xenial (1) r.sunhours.1grass.gz

NAME

       r.sunhours  - Calculates solar elevation, solar azimuth, and sun hours.
       Solar  elevation:  the angle between the direction of the geometric center of the sun’s apparent disk and
       the (idealized) horizon. Solar azimuth: 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]  [--verbose]
       [--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=integer [required]
           Year
           Options: 1950-2050

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

       day=integer [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.  Additionally, the photoperiod (sunshine hours) can be calculated.

       Sun  elevation, height, height angle, or solar altitude angle is the angle 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 (-t flag) and the solpos algorithm of NREL (-s flag).

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 1 (1st January) 2012:
       r.sunhours -s 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

       Last changed: $Date: 2014-12-23 15:09:20 +0100 (Tue, 23 Dec 2014) $

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