| getfvn |
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Table of contents
Procedure
GETFVN (Get instrument FOV parameters, by instrument name)
SUBROUTINE GETFVN ( INST,
. ROOM,
. SHAPE,
. FRAME,
. BSIGHT,
. N,
. BOUNDS )
Abstract
Return the field-of-view (FOV) parameters for a specified
instrument. The instrument is specified by name.
Required_Reading
NAIF_IDS
Keywords
FOV
INSTRUMENT
Declarations
IMPLICIT NONE
INCLUDE 'zzctr.inc'
CHARACTER*(*) INST
INTEGER ROOM
CHARACTER*(*) SHAPE
CHARACTER*(*) FRAME
DOUBLE PRECISION BSIGHT ( 3 )
INTEGER N
DOUBLE PRECISION BOUNDS ( 3, * )
Brief_I/O
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
INST I Name of an instrument.
ROOM I Maximum number of vectors that can be returned.
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
INST is the name of an instrument, such as a
spacecraft-mounted framing camera, for which the field of
view parameters are to be retrieved from the kernel pool.
INST is case-insensitive, and leading and trailing blanks
in INST are not significant. Optionally, you may supply
the integer ID for the instrument as an integer string.
For example, both 'CASSINI_ISS_NAC' and '-82360' are
legitimate strings that indicate the CASSINI ISS NAC
camera is the instrument of interest.
ROOM is the maximum number of 3-dimensional vectors that can
be returned in BOUNDS.
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 centered on 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. In this
case two vectors are returned in BOUNDS. One of the
vectors returned in BOUNDS 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 representing the principal instrument view
direction that can be
- the central pixel view direction,
- the optical axis direction,
- the FOV geometric center view direction,
- an axis of the FOV frame,
or any other vector specified for this purpose
in the IK FOV definition. 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.
Their magnitudes will be as set in the IK (for
'CORNERS'-style FOV specifications) or the same as the
magnitude of the boresight (for 'ANGLES'-style FOV
specifications.)
Parameters
MINCOS is the lower limit on the value of the cosine of the
cross or reference angles in the 'ANGLES' specification
cases. See the header of the routine GETFOV for its
current value.
Exceptions
1) If the name of the instrument cannot be translated to its
NAIF ID code, the error SPICE(IDCODENOTFOUND) is signaled.
2) If the frame associated with the instrument can not be found,
an error is signaled by a routine in the call tree of this
routine.
3) If the shape of the instrument field of view can not be found
in the kernel pool, an error is signaled by a routine in the
call tree of this routine.
4) If the FOV_SHAPE specified by the instrument kernel is not
one of the four values: 'CIRCLE', 'POLYGON', 'ELLIPSE', or
'RECTANGLE', an error is signaled by a routine in the call
tree of this routine. If the 'ANGLES' specification is used,
FOV_SHAPE must be one of the three values: 'CIRCLE',
'ELLIPSE', or 'RECTANGLE'.
5) If the direction of the boresight cannot be located in the
kernel pool, an error is signaled by a routine in the call
tree of this routine.
6) If the number of components for the boresight vector in the
kernel pool is not 3, or they are not numeric, an error is
signaled by a routine in the call tree of this routine.
7) If the boresight vector is the zero vector, an error is
signaled by a routine in the call tree of this routine.
8) If the 'ANGLES' specification is not present in the kernel
pool and the boundary vectors for the edge of the field of
view cannot be found in the kernel pool, an error is signaled
by a routine in the call tree of this routine.
9) If there is insufficient room (as specified by the argument
ROOM) to return all of the vectors associated with the
boundary of the field of view, an error is signaled by a
routine in the call tree of this routine.
10) If the number of components of vectors making up the field of
view is not a multiple of 3, an error is signaled by a routine
in the call tree of this routine.
11) 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, an error is signaled by a routine in the call tree of
this routine.
12) If the reference vector for the 'ANGLES' specification can not
be found in the kernel pool, an error is signaled by a routine
in the call tree of this routine.
