Multiple Altitude Research Articles

Vertical Gradient of the Geomagnetic Field by Multiple Altitude Aeromagnetic Survey

Vertical Gradient of the Geomagnetic Field by Multiple Altitude Aeromagnetic Survey

Mixed FSO/RF Based Multiple HAPs Assisted Multiuser Multiantenna Terrestrial Communication

In this work, a mixed free-space optics (FSO)/radio-frequency (RF) based multiple serial high altitude platforms (HAPs) assisted multiuser multiantenna terrestrial communication system is considered. For the considered multi-hop system, earth station to HAP and HAP to HAP links are assumed as FSO links, and HAP to terrestrial mobile users (MUs) link is assumed as RF link. At the FSO detector both the heterodyne detection and intensity modulation direct detection techniques are considered. Atmospheric turbulence of the ES to HAP FSO link is modeled with Gamma-Gamma fading along with the pointing error impairments. As HAP situates in the stratosphere, negligible atmospheric turbulence exists at HAP altitude (20 km), hence, only pointing error is considered for the inter HAP links. Further, the HAP consists of multiantenna array to provide high data-rates to the terrestrial users via RF links, considered to be Nakagami-m distributed. The intermediate HAPs perform selective decode-and-forward relaying and opportunistic user scheduling is performed for the best user selection. For the performance analysis, analytical expression of overall outage probability is obtained and the impact of various selection parameters like pointing error, FSO detection type, MU selection, number of antennas, and RF fading severity are observed on the outage performance. Asymptotic outage probability is also derived to obtain the diversity order of the considered communication system. Further, considering various modulation schemes, a generalized average bit-error-rate expression is derived and the impact of pointing error, FSO detection type, MU selection, number of antennas, and RF fading severity are observed on its performance. Finally, derived results are validated through Monte-Carlo simulations.

Reinforcement learning versus swarm intelligence for autonomous multi-HAPS coordination

This work analyses the performance of Reinforcement Learning (RL) versus Swarm Intelligence (SI) for coordinating multiple unmanned High Altitude Platform Stations (HAPS) for communications area coverage. It builds upon previous work which looked at various elements of both algorithms. The main aim of this paper is to address the continuous state-space challenge within this work by using partitioning to manage the high dimensionality problem. This enabled comparing the performance of the classical cases of both RL and SI establishing a baseline for future comparisons of improved versions. From previous work, SI was observed to perform better across various key performance indicators. However, after tuning parameters and empirically choosing suitable partitioning ratio for the RL state space, it was observed that the SI algorithm still maintained superior coordination capability by achieving higher mean overall user coverage (about 20% better than the RL algorithm), in addition to faster convergence rates. Though the RL technique showed better average peak user coverage, the unpredictable coverage dip was a key weakness, making SI a more suitable algorithm within the context of this work.

Deep learning based banana plant detection and counting using high-resolution red-green-blue (RGB) images collected from unmanned aerial vehicle (UAV).

The production of banana—one of the highly consumed fruits—is highly affected due to loss of certain number of banana plants in an early phase of vegetation. This affects the ability of farmers to forecast and estimate the production of banana. In this paper, we propose a deep learning (DL) based method to precisely detect and count banana plants on a farm exclusive of other plants, using high resolution RGB aerial images collected from Unmanned Aerial Vehicle (UAV). An attempt to detect the plants on the normal RGB images resulted less than 78.8% recall for our sample images of a commercial banana farm in Thailand. To improve this result, we use three image processing methods—Linear Contrast Stretch, Synthetic Color Transform and Triangular Greenness Index—to enhance the vegetative properties of orthomosaic, generating multiple variants of orthomosaic. Then we separately train a parameter-optimized Convolutional Neural Network (CNN) on manually interpreted banana plant samples seen on each image variants, to produce multiple results of detection on our region of interest. 96.4%, 85.1% and 75.8% of plants were correctly detected on three of our dataset collected from multiple altitude of 40, 50 and 60 meters, of same farm. Further discussion on results obtained from combination of multiple altitude variants are also discussed later in the research, in an attempt to find better altitude combination for data collection from UAV for the detection of banana plants. The results showed that merging the detection results of 40 and 50 meter dataset could detect the plants missed by each other, increasing recall upto 99%.

