sun_position.m

根据经度纬度时间

function sun = sun_position(time, location)
% sun = sun_position(time, location)
%
% This function compute the sun position (zenith and azimuth angle at the observer
% location) as a function of the observer local time and position. 
%
% It is an implementation of the algorithm presented by Reda et Andreas in:
%   Reda, I., Andreas, A. (2003) Solar position algorithm for solar
%   radiation application. National Renewable Energy Laboratory (NREL)
%   Technical report NREL/TP-560-34302. 
% This document is avalaible at www.osti.gov/bridge
%
% This algorithm is based on numerical approximation of the exact equations.
% The authors of the original paper state that this algorithm should be
% precise at +/- 0.0003 degrees. I have compared it to NOAA solar table
% (http://www.srrb.noaa.gov/highlights/sunrise/azel.html) and to USNO solar
% table (http://aa.usno.navy.mil/data/docs/AltAz.html) and found very good
% correspondance (up to the precision of those tables), except for large
% zenith angle, where the refraction by the atmosphere is significant 
% (difference of about 1 degree). Note that in this code the correction 
% for refraction in the atmosphere as been implemented for a temperature 
% of 10C (283 kelvins) and a pressure of 1010 mbar. See the subfunction 
% 玸un_topocentric_zenith_angle_calculation