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From launch to transmission: satellite communication theory and SNG
Published in Jonathan Higgins, Satellite Newsgathering, 2012
The satellite has to be ‘seen’ from the Earth by any transmitter or receiver that is going to work through it. The transmitter is referred to as the ‘uplink’ and the receiver as the ‘downlink’. Both the uplink and the downlink have to be accurately pointed at the satellite, and the ‘azimuth’ and ‘elevation’ of alignment to the satellite have to be calculated. Azimuth is the compass bearing direction to the satellite in the horizontal plane from a point on the Earth's surface, and elevation is the angle of the satellite above the horizon from that location. Both of these parameters vary according to the longitude and latitude of the location on the Earth's surface and define the ‘look angle’ of the uplink or the downlink toward the satellite (Figure 2.14).
Chapter 2
Published in Pearson Frederick, Map Projections:, 2018
Azimuth is the means of measuring the direction of a second point from a given point and is an important quantity on both the model of the Earth and on the map. The azimuth, α, of point P′ in relation to point P is given in Figures 1 and 2 for both the Earth and the map. For the Earth, azimuth is the angle between the meridian containing point P, and the line between P and P′. In a like manner on the map, azimuth is the angle between the representation of the meridian containing P, and the line between P and P′. The convention used in this text is that azimuth is measured from the north in a clockwise manner. Azimuth ranges from 0° to 360°.
Satellite communications
Published in J. Dunlop, D. G. Smith, Telecommunications Engineering, 2017
Again, the case of a geostationary satellite is a much simplified version of the general case. The point at which a line between the satellite and the centre of the earth intersects the earth’s surface is called the sub-satellite point. There are two angles of intersect between the earth station and the satellite: the elevation and the azimuth. The elevation is the angle of the satellite above the horizon, from the earth station, and the azimuth is the angle between the line of longitude through the earth and the direction of the sub-satellite point. These are shown diagrammatically in Figs. 14.2 and 14.3.
Comprehensive solar energy resource characterisation for an intricate Indian province
Published in International Journal of Ambient Energy, 2021
Subhadeep Bhattacharjee, Rahul Bhattacharjee
The solar azimuth is the angle on the horizontal plane between the projection of the beam radiation and the north–south direction line (Bhattacharjee 2013). Azimuth angle – the direction of the sun calculated in the horizontal plane from the north in a clockwise direction (thus east = 90°, south = 180° and west = 270°, while north can be 0° or 360°); Sometimes it is found use of 0° for south (in the northern hemisphere) and have −90° for east and +90° for west, or the opposite for the southern hemisphere, taking 0° for north and going through east to +180° and through west to –180° (Labed and Lorenzo 2004). The convention considered in this study is the only one generally most applicable.
Deployment optimization for camera network coupling with geographic environment
Published in Annals of GIS, 2018
Ziran Wang, Meizhen Wang, Xuejun Liu, Yanan Zhang
The camera is a directional sensor, whose coverage is mainly decided by parameters such as location, height, the camera’s inner parameters and its gestures. The camera model described in this paper is shown in Figure 1(a), which is expressed as a tuple ; in this tuple, is the position of the camera’s optical centre in the geographic coordinate system; are, respectively, the azimuth angle and the pitch angle. The azimuth angle is the vertical angle between the north direction line of a particular point and the target direction line in the clockwise direction. The pitch angle is the horizontal angle between the vertical direction line of a particular point and the target direction line in the clockwise direction. are respectively the width, height and focal length of the imaging chip. The quadrilateral in grey in Figure 1(a) is the theoretical coverage of the current camera, which is projected from the pyramid formed by C-D1D2D3D4 to the ground.
The angular characteristics of Moon-based Earth observations
Published in International Journal of Digital Earth, 2020
Huadong Guo, Yuanzhen Ren, Guang Liu, Hanlin Ye
Meanwhile, the angular information and characteristics of remote sensing have received attention recently due to their extensive influence on observations. The typical angular parameters are zenith angle, elevation angle and azimuth angle. These are defined as follows: Zenith angle means the angle between a direction of interest and the local zenith. Elevation angle means the angle between a direction of interest and the local horizon, and thus the elevation angle and zenith angle are redundant. The azimuth angle is the angle between the north vector and the vector of the object of interest on the horizontal plane. The relative azimuth angle is the angle between the vector to the Sun and the vector to the viewing point on the horizontal plane. In the field of atmospheric science, the view zenith angle (VZA) influences observations of atmospheric composition, such as the total ozone column; and the solar zenith angle (SZA) affects the diffuse reflectance and transmittance of an optically stationary atmospheric boundary layer (Antón et al. 2011; De Abreu 2010). Solar zenith angle influences albedo in energy budgeting, implying that the SZA dependence of land surface albedo should not be neglected (Grant, Prata, and Cechet 2000). Furthermore, the relative azimuth and solar zenith angles must also be considered when interpreting thermal radiances observed over land surfaces, and the VZA dependence of window and longwave radiances in clear scenes depends on the SZA (Minnis, Gambheer, and Doelling 2004). In oceanography, increasing SZAs correspond to greater increases in spectral reflectance of sea foam layers, greatly affecting ocean color remote sensing and aerosol optical thickness retrieval from satellite observations (Ma et al. 2015). In addition, the variation of the diffuse attenuation of downwelling irradiance is associated with the sun angle; the correction of sun-angle dependence is essential for ocean color remote sensing (Lin et al. 2016). Considering vegetation and photosynthesis, the canopy Photochemical Reflectance Index derived from field hyperspectral observations displayed sensitivity to both the VZA and relative azimuth angle at all growth stages (Cheng et al. 2012). Moreover, the SZA is the main factor in determining the features of O2 absorption bands, one of the main variables driving solar radiation spectrum variation, affecting sun-induced chlorophyll fluorescence (Zhang et al. 2017). When dealing with land use and landscapes, the VZA can strongly affect the observed middle infrared radiance of urbanized landscapes, which has the potential to monitor hot spots and urban growth. Furthermore, certain types of ground surfaces may not adhere to the Lambertian property (equal emissions in all directions) in thermal infrared regions based on their geometric structure (Krehbiel, Kovalskyy, and Henebry 2013; Tu et al. 2017). Thus, remote sensing measurements over a wide angular range are helpful in characterizing a variety of terrestrial surfaces, as well as clouds and smoke embedded in the atmosphere (Gatebe and King 2016).