13) If the reference vector stored in the kernel pool to support
the 'ANGLES' specification contains an incorrect number of
components, contains 3 character components, or is parallel to
the boresight, an error is signaled by a routine in the call
tree of this routine.
14) If the 'ANGLES' specification is present in the kernel pool
and the reference angle stored in the kernel pool to support
the 'ANGLES' specification is absent from the kernel pool, an
error is signaled by a routine in the call tree of this
routine.
15) If the keyword that stores the angular units for the angles
used in the 'ANGLES' specification is absent from the kernel
pool, an error is signaled by a routine in the call tree of
this routine.
16) If the value used for the units in the 'ANGLES' specification
is not one of the supported angular units of CONVRT, an error
is signaled by a routine in the call tree of this routine.
17) If the keyword that stores the cross angle for the 'ANGLES'
specification is needed and is absent from the kernel pool, an
error is signaled by a routine in the call tree of this
routine.
18) If the angles for the 'RECTANGLE'/'ANGLES' specification case
have cosines that are less than those stored in the parameter
MINCOS defined in the GETFOV routine, an error is signaled by
a routine in the call tree of this routine.
19) If the class specification contains something other than
'ANGLES' or 'CORNERS', an error is signaled by a routine in
the call tree of this routine.
20) 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 'CORNERS' specification is to be utilized.
Files
Appropriate SPICE kernels must be loaded by the calling program
before this routine is called.
This routine relies upon having successfully loaded an instrument
kernel (IK file) via the routine FURNSH prior to calling this
routine.
The name INST must be associated with an NAIF ID code, normally
through a frames kernel (FK file) or instrument kernel (IK file).
Kernel data are normally loaded via FURNSH once per program run,
NOT every time this routine is called.
Particulars
This routine provides a common interface for retrieving from the
kernel pool the geometric characteristics of an instrument field
of view for a wide variety of remote sensing instruments
across many different space missions.
This routine is identical in function to the routine GETFOV except
that it allows you to refer to an instrument by name (via a
character string) instead of by its NAIF instrument ID.
Given the NAIF instrument name, (and having "loaded" the
instrument field of view description and instrument name to NAIF
ID mapping) this routine returns the boresight 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 that 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 which
corresponds to the INST name 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'), four (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 vectors should
be listed in either
clockwise or
counterclockwise order.
This is required by some
SPICE routines that make
use of FOV specifications.
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 which corresponds to the INST name 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. The
the FOV angular half-extents
are measured from the
boresight vector.
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. The
the FOV angular half-extents
are measured from the
boresight vector. 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 are
acceptable.
The INS<INSTID>_FOV_REF_ANGLE and INS<INSTID>_FOV_CROSS_ANGLE
keywords can have any values for the 'CIRCLE' and 'ELLIPSE'
FOV shapes but must satisfy the condition COS( ANGLE ) > 0 for
the 'RECTANGLE' shape.
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 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) Load an IK, fetch the parameters for each of the FOVs defined
within and print these parameters to the screen.
Use the kernel shown below, an IK defining four FOVs of
various shapes and sizes, to load the FOV definitions, and the
mapping between their NAMES and NAIF IDs.
KPL/IK
File name: getfvn_ex1.ti
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 keywords below define the INSTRUMENT name to NAIF ID
mappings for this example. For convenience we will keep them
in the example's IK although they could be placed elsewhere
(normally on the mission's frames kernel)
\begindata
NAIF_BODY_NAME += ( 'SC999_INST001' )
NAIF_BODY_CODE += ( -999001 )
NAIF_BODY_NAME += ( 'SC999_INST002' )
NAIF_BODY_CODE += ( -999002 )
NAIF_BODY_NAME += ( 'SC999_INST003' )
NAIF_BODY_CODE += ( -999003 )
NAIF_BODY_NAME += ( 'SC999_INST004' )
NAIF_BODY_CODE += ( -999004 )
\begintext
End of IK
Example code begins here.
