing of data from satellite synthetic aperture radar are reviewed in conjunction with problems of absolute phase restoration errors measurement. We demonstrate, that despite the existing diversity of interferometric algorithms (i.e. phase noise filtration algorithms, phase unwrapping algorithms), the existing ways of accuracy assessment of the obtained result implies an end-to-end DEM validation, which complicates the comparative study of InSAR processing algorithms efficiency analysis. So, the author’s proposals for such analysis, based on reference DEM backward geocoding and error functions analysis, are reviewed. This approach allows identifying optimal values and combinations of parameters for interferometric algorithms at each processing stage, and it is applicable for remote sensing radar data obtained by different radar systems in different imaging modes

Phase noise suppression in interferometric radar data using goldstein noise filtration

The article is devoted the coherence maps utilization for the phase noise filtration using the Goldstein filter for interferometric synthesized aperture radar (InSAR) images. For the ALOS PALSAR data (FBS imaging mode), four coherence estimation techniques (classical, difference slope compensation, Fourier slope compensation, and «peak-Fourier») were researched as the Goldstein filter parameter. The filtered interferograms were compared with the reference ground control points reprojected into the radar coordinate system. It is shown that the coherence estimation method affects the quality of the phase noise suppression. © 2020 American Institute of Physics Inc.. All rights reserved.This work was supported by the Center of Excellence "Geoinformation technologies and geophysical data complex interpretation" of the Ural Federal University Program (Act 211 Government of the Russian Federation, contract N 02.A03.21.0006)

Investigation and modification of the inversed vortex phase field method for phase unwrapping

Поступила: 12.07.2021. Принята в печать: 05.08.2021.Received: 12.07.2021. Accepted: 05.08.2021.Предложена модификация метода встречного вихревого поля для развертывания фазы при интерферометрической обработке данных космических радиолокаторов с синтезированной апертурой. Модификация включает в себя выделение и развертывание низкочастотной фазы, получение интерферограммы остаточной фазы и ее фильтровую обработку. Произведена оценка точности получаемых при помощи алгоритма цифровых моделей рельефа на примере интерферометрической обработки радиолокационных данных ALOS PALSAR с использованием эталонных высотных данных. Произведено сравнение точности с другими распространенными алгоритмами развертывания фазы.The paper focuses on the problem of the phase unwrapping in spaceborne remote-sensing interferometric synthesized aperture radar (InSAR) systems. Major unwrapping methods and techniques are considered and the modification of the inversed vortex phase field method of phase unwrapping for interferometric data processing of space-borne synthesized aperture radars is proposed. The modification includes the separation and unwrapping of the low-frequency phase only, and obtaining of the residual phase interferogram, which phase range does not exceed 1–2 ambiguity height values. This approach significantly reduces the number of phase residues and increases the processing speed. The other modification implies filter processing of the residual phase without phase unwrapping, which includes iterative separation of the low-frequency using the Gaussian filter and phase subtraction. This approach moves phase fringes to the relief inflection areas, and is similar to the minimum-cost flow unwrapping results. The computational complexity of the algorithm is proportional to the interferogram size and the number of the phase residues of the lowfrequency phase interferogram. The accuracy of digital elevation models obtained by the algorithm was estimated using the ALOS PALSAR radar data and the reference altitude data. The results show, that the accuracy is compared with the minimum-cost flow method, but has less computational complexity

The problem of quality assessing for the methods of coherence maps calculation in InSAR remote sensing of the Earth data processing

Interferometric coherence is an important indicator of the quality of interferograms obtained by synthetic aperture interferometric radars (InSAR), because the areas with low coherence are not suitable for interferometric data processing. The coherence value is used as a parameter for adaptive phase noise suppression algorithms. It can also be used for surface classification tasks. The paper investigates the problem of the coherence estimate reducing under the influence of the topographic phase slope and considers ways to reduce the impact of the slope on the estimate value. The paper presents a comparative efficiency analysis of four methods for coherence maps calculation used for the phase noise suppression on the interferograms by a spectral adaptive filter in interferometric data processing for the Earth's remote sensing space radar ALOS PALSAR. © Published under licence by IOP Publishing Ltd

Влияние снежного покрова на охлаждение поверхностного слоя ледника Восточный Грёнфьорд (Шпицберген)

The purpose of this research is to estimate the effect of snow cover on the store of cold of the glacier surface layer. The store of cold is a complex parameter that shows the degree of cooling of the surface layer of the glacier at the end of the cold period. This value is determined with regard for the dynamics of air temperature and snow cover, changes in the density and structure of snow, and the moisture content (water store) in the snow and firn layer by the beginning of the cold period. Analysis of data from measurements of the thermal regime of the upper 11‑meter layer of the East Grenfjord Glacier demonstrated that effect of the snow cover depth (thickness) on the store of cold is ambiguous: when the depth increases, the store of cold can both increase and decrease. For example, in the colder winter of 2013, the store of cold in the upper 11‑meter layer of the glacier was smaller than the similar value in the warmer and snowier winter of 2014. It was found that this was caused by influence of thaws and rains in the winter of 2014. They could produce changes in the structure of the snow cover: an increase in its density and hardness after freezing of ice grains, as well as increase thermal conductivity that could result in more significant cooling of the surface layer of the glacier this winter. Numerical experiments made possible to establish the dependence of the store of cold in the upper layer of the glacier on meteorological conditions and the snow depth. Calculations have shown that with the depth of 50 cm, a rise of winter air temperature by 1 °C reduces the store of cold, on average, by 8.5 MJ/m2, whereas with a snow thickness of 200 cm, the decrease is 6 MJ/m2. Increasing the snow thickness from 50 to 100 cm reduces the store of cold by 11 MJ/m2 at −6 °C, and by 15 MJ/m2 at −10 °C. And growth of snow thickness from 150 to 200 cm decreases the store of cold by 4 MJ/m2 at the temperature of −6 °C, and by 3 MJ/m2 at −10 °C. According to calculations for the compact snow with a thickness of 150 cm at −10 °C, the store of cold increases by 12% as compared with the average snow hardness. A more significant difference in the value of the store of cold happens when the stratigraphy of the snow cover is not taken into account. Note also, that when modeling the temperature regime and estimating the store of cold in the ice at the end of the cold period, one should take into account the moisture content of the upper 1-m ice layer at the end of the ablation period.На основе математического моделирования оценено влияния параметров снежного покрова и температуры воздуха на запас холода поверхностного слоя ледника Восточный Грёнфьорд. При увеличении толщины снежного покрова может происходить как уменьшение, так и увеличение запаса холода. Причина этого заключается в разной стратиграфии снежного покрова из-за оттепе‑ лей и жидких осадков. Рассмотрено влияние твёрдости снега и стратиграфии снежного покрова на запас холода верхнего слоя ледника