Atmospheric Horizontal-Inhomogeneity Effects on the Optical Depths Determined by the Double-Elevation-Angle Lidar Technique

1989 ◽  
Author(s):  
Merle R. Paulson
Keyword(s):  
Elevation Angle ◽  
Horizontal Inhomogeneity

The elevation angle of the vagina (EAV) following different pelvic reconstructive procedures

2018 ◽  
Author(s):  
J Neymeyer ◽  
AY Weintraub ◽  
S Weinberger ◽  
DE Moldovan ◽  
K Kornienko ◽  
...  
Keyword(s):  
Elevation Angle ◽  
Reconstructive Procedures

scholarly journals Accuracy of Doppler Determinations of Station Positions

1972 ◽  
Vol 48 ◽  
pp. 101-103
Author(s):  
R. J. Anderle
Keyword(s):  
Elevation Angle ◽  
High Elevation ◽  
Time Of Day ◽  
Satellite Observations ◽  
Standard Errors ◽  
Lower Elevation ◽  
Self Consistent

Locations of Doppler satellite observing stations have been revised to obtain a set which is more self-consistent and more consistent with the CIO pole. Residuals of satellite observations for 1970 have been analyzed using the new coordinates to determine mean and standard errors for five days of observations of latitude versus station, time of day, and elevation angle. The accuracy of the determination of latitude is about 4 meters at moderate and high elevation angles. But since more satellite passes occur at lower elevation angles, the accuracy of determination of a component of position based on five days of observation of one satellite is only about 2 meters.

scholarly journals Spectral albedo of coastal landfast sea ice in Prydz Bay, Antarctica

2020 ◽  
pp. 1-11
Author(s):  
Guanghua Hao ◽  
Roberta Pirazzini ◽  
Qinghua Yang ◽  
Zhongxiang Tian ◽  
Changwei Liu
Keyword(s):  
Sea Ice ◽  
Near Infrared ◽  
Elevation Angle ◽  
Early Summer ◽  
Prydz Bay ◽  
Katabatic Wind ◽  
Surface Conditions ◽  
Zhongshan Station ◽  
Landfast Sea Ice ◽  
Two Phases

Abstract The surface spectral albedo was measured over coastal landfast sea ice in Prydz Bay (off Zhongshan Station), East Antarctica from 5 October to 26 November of 2016. The mean albedo decreased from late-spring to early-summer, mainly responding to the change in surface conditions from dry (phase I) to wet (phase II). The evolution of the albedo was strongly influenced by the surface conditions, with alternation of frequent snowfall events and katabatic wind that induce snow blowing at the surface. The two phases and day-to-day albedo variability were more pronounced in the near-infrared albedo wavelengths than in the visible ones, as the near-infrared photons are more sensitive to snow metamorphism, and to changes in the uppermost millimeters and water content of the surface. The albedo diurnal cycle during clear sky conditions was asymmetric with respect to noon, decreasing from morning to evening over full and patchy snow cover, and decreasing more rapidly in the morning over bare ice. We conclude that snow and ice metamorphism and surface melting dominated over the solar elevation angle dependency in shaping the albedo evolution. However, we realize that more detailed surface observations are needed to clarify and quantify the role of the various surface processes.

scholarly journals Measurement of the Sea Surface Height with Airborne GNSS Reflectometry and Delay Bias Calibration

2021 ◽  
Vol 13 (15) ◽  
pp. 3014
Author(s):  
Feng Wang ◽  
Dongkai Yang ◽  
Guodong Zhang ◽  
Jin Xing ◽  
Bo Zhang ◽  
...  
Keyword(s):  
Wind Speed ◽  
Arrival Time ◽  
Elevation Angle ◽  
Satellite System ◽  
Sea Surface Height ◽  
Antenna Pattern ◽  
Sea Surface ◽  
Observation Method ◽  
Global Navigation Satellite ◽  
The Impact

Sea surface height can be measured with the delay between reflected and direct global navigation satellite system (GNSS) signals. The arrival time of a feature point, such as the waveform peak, the peak of the derivative waveform, and the fraction of the peak waveform is not the true arrival time of the specular signal; there is a bias between them. This paper aims to analyze and calibrate the bias to improve the accuracy of sea surface height measured by using the reflected signals of GPS CA, Galileo E1b and BeiDou B1I. First, the influencing factors of the delay bias, including the elevation angle, receiver height, wind speed, pseudorandom noise (PRN) code of GPS CA, Galileo E1b and BeiDou B1I, and the down-looking antenna pattern are explored based on the Z-V model. The results show that (1) with increasing elevation angle, receiver height, and wind speed, the delay bias tends to decrease; (2) the impact of the PRN code is uncoupled from the elevation angle, receiver height, and wind speed, so the delay biases of Galileo E1b and BeiDou B1I can be derived from that of GPS CA by multiplication by the constants 0.32 and 0.54, respectively; and (3) the influence of the down-looking antenna pattern on the delay bias is lower than 1 m, which is less than that of other factors; hence, the effect of the down-looking antenna pattern is ignored in this paper. Second, an analytical model and a neural network are proposed based on the assumption that the influence of all factors on the delay bias are uncoupled and coupled, respectively, to calibrate the delay bias. The results of the simulation and experiment show that compared to the meter-level bias before the calibration, the calibrated bias decreases the decimeter level. Based on the fact that the specular points of several satellites are visible to the down-looking antenna, the multi-observation method is proposed to calibrate the bias for the case of unknown wind speed, and the same calibration results can be obtained when the proper combination of satellites is selected.

