1NGGCOG(3NCARG)                   NCAR GRAPHICS                  NGGCOG(3NCARG)
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NAME

6       NGGCOG - Returns the latitudes and longitudes of a set of points
7       approximating a circle at a given point on the surface of the globe.
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SYNOPSIS

10       CALL NGGCOG (CLAT,CLON,CRAD,ALAT,ALON,NPTS)
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C-BINDING SYNOPSIS

13       #include <ncarg/ncargC.h>
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15       void c_nggcog(float clat, float clon, float crad, float *alat,
16       float *alon, int npts)
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DESCRIPTION

19       CLAT        (an input expression of type REAL) is the latitude, in
20                   degrees, of a point on the globe defining the center of the
21                   circle.
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23       CLON        (an input expression of type REAL) is the longitude, in
24                   degrees, of a point on the globe defining the center of the
25                   circle.
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27       CRAD        (an input expression of type REAL) specifies the radius of
28                   the circle.  This is given as a great-circle distance, in
29                   degrees.
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31       ALAT        (an output array, of type REAL, dimensioned NPTS) is an
32                   array in which the latitudes of points on the circle are to
33                   be returned.
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35       ALON        (an output array, of type REAL, dimensioned NPTS) is an
36                   array in which the longitudes of points on the circle are
37                   to be returned.
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39       NPTS        (an input expression, of type INTEGER) is the desired
40                   number of points to be used to represent the circle.  Its
41                   value determines how accurately the circle will be
42                   represented.
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C-BINDING DESCRIPTION

45       The C binding argument descriptions are the same as the FORTRAN
46       argument descriptions.
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USAGE

49       Let C represent (CLAT,CLON) and let O represent the center of the
50       globe.  The circle is the set of all points P on the globe such that
51       the angle POC is of the size specified by CRAD.
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53       SIN and COS are used to generate points representing a circle having
54       the desired radius and centered at the North Pole.  These points are
55       then subjected to two rotations - one that brings the circle down to
56       the desired latitude, and another that carries it to the desired
57       longitude.
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EXAMPLES

60       Use the ncargex command to see the following relevant example: cpex10.
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ACCESS

63       To use NGGCOG or c_nggcog, load the NCAR Graphics libraries ncarg,
64       ncarg_gks, and ncarg_c, preferably in that order.
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MESSAGES

67       None.
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SEE ALSO

70       Online: nggsog(3NCARG), ngritd(3NCARG).
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73       Copyright (C) 1987-2009
74       University Corporation for Atmospheric Research
75       The use of this Software is governed by a License Agreement.
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79UNIX                              March 1993                    NGGCOG(3NCARG)
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