1 /*
2 ** libproj -- library of cartographic projections
3 **
4 ** Copyright (c) 2003, 2006 Gerald I. Evenden
5 */
6 static const char
7 LIBPROJ_ID[] = "Id";
8 /*
9 ** Permission is hereby granted, free of charge, to any person obtaining
10 ** a copy of this software and associated documentation files (the
11 ** "Software"), to deal in the Software without restriction, including
12 ** without limitation the rights to use, copy, modify, merge, publish,
13 ** distribute, sublicense, and/or sell copies of the Software, and to
14 ** permit persons to whom the Software is furnished to do so, subject to
15 ** the following conditions:
16 **
17 ** The above copyright notice and this permission notice shall be
18 ** included in all copies or substantial portions of the Software.
19 **
20 ** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 ** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
22 ** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
23 ** IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
24 ** CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
25 ** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
26 ** SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
27 */
28 /* determine small t */
29 #include "proj_config.h"
30 #include <math.h>
31 #define HALFPI 1.5707963267948966
32 PROJ_EXPORT double
proj_tsfn(double phi,double sinphi,double e)33 proj_tsfn(double phi, double sinphi, double e) {
34 sinphi *= e;
35 return (tan (.5 * (HALFPI - phi)) /
36 pow((1. - sinphi) / (1. + sinphi), .5 * e));
37 }
38 /* Revision log
39 ** Log: proj_tsfn.c
40 ** Revision 3.1 2006/01/11 01:38:18 gie
41 ** Initial
42 **
43 */
44