Index Page dskrb2_c

A B C D E F G H I J K L M N O P Q R S T U V W X

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

       void dskrb2_c ( SpiceInt           nv,
                       ConstSpiceDouble   vrtces[][3],
                       SpiceInt           np,
                       ConstSpiceInt      plates[][3],
                       SpiceInt           corsys,
                       ConstSpiceDouble   corpar[],
                       SpiceDouble      * mncor3,
                       SpiceDouble      * mxcor3       )

#### Abstract

       Determine range bounds for a set of triangular plates to
       be stored in a type 2 DSK segment.

#### Required_Reading

       DSK

#### Keywords

       DAS
       DSK
       FILES
       PLATE
       TOPOGRAPHY

#### Brief_I/O

       Variable  I/O  Description
       --------  ---  --------------------------------------------------
       nv         I   Number of vertices.
       vrtces     I   Vertices.
       np         I   Number of plates.
       plates     I   Plates.
       corsys     I   DSK coordinate system code.
       corpar     I   DSK coordinate system parameters.
       mncor3     O   Lower bound on range of third coordinate.
       mxcor3     O   Upper bound on range of third coordinate.

#### Detailed_Input

       nv          is the number of vertices belonging to the input
                   set of plates.

       vrtces      is an array of coordinates of the vertices. The Ith
                   vertex occupies elements [I-1][0:2] of this array.

       np          is the number of plates in the input plate set.

       plates      is an array representing the triangular plates of a
                   shape model. The elements of `plates' are vertex
                   indices; vertex indices are 1-based. The vertex
                   indices of the Ith plate occupy elements [I-1][0:2] of
                   this array.

       corsys      is an integer parameter identifying the coordinate
                   system in which the bounds are to be computed. The
                   bounds apply to the third coordinate in each system:

                      Latitudinal:           radius
                      Planetodetic:          altitude
                      Rectangular:           Z

       corpar     is an array of parameters associated with the coordinate
                  system. Currently the only supported system that has
                  associated parameters is the planetodetic system. For
                  planetodetic coordinates,

                     corpar[0] is the equatorial radius

                     corpar[1] is the flattening coefficient. Let `re' and
                     `rp' represent, respectively, the equatorial and
                     polar radii of the reference ellipsoid of the
                     system. Then

                         corpar[1] = ( re - rp ) / re

#### Detailed_Output

       mncor3    is a lower bound on the range of the third coordinate
                 of the system identified by `corsys' and `corpar', taken
                 over all plates.

                 For latitudinal and rectangular coordinates, `mncor3'
                 is the greatest lower bound of the third coordinate.

                 For planetodetic coordinates, `mncor3' is an
                 approximation: it is less than or equal to the greatest
                 lower bound.

       mxcor3    is the least upper bound on the range of the third
                 coordinate of the system identified by `corsys' and
                 `corpar', taken over all plates.

#### Parameters

       See the include file dskdsc.inc for declarations of the public DSK
       type 2 parameters used by this routine.

#### Exceptions

       1)  If the input coordinate system is not recognized, the error
           SPICE(NOTSUPPORTED) is signaled.

       2)  If a conversion from rectangular to planetodetic coordinates
           fails, the error will be signaled by a routine in the call
           tree of this routine.

#### Files

       None.

#### Particulars

       Users planning to create DSK files should consider whether the
       SPICE DSK creation utility MKDSK may be suitable for their needs.

       This routine supports use of the DSK type 2 segment writer dskw02_c
       by computing bounds on the range of the third coordinates of
       the input plate set.

#### Examples

       The numerical results shown for this example 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) Create a three-segment DSK file using plate model data for
          Phobos. Use latitudinal, rectangular, and planetodetic
          coordinates in the respective segments. This is not a
          realistic example, but it serves to demonstrate use of
          the supported coordinate systems.

          For simplicity, use an existing DSK file to provide the
          input plate and vertex data. The selected input file has one
          segment.

          Example code begins here.

             /.

             Example program for dskw02_c, dskmi2_c, and dskrb2_c

             Create a three-segment DSK file using plate model data for
             Phobos. Use latitudinal, rectangular, and planetodetic
             coordinates in the respective segments.

             For simplicity, use an existing DSK file to provide the
             input plate and vertex data. The selected input file has one
             segment.

