getfov_c

Index Page getfov_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 getfov_c ( SpiceInt        instid,
                       SpiceInt        room,
                       SpiceInt        shapelen,
                       SpiceInt        framelen,
                       SpiceChar     * shape,
                       SpiceChar     * frame,
                       SpiceDouble     bsight [3],
                       SpiceInt      * n,
                       SpiceDouble     bounds [][3] )
#### Abstract
       This routine returns the field-of-view (FOV) parameters for a
       specified instrument.
#### Required_Reading
       None.
#### Keywords
       INSTRUMENT
#### Brief_I/O
       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       instid     I   NAIF ID of an instrument.
       room       I   Maximum number of vectors that can be returned.
       shapelen   I   Space available in the string `shape'.
       framelen   I   Space available in the string `frame'.
       shape      O   Instrument FOV shape.
       frame      O   Name of the frame in which FOV vectors are defined.
       bsight     O   Boresight vector.
       n          O   Number of boundary vectors returned.
       bounds     O   FOV boundary vectors.
#### Detailed_Input
       instid     is the NAIF ID of an instrument.

       room       is the maximum number of 3D vectors that can be returned
                  in `bounds'.

       shapelen   is the available space in the `shape' string, counting
                  room for the terminating null.  Up to shapelen-1 "data"
                  characters will be assigned to the output string `shape'.

       framelen   is the available space in the `frame' string, counting
                  room for the terminating null.  Up to framelen-1 "data"
                  characters will be assigned to the output string `frame'.
#### Detailed_Output
       shape      is a character string that describes the "shape" of
                  the field of view.  Possible values returned are:

                     "POLYGON"
                     "RECTANGLE"
                     "CIRCLE"
                     "ELLIPSE"

                  If the value of `shape' is "POLYGON" the field of view of
                  the instrument is a pyramidal polyhedron. The vertex of
                  the pyramid is at the instrument focal point. The rays
                  along the edges of the pyramid are parallel to the
                  vectors returned in `bounds'.

                  If the value of `shape' is "RECTANGLE" the field of view
                  of the instrument is a rectangular pyramid. The vertex of
                  the pyramid is at the instrument focal point.  The rays
                  along the edges of the pyramid are parallel to the
                  vectors returned in `bounds'.  Moreover, in this case,
                  the boresight points along the axis of symmetry of the
                  rectangular pyramid.

                  If the value of `shape' is "CIRCLE" the field of view of
                  the instrument is a circular cone about the boresight
                  vector.  The vertex of the cone is at the instrument
                  focal point.  A single vector will be returned in
                  `bounds'.  This vector will be parallel to a ray that
                  lies in the cone that makes up the boundary of the field
                  of view.

                  If the value of `shape' is "ELLIPSE" the field of view of
                  the instrument is an elliptical cone with the boresight
                  vector as the axis of the cone.  The vertex of the cone
                  is at the instrument focal point. Two vectors are
                  returned in `bounds'. One of the vectors points to the
                  end of the semi-major axis of a perpendicular cross
                  section of the elliptic cone.  The other vector points to
                  the end of the semi-minor axis of a perpendicular cross
                  section of the cone.

       frame      is the name of the reference frame in which the field of
                  view boundary vectors are defined.

       bsight     is a vector that points in the direction of the
                  center of the field of view.  The length of bsight
                  is not specified other than being non-zero.

       n          is the number of boundary vectors returned.

       bounds     is an array of vectors that point to the "corners"
                  of the instrument field of view.  (See the discussion
                  accompanying `shape' for an expansion of the term
                  "corner of the field of view.")  Note that the vectors
                  returned in `bounds' are not necessarily unit vectors.
#### Parameters
       MINCOS     This parameter is the lower limit on the value of the
                  cosine of the cross or reference angles in the ANGLES
                  specification cases (see Particulars for further
                  discussion). The parameter and its current value,
                  1.0x10^(-15), are employed in the C code derived from the
                  Fortran version of GETFOV that this wrapper invokes.
#### Exceptions
       1) The error SPICE(NULLPOINTER) is signaled if either the `shape' or
          `frame' string pointers are null.

