scem.1 (4106B)
1 .\" Copyright (C) 2025 |Méso|Star> (contact@meso-star.com) 2 .\" 3 .\" This program is free software: you can redistribute it and/or modify 4 .\" it under the terms of the GNU General Public License as published by 5 .\" the Free Software Foundation, either version 3 of the License, or 6 .\" (at your option) any later version. 7 .\" 8 .\" This program is distributed in the hope that it will be useful, 9 .\" but WITHOUT ANY WARRANTY; without even the implied warranty of 10 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 11 .\" GNU Lesser General Public License for more details. 12 .\" 13 .\" You should have received a copy of the GNU Lesser General Public License 14 .\" along with this program. If not, see <http://www.gnu.org/licenses/>. 15 .Dd October 17, 2025 16 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 17 .Dt SCEM 1 18 .Os 19 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 20 .Sh NAME 21 .Nm scem 22 .Nd compute the position of the sun 23 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 24 .Sh SYNOPSIS 25 .Nm 26 .Op Fl hvr 27 .Op Fl a Ar algo 28 .Op Fl d Ar utc_date 29 .Ar latitude 30 .Ar longitude 31 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 32 .Sh DESCRIPTION 33 .Nm 34 computes the position of the sun relative to a given point on the Earth's 35 surface, on a given date. 36 .Pp 37 The longitude of the Earth's position is between 38 .Bq -180, 180 39 decimal degrees relative to Greenwich. 40 The angle is positive towards the east. 41 The latitude of the Earth's position is between 42 .Bq -90, 90 43 decimal degrees relative to the equator. 44 It is positive towards the north. 45 .Pp 46 On output, 47 .Nm 48 displays the position of the sun in zenith and azimuth on the standard 49 output. 50 The message is formatted as follows: 51 .Bd -literal -offset Ds 52 "%f %f\\n", zenith, azimuth 53 .Ed 54 .Pp 55 The zenith angle is between 56 .Bq -90, 90 57 degrees. 58 It defines the elevation of the sun relative to the horizon. 59 The azimuth angle ranges from 60 .Bq 0, 360 61 degrees, with 0° indicating north, 62 90° east, 63 180° south, 64 and 270° west. 65 .Pp 66 The options are as follows 67 .Bl -tag -width Ds 68 .\"""""""""""""""""""""""""""""""""""""" 69 .It Fl a Ar algo 70 Defines the algorithm to be used to calculate the position of the sun. 71 By default, use the 72 .Cm meeus 73 algorithm. 74 .Pp 75 The solar position algorithms are as follows: 76 .Bl -tag -width Ds 77 .It Cm meeus 78 The algorithm described in the Jean Meeus' book, 79 .Dq Astronomical Algorithm . 80 .It Cm psa 81 The algorithm developed by the 82 .Dq Plataforma Solar de Almería . 83 .El 84 .\"""""""""""""""""""""""""""""""""""""" 85 .It Fl d Ar utc_date 86 Date on which the position of the sun is calculated at the specified 87 location. 88 Must be defined in Coordinated Universal Time 89 .Pq UTC+00:00 . 90 By default, use the local date. 91 .Pp 92 The date must be in the format 93 .Dq YYYY-MM-DDThh:mm:ss , 94 i.e., as printed for the current date by the following date command: 95 .Bd -literal -offset Ds 96 date -u +"%Y-%m-%dT%H:%M:%S" 97 .Ed 98 .\"""""""""""""""""""""""""""""""""""""" 99 .It Fl h 100 Output short help and exit. 101 .\"""""""""""""""""""""""""""""""""""""" 102 .It Fl v 103 Make 104 .Nm 105 verbose. 106 .\"""""""""""""""""""""""""""""""""""""" 107 .It Fl r 108 The solar output coordinates are defined in radians rather than degrees. 109 .El 110 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 111 .Sh EXIT 112 .Ex -std 113 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 114 .Sh EXAMPLES 115 Calculate the position of the sun on the current date for a latitude of 116 43.559962° east and a longitude of 1.468150° north: 117 .Bd -literal -offset Ds 118 scem 43.559962 1.468150 119 .Ed 120 .Pp 121 Same as above, but setting the observation date to October 21, 2015, at 122 7:28:00 a.m.: 123 .Bd -literal -offset Ds 124 scem -d 2015-10-21T7:28:00 43.559962 1.468150 125 .Ed 126 .\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" 127 .Sh SEE ALSO 128 .Rs 129 .%A Jean Meeus 130 .%B Astronomical Algorithms 131 .%D 1991 132 .Re 133 .Rs 134 .%A Manuel Blanco-Muriel 135 .%A Diego C. Alarcón-Padilla 136 .%A Teodoro López-Moratalla 137 .%A Martín Lara-Coira 138 .%T Computing the solar vector 139 .%J Solar Energy 140 .%V 70 141 .%N 5 142 .%D 2001 143 .%P 431-441 144 .Re