| llgrid_pl02 |
|
Table of contents
Procedure
llgrid_pl02 ( Lon/lat grid using DSK type 2 plate model )
void llgrid_pl02 ( SpiceInt handle,
ConstSpiceDLADescr * dladsc,
SpiceInt npts,
ConstSpiceDouble grid [][2],
SpiceDouble srfpts [][3],
SpiceInt pltids [] )
AbstractDeprecated: This routine has been superseded by the CSPICE routine latsrf_c. This routine is supported for purposes of backward compatibility only. Given the planetocentric longitude and latitude values of a set of surface points on a specified target body, compute the corresponding rectangular coordinates of those points. The target body's surface is represented by a triangular plate model contained in a type 2 DSK segment. Required_ReadingFRAMES PCK SPK TIME KeywordsGEOMETRY Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- handle I DSK handle. dladsc I DLA descriptor of target body segment. npts I Number of grid coordinate pairs. grid I Lon/lat values of surface points (radians). srfpts O Rectangular coordinates of surface points. pltids O DSK plate IDs of surface points. Detailed_Input
handle is the DAS file handle of a DSK file open for read
access. This kernel must contain a type 2 segment
that provides a plate model representing the entire
surface of the target body.
dladsc is the DLA descriptor of a DSK segment representing
the surface of a target body.
npts is the number of longitude/latitude pairs in the array
of grid points `grid'.
grid is an array of planetocentric longitude/latitude pairs
to be mapped to surface points on the target body.
`grid' should be declared by the caller
SpiceDouble grid [npts][2];
Elements
grid[i][0]
grid[i][1]
are, respectively, the planetocentric longitude and
latitude of the ith grid point.
Units are radians.
Detailed_Output
srfpts is an array containing the rectangular (Cartesian)
coordinates of the surface points on the target body,
expressed relative to the body-fixed reference frame of
the target body, corresponding to the input grid points.
`srfpts' should be declared by the caller
SpiceDouble srfpts [npts][3];
pltids is an array of integer ID codes of the plates on which
the surface points are located. The ith plate ID
corresponds to the ith surface point. These ID codes can
be use to look up data associated with the plate, such
as the plate's vertices or outward normal vector.
`pltids' should be declared by the caller
SpiceInt pltids [npts];
ParametersNone. Exceptions
If any of the listed errors occur, the output arguments are
left unchanged.
1) If a DSK providing a DSK type 2 plate model has not been
loaded prior to calling llgrid_pl02, an error is signaled by a
routine in the call tree of this routine.
2) If the segment associated with the input DLA descriptor is not
of data type 2, the error SPICE(WRONGDATATYPE) is signaled.
3) If a surface point cannot be computed because the ray corresponding
to a longitude/latitude pair fails to intersect the target
surface as defined by the plate model, the error
SPICE(NOINTERCEPT) is signaled.
Files
The following data are required:
- DSK data: a DSK file containing a plate model representing the
target body's surface must be loaded. This kernel must contain
a type 2 segment that contains data for the entire surface of
the target body.
In all cases, kernel data are normally loaded once per program
run, NOT every time this routine is called.
Particulars
See the headers of the CSPICE routines
reclat_c
latrec_c
for detailed definitions of Planetocentric coordinates.
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) Find the surface points on a target body corresponding to a given
planetocentric longitude/latitude grid.
Use the DSK kernel below to provide the plate model representation
of the surface of Phobos.
phobos_3_3.bds
Example code begins here.
/.
Program llgrid_pl02_ex1
./
#include <stdio.h>
#include <math.h>
#include "SpiceUsr.h"
int main()
{
/.
Local parameters
./
#define FILSIZ 256
#define NAMLEN 33
#define NLAT 9
#define NLON 9
#define MAXGRID ( NLAT * NLON )
#define TOL ( 1.e-12 )
/.
Local variables
./
SpiceBoolean found;
SpiceChar dsk [ FILSIZ ];
SpiceDLADescr dladsc;
SpiceDouble grid [ MAXGRID ][2];
SpiceDouble lat;
SpiceDouble lon;
SpiceDouble srfpts [ MAXGRID ][3];
SpiceDouble xlat;
SpiceDouble xlon;
SpiceDouble xr;
SpiceInt handle;
SpiceInt i;
SpiceInt j;
SpiceInt n;
SpiceInt npts;
SpiceInt pltids [ MAXGRID ];
/.