       2) The user must pass values indicating the length of the `shape'
          and `frame' strings.  If these values are not at least 2, the
          error SPICE(STRINGTOOSHORT) is signaled.

       3) The error SPICE(FRAMEMISSING) is signaled if the reference frame
          associated with the instrument can not be found in the kernel
          pool.

       4) The error SPICE(SHAPEMISSING) is signaled if the shape of the
          instrument field of view can not be found in the kernel pool.

       5) The error SPICE(SHAPENOTSUPPORTED) is signaled if the shape
          specified by the instrument kernel is not one of the four
          values: 'CIRCLE', 'POLYGON', 'ELLIPSE', 'RECTANGLE'.  If the
          ANGLES specification is used it must be: 'CIRCLE', 'ELLIPSE', or
         'RECTANGLE'.

       6) The error SPICE(BORESIGHTMISSING) is signaled if the direction
          of the boresight cannot be located in the kernel pool.

       7) The error SPICE(BADBORESIGHTSPEC) is signaled if the number of
          components for the boresight vector in the kernel pool is not 3.

       8) The error SPICE(BOUNDARYMISSING) is signaled if the boundary
          vectors for the edge of the field of view cannot be found in the
          kernel pool.

       9) The error SPICE(BOUNDARYTOOBIG) is signaled if there is
          insufficient room (as specified by the variable `room') to return
          all of the vectors associated with the boundary of the field of
          view.

      10) The error SPICE(BADBOUNDARY) is signaled if the number of
          components of vectors making up the field of view is not a
          multiple of 3.

      11) The error SPICE(BADBOUNDARY) is signaled if the number of
          components of vectors making up the field of view is not
          compatible with the shape specified for the field of view.

      12) The error SPICE(REFVECTORMISSING) is signaled if the
          reference vector for the ANGLES spec can not be found
          in the kernel pool.

      13) The error SPICE(BADREFVECTORSPEC) is signaled if the
          reference vector stored in the kernel pool to support
          the ANGLES spec contains an incorrect number of components,
          contains 3 character components, or is parallel to the
          boresight.

      14) The error SPICE(REFANGLEMISSING) is signaled if the reference
          angle that supports the ANGLES spec is absent from the kernel
          pool.

      15) The error SPICE(UNITSMISSING) is signaled if the
          keyword that stores the angular units for the angles
          used in the ANGLES spec is absent from the kernel pool.

      16) The error SPICE(CROSSANGLEMISSING) is signaled if the
          keyword that stores the cross angle for the ANGLES spec
          is needed and is absent from the kernel pool.

      17) The error SPICE(BADBOUNDARY) is signaled if the angles
          for the RECTANGLE/ANGLES spec case have cosines that
          are less than those stored in the parameter MINCOS.

      18) The error SPICE(UNSUPPORTEDSPEC) is signaled if the
          class specification contains something other than 'ANGLES'
          or 'CORNERS'.

      19) In the event that the CLASS_SPEC keyword is absent from the
          kernel pool for the instrument whose FOV is sought, this
          module assumes the default CORNERS specification is to be
          utilized.
#### Files
       This routine relies upon having successfully loaded an instrument
       kernel (IK-file) via the routine furnsh_c prior to calling this
       routine.
#### Particulars
       This routine provides a common interface to retrieving
       the geometric characteristics of an instrument field of
       view for a wide variety of remote sensing instruments
       across many different space missions.

       Given the NAIF instrument ID, (and having "loaded" the
       instrument field of view description via the routine furnsh_c)
       this routine returns the bore-sight of the instrument, the
       "shape" of the field of view, a collection of vectors
       that point along the edges of the field of view, and the
       name of the reference frame in which these vectors are defined.

