/* ASCEND modelling environment
Copyright (C) 2011 Carnegie Mellon University
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
*/
/* WARNING: this is a FIRST DRAFT of the code and HAS NOT BEEN CHECKED yet. */
/** @FILE
Code reproduced with minor cosmetic changes from:
R Grena (2008), An algorithm for the computation of the solar position,
Solar Energy (82), pp 462-470.
This header file contains the declaration of a class which includes all the
input and output data, and the function that performs the calculation.
To calculate the sun position, follow these steps:
1. include this file.
2. declare a variable of type SunCoord.
3. Initialise the variable given the 9 input quantities required.
This can be done in the declaration, listing the quantities between
commas, or calling the function SetCoord(). In both cases, only the first
four quantities are required; the others default to standard values
(pressure = 1 atm, T = 20 °C, 0 for all the other quantities) if omitted.
Longitude and latitude must be given in RADIANS, pressure in ATM,
temperature in °C.
Day, Month and Year are integer, UT in decimal hour from 0 to 24 (e.g.
3:30 pm becomes 15.5).
4. Call the Calculate() method of the SunCoord object.
Example:
(see the original publication)
Warning: in order to improve accessibility and efficiency, there is not
access control in the class. The user is free to directly access and
modify all the data and there is not any control of consistency. Some
caution in the use of the class is advisable.
*/
#ifndef SUNPOS_GRENA_H
#define SUNPOS_GRENA_H
#include
#include
#ifndef PI
# define PI 3.14159265358979
#endif
/**
Structure to hold sun position data, both input data as well as calculated
output data.
FIXME convert fields p, T to base SI units Pa and K.
*/
typedef struct SunPos_struct{
// input data
double t; ///< Ephemeris Julian Day, offset such that 0 = noon 1 Jan 2003.
double latitude; ///< Latitude (N = positive??), in RADIANS.
double longitude; ///< Longitude (E = positive??), in RADIANS.
double p; ///< Pressure, in ATM (used for refraction calculation)
double T; ///< Temperature, in °C (used for refraction calculation)
} SunPos;
// functions
/** Calculate time given the input date fields and store it in the SunPos object.
@param UT fractional universal time (GMT) in hours from midnight (or fractional hours as required)
@param Day Day of the month, starting at 1??
@param Month Month of the year, starting at 1??
@param Year Year, eg 2011.
@param Delta_t Difference between UT and Terrestrial Time, in seconds.
*/
void SunPos_calc_time(SunPos *S, double UT, int Day, int Month, int Year, double Delta_t);
/** Set time directly in days since noon 1 Jan 2003 UTC. */
void SunPos_set_time(SunPos *S, double t);
/** Set location of observer on Earth
@param latitude latitude in RADIANS!
@param longitude longitude in RADIANS!
*/
void SunPos_set_lat_long(SunPos *S, double latitude, double longitude);
/** Set local atmospheric conditions
@param p Pressure in ATM
@param T Temperature in °C
*/
void SunPos_set_pressure_temp(SunPos *S, double p, double T)
/**
Calculate the sun position in local spherical coordinates.
@param S sun position input data object (set using above functions)
@param zenith zenith angle in radians (output)
@param azimuth azimuth angle in radians (output)
*/
void SunPos_calc_zen_azi(SunPos *S, double *zenith, double *azimuth);