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

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

KEYWORDS
       raster, solar, sun energy, sun position

SYNOPSIS
       r.sunhours
       r.sunhours --help
       r.sunhours  [-ts]   [elevation=name]    [azimuth=name]	[sunhour=name]
       year=integer	 [month=integer]      day=integer	[hour=integer]
       [minute=integer]	   [second=integer]   [--overwrite]  [--help]  [--ver-
       bose]  [--quiet]	 [--ui]

   Flags:
       -t
	   Time	is local sidereal time,	not Greenwich standard time

       -s
	   Do not use SOLPOS algorithm of NREL

       --overwrite
	   Allow output	files to overwrite existing files

       --help
	   Print usage summary

       --verbose
	   Verbose module output

       --quiet
	   Quiet module	output

       --ui
	   Force launching GUI dialog

   Parameters:
       elevation=name
	   Output raster map with solar	elevation angle
	   Name	for output raster map

       azimuth=name
	   Output raster map with solar	azimuth	angle
	   Name	for output raster map

       sunhour=name
	   Output raster map with sunshine hours
	   Sunshine hours require SOLPOS use and Greenwich standard time

       year=integerA [required]
	   Year
	   Options: 1950-2050

       month=integer
	   Month
	   If not given, day is	interpreted as day of the year
	   Options: 1-12

       day=integerA [required]
	   Day
	   Options: 1-366

       hour=integer
	   Hour
	   Options: 0-24
	   Default: 12

       minute=integer
	   Minutes
	   Options: 0-60
	   Default: 0

       second=integer
	   Seconds
	   Options: 0-60
	   Default: 0

DESCRIPTION
       r.sunhours calculates sun elevation and	sun  azimuth  angles  for  the
       given  time of day and each grid	cell in	the current region.  Addition-
       ally, the photoperiod (sunshine hours on	flat terrain)  can  be	calcu-
       lated.

       Sun elevation, height, height angle, or solar altitude angle is the an-
       gle in degrees between the horizon and a	line that points from the site
       towards the centre of the sun.

       The  sun	 azimuth angle is here defined as the azimuth angle in degrees
       of the sun from due north in a clockwise	direction.

       The time	used here is defined such that 12:00 (high noon) is  the  time
       when  the  sun  has reached its highest point in	the sky	at the current
       site, unless the	-t flag	is used	in which case time is  interpreted  as
       Greenwich standard time.

       If  a  sunhour  output map is specified,	the module calculates sunshine
       hours for the given day.	This option requires both Greenwhich  standard
       time and	the use	of the SOLPOS algorithm	by NREL.

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

EXAMPLES
   Calculating a sun elevation angle map
       Calculate the sun elevation angle map for 2010-10-11  at	 14:00h	 solar
       time:
       # set computational region to North Carolina state extent
       g.region	n=318500 s=-16000 w=124000 e=963000 res=500 -p
       r.sunhours elevation=sun_elev year=2010 month=10	day=11 hour=14 minute=00
       # visualize
       d.mon wx0
       d.rast sun_elev
       d.vect nc_state type=boundary
       d.legend	sun_elev -s

       Sun  angle  map	(in  degree)  of  North	Carolina for the 2010-10-11 at
       14:00h solar time

   Calculate map of photoperiod	(insolation time)
       Calculate photoperiod of	day-of-year 001	(1st January) of 2012 for  the
       current	computational region, ignoring cast shadow effects of the ter-
       rain:
       g.region	-p
       r.sunhours sunhour=photoperiod_doy_001 year=2012	day=1

Acknowledgements
       Acknowledgements: National Renewable Energy Laboratory for their	SOLPOS
       2.0 sun position	algorithm.

SEE ALSO
	g.region, r.sun, r.sunmask

AUTHOR
       Markus Metz

SOURCE CODE
       Available at: r.sunhours	source code (history)

       Main  index  | Raster index | Topics index | Keywords index | Graphical
       index | Full index

       A(C) 2003-2020 GRASS Development	Team, GRASS GIS	7.8.3 Reference	Manual

GRASS 7.8.3							 r.sunhours(1)

NAME | KEYWORDS | SYNOPSIS | DESCRIPTION | NOTES | EXAMPLES | Acknowledgements | SEE ALSO | AUTHOR | SOURCE CODE

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