johnpye/nrel/spa.h



/////////////////////////////////////////////
//          HEADER FILE for SPA.C          //
//                                         //
//      Solar Position Algorithm (SPA)     //
//                   for                   //
//        Solar Radiation Application      //
//                                         //
//               May 12, 2003              //
//                                         //
//   Filename: SPA.H                       //
//                                         //
//   Afshin Michael Andreas                //
//   afshin_andreas@nrel.gov (303)384-6383 //
//                                         //
//   Measurement & Instrumentation Team    //
//   Solar Radiation Research Laboratory   //
//   National Renewable Energy Laboratory  //
//   1617 Cole Blvd, Golden, CO 80401      //
/////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////
//                                                                    //
// Usage:                                                             //
//                                                                    //
//   1) In calling program, include this header file,                 //
//      by adding this line to the top of file:                       //
//           #include "spa.h"                                         //
//                                                                    //
//   2) In calling program, declare the SPA structure:                //
//           spa_data spa;                                            //
//                                                                    //
//   3) Enter the required input values into SPA structure            //
//      (input values listed in comments below)                       //
//                                                                    //
//   4) Call the SPA calculate function and pass the SPA structure    //
//      (prototype is declared at the end of this header file):       //
//           spa_calculate(&spa);                                     //
//                                                                    //
//   Selected output values (listed in comments below) will be        //
//   computed and returned in the passed SPA structure.  Output       //
//   will based on function code selected from enumeration below.     //
//                                                                    //
//   Note: A non-zero return code from spa_calculate() indicates that //
//         one of the input values did not pass simple bounds tests.  //
//         The valid input ranges and return error codes are also     //
//         listed below.                                              //
//                                                                    //
////////////////////////////////////////////////////////////////////////

#ifndef __solar_position_algorithm_header
#define __solar_position_algorithm_header


//enumeration for function codes to select desired final outputs from SPA
enum {
    SPA_ZA,           //calculate zenith and azimuth
    SPA_ZA_INC,       //calculate zenith, azimuth, and incidence
    SPA_ZA_RTS,       //calculate zenith, azimuth, and sun rise/transit/set values
    SPA_ALL,          //calculate all SPA output values
};

typedef struct
{
    //----------------------INPUT VALUES------------------------

    int year;            // 4-digit year,    valid range: -2000 to 6000, error code: 1
    int month;           // 2-digit month,         valid range: 1 to 12, error code: 2
    int day;             // 2-digit day,           valid range: 1 to 31, error code: 3
    int hour;            // Observer local hour,   valid range: 0 to 24, error code: 4
    int minute;          // Observer local minute, valid range: 0 to 59, error code: 5
    int second;          // Observer local second, valid range: 0 to 59, error code: 6

    double delta_t;      // Difference between earth rotation time and terrestrial time
                         // It is derived from observation only and is reported in this
                         // bulletin: http://maia.usno.navy.mil/ser7/ser7.dat,
                         // where delta_t = 32.184 + (TAI-UTC) + DUT1
                         // valid range: -8000 to 8000 seconds, error code: 7

    double timezone;     // Observer time zone (negative west of Greenwich)
                         // valid range: -18   to   18 hours,   error code: 8

    double longitude;    // Observer longitude (negative west of Greenwich)
                         // valid range: -180  to  180 degrees, error code: 9

    double latitude;     // Observer latitude (negative south of equator)
                         // valid range: -90   to   90 degrees, error code: 10

    double elevation;    // Observer elevation [meters]
                         // valid range: -6500000 or higher meters,    error code: 11

    double pressure;     // Annual average local pressure [millibars]
                         // valid range:    0 to 5000 millibars,       error code: 12

    double temperature;  // Annual average local temperature [degrees Celsius]
                         // valid range: -273 to 6000 degrees Celsius, error code; 13

    double slope;        // Surface slope (measured from the horizontal plane)
                         // valid range: -360 to 360 degrees, error code: 14

    double azm_rotation; // Surface azimuth rotation (measured from south to projection of
                         //     surface normal on horizontal plane, negative west)
                         // valid range: -360 to 360 degrees, error code: 15

    double atmos_refract;// Atmospheric refraction at sunrise and sunset (0.5667 deg is typical)
                         // valid range: -5   to   5 degrees, error code: 16

    int function;        // Switch to choose functions for desired output (from enumeration)

