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 
 
Wed Apr  5 17:54:32 2017