JNISpice
version 2.0.0

spice.basic
Class SurfaceIntercept

java.lang.Object
  extended by spice.basic.SurfaceIntercept
Direct Known Subclasses:
SurfaceInterceptWithDSKInfo

public class SurfaceIntercept
extends java.lang.Object

Class SurfaceIntercept supports ray-target surface intercept computations.

Surface intercept computations are performed by creation of SurfaceIntercept objects. Each SurfaceIntercept instance consists of:

If a surface intercept computation does not find a point of intersection, an attempt to access a member, other than the "found" flag, of the resulting SurfaceIntercept instance will cause a PointNotFoundException to be thrown.

For functionality similar to that of the SPICE routine SINCPT, see the constructor SurfaceIntercept( String, Body, Time, ReferenceFrame, AberrationCorrection, Body, ReferenceFrame, Vector3 ).

For functionality similar to that of the SPICE routine DSKXV, see the method create( boolean, Body, Surface[], Time, ReferenceFrame, Vector3[], Vector3[]).

For functionality similar to that of the SPICE routine DSKXSI, see the constructor SurfaceInterceptWithDSKInfo.SurfaceInterceptWithDSKInfo( boolean, Body, Surface[], Time, ReferenceFrame, Vector3, Vector3 ).

Code examples are provided in the detailed documentation for the constructors and methods.

Files

Appropriate SPICE kernels must be loaded by the calling program before methods of this class are called.

The following data are required:

The following data may be required:

Kernel data are normally loaded once per program run, NOT every time a method of this class is called.

Class SurfaceIntercept Particulars

Using DSK data

DSK loading and unloading

DSK files providing data used by this class are loaded by calling KernelDatabase.load(java.lang.String) and can be unloaded by calling KernelDatabase.unload(java.lang.String) or KernelDatabase.clear(). See the documentation of KernelDatabase.load(java.lang.String) for limits on numbers of loaded DSK files. For run-time efficiency, it's desirable to avoid frequent loading and unloading of DSK files. When there is a reason to use multiple versions of data for a given target body---for example, if topographic data at varying resolutions are to be used---the surface list can be used to select DSK data to be used for a given computation. It is not necessary to unload the data that are not to be used. This recommendation presumes that DSKs containing different versions of surface data for a given body have different surface ID codes.

DSK data priority

A DSK coverage overlap occurs when two segments in loaded DSK files cover part or all of the same domain---for example, a given longitude-latitude rectangle---and when the time intervals of the segments overlap as well.

When DSK data selection is prioritized, in case of a coverage overlap, if the two competing segments are in different DSK files, the segment in the DSK file loaded last takes precedence. If the two segments are in the same file, the segment located closer to the end of the file takes precedence.

When DSK data selection is unprioritized, data from competing segments are combined. For example, if two competing segments both represent a surface as a set of triangular plates, the union of those sets of plates is considered to represent the surface.

Currently only unprioritized data selection is supported. Because prioritized data selection may be the default behavior in a later version of the routine, the UNPRIORITIZED keyword is required in the constructors' `method' arguments.

Version and Date

Version 2.0.0 10-JAN-2017 (NJB)

   Access of fields has been changed from private to
   package private.

   Added vectorized creation method using arrays of ray
   vertices and directions as inputs.  

   Added copy constructor.

   Changed private fields: inputs are now stored in a 
   separate object of an inner class. There are 
   separate inner classes for the different types of
   intercept methods: FullInputs, RayArrayInputs, and
   SurfaceInterceptWithDSKInfo.RayInputs. 

Version 1.0.0 24-NOV-2009 (NJB)


Field Summary
static java.lang.String ELLIPSOID
           
 
Constructor Summary
SurfaceIntercept()
          No-arguments constructor.
SurfaceIntercept(java.lang.String method, Body target, Time time, ReferenceFrame fixRef, AberrationCorrection abcorr, Body observer, ReferenceFrame rayRef, Vector3 rayDir)
          Find a specified surface intercept point; create a SurfaceIntercept instance containing the result.
SurfaceIntercept(SurfaceIntercept surfx)
          Copy constructor.
 
Method Summary
static SurfaceIntercept[] create(boolean prioritized, Body target, Surface[] surfList, Time t, ReferenceFrame fixref, Vector3[] rayVertices, Vector3[] rayDirections)
          Vectorized SurfaceIntercept creation method.
 Vector3 getIntercept()
          Return the surface intercept.
 Vector3 getSurfaceVector()
          Return the observer to intercept vector.
 TDBTime getTargetEpoch()
          Return the target epoch.
 boolean wasFound()
          Indicate whether the intercept was found.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

ELLIPSOID

public static final java.lang.String ELLIPSOID
See Also:
Constant Field Values
Constructor Detail

SurfaceIntercept

public SurfaceIntercept()
No-arguments constructor.