       Currently this routine supports two classes of specifications
       for FOV definitions: "corners" and "angles".

       The "corners" specification requires the following keywords
       defining the shape, boresight, boundary vectors, and reference
       frame of the FOV be provided in one of the text kernel files
       (normally an IK file) loaded into the kernel pool (in the
       keywords below <INSTID> is replaced with the instrument ID as
       passed into the module):

          INS<INSTID>_FOV_CLASS_SPEC         must be set to 'CORNERS' or
                                             omitted to indicate the
                                             "corners"-class
                                             specification.

          INS<INSTID>_FOV_SHAPE              must be set to one of these
                                             values:

                                                'CIRCLE'
                                                'ELLIPSE'
                                                'RECTANGLE'
                                                'POLYGON'

          INS<INSTID>_FOV_FRAME              must contain the name of
                                             the frame in which the
                                             boresight and boundary
                                             corner vectors are defined.

          INS<INSTID>_BORESIGHT              must be set to a 3D vector
                                             defining the boresight in
                                             the FOV frame specified in
                                             the FOV_FRAME keyword.

          INS<INSTID>_FOV_BOUNDARY   or
          INS<INSTID>_FOV_BOUNDARY_CORNERS   must be set to one (for
                                             FOV_SHAPE = 'CIRCLE'), two
                                             (for FOV_SHAPE =
                                             'ELLIPSE'), three (for
                                             FOV_SHAPE = 'RECTANGLE'),
                                             or three or more (for
                                             'POLYGON') 3D vectors
                                             defining the corners of the
                                             FOV in the FOV frame
                                             specified in the FOV_FRAME
                                             keyword.

       The "angles" specification requires the following keywords
       defining the shape, boresight, reference vector, reference and
       cross angular extents of the FOV be provided in one of the text
       kernel files (normally an IK file) loaded into the kernel
       pool (in the keywords below <INSTID> is replaced with the
       instrument ID as passed into the module):

          INS<INSTID>_FOV_CLASS_SPEC         must be set to  'ANGLES' to
                                             indicate the "angles"-class
                                             specification.

          INS<INSTID>_FOV_SHAPE              must be set to one of these
                                             values:

                                                'CIRCLE'
                                                'ELLIPSE'
                                                'RECTANGLE'

          INS<INSTID>_FOV_FRAME              must contain the name of
                                             the frame in which the
                                             boresight and the computed
                                             boundary corner vectors are
                                             defined.

          INS<INSTID>_BORESIGHT              must be set to a 3D vector
                                             defining the boresight in
                                             the FOV frame specified in
                                             the FOV_FRAME keyword.

          INS<INSTID>_FOV_REF_VECTOR         must be set to a 3D vector
                                             that together with the
                                             boresight vector defines
                                             the plane in which the
                                             first angular extent of the
                                             FOV specified in the
                                             FOV_REF_ANGLE keyword is
                                             measured.

          INS<INSTID>_FOV_REF_ANGLE          must be set to the angle
                                             that is 1/2 of the total
                                             FOV angular extent in the
                                             plane defined by the
                                             boresight and the vector
                                             specified in the
                                             FOV_REF_VECTOR keyword.

          INS<INSTID>_FOV_CROSS_ANGLE        must be set to the angle
                                             that is 1/2 of the total
                                             FOV angular extent in the
                                             plane containing the
                                             boresight and perpendicular
                                             to the plane defined by the
                                             boresight and the vector
                                             specified in the
                                             FOV_REF_VECTOR keyword.
                                             This keyword is not
                                             required for FOV_SHAPE =
                                             'CIRCLE'.

          INS<INSTID>_FOV_ANGLE_UNITS        must specify units for the
                                             angles given in the
                                             FOV_REF_ANGLE and
                                             FOV_CROSS_ANGLE keywords.
                                             Any angular units
                                             recognized by convrt_c are
                                             acceptable.