Prompt for the name of the DSK to read and the name of
the target body.
./
prompt_c ( "Enter DSK name > ", FILSIZ, dsk );
/.
Open the DSK file for read access.
We use the DAS-level interface for
this function.
./
dasopr_c ( dsk, &handle );
/.
Begin a forward search through the
kernel, treating the file as a DLA.
In this example, it's a very short
search.
./
dlabfs_c ( handle, &dladsc, &found );
if ( !found )
{
/.
We arrive here only if the kernel
contains no segments. This is
unexpected, but we're prepared for it.
./
setmsg_c ( "No segments found in DSK file #.");
errch_c ( "#", dsk );
sigerr_c ( "SPICE(NODATA)" );
}
/.
If we made it this far, DLADSC is the
DLA descriptor of the first segment.
Now generate the grid points. We generate
points along latitude bands, working from
north to south. The latitude range is selected
to range from +80 to -80 degrees. Longitude
ranges from 0 to 350 degrees. The increment
is 20 degrees for latitude and 40 degrees for
longitude.
./
n = 0;
for ( i = 0; i < NLAT; i++ )
{
lat = rpd_c() * ( 80.0 - 20.0*i );
for ( j = 0; j < NLON; j++ )
{
lon = rpd_c() * 40.0*j;
grid[n][0] = lon;
grid[n][1] = lat;
++n;
}
}
npts = n - 1;
/.
Find the surface points corresponding to the grid points.
./
llgrid_pl02 ( handle,
&dladsc,
npts,
(ConstSpiceDouble (*)[2])grid,
srfpts,
pltids );
/.
Print out the surface points in latitudinal
coordinates and compare the derived lon/lat values
to those of the input grid.
./
for ( i = 0; i < npts; i++ )
{
/.
Use recrad_c rather than reclat_c to produce
non-negative longitudes.
./
recrad_c ( srfpts[i], &xr, &xlon, &xlat );
printf ( "\n"
"Intercept for grid point %d:\n"
" Plate ID: %d\n"
" Cartesian Coordinates: (%e %e %e)\n"
" Latitudinal Coordinates:\n"
" Longitude (deg): %f\n"
" Latitude (deg): %f\n"
" Radius (km): %f\n"
"\n"
"Original grid coordinates:\n"
" Longitude (deg): %f\n"
" Latitude (deg): %f\n"
"\n",
(int)i,
(int)pltids[i],
srfpts[i][0], srfpts[i][1], srfpts[i][2],
xlon * dpr_c(),
xlat * dpr_c(),
xr,
grid[i][0] * dpr_c(),
grid[i][1] * dpr_c() );
/.
Perform sanity checks on the intercept
coordinates. Stop the program if any error
is larger than our tolerance value.
./
lon = grid[i][0];
lat = grid[i][1];
if ( fabs(xlat-lat) > TOL )
{
sigerr_c ( "Latitude error!" );
}
if ( (xlon - lon) > pi_c() )
{
xlon -= twopi_c();
}
if ( (xlon - lon) > TOL )
{
sigerr_c ( "Longitude error!" );
}
}
/.
Close the kernel. This isn't necessary in a stand-
alone program, but it's good practice in subroutines
because it frees program and system resources.