scholarly journals JOINT AZIMUTH AND ELEVATION ANGLE ESTIMATION USING MATRIX COMPLETION METHOD

2017 ◽  
Vol 57 ◽  
pp. 197-203
Author(s):  
Peixiang Tan ◽  
Yuntao Wu ◽  
Ge Yan ◽  
Jieyi Deng
Keyword(s):  
Matrix Completion ◽  
Elevation Angle ◽  
Angle Estimation

scholarly journals Comparison of solar power measurements in alpine areas using a mobile dual-axis tracking system

2019 ◽  
Vol 2 (S1) ◽  
Author(s):  
Jelenko Karpić ◽  
Ekanki Sharma ◽  
Tamer Khatib ◽  
Wilfried Elmenreich
Keyword(s):  
High Altitude ◽  
Peak Power ◽  
Power Plants ◽  
Low Cost ◽  
Elevation Angle ◽  
Test Site ◽  
Maximum Power ◽  
Maximum Power Point ◽  
Photovoltaic Power ◽  
Power Point

Abstract The rising demand for sustainable energy requires to identify the sites for photovoltaic systems with the best performance. This paper tackles the question of feasibility of photovoltaic power plants at high altitude. A direct comparison between an alpine and an urban area site is conducted in the south of Austria. Two low-cost automatic photovoltaic power measurement devices with dual-axis sun tracking and maximum power point tracking are deployed at two test sites. The system periodically performs a scan over the southern semihemisphere and executes maximum power point adjustment in order to assess the performance for a given direction. The gathered data shows a higher photovoltaic power yield in the higher altitude test site. Furthermore, the high altitude photovoltaic power as a function of azimuth and elevation angle appears to be not only higher but also more flat than in lower altitudes. This indicates a lower power loss in case of deviation from the optimal solar angles. The results show that even on low-cost hardware a difference in photovoltaic power can be observed, even though in this experiment it amounts to less than 5% increase of peak power in higher altitudes. However, the measured peak powers on the mountain are more stable and therefore closer to a constant level than the heavily fluctuating peak power values at the low altitude site. Additionally, a slight shift in optimal elevation angles between altitudes can be observed, as the optimum angle turns out to be lower on the high altitude site. This angle shift could be caused by snow reflections on the mountainous test site.

scholarly journals Long-Term Observations of Microwave Brightness Temperatures over a Metropolitan Area: Comparison of Radiometric Data and Spectra Simulated with the Use of Radiosonde Measurements

2021 ◽  
Vol 13 (11) ◽  
pp. 2061
Author(s):  
Mikhail V. Belikovich ◽  
Mikhail Yu. Kulikov ◽  
Dmitry S. Makarov ◽  
Natalya K. Skalyga ◽  
Vitaly G. Ryskin ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Elevation Angle ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Systematic Bias ◽  
Tropospheric Temperature ◽  
Absorption Model ◽  
60 Ghz ◽  
Error Budget ◽  
The Difference

Ground-based microwave radiometers are increasingly used in operational meteorology and nowcasting. These instruments continuously measure the spectra of downwelling atmospheric radiation in the range 20–60 GHz used for the retrieval of tropospheric temperature and water vapor profiles. Spectroscopic uncertainty is an important part of the retrieval error budget, as it leads to systematic bias. In this study, we analyze the difference between observed and simulated microwave spectra obtained from more than four years of microwave and radiosonde observations over Nizhny Novgorod (56.2° N, 44° E). We focus on zenith-measured and elevation-scanning data in clear-sky conditions. The simulated spectra are calculated by a radiative transfer model with the use of radiosonde profiles and different absorption models, corresponding to the latest spectroscopy research. In the case of zenith-measurements, we found a systematic bias (up to ~2 K) of simulated spectra at 51–54 GHz. The sign of bias depends on the absorption model. A thorough investigation of the error budget points to a spectroscopic nature of the observed differences. The dependence of the results on the elevation angle and absorption model can be explained by the basic properties of radiative transfer and by cloud contamination at elevation angles.

scholarly journals Measurements of the 3.3 μm Diffuse Galactic Emission Feature with AROME

1990 ◽  
Vol 139 ◽  
pp. 212-213
Author(s):  
M. Giard ◽  
F. Pajot ◽  
J. M. Lamarre ◽  
G. Serra
Keyword(s):  
Surface Brightness ◽  
Galactic Plane ◽  
Elevation Angle ◽  
Emission Feature ◽  
Field Of View ◽  
Interstellar Matter ◽  
Galactic Emission ◽  
Polycyclic Aromatic ◽  
Hydrocarbon Molecules ◽  
Ir Emission

AROME∗ is a balloon-borne experiment which was built to carry out measurements of IR emission features in the diffuse galactic flux. The field of view is 0.5° and surface brightness gradients are detected through azimuthal scanning at a constant elevation angle. The detection of a feature is done by comparison of the fluxes measured in narrow and wide photometric bands centered on the feature's wavelength. Two flights have been performed (August 1987, October 1988), which detected a 3.3 μm feature in the direction of the galactic plane −6° < b < 6°, 60° > l > −50°. Since this feature is characteristic of aromatic C-H bonds, we assigned it to the emission of transiently heated polycyclic aromatic hydrocarbon molecules (PAHs). With this assumption, AROME measurements show that PAHs are an ubiquitous component of the interstellar matter which contain about 10% of the available cosmic carbon.

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