Solar Elevation Angle and Solar Culmination Determination using Celestial Observation; A Case Study Of Hadejia Jigawa State, Nigeria

Radiometric changes observed in multi-temporal optical satellite images have an important role in efforts to characterize selective-logging areas. The aim of this study was to analyze the multi-temporal behavior of spectral-mixture responses in satellite images in simulated selective-logging areas in the Amazon forest, considering red/near-infrared spectral relationships. Forest edges were used to infer the selective-logging infrastructure using differently oriented edges in the transition between forest and deforested areas in satellite images. TM/Landsat-5 images acquired at three dates with different solar-illumination geometries were used in this analysis. The method assumed that the radiometric responses between forest with selective-logging effects and forest edges in contact with recent clear-cuts are related. The spatial frequency attributes of red/near infrared bands for edge areas were analyzed. Analysis of dispersion diagrams showed two groups of pixels that represent selective-logging areas. The attributes for size and radiometric distance representing these two groups were related to solar-elevation angle. The results suggest that detection of timber exploitation areas is limited because of the complexity of the selective-logging radiometric response. Thus, the accuracy of detecting selective logging can be influenced by the solar-elevation angle at the time of image acquisition. We conclude that images with lower solar-elevation angles are less reliable for delineation of selecting logging.

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Effectively Extracting Iceberg Freeboard Using Bi-Temporal Landsat-8 Panchromatic Image Shadows

Remote Sensing ◽

10.3390/rs13030430 ◽

2021 ◽

Vol 13 (3) ◽

pp. 430

Author(s):

Zhenfu Guan ◽

Xiao Cheng ◽

Yan Liu ◽

Teng Li ◽

Baogang Zhang ◽

...

Keyword(s):

Southern Ocean ◽

Global Climate ◽

Elevation Angle ◽

Freshwater Flux ◽

Landsat 8 ◽

Solar Elevation ◽

Panchromatic Image ◽

Aerial Vehicle ◽

Data Gap

The freshwater flux from icebergs into the Southern Ocean plays an important role in the global climate through its impact on the deep-water formation. Large uncertainties exist in the ice volume transported by Southern Ocean icebergs due to the sparse spatial and temporal coverage of observations, especially observations of ice thickness. The iceberg freeboard is a critical geometric parameter for measuring the thickness of an iceberg and then estimating its volume. This study developed a new, highly efficient shadow-height method to precisely measure the freeboard of various icebergs surrounded by sea ice using Landsat-8 Operational Land Imager 15-m bi-temporal panchromatic image shadows at low-solar-elevation angles. We evaluated and validated shadow length precision according to bi-temporal measurements and comparison with the measurements from the unmanned aerial vehicle. We determined freeboard precision according to shadow length precision and solar elevation angle. In our case study area, 4832 available freeboard measuring points with shadow length precision better than 2 pixels covered 376 icebergs with sizes ranging from 0.002 to 0.7 km² and with freeboard ranging from 2.3 to 83.4 m. At the solar elevation angles of 5.2°, the freeboard precision of 64.1% data could reach 1 m and 86.9% could reach 2 m. Our proposed method effectively filled in the data gap of existing freeboard measurement methods.

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Extracting icebergs freeboard from the shadows in Landsat-8 panchromatic images

10.5194/egusphere-egu2020-12810 ◽

2020 ◽

Author(s):

Zhenfu Guan ◽

Yan Liu

Keyword(s):

Large Scale ◽

Accuracy Assessment ◽

Elevation Angle ◽

Absolute Error ◽

Landsat 8 ◽

High Precision Measurement ◽

Solar Elevation ◽

The Mean ◽

The Antarctic ◽

Solar Elevation Angle

Abstract:&#160;The iceberg freeboard is an important geometric parameter for measuring the thickness of the iceberg and then estimating its volume. Based on the fact that the iceberg can cast elongated shadow on the surface of sea ice in winter, this paper proposes a method to measure the iceberg freeboard using shadow length and the predefined or estimated solar elevation angle. Three Landsat-8 panchromatic images are selected to test our method, with center solar elevation angle of respectively 5.43&#176;, 7.49&#176;and 11.01&#176; on August 29, September 7, and 16 September in 2016. Shadow lengths of five isolated tabular icebergs are automatically extracted to calculate the freeboard height. For the accuracy assessment, we use the matching&#160;points at the different time as cross validation. The results show that the measurement error of shadow length is less than one pixel. When the sun elevation angle is lower than 11.01&#176;, the Root Mean Square Error (RMSE) of the iceberg freeboard from the panchromatic 15 m image is less than 2.0 m, and the Mean Absolute Error (MAE) is less than 1.5 m. Such experiment shows that: under the angle of low solar elevation in winter, the landsat-8 panchromatic 15 m image can be used for high-precision measurement of the iceberg freeboard, and has the potential to measure the Antarctic iceberg freeboard in large scale.Key words:&#160;Antarctic, icebergs, freeboard, shadow altimetry, Landsat-8&#160;

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Solar elevation angle probability distribution

Solar Energy ◽

10.1016/0038-092x(80)90308-4 ◽

1980 ◽

Vol 24 (4) ◽

pp. 417-420 ◽

Cited By ~ 3

Author(s):