    //-----------------Intermediate OUTPUT VALUES--------------------

    double jd;          //Julian day
    double jc;          //Julian century

    double jde;         //Julian ephemeris day
    double jce;         //Julian ephemeris century
    double jme;         //Julian ephemeris millennium

    double l;           //earth heliocentric longitude [degrees]
    double b;           //earth heliocentric latitude [degrees]
    double r;           //earth radius vector [Astronomical Units, AU]

    double theta;       //geocentric longitude [degrees]
    double beta;        //geocentric latitude [degrees]

    double x0;          //mean elongation (moon-sun) [degrees]
    double x1;          //mean anomaly (sun) [degrees]
    double x2;          //mean anomaly (moon) [degrees]
    double x3;          //argument latitude (moon) [degrees]
    double x4;          //ascending longitude (moon) [degrees]

    double del_psi;     //nutation longitude [degrees]
    double del_epsilon; //nutation obliquity [degrees]
    double epsilon0;    //ecliptic mean obliquity [arc seconds]
    double epsilon;     //ecliptic true obliquity  [degrees]

    double del_tau;     //aberration correction [degrees]
    double lamda;       //apparent sun longitude [degrees]
    double nu0;         //Greenwich mean sidereal time [degrees]
    double nu;          //Greenwich sidereal time [degrees]

    double alpha;       //geocentric sun right ascension [degrees]
    double delta;       //geocentric sun declination [degrees]

    double h;           //observer hour angle [degrees]
    double xi;          //sun equatorial horizontal parallax [degrees]
    double del_alpha;   //sun right ascension parallax [degrees]
    double delta_prime; //topocentric sun declination [degrees]
    double alpha_prime; //topocentric sun right ascension [degrees]
    double h_prime;     //topocentric local hour angle [degrees]

    double e0;          //topocentric elevation angle (uncorrected) [degrees]
    double del_e;       //atmospheric refraction correction [degrees]
    double e;           //topocentric elevation angle (corrected) [degrees]

    double eot;         //equation of time [minutes]
    double srha;        //sunrise hour angle [degrees]
    double ssha;        //sunset hour angle [degrees]
    double sta;         //sun transit altitude [degrees]

    //---------------------Final OUTPUT VALUES------------------------

    double zenith;      //topocentric zenith angle [degrees]
    double azimuth180;  //topocentric azimuth angle (westward from south) [-180 to 180 degrees]
    double azimuth;     //topocentric azimuth angle (eastward from north) [   0 to 360 degrees]
    double incidence;   //surface incidence angle [degrees]

    double suntransit;  //local sun transit time (or solar noon) [fractional hour]
    double sunrise;     //local sunrise time (+/- 30 seconds) [fractional hour]
    double sunset;      //local sunset time (+/- 30 seconds) [fractional hour]

} spa_data;

//Calculate SPA output values (in structure) based on input values passed in structure
int spa_calculate(spa_data *spa);

