00001 /* ***************************************************** */ 00002 /* Compute distance in meters for */ 00003 /* two latitude and longitude points. */ 00004 /* distance_point.c */ 00005 /* ***************************************************** */ 00006 /* Author: Christian Page, CERFACS, Toulouse, France. */ 00007 /* ***************************************************** */ 00012 /* LICENSE BEGIN 00013 00014 Copyright Cerfacs (Christian Page) (2015) 00015 00016 christian.page@cerfacs.fr 00017 00018 This software is a computer program whose purpose is to downscale climate 00019 scenarios using a statistical methodology based on weather regimes. 00020 00021 This software is governed by the CeCILL license under French law and 00022 abiding by the rules of distribution of free software. You can use, 00023 modify and/ or redistribute the software under the terms of the CeCILL 00024 license as circulated by CEA, CNRS and INRIA at the following URL 00025 "http://www.cecill.info". 00026 00027 As a counterpart to the access to the source code and rights to copy, 00028 modify and redistribute granted by the license, users are provided only 00029 with a limited warranty and the software's author, the holder of the 00030 economic rights, and the successive licensors have only limited 00031 liability. 00032 00033 In this respect, the user's attention is drawn to the risks associated 00034 with loading, using, modifying and/or developing or reproducing the 00035 software by the user in light of its specific status of free software, 00036 that may mean that it is complicated to manipulate, and that also 00037 therefore means that it is reserved for developers and experienced 00038 professionals having in-depth computer knowledge. Users are therefore 00039 encouraged to load and test the software's suitability as regards their 00040 requirements in conditions enabling the security of their systems and/or 00041 data to be ensured and, more generally, to use and operate it in the 00042 same conditions as regards security. 00043 00044 The fact that you are presently reading this means that you have had 00045 knowledge of the CeCILL license and that you accept its terms. 00046 00047 LICENSE END */ 00048 00049 00050 00051 00052 00053 00054 00055 #include <utils.h> 00056 00058 double 00059 distance_point(double lon0, double lat0, double lon1, double lat1) 00060 { 00070 /* Earth equatorial radius, meters, Clarke 1866 ellipsoid */ 00071 const double r_earth = 6378206.4; 00072 const double degtorad = M_PI / 180.0; 00073 00074 double coslt1; 00075 double coslt0; 00076 double sinlt1; 00077 double sinlt0; 00078 double cosl0l1; 00079 double cosc; 00080 00081 coslt1 = cos(lat1 * degtorad); 00082 sinlt1 = sin(lat1 * degtorad); 00083 coslt0 = cos(lat0 * degtorad); 00084 sinlt0 = sin(lat0 * degtorad); 00085 00086 cosl0l1 = cos((lon1-lon0) * degtorad); 00087 00088 /* Cos of angle between points */ 00089 cosc = sinlt0 * sinlt1 + coslt0 * coslt1 * cosl0l1; 00090 00091 /* Restrict range between 1 and -1 */ 00092 if (cosc > 1.0) 00093 cosc = 1.0; 00094 else if (cosc < -1.0) 00095 cosc = -1.0; 00096 00097 return (acos(cosc) * r_earth); 00098 }