       This routine is intended to be an intermediate level routine.
       It is expected that users of this routine will be familiar
       with the SPICE frames subsystem and will be comfortable writing
       software to further manipulate the vectors retrieved by this
       routine.
#### Examples
       The example program in this section loads the IK file
       'example.ti' with the following contents defining four FOVs of
       various shapes and sizes:

          KPL/IK

          The keywords below define a circular, 10-degree wide FOV with
          the boresight along the +Z axis of the 'SC999_INST001' frame
          for an instrument with ID -999001 using the "angles"-class
          specification.

          \begindata
             INS-999001_FOV_CLASS_SPEC       = 'ANGLES'
             INS-999001_FOV_SHAPE            = 'CIRCLE'
             INS-999001_FOV_FRAME            = 'SC999_INST001'
             INS-999001_BORESIGHT            = ( 0.0, 0.0, 1.0 )
             INS-999001_FOV_REF_VECTOR       = ( 1.0, 0.0, 0.0 )
             INS-999001_FOV_REF_ANGLE        = ( 5.0 )
             INS-999001_FOV_ANGLE_UNITS      = ( 'DEGREES' )
          \begintext

          The keywords below define an elliptical FOV with 2- and
          4-degree angular extents in the XZ and XY planes and the
          boresight along the +X axis of the 'SC999_INST002' frame for
          an instrument with ID -999002 using the "corners"-class
          specification.

          \begindata
             INS-999002_FOV_SHAPE            = 'ELLIPSE'
             INS-999002_FOV_FRAME            = 'SC999_INST002'
             INS-999002_BORESIGHT            = ( 1.0, 0.0, 0.0 )
             INS-999002_FOV_BOUNDARY_CORNERS = ( 1.0, 0.0, 0.01745506,
                                                 1.0, 0.03492077, 0.0 )
          \begintext

          The keywords below define a rectangular FOV with 1.2- and
          0.2-degree angular extents in the ZX and ZY planes and the
          boresight along the +Z axis of the 'SC999_INST003' frame for
          an instrument with ID -999003 using the "angles"-class
          specification.

          \begindata
             INS-999003_FOV_CLASS_SPEC       = 'ANGLES'
             INS-999003_FOV_SHAPE            = 'RECTANGLE'
             INS-999003_FOV_FRAME            = 'SC999_INST003'
             INS-999003_BORESIGHT            = ( 0.0, 0.0, 1.0 )
             INS-999003_FOV_REF_VECTOR       = ( 1.0, 0.0, 0.0 )
             INS-999003_FOV_REF_ANGLE        = ( 0.6 )
             INS-999003_FOV_CROSS_ANGLE      = ( 0.1 )
             INS-999003_FOV_ANGLE_UNITS      = ( 'DEGREES' )
          \begintext

          The keywords below define a triangular FOV with the boresight
          along the +Y axis of the 'SC999_INST004' frame for an
          instrument with ID -999004 using the "corners"-class
          specification.

          \begindata
             INS-999004_FOV_SHAPE            = 'POLYGON'
             INS-999004_FOV_FRAME            = 'SC999_INST004'
             INS-999004_BORESIGHT            = (  0.0,  1.0,  0.0 )
             INS-999004_FOV_BOUNDARY_CORNERS = (  0.0,  0.8,  0.5,
                                                  0.4,  0.8, -0.2,
                                                 -0.4,  0.8, -0.2 )
          \begintext

       The program shown below loads the IK, fetches parameters for each
       of the four FOVs and prints these parameters to the screen.

