The algorithm employs the equations and terminology from : Hofierka, J., Suri, M. (2002, september 11). The solar radiation model for Open source GIS: implementation and applications. Trento, Italy.
Module is based on R script orginaly written by Michal Gallay.
Inputs require a text file, which is read by this script and the values containend enter the algortithm. The format of the input file should be: point;latitude;longitude;increment;day_start;day_end;slope_value;aspect_value;elevation_value point - ID of the point (number or text string) latitude - latitude of the point in decimal degrees longtitude of the point in decimal degrees increment - time increment in decimal hours (24.0 for one day) day_start - day of of the beginning (1 for January 1, 365 for December 31) day_end - day of of the end (1 for January 1, 365 for December 31) slope_value - slope inclination value in degrees aspect_value - aspect (orientation) in degrees (0 = north, 90 = east, 180 = south, 270 = west) elevation_value - elevation above sea level in m ( Values must be separated with ";" (semicolon).
If output file is not specified by user, then the results are saved in a new file_solar_incidence_angle.csv text file. The format of the output file is: 1;point;latitude;slope_angle;aspect_angle;day;time;inclined_sun_angle;inclined_sunset_time;horiz_sun_angle;horiz_sunset_time;sun_azimuth
Output text file contains header and computed values in one line per point and time step separated by ";" (semicolon). Output variables: point - point ID latitude - latitude in decimal degrees longitude - longitude in decimal degrees elevation - elavation in m above sea level slope_angle - slope inclination in degrees aspect_angle - aspect (orientation) in degrees (0 = north, 90 = east, 180 = south, 270 = west) day - day of year (1 for January 1, 365 for December 31) time - time in decimal hours inclined_sun_angle - sun angle above inclined surface in degrees inclined_sunset_time - local sunset time on inclined surface in decimal hours horiz_sun_angle - sun angle above horizontal surface in degrees, negative value when sun is below horizon (at night) horiz_sunset_time - local sunset time (astronomic) in decimal hours sun_azimuth - sun azimuth in degrees (0 = north, 90 = east, 180 = south, 270 = west) max_sun_angle - maximal sun angle above inclined surface in degrees delta_sun_angle - delta of the sun angle from maximal maximal sun angle above inclined surface in degrees
The inclined_sunset_time can return NaN (no value) if (-C_33/C_31) returns value out of <-1;1>, e.g. arccos(-1.2) doesn't exist, This problem needs a closer look, but other variables are safe and reliable.
If point is outside of the current region and slope and aspect are going to be read from rasters, 0 is used for slope and aspect and * is writen to output in the fields elevation, slope_angle and aspect_angle.
r.sunangle -s input_file=vstup.txt
r.sunangle input_file=vstup.txt elev=dmr slope=sklon aspect=orient
Last changed: $Date: 2014-08-15 14:00:00 +0100 $
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