Готові списки джерел за темами / Zenith angle measurement

Добірка наукової літератури з теми "Zenith angle measurement"

Автор: Grafiati
Опубліковано: 30 травня 2022
Оновлено: 31 травня 2022

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Статті в журналах з теми "Zenith angle measurement"

1

Yang, Yao, Wanchao Ma, Zhe Wang, Kai Zhang, and Xikui Miao. "Research on Improved Method of Schlick Model Based on BRDF Measurement." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 36, no. 6 (December 2018): 1069–75. http://dx.doi.org/10.1051/jnwpu/20183661069.

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In simulating an infrared scene, the Schlick model uses a commonly-used bidirectional reflection distributional function(BRDF) model. Through simulation and BRDF measurement, this paper points out that the Schlick model is in better agreement with the actual output when the emerging zenith angle is smaller than the incident zenith angle. But when the emerging zenith angle is a certain angle larger than the incident zenith angle, the output of the function value may increase with the increasing emerging zenith angle and may not be in agreement with the actual output. In this paper, a new improved Schlick model is proposed, and a cosine compensation function is designed based on Lambert reflection principle. When the zenith angle is larger than the incident zenith angle, which guarantees the monotonous decreasing of the output of the function through the compensation function when the emerging zenith angle is larger than the incident zenith angle. The results on comparison with experimental data show that the improved Schlick model is basically in agreement with experimental results. The results on comparison with the heightened illumination effect of the fighters model show that the heightened illumination effect produced with the improved Schlick model is superior to that produced with the original Schlick model.
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2

Blanc, P., and L. Wald. "On the effective solar zenith and azimuth angles to use with measurements of hourly irradiation." Advances in Science and Research 13 (February 2, 2016): 1–6. http://dx.doi.org/10.5194/asr-13-1-2016.

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Abstract. Several common practices are tested for assessing the effective solar zenith angle that can be associated to each measurement in time-series of in situ or satellite-derived measurements of hourly irradiation on horizontal surface. High quality 1 min measurements of direct irradiation collected by the BSRN stations in Carpentras in France and Payerne in Switzerland, are aggregated to yield time series of hourly direct irradiation on both horizontal and normal planes. Time series of hourly direct horizontal irradiation are reconstructed from those of hourly direct normal irradiation and estimates of the effective solar zenith angle by one of the six practices. Differences between estimated and actual time series of the direct horizontal irradiation indicate the performances of six practices. Several of them yield satisfactory estimates of the effective solar angles. The most accurate results are obtained if the effective angle is computed by two time series of the direct horizontal and normal irradiations that should be observed if the sky were cloud-free. If not possible, then the most accurate results are obtained from using irradiation at the top of atmosphere. Performances show a tendency to decrease during sunrise and sunset hours. The effective solar azimuth angle is computed from the effective solar zenith angle.
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3

Anandan, V. K., I. Srinivasa Rao, and P. Narasimha Reddy. "A Study on Optimum Tilt Angle for Wind Estimation Using Indian MST Radar." Journal of Atmospheric and Oceanic Technology 25, no. 9 (September 1, 2008): 1579–89. http://dx.doi.org/10.1175/2008jtecha1030.1.

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Abstract The effect of tilt angle on horizontal wind estimation is studied using Indian mesosphere–stratosphere–troposphere (MST) radar located at Gadanki (13.45°N, 79.18°E). It operates in Doppler beam swinging (DBS) mode with a beamwidth of 3°. Horizontal winds are computed for different tilt angles from 3° to 15° with an increment of 3° from a height range of 3.6–18 km. The effective beam pointing angle (θeff) is calculated to determine the effect of aspect sensitivity on the determination of horizontal wind components. For different tilt angles radar-derived winds are compared with simultaneous GPS sonde wind measurements, which were launched from a nearby site. The first method utilizes direct comparison of radar-derived winds with those of GPS sondes using the actual beam pointing angle; the second method uses the effective beam pointing angle derived from the ratios of two oblique beams. For this study a variety of statistics were explored in terms of standard deviation, correlation coefficient, and percentage error. From the results it is observed that in agreement with previous studies, the effective beam pointing angle deviates from the actual beam pointing angle, which results in the underestimation of horizontal wind components, and also when tilt angle is close to zenith and far from zenith, the estimation of horizontal winds is found to be far from true values at different heights. Radar wind estimation has better agreement with GPS sonde measurement when the off-zenith angle is around 10°. It is also found that correction to the actual beam pointing angle provides 3%–6% improved agreement between the radar and GPS wind measurements.
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4

