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cyllat_c

 Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input Detailed_Output Parameters Exceptions Files Particulars Examples Restrictions Literature_References Author_and_Institution Version Index_Entries

#### Procedure

```   cyllat_c ( Cylindrical to latitudinal )

void cyllat_c ( SpiceDouble    r,
SpiceDouble    clon,
SpiceDouble    z,
SpiceDouble *  lon,
SpiceDouble *  lat )

```

#### Abstract

```   Convert from cylindrical to latitudinal coordinates.
```

```   None.
```

#### Keywords

```   CONVERSION
COORDINATES

```

#### Brief_I/O

```   VARIABLE  I/O  DESCRIPTION
--------  ---  --------------------------------------------------
r          I   Distance of point from z axis.
clon       I   Cylindrical angle of point from XZ plane (radians).
z          I   Height of point above XY plane.
radius     O   Distance of point from origin.
lon        O   Longitude of point (radians).
lat        O   Latitude of point (radians).
```

#### Detailed_Input

```   r           is the distance of the input point from Z axis.

clon        is the cylindrical angle of the point from XZ plane

z           is the height of the point above XY plane.
```

#### Detailed_Output

```   radius      is the distance of the input point from origin.

lon         is the longitude (i.e. angle from the XZ plane) of the
input point (radians). `lon' is set equal to `clon'.

lat         is the latitude (i.e. angle above the XY plane) of the
input point (radians). The range of `lat' is [-pi, pi].
```

#### Parameters

```   None.
```

#### Exceptions

```   Error free.
```

#### Files

```   None.
```

#### Particulars

```   This routine converts coordinates given in cylindrical
coordinates to coordinates in latitudinal coordinates.

Latitudinal coordinates are defined by a distance from a central
reference point, an angle from a reference meridian, and an angle
above the equator of a sphere centered at the central reference
point.
```

