void gfstol_c ( SpiceDouble value )
Override the default GF convergence value used in the high
level GF routines.
GF
GEOMETRY
Variable I/O Description
-------- --- --------------------------------------------------
value I Double precision value returned or to store.
value The scalar double precision value to use as the GF subsystem
convergence tolerance. This value will override the default
tolerance, SPICE_GF_CNVTOL, defined in SpiceGF.h Units are
TDB seconds.
None.
None.
1) The error SPICE(INVALIDTOL) signals if 'value' is not strictly
greater-than-zero.
None.
The high level GF routines (see GF.REQ for a listing) use a
default value for the convergence tolerance, SPICE_GF_CNVTOL,
defined in SpiceGF.h. It may occur that a GF search run needs a
different convergence tolerance. gfstol_c programmatically changes
the tolerance used by those routines.
The numerical results shown for these examples 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.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: standard.tm
This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.
In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.
The names and contents of the kernels referenced
by this meta-kernel are as follows:
File name Contents
--------- --------
de421.bsp Planetary ephemeris
pck00009.tpc Planet orientation and
radii
naif0009.tls Leapseconds
\begindata
KERNELS_TO_LOAD = ( 'de421.bsp',
'pck00009.tpc',
'naif0009.tls' )
\begintext
Example:
Perform a search for occultation events of the sun by earth as
observed from the Moon center. Search during the interval from
14 A.D. SEP 1 to 14 A.D. SEP 30 (Julian).
#include <stdio.h>
#include "SpiceUsr.h"
int main()
{
/.
Local constants
./
#define TIMFMT "YYYY ERA MON DD HR:MN:SC.#### ::JCAL"
#define MAXWIN 200
#define TIMLEN 41
/.
Local variables
./
SPICEDOUBLE_CELL ( cnfine, MAXWIN );
SPICEDOUBLE_CELL ( result, MAXWIN );
SpiceChar * win0;
SpiceChar * win1;
SpiceChar begstr [ TIMLEN ];
SpiceChar endstr [ TIMLEN ];
SpiceDouble et0;
SpiceDouble et1;
SpiceDouble left;
SpiceDouble right;
SpiceDouble step;
SpiceInt i;
/.
Load kernels.
./
furnsh_c ( "standard.tm" );
/.
Use an SPK covering year 14 AD.
./
furnsh_c ( "de408.bsp" );
/.
Obtain the TDB time bounds of the confinement
window, which is a single interval in this case.
./
win0 = "14 A.D. SEP 1 00:00:00";
win1 = "14 A.D. SEP 30 00:00:00";
str2et_c ( win0, &et0 );
str2et_c ( win1, &et1 );
/.
Insert the time bounds into the confinement
window.
./
wninsd_c ( et0, et1, &cnfine );
/.
Select a 3-minute step. We'll ignore any occultations
lasting less than 3 minutes.
./
step = 180.0;
/.
Perform the search. 'et[0]' and 'et[1]' have values ~-6*10^10,
SPICE_GF_CNVTOL has value 10^-6, so double precision addition or
subtraction of 'et[0]' and 'et[1]' with SPICE_GF_CNVTOL returns
a result indistinguishable from 'et[0]' and 'et[1]'.
Reduce the GF convergence tolerance by an order of magnitude
to resolve this condition.
./
gfstol_c( 1.e-5 );
gfoclt_c ( "any",
"earth", "ellipsoid", "iau_earth",
"sun", "ellipsoid", "iau_sun",
"lt", "moon", step,
&cnfine, &result );
if ( wncard_c(&result) == 0 )
{
printf ( "No occultation was found.\n" );
}
else
{
for ( i = 0; i < wncard_c(&result); i++ )
{
/.
Fetch and display each occultation interval.
./
wnfetd_c ( &result, i, &left, &right );
timout_c ( left, TIMFMT, TIMLEN, begstr );
timout_c ( right, TIMFMT, TIMLEN, endstr );
printf ( "Interval %d\n"
" Start time: %s\n"
" Stop time: %s\n",
(int)i, begstr, endstr );
}
}
return ( 0 );
}
The program outputs:
Interval 0
Start time: 14 A.D. SEP 27 05:02:02.8250
Stop time: 14 A.D. SEP 27 09:33:31.6995
None.
None.
E.D. Wright (JPL)
-CSPICE Version 1.0.1, 28-JUN-2016 (EDW)
Edit to header, correct Required Reading entry eliminating ".REQ"
suffix.
Edit to Example code, SpiceInts output as ints using
explicit casting.
-CSPICE Version 1.0.0, 27-SEP-2010
change default convergence tolerance for GF routines
Link to routine gfstol_c source file gfstol_c.c
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