./
dascls_c ( handle );
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, using the DSK file named phobos_3_3.bds, the output
was:
Enter DSK name > phobos_3_3.bds
Intercept for grid point 0:
Plate ID: 306238
Cartesian Coordinates: (1.520878e+00 0.000000e+00 8.625327e+00)
Latitudinal Coordinates:
Longitude (deg): 0.000000
Latitude (deg): 80.000000
Radius (km): 8.758387
Original grid coordinates:
Longitude (deg): 0.000000
Latitude (deg): 80.000000
Intercept for grid point 1:
Plate ID: 317112
Cartesian Coordinates: (1.189704e+00 9.982799e-01 8.807772e+00)
Latitudinal Coordinates:
Longitude (deg): 40.000000
Latitude (deg): 80.000000
Radius (km): 8.943646
Original grid coordinates:
Longitude (deg): 40.000000
Latitude (deg): 80.000000
Intercept for grid point 2:
Plate ID: 324141
Cartesian Coordinates: (2.777752e-01 1.575341e+00 9.072029e+00)
Latitudinal Coordinates:
Longitude (deg): 80.000000
Latitude (deg): 80.000000
Radius (km): 9.211980
Original grid coordinates:
Longitude (deg): 80.000000
Latitude (deg): 80.000000
Intercept for grid point 3:
Plate ID: 327994
Cartesian Coordinates: (-8.108241e-01 1.404388e+00 9.196823e+00)
Latitudinal Coordinates:
Longitude (deg): 120.000000
Latitude (deg): 80.000000
Radius (km): 9.338699
Original grid coordinates:
Longitude (deg): 120.000000
Latitude (deg): 80.000000
Intercept for grid point 4:
Plate ID: 329431
Cartesian Coordinates: (-1.478202e+00 5.380215e-01 8.921321e+00)
Latitudinal Coordinates:
Longitude (deg): 160.000000
Latitude (deg): 80.000000
Radius (km): 9.058947
Original grid coordinates:
Longitude (deg): 160.000000
Latitude (deg): 80.000000
Intercept for grid point 5:
Plate ID: 196042
Cartesian Coordinates: (-1.498548e+00 -5.454267e-01 9.044113e+00)
Latitudinal Coordinates:
Longitude (deg): 200.000000
Latitude (deg): 80.000000
Radius (km): 9.183633
Original grid coordinates:
Longitude (deg): 200.000000
Latitude (deg): 80.000000
Intercept for grid point 6:
Plate ID: 235899
Cartesian Coordinates: (-7.824045e-01 -1.355164e+00 8.874473e+00)
Latitudinal Coordinates:
Longitude (deg): 240.000000
Latitude (deg): 80.000000
Radius (km): 9.011376
Original grid coordinates:
Longitude (deg): 240.000000
Latitude (deg): 80.000000
Intercept for grid point 7:
Plate ID: 266998
Cartesian Coordinates: (2.645121e-01 -1.500123e+00 8.638862e+00)
Latitudinal Coordinates:
Longitude (deg): 280.000000
Latitude (deg): 80.000000
Radius (km): 8.772130
[...]
Warning: incomplete output. Only 100 out of 1041 lines have
been provided.
Restrictions
1) This routine assumes that the origin of the body-fixed reference
frame associated with the target body is located in the interior
of that body.
2) The results returned by this routine may not be meaningful
if the target surface has multiple surface points associated
with some (longitude, latitude) coordinates.
Literature_ReferencesNone. Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) B.V. Semenov (JPL) Version
-CSPICE Version 2.1.0, 26-OCT-2021 (JDR)
Changed argument names "npoints", "spoints" and "plateIDs" to
"npts", "srfpts" and "pltids" for consistency with other routines.
Edited the header to comply with NAIF standard.
Index lines now state that this routine is deprecated.
-CSPICE Version 2.0.0, 23-JUL-2016 (NJB) (BVS)
Added failed_c calls.
Include file references have been updated. Now calls
zzdsksgr_ instead of dsksgr_. Integer output format
in example program has been updated.
Beta Version 1.3.0, 30-APR-2014 (NJB) (BVS)
Now includes dsk_proto.h.
Last update was 1.2.1, 07-APR-2014 (BVS)
Changed FRAME to FRAMES in the Required_Reading section.
Beta Version 1.2.0, 14-MAY-2010 (NJB)
Updated for compatibility with new DSK design.
DSK name was updated in example program.
Beta Version 1.1.0, 09-FEB-2007 (NJB)
Bug fix: type of local variable fDLADescr was changed to SpiceInt.
Beta Version 1.0.0, 06-NOV-2006 (NJB)
Index_EntriesDEPRECATED map latitudinal grid to DSK type 2 plate model |
Fri Dec 31 18:41:09 2021