Bhadra, S., V. Sagan, C. Nguyen, M. Braud, A. L. Eveland, and T. C. Mockler. "AUTOMATIC EXTRACTION OF SOLAR AND SENSOR IMAGING GEOMETRY FROM UAV-BORNE PUSH-BROOM HYPERSPECTRAL CAMERA." ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences V-3-2022 (May 17, 2022): 131–37. http://dx.doi.org/10.5194/isprs-annals-v-3-2022-131-2022.

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Abstract. Calculating solar-sensor zenith and azimuth angles for hyperspectral images collected by UAVs are important in terms of conducting bi-directional reflectance function (BRDF) correction or radiative transfer modeling-based applications in remote sensing. These applications are even more necessary to perform high-throughput phenotyping and precision agriculture tasks. This study demonstrates an automated Python framework that can calculate the solar-sensor zenith and azimuth angles for a push-broom hyperspectral camera equipped in a UAV. First, the hyperspectral images were radiometrically and geometrically corrected. Second, the high-precision Global Navigation Satellite System (GNSS) and Inertial Measurement Unit (IMU) data for the flight path was extracted and corresponding UAV points for each pixel were identified. Finally, the angles were calculated using spherical trigonometry and linear algebra. The results show that the solar zenith angle (SZA) and solar azimuth angle (SAA) calculated by our method provided higher precision angular values compared to other available tools. The viewing zenith angle (VZA) was lower near the flight path and higher near the edge of the images. The viewing azimuth angle (VAA) pattern showed higher values to the left and lower values to the right side of the flight line. The methods described in this study is easily reproducible to other study areas and applications.
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5

Bogren, W. S., J. F. Burkhart, and A. Kylling. "Tilt error in cryospheric surface radiation measurements at high latitudes: a model study." Cryosphere Discussions 9, no. 4 (August 18, 2015): 4355–76. http://dx.doi.org/10.5194/tcd-9-4355-2015.

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Abstract. We have evaluated the magnitude and makeup of error in cryospheric radiation observations due to small sensor misalignment in in-situ measurements of solar irradiance. This error is examined through simulation of diffuse and direct irradiance arriving at a detector with a cosine-response foreoptic. Emphasis is placed on assessing total error over the solar shortwave spectrum from 250 to 4500 nm, as well as supporting investigation over other relevant shortwave spectral ranges. The total measurement error introduced by sensor tilt is dominated by the direct component. For a typical high latitude albedo measurement with a solar zenith angle of 60°, a sensor tilted by 1, 3, and 5° can respectively introduce up to 2.6, 7.7, and 12.8 % error into the measured irradiance and similar errors in the derived albedo. Depending on the daily range of solar azimuth and zenith angles, significant measurement error can persist also in integrated daily irradiance and albedo.
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6

Bogren, Wiley Steven, John Faulkner Burkhart, and Arve Kylling. "Tilt error in cryospheric surface radiation measurements at high latitudes: a model study." Cryosphere 10, no. 2 (March 15, 2016): 613–22. http://dx.doi.org/10.5194/tc-10-613-2016.

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Анотація:
Abstract. We have evaluated the magnitude and makeup of error in cryospheric radiation observations due to small sensor misalignment in in situ measurements of solar irradiance. This error is examined through simulation of diffuse and direct irradiance arriving at a detector with a cosine-response fore optic. Emphasis is placed on assessing total error over the solar shortwave spectrum from 250 to 4500 nm, as well as supporting investigation over other relevant shortwave spectral ranges. The total measurement error introduced by sensor tilt is dominated by the direct component. For a typical high-latitude albedo measurement with a solar zenith angle of 60°, a sensor tilted by 1, 3, and 5° can, respectively introduce up to 2.7, 8.1, and 13.5 % error into the measured irradiance and similar errors in the derived albedo. Depending on the daily range of solar azimuth and zenith angles, significant measurement error can persist also in integrated daily irradiance and albedo. Simulations including a cloud layer demonstrate decreasing tilt error with increasing cloud optical depth.
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7

Appeltans, Simon, Angela Guerrero, Said Nawar, Jan Pieters, and Abdul M. Mouazen. "Practical Recommendations for Hyperspectral and Thermal Proximal Disease Sensing in Potato and Leek Fields." Remote Sensing 12, no. 12 (June 15, 2020): 1939. http://dx.doi.org/10.3390/rs12121939.