          #include "SpiceUsr.h"

          #define      MAXBND            4
          #define      NUMINS            4
          #define      WDSIZE            32

          int main (void)
          {

             SpiceChar    frame  [WDSIZE];
             SpiceChar    shape  [WDSIZE];

             SpiceDouble  bounds [MAXBND][3];
             SpiceDouble  bsight [3];

             SpiceInt     i;
             SpiceInt     insids [NUMINS] =
                              { -999001, -999002, -999003, -999004};
             SpiceInt     j;
             SpiceInt     n;

             furnsh_c( "example.ti" );

             printf( "--------------------------------------\n" );
             for ( i = 0; i < NUMINS; i++ ) {

                getfov_c ( insids[i], MAXBND, WDSIZE, WDSIZE,
                           shape, frame, bsight, &n, bounds );

                printf( "Instrument ID: %ld\n", insids[i] );
                printf( "    FOV shape: %s\n",  shape     );
                printf( "    FOV frame: %s\n",  frame     );
                printf( "FOV boresight: %f %f %f\n",
                          bsight[0], bsight[1], bsight[2] );
                printf( "  FOV corners: \n" );
                for ( j = 0; j < n; j++ ) {
                   printf( "               %f %f %f\n",
                           bounds[j][0], bounds[j][1], bounds[j][2] );
                }
                printf( "--------------------------------------\n" );
             }
             return(0);
          }

       The program produces the following output:

          --------------------------------------
          Instrument ID: -999001
              FOV shape: CIRCLE
              FOV frame: SC999_INST001
          FOV boresight: 0.000000 0.000000 1.000000
            FOV corners:
                         0.087156 0.000000 0.996195
          --------------------------------------
          Instrument ID: -999002
              FOV shape: ELLIPSE
              FOV frame: SC999_INST002
          FOV boresight: 1.000000 0.000000 0.000000
            FOV corners:
                         1.000000 0.000000 0.017455
                         1.000000 0.034921 0.000000
          --------------------------------------
          Instrument ID: -999003
              FOV shape: RECTANGLE
              FOV frame: SC999_INST003
          FOV boresight: 0.000000 0.000000 1.000000
            FOV corners:
                         0.010472 0.001745 0.999944
                         -0.010472 0.001745 0.999944
                         -0.010472 -0.001745 0.999944
                         0.010472 -0.001745 0.999944
          --------------------------------------
          Instrument ID: -999004
              FOV shape: POLYGON
              FOV frame: SC999_INST004
          FOV boresight: 0.000000 1.000000 0.000000
            FOV corners:
                         0.000000 0.800000 0.500000
                         0.400000 0.800000 -0.200000
                         -0.400000 0.800000 -0.200000
          --------------------------------------
#### Restrictions
       An I-kernel for the instrument specified in INSTID must have been
       loaded via a call to furnsh_c prior to calling this routine and
       must contain the specification for the instrument field of view
       consistent with the expectations of this routine.
#### Literature_References
       None.
#### Author_and_Institution
       C.H. Acton   (JPL)
       N.J. Bachman (JPL)
       B.V. Semenov (JPL)
       W.L. Taber   (JPL)
       F.S. Turner  (JPL)
#### Version
       -CSPICE Version 1.0.5, 05-FEB-2009 (BVS)

          Header update: added information about required IK keywords;
          replaced old example with a new one more focused on getfov_c and
          IK keywords.

       -CSPICE Version 1.0.4, 27-OCT-2005 (NJB)

          Header update:  replaced reference to bodvar_c with
          reference to bodvcd_c.

       -CSPICE Version 1.0.3, 28-DEC-2004 (BVS)

          Fixed typo in the header example.

       -CSPICE Version 1.0.2, 29-JUL-2003 (NJB) (CHA)

          Various header changes were made to improve clarity.  Some
          minor header corrections were made.

       -CSPICE Version 1.0.1, 18-DEC-2001 (FST)

          Updated the header of this wrapper to document the changes
          in GETFOV regarding the addition of support for the ANGLES
          specification.

       -CSPICE Version 1.0.0, 13-APR-2000 (FST)
#### Index_Entries
       return instrument's FOV parameters
#### Link to routine getfov_c source file getfov_c.c

    Thu Apr 16 08:58:10 2009