                Version 1.0.0 22-JAN-2016 (NJB)

             ./

             #include <stdio.h>
             #include "SpiceUsr.h"

             int main()
             {

                /.
                Local constants
                ./
                #define FILSIZ          256
                #define LNSIZE           81
                #define NCOR              4
                #define NSEG              3
                #define NAMLEN           21

                /.
                Local variables
                ./

                /.
                Below, we declare large arrays static to avoid stack
                overflow problems.
                ./

                SpiceBoolean            found;

                SpiceChar               cornam [ NCOR ][ NAMLEN ] =
                                        { "radius",
                                          "Z-coordinate",
                                          "Z-coordinate",
                                          "altitude" };

                SpiceChar             * dsk;
                SpiceChar             * frame;
                SpiceChar             * indsk;

                SpiceDLADescr           dladsc;

                SpiceDouble             corpar [ SPICE_DSK_NSYPAR ];
                SpiceDouble             f;
                SpiceDouble             finscl;
                SpiceDouble             first;
                SpiceDouble             last;
                SpiceDouble             mncor1;
                SpiceDouble             mncor2;
                SpiceDouble             mncor3;
                SpiceDouble             mxcor1;
                SpiceDouble             mxcor2;
                SpiceDouble             mxcor3;
                SpiceDouble             re;
                SpiceDouble             rp;

                /.
                Note: the values of SPICE_DSK02_MAXVRT and
                SPICE_DSK02_MAXPLT declared in SpiceDSK.h,
                integer spatial index dimension SPICE_DSK02_SPAISZ,
                and the workspace dimension SPICE_DSK02_MAXCEL
                are very large. Smaller buffers can be used for most
                applications.
                ./
                static SpiceDouble      spaixd [ SPICE_DSK02_SPADSZ ];
                static SpiceDouble      vrtces [ SPICE_DSK02_MAXVRT ][3];

                SpiceInt                center;
                SpiceInt                corscl;
                SpiceInt                corsys;
                SpiceInt                dclass;
                SpiceInt                handle;
                SpiceInt                i;
                SpiceInt                inhan;
                SpiceInt                np;
                SpiceInt                nv;
                static SpiceInt         plates [ SPICE_DSK02_MAXPLT ][3];
                SpiceInt                segno;
                static SpiceInt         spaixi [ SPICE_DSK02_SPAISZ ];
                SpiceInt                spaisz;
                SpiceInt                surfid;
                SpiceInt                voxpsz;
                SpiceInt                voxlsz;
                static SpiceInt         work   [ SPICE_DSK02_MAXCEL ][2];
                SpiceInt                worksz;

                /.
                Assign names of input and output DSK files.
                ./
                indsk = "phobos_3_3.bds";
                dsk   = "phobos_3_3_3seg.bds";

                /.
                Open input DSK for read access; find first segment.
                ./
                dasopr_c ( indsk, &inhan );
                dlabfs_c ( inhan, &dladsc, &found );

                /.
                Fetch vertices and plates from input DSK file.

                Note that vertex and plate indices are 1-based.
                ./
                printf ( "Reading input data...\n" );

                dskv02_c ( inhan, &dladsc, 1, SPICE_DSK02_MAXVRT,
                           &nv,   vrtces                           );
                dskp02_c ( inhan, &dladsc, 1, SPICE_DSK02_MAXPLT,
                           &np,   plates                           );

                printf ( "Done.\n" );

                /.
                Set input array sizes required by dskmi2_c.
                ./
                voxpsz = SPICE_DSK02_MAXVXP;
                voxlsz = SPICE_DSK02_MXNVLS;
                worksz = SPICE_DSK02_MAXCEL;
                spaisz = SPICE_DSK02_SPAISZ;

                /.
                Set fine and coarse voxel scales. (These usually
                need to determined by experimentation.)
                ./
                finscl = 5.0;
                corscl = 4;

                /.
                Open a new DSK file.
                ./
                dskopn_c ( dsk, dsk, 0, &handle );

                /.
                Create three segments and add them to the file.
                ./
                for ( segno = 1;  segno <= NSEG;  segno++ )
                {
                   /.
                   Create spatial index. We won't generate a
                   vertex-plate mapping, so we set the flag
                   for creating this map to "false."
                   ./
                   printf ( "Creating segment %d\n", (int)segno );
                   printf ( "Creating spatial index...\n" );

                   dskmi2_c ( nv,     vrtces,     np,     plates,
                              finscl, corscl,     worksz, voxpsz,
                              voxlsz, SPICEFALSE, spaisz, work,
                              spaixd, spaixi                    );

                   printf ( "Done.\n" );