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Thermal and hyperspectral proximal disease sensing are valuable tools towards increasing pesticide use efficiency. However, some practical aspects of the implementation of these sensors remain poorly understood. We studied an optimal measurement setup combining both sensors for disease detection in leek and potato. This was achieved by optimising the signal-to-noise ratio (SNR) based on the height of measurement above the crop canopy, off-zenith camera angle and exposure time (ET) of the sensor. Our results indicated a clear increase in SNR with increasing ET for potato. Taking into account practical constraints, the suggested setup for a hyperspectral sensor in our experiment involves (for both leek and potato) an off-zenith angle of 17°, height of 30 cm above crop canopy and ET of 1 ms, which differs from the optimal setup of the same sensor for wheat. Artificial light proved important to counteract the effect of cloud cover on hyperspectral measurements. The interference of these lamps with thermal measurements was minimal for a young leek crop but increased in older leek and after long exposure. These results indicate the importance of optimising the setup before measurements, for each type of crop.
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8

Rahlves, Charlotte, Frank Beyrich, and Siegfried Raasch. "Scan strategies for wind profiling with Doppler lidar – an large-eddy simulation (LES)-based evaluation." Atmospheric Measurement Techniques 15, no. 9 (May 9, 2022): 2839–56. http://dx.doi.org/10.5194/amt-15-2839-2022.

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Abstract. Doppler-lidar scan techniques for wind profiling rely on the assumption of a horizontally homogeneous wind field and stationarity for the duration of the scan. As this condition is mostly violated in reality, detailed knowledge of the resulting measurement error is required. The objective of this study is to quantify and compare the expected error associated with Doppler-lidar wind profiling for different scan strategies and meteorological conditions by performing virtual Doppler-lidar measurements implemented in a large-eddy simulation (LES) model. Various factors influencing the lidar retrieval error are analyzed through comparison of the wind measured by the virtual lidar with the “true” value generated by the LES. These factors include averaging interval length, zenith angle configuration, scan technique and instrument orientation (cardinal direction). For the first time, ensemble simulations are used to determine the statistically expected uncertainty of the lidar error. The analysis reveals a root-mean-square deviation (RMSD) of less than 1 m s−1 for 10 min averages of wind speed measurements in a moderately convective boundary layer, while RMSD exceeds 2 m s−1 in strongly convective conditions. Unlike instrument orientation with respect to the main flow and scanning scheme, the zenith angle configuration proved to have significant effect on the retrieval error. Horizontal wind speed error is reduced when a larger zenith angle configuration is used but is increased for measurements of vertical wind. Furthermore, we find that extending the averaging interval length of lidar measurements reduces the error. In addition, a longer duration of a full scan cycle and hence a smaller number of scans per averaging interval increases the error. Results suggest that the scan strategy has a measurable impact on the lidar retrieval error and that instrument configuration should be chosen depending on the quantity of interest and the flow conditions in which the measurement is performed.
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9

Chen, D., B. Zhou, S. Beirle, L. M. Chen, and T. Wagner. "Tropospheric NO<sub>2</sub> column densities deduced from zenith-sky DOAS measurements in Shanghai, China, and their application to satellite validation." Atmospheric Chemistry and Physics Discussions 8, no. 4 (September 3, 2008): 16713–62. http://dx.doi.org/10.5194/acpd-8-16713-2008.

