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dskrb2_c

Table of contents
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

   dskrb2_c ( DSK, determine range bounds for plate set ) 

   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 header file SpiceDSK.h 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 by a routine in the call tree
       of this routine.

   2)  If a conversion from rectangular to planetodetic coordinates
       fails, an error is 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.

      Use the DSK kernel below to provide, for simplicity, the
      input plate and vertex data. The selected input file has one
      segment.

         phobos_3_3.bds


      Example code begins here.


      /.
         Program dskrb2_ex1

         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 );
      }


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


      Reading input data...
      Done.
      Creating segment 1
      Creating spatial index...
      Done.
      Computing radius bounds of plate set...
      Done.
      Writing segment...
      Done.
      Creating segment 2
      Creating spatial index...
      Done.
      Computing Z-coordinate bounds of plate set...
      Done.
      Writing segment...
      Done.
      Creating segment 3
      Creating spatial index...
      Done.
      Computing altitude bounds of plate set...
      Done.
      Writing segment...
      Done.
      Segregating and closing DSK file...
      Done.


      Note that after run completion, a new DSK exists in the output
      directory.

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)
   J. Diaz del Rio     (ODC Space)

Version

   -CSPICE Version 1.0.1, 10-AUG-2021 (JDR)

       Edited the -Examples section to comply with NAIF standard.
       Added example's output. Corrected CSPICE include file name
       reference in -Parameters section.

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

Index_Entries

   compute range bounds for type 2 DSK segment
Fri Dec 31 18:41:05 2021