Detailed study of the Mare Crisium northern magnetic anomaly

AbstractLow‐altitude Lunar Prospector (LP) magnetometer data for Mare Crisium show two magnetic anomalies near its inner northern and southern edges. Because these features are located inside a basin, they were likely formed by slow cooling of the basin's melt, or the partially melted mantle, instead of by any impact‐related shock magnetization process. Therefore, they are important for assessing the nature of the ancient dynamo field that produced them. In this study we confine our attention to the simpler northern anomaly (CNA) and use low‐altitude (∼22 km) LP data to model its source body as a dipole and magnetized disks of different radii. We infer that the source is likely located ∼20–30 km from the surface and horizontally localized within a small region (<1° or <∼30 km radius). The surface field intensity calculated from the best fit dipole is in good agreement with that obtained from LP Electron Reflectometer data. Our magnetization directions are substantially different from two previous studies, largely due to using lower altitude data to perform our inversions. We also find a surprising sensitivity to small changes in source body latitude (∼1°). The magnetic paleopoles implied by our best fit models are distant from previous estimates by up to ∼50° of great circle arc and are substantially distant from the Moon's present rotation axis. Our results demonstrate how multiple altitude data sets must be used when estimating paleopoles and other properties of even the simplest of the Moon's magnetic anomalies.

Reachability-Based Safety and Goal Satisfaction of Unmanned Aerial Platoons on Air Highways

Recently, there has been immense interest in using unmanned aerial vehicles for civilian operations. As a result, unmanned aerial systems traffic management is needed to ensure the safety and goal satisfaction of potentially thousands of unmanned aerial vehicles flying simultaneously. Currently, the analysis of large multi-agent systems cannot tractably provide these guarantees if the agents’ set of maneuvers is unrestricted. In this paper, platoons of unmanned aerial vehicles flying on air highways is proposed to impose an airspace structure that allows for tractable analysis. For the air highway placement problem, the fast marching method is used to produce a sequence of air highways that minimizes the cost of flying from an origin to any destination. The placement of air highways can be updated in real time to accommodate sudden airspace changes. Within platoons traveling on air highways, each vehicle is modeled as a hybrid system. Using Hamilton–Jacobi reachability, safety and goal satisfaction are guaranteed for all mode transitions. For a single altitude range, the proposed approach guarantees safety for one safety breach per vehicle; in the unlikely event of multiple safety breaches, safety can be guaranteed over multiple altitude ranges. This paper demonstrates the platooning concept through simulations of three representative scenarios.

Геоморфологічна будова Передкарпатської ділянки долини Бистриці-Підбузької

The geomorphological structure of one of the least explored river valleys of the north-west part of the Fore-Carpathians was discovered. Morphological, morphometric characteristics of the BystrytsiaPidbuzka terraces, the structure features of their deposits’ sections were described. The progress of the glacial morpholithogenetic processes in the north-west part of the Fore-Carpathians was detailed. It was found that the river valley has been actively developing during the Early Pleistocene epoch, when the Galician (the fifth over-floodplain) terrace and four different-age terraces, which have formed the Loyeva level (the sixth over-floodplain terrace) till now, and starosilska terrace, which is hypsographically above the Loyeva level and below the Krasna level, were formed. The benches between the bases of the multiple altitude horizons of alluvium of the identified terraces were mainly disguised by the loess cover that is why actually they were not evident in the terrain. During the Early Pleistocene epoch (the Oka stage), at the time of the deglaciation of the adjacent to the Carpathian Mountains interfluve areas of Stryvihor–Dnister and Dnister–Bystrytsia-Pidbuzka, the glacial meltwater flowed along the river valley to the south. This was illustrated by the fact of the covering of the “warm” alluvium of the channel and flood plain facies by the periglacial alluvium in the section of the Galician terrace of the Bystrytsia-Pidbuzka River. During the deglaciation process of the north-west part of the Dnister valley, the Chukva-Vilshanyk palaeovalley was also invoked. The history of its formation and the structure requires further appraisal up to now. Younger Middle-Upper Pleistocene terraces that were obviously “hidden” in the broad bottom of the river valley morphologically were not clearly demonstrated. According to the morphometric, morphological characteristics they corresponded to the first over-floodplain terrace and BystrytsiaPidbuzka floodplain. However, it has been reliably determined that only its upper 6 meters of the total 24–26-meter of the soft sediments of the mass, which was discovered in the bottom of the BystrytsiaPidbuzka River valley, have accumulated during the Holocene. The formation time of the middle and lower parts was not accurately determined so far. It is possible that it has begun to accumulate during the period of the glacial meltwater discharge, which flowed to the river valley, through both the ChukvaVilshanyk palaeovalley and the Upper-Dnister depression. The surface of the fluvioglacial deposits was covered with the Middle-Upper Pleistocene alluvium, and the section of the mentioned mass was finished by the Holocene alluvium. From the beginning of the Holocene the river valley was surrounded by the ascending tectonic movements, which were especially active on the area that is adjacent to the Carpathians, where their base was outcropped in sections the first over-floodplain terrace and the floodplain. Key words: terrace, Loyeva level, alluvium, loess, glacial meltwater, Upper-Dnister depression, Chukva-Vilshanyk palaeovalley.