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Abstract. Zenith-sky scattered sunlight observations using differential optical absorption spectroscopy (DOAS) technique were carried out in Shanghai, China (31.3° N, 121.5° E) since December 2006. At this polluted urban site, the measurement provided NO2 total columns in the daytime. Here, we present a new method to extract time series of tropospheric vertical column densities (VCD) of NO2 from these observations. The derived tropospheric NO2 VCD is an important quantity for the estimation of emissions and for the validation of satellite observations. Our method makes use of assumptions on the relative NO2 height profiles and on the diurnal variation of the stratospheric NO2 VCD. The influence of these parameters on the retrieved tropospheric NO2 VCD is discussed; for a polluted site like Shanghai, the accuracy of our method is estimated to be <20% for solar zenith angle (SZA) lower than 85°. From simultaneously performed long-path DOAS measurement, the NO2 surface concentration at the same site was observed and the corresponding tropospheric NO2 VCD was estimated using the assumed seasonal NO2 profiles in the planetary boundary layer (PBL). By making a comparison between the tropospheric NO2 VCD from zenith-sky and long-path DOAS measurements, it was found that the former provided more realistic information about total tropospheric pollution than the latter, so it's more suitable for satellite data validation than the in situ measurement. A comparison between the tropospheric NO2 VCD from ground-based zenith-sky measurement and SCIAMACHY was also made. Satellite validation for a strongly polluted area is highly needed, but exhibits also a great challenge. Our comparison showed good agreement, considering in particular the different spatial resolutions between the two measurements.
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10

Kamil Krasuski and Artur Gos. "The Numerical Simulation of the Atmosphere Delays Impact on Radar Measurement in Aviation." Communications - Scientific letters of the University of Zilina 21, no. 4 (October 1, 2019): 19–26. http://dx.doi.org/10.26552/com.c.2019.4.19-26.

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The article presents numerical simulations with regard to determining the impact of the ionospheric and tropospheric delays on a radar-aircraft slant distance measurement. During the first experimental test, numerical calculations were made, showing the relationship between the ionosphere correction and the zenith angle in order to determine the measurement error of a radar-aircraft slant distance. During the second experimental test, numerical calculations were made demonstrating a relationship between the tropospheric correction and zenith angle in order to determine a measurement error of a radar-aircraft slant distance. The experimental test was conducted for the primary surveillance radar AVIA-W located on the grounds of the military aerodrome EPDE in Deblin. Based on the conducted research tests, it was found that the impact of the ionosphere delay can cause an error in a radar measurement above 4m. Moreover, influence of the troposphere delay can cause an error of a radar measurement by approximately 0.2m. The numerical simulation made in this research study may be used in the radiolocation of moving objects, as well as the GNSS satellite navigation in aviation.
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Дисертації з теми "Zenith angle measurement"

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Зубик, Назар Олександрович. "Інклінометр (вимірювальний перетворювач для визначення зенітного кута)". Bachelor's thesis, КПІ ім. Ігоря Сікорського, 2021. https://ela.kpi.ua/handle/123456789/42226.

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В роботі представлено спроектовану систему вимірювання зенітного кута інклінометра. Проведено огляд засобів вимірювання зенітного кута інклінометра представлено історичний огляд розвитку систем вимірювання зенітного кута на базі акселерометрів і гіроскопів. Розроблено програмну модель інклінометра та проведено дослідження в середовищі MatLab. Розроблено конструктивну схему вимірювача зенітного кута та представлена принципова схема акселерометра
Current paper presents a system designed for measuring of an inclinometer’s zenith angle. The review of measurement instruments of an inclinometer’s zenith angle is performed. In addition, the historical review of measurement systems for zenith angle based on accelerometers and gyroscopes is presented. The research and the software model of the inclinometer was performed in the MatLab environment. The constructive scheme of the zenith angle meter is developed and the principal diagram of the accelerometer is presented.
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2

Reddy, Niveditha Hanumantha. "A procedure to predict the energy harvest of photovoltaic arrays using only global horizontal radiation measurements." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-05-1355.

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This thesis uses the results of analysis of data recorded at a solar monitoring station in West Texas and the knowledge from an existing solar radiation estimation model to develop a methodology to predict the energy output from a panel at a site using only partial radiation data - global horizontal radiation measurements. The prediction using partial data is validated against estimates acquired using the complete radiation data and constraints are defined for accurate prediction. The methodology presented in this thesis can be used to accurately predict the solar power/energy incident on a collector at any location possessing global horizontal radiation measurements.
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Книги з теми "Zenith angle measurement"

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Iwatsubo, E. Y. Measurements of slope distances and zenith angles at Newberry and South Sister volcanoes, Oregon, 1985-1986. [Menlo Park, Calif.]: U.S. Geological Survey, 1988.

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2

Measurements of slope distances and zenith angles at Newberry and South Sister volcanoes, Oregon, 1985-1986. [Denver, Colo.?]: U.S. Dept. of the Interior, Geological Survey, 1988.

