Procedure

     PLNSNS ( Planetographic Longitude Sense )

     INTEGER FUNCTION PLNSNS ( BODID )

Abstract

     Indicate for a specified body whether planetographic and
     planetocentric longitude increase in the same sense.

Required_Reading

     None.

Keywords

     PCK

Declarations

     IMPLICIT NONE

     INTEGER               BODID

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     BODID      I   is the NAIF integer ID code of some solar system
                    object.

     The function returns 1 if planetographic and planetocentric
     longitude for the specified body increase in the same sense, and
     -1 if they increase in the opposite sense.

Detailed_Input

     BODID    is the NAIF id-code of some planet, asteroid, comet
              or natural satellite of a planet.

Detailed_Output

     The function returns 1 if planetographic and planetocentric
     longitude increase in the same sense for the input body, and
     -1 if they increase in the opposite sense. Planetocentric
     longitude always increases in the counterclockwise direction
     about the +Z axis of the body-fixed, body-centered reference
     frame of the specified body.

     The sense in which planetographic longitude increases for the
     body specified by BODID is based upon loaded PCK values in
     the kernel pool.

     If PCK information for the specified body can not be located in
     the kernel pool, the function returns the value 0.

Parameters

     None.

Exceptions

     Error free.

     1)  If sufficient orientation information for the object
         specified by BODID is not available in the kernel pool,
         the function returns the value 0.

Files

     A text PCK kernel must be loaded via the routine FURNSH
     that contains the orientation information for the body specified
     by BODID.

Particulars

     This routine returns the multiplicative factor needed
     to convert planetographic longitude to planetocentric
     longitude.

     This routine relies on the proper orientation for the
     specified body having been loaded in the kernel pool.

Examples

     Suppose that you have the planetographic coordinates
     of some point on the surface of an object and that you
     need to convert these coordinates to bodyfixed rectangular
     coordinates. This conversion requires knowledge of the
     sense of planetographic longitude. The code fragment below
     shows how you go about using this routine to perform the
     conversion.

     We assume that the variables LAT, LONG, HEIGHT contain the
     planetographic latitude, longitude and height above the
     reference surface of some point. Moreover, let F be the
     flattening factor for the reference spheroid.

     ( F = (Equatorial Radius - Polar Radius ) / Equatorial Radius )

     Finally, let EQRAD be the equatorial radius.

     We first need to convert planetographic longitude to
     planetocentric longitude.

        FACTOR = PLNSNS(BODID)

        IF ( FACTOR .EQ. 0 ) THEN

           WRITE (*,*) 'Sorry, we don''t have data available.'
           STOP

        END IF

     Compute the planetocentric longitude

        PCLONG = FACTOR * LONG

     Now convert the planetographic coordinates with
     planetographic longitude replaced by planetocentric
     longitude rectangular coordinates. (Note the conversion
     to planetocentric longitude is required because GEOREC
     assumes that the ordering latitude, longitude, altitude
     is a right handed ordering. Replacing planetographic
     longitude by planetocentric longitude ensures that we
     have a right handed coordinate system.)

        CALL GEOREC ( LAT, PCLONG, HEIGHT, EQRAD, F, REC )

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

     J. Diaz del Rio    (ODC Space)
     B.V. Semenov       (JPL)
     W.L. Taber         (JPL)

Version

    SPICELIB Version 1.0.2, 26-OCT-2021 (JDR)

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.0.1, 11-MAY-2009 (BVS)

        Replaced LDPOOL with FURNSN in the header. Re-ordered header
        sections.

    SPICELIB Version 1.0.0, 07-JAN-1997 (WLT)