PROGRAM GETFVN_EX1
IMPLICIT NONE
C
C Local parameters
C
INTEGER MAXBND
PARAMETER ( MAXBND = 4 )
INTEGER NUMINS
PARAMETER ( NUMINS = 4 )
INTEGER WDSIZE
PARAMETER ( WDSIZE = 32 )
C
C Local variables
C
CHARACTER*(WDSIZE) INSTNM ( NUMINS )
CHARACTER*(WDSIZE) FRAME
CHARACTER*(WDSIZE) SHAPE
DOUBLE PRECISION BOUNDS ( 3, MAXBND )
DOUBLE PRECISION BSIGHT ( 3 )
INTEGER I
INTEGER J
INTEGER N
C
C Define the instrument IDs.
C
DATA INSTNM / 'SC999_INST001',
. 'SC999_INST002',
. 'SC999_INST003',
. 'SC999_INST004' /
C
C Load the IK file.
C
CALL FURNSH( 'getfvn_ex1.ti' )
C
C For each instrument ...
C
WRITE (*,'(A)') '--------------------------------------'
DO I = 1, NUMINS
C
C ... fetch FOV parameters and ...
C
CALL GETFVN ( INSTNM(I), MAXBND,
. SHAPE, FRAME, BSIGHT, N, BOUNDS )
C
C ... print them to the screen.
C
WRITE (*,'(2A)') 'Instrument NAME: ', INSTNM(I)
WRITE (*,'(2A)') ' FOV shape: ', SHAPE
WRITE (*,'(2A)') ' FOV frame: ', frame
WRITE (*,'(A,3F12.8)') 'FOV boresight: ', BSIGHT
WRITE (*,'(A)') ' FOV corners: '
DO J = 1, N
WRITE (*,'(A,3F12.8)') ' ',
. BOUNDS(1,J), BOUNDS(2,J), BOUNDS(3,J)
END DO
WRITE (*,'(A)')
. '--------------------------------------'
END DO
END
When this program was executed on a Mac/Intel/gfortran/64-bit
platform, the output was:
--------------------------------------
Instrument NAME: SC999_INST001
FOV shape: CIRCLE
FOV frame: SC999_INST001
FOV boresight: 0.00000000 0.00000000 1.00000000
FOV corners:
0.08715574 0.00000000 0.99619470
--------------------------------------
Instrument NAME: SC999_INST002
FOV shape: ELLIPSE
FOV frame: SC999_INST002
FOV boresight: 1.00000000 0.00000000 0.00000000
FOV corners:
1.00000000 0.00000000 0.01745506
1.00000000 0.03492077 0.00000000
--------------------------------------
Instrument NAME: SC999_INST003
FOV shape: RECTANGLE
FOV frame: SC999_INST003
FOV boresight: 0.00000000 0.00000000 1.00000000
FOV corners:
0.01047177 0.00174523 0.99994365
-0.01047177 0.00174523 0.99994365
-0.01047177 -0.00174523 0.99994365
0.01047177 -0.00174523 0.99994365
--------------------------------------
Instrument NAME: SC999_INST004
FOV shape: POLYGON
FOV frame: SC999_INST004
FOV boresight: 0.00000000 1.00000000 0.00000000
FOV corners:
0.00000000 0.80000000 0.50000000
0.40000000 0.80000000 -0.20000000
-0.40000000 0.80000000 -0.20000000
--------------------------------------
Restrictions
1) This routine will not operate unless proper mapping between
the instrument name INST and a NAIF ID exists, an I-kernel for
that instrument ID has been loaded via a call to FURNSH prior
to calling this routine and this IK contains the specification
for the instrument field of view consistent with the
expectations of this routine.
Literature_References
None.
Author_and_Institution
J. Diaz del Rio (ODC Space)
M. Liukis (JPL)
B.V. Semenov (JPL)
Version
SPICELIB Version 1.0.0, 17-DEC-2021 (JDR) (BVS) (ML)
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Fri Dec 31 18:36:23 2021