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3

Y, Iwatsubo E., and Geological Survey (U.S.), eds. Measurements of slope distances and zenith angles at Augustine Volcano, Alaska, 1986, 1988, and 1989. Anchorage, Alaska: Dept. of the Interior, U.S. Geological Survey, 1998.

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Частини книг з теми "Zenith angle measurement"

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Sliney, David H., Rodney L. Wood, Patrick M. Moscato, Wesley J. Marshall, and Paul Eriksen. "Ultraviolet Exposure in the Outdoor Environment: Measurements of Ambient Ultraviolet Exposure Levels at Large Zenith Angles." In NATO ASI Series, 169–80. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4899-0661-8_12.

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2

"zenith angle measurement." In Dictionary Geotechnical Engineering/Wörterbuch GeoTechnik, 1547. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-41714-6_260007.

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Тези доповідей конференцій з теми "Zenith angle measurement"

1

Bae, Junghyun, Stylianos Chatzidakis, and Robert Bean. "Effective Solid Angle Model and Monte Carlo Method: Improved Estimations to Measure Cosmic Muon Intensity at Sea Level in All Zenith Angles." In 2021 28th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/icone28-63444.

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Abstract Cosmic muons are highly energetic and penetrative particles and these figures are used for imaging of large and dense objects such as spent nuclear fuels in casks and special nuclear materials in cargo. Cosmic muon intensity depends on the incident angle (zenith angle, φ), and it is known that I(φ) = I0 cos2 φ at sea level. Low intensity of cosmic muon requires long measurement time to acquire statistically meaningful counts. Therefore, high-energy particle simulations e.g., GEANT4, are often used to guide measurement studies. However, the measurable cosmic muon count rate changes upon detector geometry and configuration. Here we develop an “effective solid angle” model to estimate experimental results more accurately than the simple cosine-squared model. We show that the cosine-squared model has large error at high zenith angles (φ ≥ 60°), whereas our model provides improved estimations at all zenith angles. We anticipate our model will enhance the ability to estimate actual measurable cosmic muon count rates in muon imaging applications by reducing the gap between simulation and measurement results. This will increase the value of modeling results and improve the quality of experiments and applications in muon detection and imaging.
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2

Walters, Donald L. "Saturation And The Zenith Angle Dependence Of Atmospheric Isoplanatic Angle Measurements." In 1985 Technical Symposium East, edited by Jacques E. Ludman. SPIE, 1986. http://dx.doi.org/10.1117/12.948992.

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3

Walters, Donald L. "Saturation And The Zenith Angle Dependence Of Atmospheric Isoplanatic Angle Measurements." In 1985 Technical Symposium East, edited by Richard Gomez. SPIE, 1985. http://dx.doi.org/10.1117/12.948394.

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4

Thilak, Vimal, David Voelz, Charles Creusere, and Srikanth Damarla. "Estimating the refractive index and reflected zenith angle of a target using multiple polarization measurements." In Defense and Security Symposium, edited by Dennis H. Goldstein and David B. Chenault. SPIE, 2006. http://dx.doi.org/10.1117/12.666183.

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5

Myers, Daryl R., Thomas L. Stoffel, Ibrahim Reda, Stephen M. Wilcox, and Afshin M. Andreas. "Recent Progress in Reducing the Uncertainty in and Improving Pyranometer Calibrations." In ASME 2001 Solar Engineering: International Solar Energy Conference (FORUM 2001: Solar Energy — The Power to Choose). American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/sed2001-126.

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Abstract The Measurements and Instrumentation Team within the Distributed Energy Resources Center at the National Renewable Energy Laboratory, NREL, calibrates pyranometers for outdoor testing solar energy conversion systems. The team also supports climate change research programs. These activities led NREL to improve pyranometer calibrations. Low thermal-offset radiometers measuring the sky diffuse component of the reference solar irradiance removes bias errors on the order of 20 Watts per square meter (W/m2) in the calibration reference irradiance. Zenith angle dependent corrections to responsivities of pyranometers removes 15 to 30 W/m2 bias errors from field measurements. Detailed uncertainty analysis of our outdoor calibration process shows a 20% reduction in the uncertainty in the responsivity of pyranometers. These improvements affect photovoltaic module and array performance characterization, assessment of solar resources for design, sizing, and deployment of solar renewable energy systems, and ground-based validation of satellite-derived solar radiation fluxes.
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