Channel allocation for hot spot areas in HAPS communication based on the prediction of mobile user characteristics

AbstractHigh altitude platform station (HAPS) communication employs multiple high altitude platforms with the same bandwidth in order to serve the same region. This working mode greatly increases user capacity and improves frequency spectrum utilization, thus endowing HAPS communication with its superiority in solving hot spot issues. In this study, a standard for deciding the minimum distance in mobile user access systems was derived. Using this standard, channel allocation approaches based on the prediction of user number change and call volume change were proposed. These proposed approaches could effectively remove the problem of insufficient or wasted channels caused by the lack of proactive cooperation in conventional channel allocation methods. These approaches are validated through simulation, in which the proposed channel allocation approaches demonstrated the reasonable allocation of channels and the avoidance of call blocking while improving the utilization of channels.

Geopotential field anomaly continuation with multi-altitude observations

Conventional gravity and magnetic anomaly continuation invokes the standard Poisson boundary condition of a zero anomaly at an infinite vertical distance from the observation surface. This simple continuation is limited, however, where multiple altitude slices of the anomaly field have been observed. Increasingly, areas are becoming available which are constrained by multiple boundary conditions from surface, airborne, and satellite surveys. This paper describes the implementation of continuation with multi-altitude boundary conditions in Cartesian and spherical coordinates and investigates the advantages and limitations of these applications. Continuations by EPS (equivalent point source) inversion and the FT (Fourier transform), as well as by SCHA (spherical cap harmonic analysis) are considered. These methods were selected because they are especially well suited for analyzing multi-altitude data over finite patches of the earth such as those covered by the ADMAP database. In general, continuations constrained by multi-altitude data surfaces are invariably superior to those constrained by a single altitude data surface due to anomaly measurement errors and the non-uniqueness of continuation.

Reproducibility of Performance Changes to Simulated Live High/Train Low Altitude

Elite athletes often undertake multiple altitude exposures within and between training years in an attempt to improve sea level performance. To quantify the reproducibility of responses to live high/train low (LHTL) altitude exposure in the same group of athletes. Sixteen highly trained runners with maximal aerobic power (VO2max) of 73.1 +/- 4.6 and 64.4 +/- 3.2 mL x kg(-1) x min(-1) (mean +/- SD) for males and females, respectively, completed 2 x 3-wk blocks of simulated LHTL (14 h x d(-1), 3000 m) or resided near sea level (600 m) in a controlled study design. Changes in the 4.5-km time trial performance and physiological measures including VO2max, running economy and hemoglobin mass (Hb(mass)) were assessed. Time trial performance showed small and variable changes after each 3-wk altitude block in both the LHTL (mean [+/-90% confidence limits]: -1.4% [+/-1.1%] and 0.7% [+/-1.3%]) and the control (0.5% [+/-1.5%] and -0.7% [+/-0.8%]) groups. The LHTL group demonstrated reproducible improvements in VO2max (2.1% [+/-2.1%] and 2.1% [+/-3.9%]) and Hb(mass) (2.8% [+/-2.1%] and 2.7% [+/-1.8%]) after each 3-wk block. Compared with those in the control group, the runners in the LHTL group were substantially faster after the first 3-wk block (LHTL - control = -1.9% [+/-1.8%]) and had substantially higher Hb(mass) after the second 3-wk block (4.2% [+/-2.1%]). There was no substantial difference in the change in mean VO2max between the groups after the first (1.2% [+/-3.3%]) or second 3-wk block (1.4% [+/-4.6%]). Three-week LHTL altitude exposure can induce reproducible mean improvements in VO2max and Hb(mass) in highly trained runners, but changes in time trial performance seem to be more variable. Competitive performance is dependent not only on improvements in physiological capacities that underpin performance but also on a complex interaction of many factors including fitness, fatigue, and motivation.