D.C. Larson ◽

C.R. Acquista

Keyword(s):

Probability Distribution ◽

Elevation Angle ◽

Solar Elevation ◽

Solar Elevation Angle

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Latitude and Weather Influences on Sun Light Quality and the Relationship to Tree Growth

Forests ◽

10.3390/f10080610 ◽

2019 ◽

Vol 10 (8) ◽

pp. 610 ◽

Cited By ~ 7

Author(s):

Camilo Chiang ◽

Jorunn E. Olsen ◽

David Basler ◽

Daniel Bånkestad ◽

Günter Hoch

Keyword(s):

Light Quality ◽

Elevation Angle ◽

Spectral Composition ◽

Weather Conditions ◽

Seasonal Adjustment ◽

Light Climate ◽

Solar Elevation ◽

Light Quantity ◽

R:Fr Ratio ◽

Solar Elevation Angle

Natural changes in photoperiod, light quantity, and quality play a key role in plant signaling, enabling daily and seasonal adjustment of growth and development. Growing concern about the global climate crisis together with scattered reports about the interactive effects of temperature and light parameters on plants necessitates more detailed information about these effects. Furthermore, the actual light emitting diode (LED) lighting technology allows mimicking of light climate scenarios more similar to natural conditions, but to fully exploit this in plant cultivation, easy-to-apply knowledge about the natural variation in light quantity and spectral distribution is required. Here, we aimed to provide detailed information about short and long-term variation in the natural light climate, by recording the light quantity and quality at an open site in Switzerland every minute for a whole year, and to analyze its relationship to a set of previous tree seedling growth experiments. Changes in the spectral composition as a function of solar elevation angle and weather conditions were analyzed. At a solar elevation angle lower than 20°, the weather conditions have a significant effect on the proportions of blue (B) and red (R) light, whereas the proportion of green (G) light is almost constant. At a low solar elevation, the red to far red (R:FR) ratio fluctuates between 0.8 in cloudy conditions and 1.3 on sunny days. As the duration of periods with low solar angles increases with increasing latitude, an analysis of previous experiments on tree seedlings shows that the effect of the R:FR ratio correlates with the responses of plants from different latitudes to light quality. We suggest an evolutionary adaptation where growth in seedlings of selected tree species from high latitudes is more dependent on detection of light quantity of specific light qualities than in such seedlings originating from lower latitudes.

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Inclusion of Solar Elevation Angle in Land Surface Albedo Parameterization Over Bare Soil Surface

Journal of Advances in Modeling Earth Systems ◽

10.1002/2017ms001109 ◽

2017 ◽

Vol 9 (8) ◽

pp. 3069-3081 ◽

Cited By ~ 8

Author(s):

Zhiyuan Zheng ◽

Zhigang Wei ◽

Zhiping Wen ◽

Wenjie Dong ◽

Zhenchao Li ◽

...

Keyword(s):

Land Surface ◽

Surface Albedo ◽

Elevation Angle ◽

Soil Surface ◽

Bare Soil ◽

Solar Elevation ◽

Solar Elevation Angle

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Dual-Band of Light Intensity Detection Equipment for Photosynthetic Based on the Solar Elevation Angle

2013 Fourth International Conference on Digital Manufacturing & Automation ◽

10.1109/icdma.2013.120 ◽

2013 ◽

Author(s):

Zhengdao Liu ◽

Jin Hu ◽

Hongpan Fan ◽

Yan Liang ◽

Junfeng Qiao

Keyword(s):

Light Intensity ◽

Elevation Angle ◽

Dual Band ◽

Solar Elevation ◽

Solar Elevation Angle

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Radiation balance diversity on NW Spitsbergen in 2010–2014

Polish Polar Research ◽

10.1515/popore-2017-0005 ◽

2017 ◽

Vol 38 (1) ◽

pp. 61-82 ◽

Cited By ~ 3

Author(s):

Marek Kejna ◽

Marion Maturilli ◽

Andrzej Araźny ◽

Ireneusz Sobota

Keyword(s):

Elevation Angle ◽

Radiation Balance ◽

The Sun ◽

Net Income ◽

Annual Variations ◽

Solar Elevation ◽

Diurnal Course ◽

Polar Day ◽

Solar Elevation Angle ◽

North Western

AbstractThis article presents the results of observations of selected fluxes of the radiation balance in north-western Spitsbergen in the years from 2010 to 2014. Measurements were taken in Ny-Ålesund and in the area of Kaffiøyra, on different surface types occurring in the Polar zone: moraine, tundra, snow and ice. Substantial differences in the radiation balance among the various types of surface were observed. The observations carried out in the summer seasons of 2010–2014 in the area of Kaffiøyra demonstrated that the considerable reflection of solar radiation on the Waldemar Glacier (albedo 55%) resulted in a smaller solar energy net income. During the polar day, a diurnal course of the components of the radiation balance was apparently related to the solar elevation angle. When the sun was low over the horizon, the radiation balance became negative, especially on the glacier. Diurnal, annual and multi-annual variations in the radiation balance have a significant influence on the functioning of the environment in polar conditions.

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