#### Examples

```   The numerical results shown for these examples may differ across
platforms. The results depend on the SPICE kernels used as
input, the compiler and supporting libraries, and the machine
specific arithmetic implementation.

1) Compute the cylindrical coordinates of the position of the
Moon as seen from the Earth, and convert them to latitudinal
and rectangular coordinates.

Use the meta-kernel shown below to load the required SPICE
kernels.

KPL/MK

File name: cyllat_ex1.tm

This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.

In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.

The names and contents of the kernels referenced
by this meta-kernel are as follows:

File name                     Contents
---------                     --------
de421.bsp                     Planetary ephemeris
naif0012.tls                  Leapseconds

\begindata

'naif0012.tls'  )

\begintext

End of meta-kernel

Example code begins here.

/.
Program cyllat_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"

int main( )
{

/.
Local variables
./
SpiceDouble          clon;
SpiceDouble          et;
SpiceDouble          lat;
SpiceDouble          lon;
SpiceDouble          lt;
SpiceDouble          pos    [3];
SpiceDouble          rectan [3];
SpiceDouble          r;
SpiceDouble          z;

/.
Load SPK and LSK kernels, use a meta kernel for
convenience.
./
furnsh_c ( "cyllat_ex1.tm" );

/.
Look up the geometric state of the Moon as seen from
the Earth at 2017 Mar 20, relative to the J2000
reference frame.
./
str2et_c ( "2017 Mar 20", &et );

spkpos_c ( "Moon", et, "J2000", "NONE", "Earth", pos, &lt );

/.
Convert the position vector `pos' to cylindrical
coordinates.
./
reccyl_c ( pos, &r, &clon, &z );

/.
Convert the cylindrical coordinates to latitudinal.
./
cyllat_c ( r, clon, z, &radius, &lon, &lat );

/.
Convert the latitudinal coordinates to rectangular.
./
latrec_c ( radius, lon, lat, rectan );

printf( " \n" );
printf( "Original rectangular coordinates:\n" );
printf( " \n" );
printf( " X          (km):  %19.8f\n", pos[0] );
printf( " Y          (km):  %19.8f\n", pos[1] );
printf( " Z          (km):  %19.8f\n", pos[2] );
printf( " \n" );
printf( "Cylindrical coordinates:\n" );
printf( " \n" );
printf( " Radius     (km):  %19.8f\n", r );
printf( " Longitude (deg):  %19.8f\n", clon*dpr_c ( ) );
printf( " Z          (km):  %19.8f\n", z );
printf( " \n" );
printf( "Latitudinal coordinates:\n" );
printf( " \n" );
printf( " Longitude (deg):  %19.8f\n", lon*dpr_c ( ) );
printf( " Latitude  (deg):  %19.8f\n", lat*dpr_c ( ) );
printf( " \n" );
printf( "Rectangular coordinates from latrec_c:\n" );
printf( " \n" );
printf( " X          (km):  %19.8f\n", rectan[0] );
printf( " Y          (km):  %19.8f\n", rectan[1] );
printf( " Z          (km):  %19.8f\n", rectan[2] );
printf( " \n" );

return ( 0 );
}

When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:

Original rectangular coordinates:

X          (km):      -55658.44323296
Y          (km):     -379226.32931475
Z          (km):     -126505.93063865

Cylindrical coordinates:

Longitude (deg):         261.65040211
Z          (km):     -126505.93063865

Latitudinal coordinates:

Longitude (deg):         261.65040211
Latitude  (deg):         -18.26566077

Rectangular coordinates from latrec_c:

X          (km):      -55658.44323296
Y          (km):     -379226.32931475
Z          (km):     -126505.93063865

2) Create a table showing a variety of cylindrical coordinates
and the corresponding latitudinal coordinates.

Corresponding latitudinal and cylindrical coordinates are
listed to three decimal places. All input and output angles
are in degrees.

Example code begins here.

/.
Program cyllat_ex2
./
#include <stdio.h>
#include "SpiceUsr.h"

int main( )
{

/.
Local parameters.
./
#define NREC         11

/.
Local variables.
./
SpiceDouble          lat;
SpiceDouble          lon;
SpiceDouble          rclon;

SpiceInt             i;

/.
Define the input cylindrical coordinates. Angles
in degrees.
./

SpiceDouble          r      [NREC] = { 0.0, 1.0, 1.0,
0.0, 1.0, 1.0,
0.0, 1.0, 1.0,
0.0, 0.0      };

SpiceDouble          clon   [NREC] = {   0.0,   0.0,  90.0,
0.0, 180.0, -90.0,
0.0,  45.0, 180.0,
180.0,  33.0        };

SpiceDouble          z      [NREC] = {  0.0,  0.0,  0.0,
1.0,  1.0,  0.0,
-1.0,  0.0, -1.0,
1.0,  0.0          };

/.
Print the banner.
./
printf( "    r       clon      z      radius    lon      lat \n" );
printf( " -------  -------  -------  -------  -------  ------- \n" );

/.
Do the conversion. Output angles in degrees.
./
for ( i = 0; i < NREC; i++ )
{

rclon = clon[i] * rpd_c ( );

cyllat_c ( r[i], rclon, z[i], &radius, &lon, &lat );

printf( "%8.3f %8.3f %8.3f ", r[i], clon[i], z[i] );
printf( "%8.3f %8.3f %8.3f\n", radius, lon * dpr_c ( ),
lat * dpr_c ( ) );

}

return ( 0 );
}

When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:

r       clon      z      radius    lon      lat
-------  -------  -------  -------  -------  -------
0.000    0.000    0.000    0.000    0.000    0.000
1.000    0.000    0.000    1.000    0.000    0.000
1.000   90.000    0.000    1.000   90.000    0.000
0.000    0.000    1.000    1.000    0.000   90.000
1.000  180.000    1.000    1.414  180.000   45.000
1.000  -90.000    0.000    1.000  -90.000    0.000
0.000    0.000   -1.000    1.000    0.000  -90.000
1.000   45.000    0.000    1.000   45.000    0.000
1.000  180.000   -1.000    1.414  180.000  -45.000
0.000  180.000    1.000    1.000  180.000   90.000
0.000   33.000    0.000    0.000   33.000    0.000
```

#### Restrictions

```   None.
```

#### Literature_References

```   None.
```

#### Author_and_Institution

```   N.J. Bachman        (JPL)
J. Diaz del Rio     (ODC Space)
B.V. Semenov        (JPL)
W.L. Taber          (JPL)
E.D. Wright         (JPL)
```

#### Version

```   -CSPICE Version 1.2.0, 02-JUL-2021 (JDR)

Changed the input argument name "lonc" to "clon" for consistency
with other routines.

Edited the header to comply with NAIF standard.

-CSPICE Version 1.1.1, 26-JUL-2016 (BVS)

-CSPICE Version 1.1.0, 23-JUL-2001 (NJB)

Removed tab characters from source file.

-CSPICE Version 1.0.1, 08-FEB-1998 (EDW)

Corrected and clarified header entries. Removed return call.

-CSPICE Version 1.0.0, 25-OCT-1997 (EDW) (WLT)
```

#### Index_Entries

```   cylindrical to latitudinal
```
`Fri Dec 31 18:41:03 2021`