#endif
1
2
3	/////////////////////////////////////////////
4	// HEADER FILE for SPA.C //
5	// //
6	// Solar Position Algorithm (SPA) //
7	// for //
8	// Solar Radiation Application //
9	// //
10	// May 12, 2003 //
11	// //
12	// Filename: SPA.H //
13	// //
14	// Afshin Michael Andreas //
15	// afshin_andreas@nrel.gov (303)384-6383 //
16	// //
17	// Measurement & Instrumentation Team //
18	// Solar Radiation Research Laboratory //
19	// National Renewable Energy Laboratory //
20	// 1617 Cole Blvd, Golden, CO 80401 //
21	/////////////////////////////////////////////
22
23	////////////////////////////////////////////////////////////////////////
24	// //
25	// Usage: //
26	// //
27	// 1) In calling program, include this header file, //
28	// by adding this line to the top of file: //
29	// #include "spa.h" //
30	// //
31	// 2) In calling program, declare the SPA structure: //
32	// spa_data spa; //
33	// //
34	// 3) Enter the required input values into SPA structure //
35	// (input values listed in comments below) //
36	// //
37	// 4) Call the SPA calculate function and pass the SPA structure //
38	// (prototype is declared at the end of this header file): //
39	// spa_calculate(&spa); //
40	// //
41	// Selected output values (listed in comments below) will be //
42	// computed and returned in the passed SPA structure. Output //
43	// will based on function code selected from enumeration below. //
44	// //
45	// Note: A non-zero return code from spa_calculate() indicates that //
46	// one of the input values did not pass simple bounds tests. //
47	// The valid input ranges and return error codes are also //
48	// listed below. //
49	// //
50	////////////////////////////////////////////////////////////////////////
51
52	#ifndef __solar_position_algorithm_header
53	#define __solar_position_algorithm_header
54
55
56	//enumeration for function codes to select desired final outputs from SPA
57	enum {
58	SPA_ZA, //calculate zenith and azimuth
59	SPA_ZA_INC, //calculate zenith, azimuth, and incidence
60	SPA_ZA_RTS, //calculate zenith, azimuth, and sun rise/transit/set values
61	SPA_ALL, //calculate all SPA output values
62	};
63
64	typedef struct
65	{
66	//----------------------INPUT VALUES------------------------
67
68	int year; // 4-digit year, valid range: -2000 to 6000, error code: 1
69	int month; // 2-digit month, valid range: 1 to 12, error code: 2
70	int day; // 2-digit day, valid range: 1 to 31, error code: 3
71	int hour; // Observer local hour, valid range: 0 to 24, error code: 4
72	int minute; // Observer local minute, valid range: 0 to 59, error code: 5
73	int second; // Observer local second, valid range: 0 to 59, error code: 6
74
75	double delta_t; // Difference between earth rotation time and terrestrial time
76	// It is derived from observation only and is reported in this
77	// bulletin: http://maia.usno.navy.mil/ser7/ser7.dat,
78	// where delta_t = 32.184 + (TAI-UTC) + DUT1
79	// valid range: -8000 to 8000 seconds, error code: 7
80
81	double timezone; // Observer time zone (negative west of Greenwich)
82	// valid range: -18 to 18 hours, error code: 8
83
84	double longitude; // Observer longitude (negative west of Greenwich)
85	// valid range: -180 to 180 degrees, error code: 9
86
87	double latitude; // Observer latitude (negative south of equator)
88	// valid range: -90 to 90 degrees, error code: 10
89
90	double elevation; // Observer elevation [meters]
91	// valid range: -6500000 or higher meters, error code: 11
92
93	double pressure; // Annual average local pressure [millibars]
94	// valid range: 0 to 5000 millibars, error code: 12
95
96	double temperature; // Annual average local temperature [degrees Celsius]
97	// valid range: -273 to 6000 degrees Celsius, error code; 13
98
99	double slope; // Surface slope (measured from the horizontal plane)
100	// valid range: -360 to 360 degrees, error code: 14
101
102	double azm_rotation; // Surface azimuth rotation (measured from south to projection of
103	// surface normal on horizontal plane, negative west)
104	// valid range: -360 to 360 degrees, error code: 15
105
106	double atmos_refract;// Atmospheric refraction at sunrise and sunset (0.5667 deg is typical)
107	// valid range: -5 to 5 degrees, error code: 16
108
109	int function; // Switch to choose functions for desired output (from enumeration)
110
111	//-----------------Intermediate OUTPUT VALUES--------------------
112
113	double jd; //Julian day
114	double jc; //Julian century
115
116	double jde; //Julian ephemeris day
117	double jce; //Julian ephemeris century
118	double jme; //Julian ephemeris millennium
119
120	double l; //earth heliocentric longitude [degrees]
121	double b; //earth heliocentric latitude [degrees]
122	double r; //earth radius vector [Astronomical Units, AU]
123
124	double theta; //geocentric longitude [degrees]
125	double beta; //geocentric latitude [degrees]
126
127	double x0; //mean elongation (moon-sun) [degrees]
128	double x1; //mean anomaly (sun) [degrees]
129	double x2; //mean anomaly (moon) [degrees]
130	double x3; //argument latitude (moon) [degrees]
131	double x4; //ascending longitude (moon) [degrees]
132
133	double del_psi; //nutation longitude [degrees]
134	double del_epsilon; //nutation obliquity [degrees]
135	double epsilon0; //ecliptic mean obliquity [arc seconds]
136	double epsilon; //ecliptic true obliquity [degrees]
137
138	double del_tau; //aberration correction [degrees]
139	double lamda; //apparent sun longitude [degrees]
140	double nu0; //Greenwich mean sidereal time [degrees]
141	double nu; //Greenwich sidereal time [degrees]
142
143	double alpha; //geocentric sun right ascension [degrees]
144	double delta; //geocentric sun declination [degrees]
145
146	double h; //observer hour angle [degrees]
147	double xi; //sun equatorial horizontal parallax [degrees]
148	double del_alpha; //sun right ascension parallax [degrees]
149	double delta_prime; //topocentric sun declination [degrees]
150	double alpha_prime; //topocentric sun right ascension [degrees]
151	double h_prime; //topocentric local hour angle [degrees]
152
153	double e0; //topocentric elevation angle (uncorrected) [degrees]
154	double del_e; //atmospheric refraction correction [degrees]
155	double e; //topocentric elevation angle (corrected) [degrees]
156
157	double eot; //equation of time [minutes]
158	double srha; //sunrise hour angle [degrees]
159	double ssha; //sunset hour angle [degrees]
160	double sta; //sun transit altitude [degrees]
161
162	//---------------------Final OUTPUT VALUES------------------------
163
164	double zenith; //topocentric zenith angle [degrees]
165	double azimuth180; //topocentric azimuth angle (westward from south) [-180 to 180 degrees]
166	double azimuth; //topocentric azimuth angle (eastward from north) [ 0 to 360 degrees]
167	double incidence; //surface incidence angle [degrees]
168
169	double suntransit; //local sun transit time (or solar noon) [fractional hour]
170	double sunrise; //local sunrise time (+/- 30 seconds) [fractional hour]
171	double sunset; //local sunset time (+/- 30 seconds) [fractional hour]
172
173	} spa_data;
174
175	//Calculate SPA output values (in structure) based on input values passed in structure
176	int spa_calculate(spa_data *spa);
177
178	#endif