                   /.
                   Set up inputs describing segment attributes:

                   - Central body: Phobos
                   - Surface ID code: user's choice.
                     We use the segment number here.
                   - Data class: general (arbitrary) shape
                   - Body-fixed reference frame
                   - Time coverage bounds (TBD)
                   ./
                   center = 401;
                   surfid = segno;
                   dclass = SPICE_DSK_GENCLS;
                   frame  = "IAU_PHOBOS";

                   first = -50 * jyear_c();
                   last  =  50 * jyear_c();

                   /.
                   Set the coordinate system and coordinate system
                   bounds based on the segment index.

                   Zero out the coordinate parameters to start.
                   ./
                   for ( i = 0;  i < SPICE_DSK_NSYPAR;  i++ )
                   {
                      corpar[i] = 0.0;
                   }

                   if ( segno == 1 )
                   {
                      /.
                      Use planetocentric latitudinal coordinates. Set
                      the longitude and latitude bounds.
                      ./
                      corsys = SPICE_DSK_LATSYS;

                      mncor1 = -pi_c();
                      mxcor1 =  pi_c();
                      mncor2 = -pi_c()/2;
                      mxcor2 =  pi_c()/2;
                   }
                   else if ( segno == 2 )
                   {

                      /.
                      Use rectangular coordinates. Set the
                      X and Y bounds.

                      The bounds shown here were derived from
                      the plate data. They lie slightly outside
                      of the range spanned by the plates.
                      ./
                      corsys = SPICE_DSK_RECSYS;

                      mncor1 = -1.3;
                      mxcor1 =  1.31;
                      mncor2 = -1.21;
                      mxcor2 =  1.2;
                   }
                   else
                   {
                      /.
                      Set the coordinate system to planetodetic.
                      ./
                      corsys    = SPICE_DSK_PDTSYS;

                      mncor1    = -pi_c();
                      mxcor1    =  pi_c();
                      mncor2    = -pi_c()/2;
                      mxcor2    =  pi_c()/2;

                      /.
                      We'll use equatorial and polar radii from
                      pck00010.tpc. These normally would be fetched
                      at run time, but for simplicity, we'll use
                      hard-coded values.
                      ./
                      re        = 13.0;
                      rp        =  9.1;
                      f         = ( re - rp ) / re;

                      corpar[0] = re;
                      corpar[1] = f;
                   }
                   /.
                   Compute plate model radius bounds.
                   ./
                   printf ( "Computing %s bounds of plate set...\n",
                            cornam[corsys-1]                        );

                   dskrb2_c ( nv,     vrtces, np,      plates,
                              corsys, corpar, &mncor3, &mxcor3 );

                   printf ( "Done.\n" );

                   /.
                   Write the segment to the file.
                   ./
                   printf ( "Writing segment...\n" );

                   dskw02_c ( handle,
                              center, surfid, dclass, frame,  corsys,
                              corpar, mncor1, mxcor1, mncor2, mxcor2,
                              mncor3, mxcor3, first,  last,   nv,
                              vrtces, np,     plates, spaixd, spaixi );

                   printf ( "Done.\n" );
                }

                /.
                Segregate the data records in the DSK file and
                close the file.
                ./
                printf ( "Segregating and closing DSK file...\n" );

                dskcls_c ( handle, SPICETRUE );

                printf ( "Done.\n" );

                return ( 0 );
             }

#### Restrictions

       1)  For planetodetic coordinates, the computation of the lower
           altitude bound requires that the surface at altitude `mncor3' be
           convex. This is the case for realistic geometries, but can be
           false if a plate is very large compared to the overall shape
           model.

#### Literature_References

       None.

#### Author_and_Institution

       N.J. Bachman    (JPL)

#### Version

       -CSPICE Version 1.0.0, 04-APR-2017 (NJB)

#### Index_Entries

       compute range bounds for type 2 dsk segment

#### Link to routine dskrb2_c source file dskrb2_c.c

    Wed Apr  5 17:54:32 2017