| 1 | /*
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| 2 | *+
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| 3 | * Name:
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| 4 | * palDtp2s
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| 5 |
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| 6 | * Purpose:
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| 7 | * Tangent plane to spherical coordinates
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| 8 |
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| 9 | * Language:
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| 10 | * Starlink ANSI C
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| 11 |
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| 12 | * Type of Module:
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| 13 | * Library routine
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| 14 |
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| 15 | * Invocation:
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| 16 | * palDtp2s( double xi, double eta, double raz, double decz,
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| 17 | * double *ra, double *dec);
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| 18 |
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| 19 | * Arguments:
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| 20 | * xi = double (Given)
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| 21 | * First rectangular coordinate on tangent plane (radians)
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| 22 | * eta = double (Given)
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| 23 | * Second rectangular coordinate on tangent plane (radians)
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| 24 | * raz = double (Given)
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| 25 | * RA spherical coordinate of tangent point (radians)
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| 26 | * decz = double (Given)
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| 27 | * Dec spherical coordinate of tangent point (radians)
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| 28 | * ra = double * (Returned)
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| 29 | * RA spherical coordinate of point to be projected (radians)
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| 30 | * dec = double * (Returned)
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| 31 | * Dec spherical coordinate of point to be projected (radians)
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| 32 |
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| 33 | * Description:
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| 34 | * Transform tangent plane coordinates into spherical.
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| 35 |
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| 36 | * Authors:
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| 37 | * PTW: Pat Wallace (STFC)
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| 38 | * TIMJ: Tim Jenness (JAC, Hawaii)
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| 39 | * {enter_new_authors_here}
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| 40 |
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| 41 | * History:
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| 42 | * 2012-02-08 (TIMJ):
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| 43 | * Initial version with documentation taken from Fortran SLA
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| 44 | * Adapted with permission from the Fortran SLALIB library.
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| 45 | * {enter_further_changes_here}
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| 46 |
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| 47 | * Copyright:
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| 48 | * Copyright (C) 1995 Rutherford Appleton Laboratory
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| 49 | * Copyright (C) 2012 Science and Technology Facilities Council.
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| 50 | * All Rights Reserved.
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| 51 |
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| 52 | * Licence:
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| 53 | * This program is free software: you can redistribute it and/or
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| 54 | * modify it under the terms of the GNU Lesser General Public
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| 55 | * License as published by the Free Software Foundation, either
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| 56 | * version 3 of the License, or (at your option) any later
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| 57 | * version.
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| 58 | *
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| 59 | * This program is distributed in the hope that it will be useful,
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| 60 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 61 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 62 | * GNU Lesser General Public License for more details.
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| 63 | *
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| 64 | * You should have received a copy of the GNU Lesser General
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| 65 | * License along with this program. If not, see
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| 66 | * <http://www.gnu.org/licenses/>.
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| 67 |
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| 68 | * Bugs:
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| 69 | * {note_any_bugs_here}
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| 70 | *-
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| 71 | */
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| 72 |
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| 73 | #include "pal.h"
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| 74 | #include "pal1sofa.h"
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| 75 |
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| 76 | #include <math.h>
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| 77 |
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| 78 | void
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| 79 | palDtp2s ( double xi, double eta, double raz, double decz,
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| 80 | double *ra, double *dec ) {
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| 81 |
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| 82 | double cdecz;
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| 83 | double denom;
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| 84 | double sdecz;
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| 85 | double d;
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| 86 |
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| 87 | sdecz = sin(decz);
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| 88 | cdecz = cos(decz);
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| 89 | denom = cdecz - eta * sdecz;
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| 90 | d = atan2(xi, denom) + raz;
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| 91 | *ra = eraAnp(d);
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| 92 | *dec = atan2(sdecz + eta * cdecz, sqrt(xi * xi + denom * denom));
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| 93 |
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| 94 | return;
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| 95 | }
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