Soil moisture mapping and AMSR-E validation using the PSR in SMEX02

Field experiments (SMEX02) were conducted to evaluate the effects of dense agricultural crop conditions on soil moisture retrieval using passive microwave remote sensing. Aircraft observations were collected using a new version of the Polarimetric Scanning Radiometer (PSR) that provided four C band and four X band frequencies. Observations were also available from the Aqua satellite Advanced Microwave Scanning Radiometer (AMSR-E) at these same frequencies. SMEX02 was conducted over a three-week period during the summer near Ames, Iowa. Corn and soybeans dominate the region. During the study period the corn was approaching its peak water content state and the soybeans were at the mid point of the growth cycle. Aircraft observations are compared to ground observations. Subsequently models are developed to describe the effects of corn and soybeans on soil moisture retrieval. Multiple altitude aircraft brightness temperatures were compared to AMSR-E observations to understand brightness temperature scaling and provide validation. The X-band observations from the two sensors were in reasonable agreement. The AMSR-E C-band observations were contaminated with anthropogenic RFI, which made comparison to the PSR invalid. Aircraft data along with ancillary data were used in a retrieval algorithm to map soil moisture. The PSR estimated soil moisture retrievals on a field-by-field comparison had a standard error of estimate (SEE) of 5.5%. The error reduced when high altitude soil moisture estimates were aggregated to 25 km resolution (same as AMSR-E EASE grid product resolution) (SEE ∼ 2.85%). These soil moisture products provide a validation of the AMSR retrievals. PSR/CX soil moisture images show spatial and temporal patterns consistent with meteorological and soil conditions. The dynamic range of the PSR/CX observations indicates that reasonable soil moisture estimates can be obtained from AMSR, even in areas of high vegetation biomass content (∼ 4–8 kg/m2).

Performance of Multiple High Altitude Platforms using Directive HAP and User Antennas

This paper examines the behaviour of system capacity in High Altitude Platform (HAP) communications systems as a function of antenna directivity and HAP positioning. Antenna models for the user and the HAP are discussed, and it is shown that a flat sidelobe antenna pattern is suitable for modelling multiple HAP constellations when HAPs are located outside the coverage area. Using a single HAP scenario it is shown how narrowing the HAP antenna beamwidth may give better downlink Carrier-to-Noise Ratio (CNR) over the most of the coverage area. The roles of the HAP antenna beamwidth, HAP antenna pointing and HAP spacing radius are investigated. An equation is derived to determine the location of the peak CNR combined with these three parameters. A more complex multiple HAP scenario where all HAP's operate on the same channel and interfere with each other is also assessed in terms of the Carrier to Interference plus Noise Ratio (CINR) and spectral efficiency. It is shown that locating HAPs at a specific spacing radius that is outside the coverage area can improve performance. Using these techniques the combined bandwidth efficiency is shown to increase almost pro-rata when the number of HAPs is increased up to 16.

Correction of thermal imagery for atmospheric effects using aircraft measurement and atmospheric modeling techniques

Airborne measurements of atmospheric-path transmission and atmospheric-path (upwelled) radiance in the 8–14-μm band were obtained by applying a multiple altitude and a dual-view angle calibration technique to thermal IR line scanner data. A spectrally corrected lowtran code was used to generate path transmission and upwelled radiance values corresponding to the empirical measurements. Using lowtran and the multiple-altitude method, calibration of thermograms to account for atmospheric effects yields computed surface temperatures within 0.7°C of concurrent kinetic temperature readings. The angular calibration method results in similar computed surface temperature errors for 304.8-m (1000-ft) altitude data and increasing by 1.2°C/304.8-m up to a 1828.8-m (6000-ft) altitude. This paper contains results of a comparative analysis of these approaches for atmospheric calibration.