1r.sunhours(1)               GRASS GIS User's Manual              r.sunhours(1)
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NAME

6       r.sunhours  - Calculates solar elevation, solar azimuth, and sun hours.
7       Solar  elevation: the angle between the direction of the geometric cen‐
8       ter of the sun’s apparent disk and the (idealized) horizon.  Solar  az‐
9       imuth: the angle from due north in clockwise direction.
10

KEYWORDS

12       raster, solar, sun energy, sun position
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SYNOPSIS

15       r.sunhours
16       r.sunhours --help
17       r.sunhours  [-ts]   [elevation=name]    [azimuth=name]   [sunhour=name]
18       year=integer      [month=integer]      day=integer       [hour=integer]
19       [minute=integer]    [second=integer]   [--overwrite]  [--help]  [--ver‐
20       bose]  [--quiet]  [--ui]
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22   Flags:
23       -t
24           Time is local sidereal time, not Greenwich standard time
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26       -s
27           Do not use SOLPOS algorithm of NREL
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29       --overwrite
30           Allow output files to overwrite existing files
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32       --help
33           Print usage summary
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35       --verbose
36           Verbose module output
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38       --quiet
39           Quiet module output
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41       --ui
42           Force launching GUI dialog
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44   Parameters:
45       elevation=name
46           Output raster map with solar elevation angle
47           Name for output raster map
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49       azimuth=name
50           Output raster map with solar azimuth angle
51           Name for output raster map
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53       sunhour=name
54           Output raster map with sunshine hours
55           Sunshine hours require SOLPOS use and Greenwich standard time
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57       year=integer [required]
58           Year
59           Options: 1950-2050
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61       month=integer
62           Month
63           If not given, day is interpreted as day of the year
64           Options: 1-12
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66       day=integer [required]
67           Day
68           Options: 1-366
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70       hour=integer
71           Hour
72           Options: 0-24
73           Default: 12
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75       minute=integer
76           Minutes
77           Options: 0-60
78           Default: 0
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80       second=integer
81           Seconds
82           Options: 0-60
83           Default: 0
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DESCRIPTION

86       r.sunhours calculates sun elevation and  sun  azimuth  angles  for  the
87       given  time of day and each grid cell in the current region.  Addition‐
88       ally, the photoperiod (sunshine hours on flat terrain)  can  be  calcu‐
89       lated.
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91       Sun elevation, height, height angle, or solar altitude angle is the an‐
92       gle in degrees between the horizon and a line that points from the site
93       towards the centre of the sun.
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95       The  sun  azimuth angle is here defined as the azimuth angle in degrees
96       of the sun from due north in a clockwise direction.
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98       The time used here is defined such that 12:00 (high noon) is  the  time
99       when  the  sun  has reached its highest point in the sky at the current
100       site, unless the -t flag is used in which case time is  interpreted  as
101       Greenwich standard time.
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103       If  a  sunhour  output map is specified, the module calculates sunshine
104       hours for the given day. This option requires both Greenwhich  standard
105       time and the use of the SOLPOS algorithm by NREL.
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NOTES

108       To  consider  also  cast shadow effects of the terrain, r.sun has to be
109       used.
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EXAMPLES

112   Calculating a sun elevation angle map
113       Calculate the sun elevation angle map for 2010-10-11  at  14:00h  solar
114       time:
115       # set computational region to North Carolina state extent
116       g.region n=318500 s=-16000 w=124000 e=963000 res=500 -p
117       r.sunhours elevation=sun_elev year=2010 month=10 day=11 hour=14 minute=00
118       # visualize
119       d.mon wx0
120       d.rast sun_elev
121       d.vect nc_state type=boundary
122       d.legend sun_elev -s
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124       Sun  angle  map  (in  degree)  of  North Carolina for the 2010-10-11 at
125       14:00h solar time
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127   Calculate map of photoperiod (insolation time)
128       Calculate photoperiod of day-of-year 001 (1st January) of 2012 for  the
129       current  computational region, ignoring cast shadow effects of the ter‐
130       rain:
131       g.region -p
132       r.sunhours sunhour=photoperiod_doy_001 year=2012 day=1
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Acknowledgements

135       Acknowledgements: National Renewable Energy Laboratory for their SOLPOS
136       2.0 sun position algorithm.
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SEE ALSO

139        g.region, r.sun, r.sunmask
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AUTHOR

142       Markus Metz
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SOURCE CODE

145       Available at: r.sunhours source code (history)
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147       Accessed: Saturday Oct 28 18:18:00 2023
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149       Main  index  | Raster index | Topics index | Keywords index | Graphical
150       index | Full index
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152       © 2003-2023 GRASS Development Team, GRASS GIS 8.3.1 Reference Manual
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156GRASS 8.3.1                                                      r.sunhours(1)
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