| dskrb2_c |
|
Table of contents
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 )
AbstractDetermine range bounds for a set of triangular plates to be stored in a type 2 DSK segment. Required_ReadingDSK KeywordsDAS DSK FILES PLATE TOPOGRAPHY Brief_I/OVARIABLE 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.
ParametersSee 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.
FilesNone. ParticularsUsers 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_ReferencesNone. Author_and_InstitutionN.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_Entriescompute range bounds for type 2 DSK segment |
Fri Dec 31 18:41:05 2021