SurfaceIntercept

public SurfaceIntercept(SurfaceIntercept surfx)
                 throws SpiceException
Copy constructor. This constructor creates a deep copy.

Throws:
SpiceException

SurfaceIntercept

public SurfaceIntercept(java.lang.String method,
                        Body target,
                        Time time,
                        ReferenceFrame fixRef,
                        AberrationCorrection abcorr,
                        Body observer,
                        ReferenceFrame rayRef,
                        Vector3 rayDir)
                 throws SpiceException
Find a specified surface intercept point; create a SurfaceIntercept instance containing the result.

Code Examples

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.

  1. Compute surface intercept points on Mars for the boresight and FOV boundary vectors of the MGS MOC narrow angle camera. The intercepts are computed for a single observation epoch. Converged Newtonian light time and stellar aberration corrections are used. For simplicity, camera distortion is ignored.

    Intercepts are computed using both triaxial ellipsoid and topographic surface models.

    The topographic model is based on data from the MGS MOLA DEM megr90n000cb, which has a resolution of 4 pixels/degree. A triangular plate model was produced by computing a 720 x 1440 grid of interpolated heights from this DEM, then tessellating the height grid. The plate model is stored in a type 2 segment in the referenced DSK file.

    Use the meta-kernel shown below to load the required SPICE kernels.

    KPL/MK 
    
    File: SurfaceIntercept_ex1.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 
       ---------                        -------- 
       de430.bsp                        Planetary ephemeris 
       mar097.bsp                       Mars satellite ephemeris 
       pck00010.tpc                     Planet orientation and 
                                        radii 
       naif0011.tls                     Leapseconds  
       mgs_moc_v20.ti                   MGS MOC instrument 
                                        parameters 
       mgs_sclkscet_00061.tsc           MGS SCLK coefficients 
       mgs_sc_ext12.bc                  MGS s/c bus attitude 
       mgs_ext12_ipng_mgs95j.bsp        MGS ephemeris 
       megr90n000cb_plate.bds           Plate model based on 
                                        MEGDR DEM, resolution 
                                        4 pixels/degree. 
    
    \begindata 
    
       KERNELS_TO_LOAD = ( 'de430.bsp', 
                           'mar097.bsp', 
                           'pck00010.tpc', 
                           'naif0012.tls', 
                           'mgs_moc_v20.ti', 
                           'mgs_sclkscet_00061.tsc', 
                           'mgs_sc_ext12.bc', 
                           'mgs_ext12_ipng_mgs95j.bsp', 
                           'megr90n000cb_plate.bds'      ) 
    \begintext 
    

    Example code begins here.

    //
    // Program SurfaceInterceptEx1
    //
    // Compute surface intercept points on Mars 
    // for the boresight and FOV boundary vectors of the MGS MOC 
    // narrow angle camera.
    //
    import spice.basic.*;
    import static spice.basic.AngularUnits.*;
    
    public class SurfaceInterceptEx1
    {
       //
       // Load SPICE shared library.
       //
       static{ System.loadLibrary( "JNISpice" ); }
    
    
       public static void main( String[] args )
    
          throws SpiceException
       {
          //
          // Local constants
          //
          final String                      META   = "SurfaceInterceptEx1.tm";
    
          final int                         NMETH  = 2;
    
          //
          // Local variables
          //
          AberrationCorrection              abcorr = 
                                               new AberrationCorrection( "CN+S" );
    
          Body                              obsrvr = new Body( "MGS"  );
          Body                              target = new Body( "Mars" );
    
          FOV                               MOCNACFov;
    
          String                            camnam = "MGS_MOC_NA";
          Instrument                        camera = new Instrument( camnam );
    
          LatitudinalCoordinates            latCoords;
    
          ReferenceFrame                    fixref =
                                               new ReferenceFrame( "IAU_MARS" );
    
          ReferenceFrame                    dref;
    
          String[]                          methds = {
                                                        "Ellipsoid",
                                                        "DSK/Unprioritized" 
                                                     };
    
          String[]                          srftyp = 
                                            { 
                                               "Ellipsoid", 
                                               "MGS/MOLA topography, 4 pixel/deg"
                                            };
    
          String                            utc      = "2003 OCT 13 06:00:00 UTC";
          String                            title;
    
          SurfaceIntercept                  surfx;
    
          TDBTime                           et;
          Time                              trgepc;
    
          Vector3[]                         bounds;
          Vector3                           bsight;
          Vector3                           dvec;
          Vector3                           spoint;
          Vector3                           srfvec;
    
          boolean                           found;
    
          double                            dist;  
          double                            lat;
          double                            lon;
          double                            radius;
    
          int                               i;
          int                               j;
          int                               ncornr;    
    
    
          try
          {
             //
             // Load kernels.
             //
             KernelDatabase.load( META );
    
             //
             // Convert the UTC request time to ET (seconds past
             // J2000, TDB). 
             //
             et = new TDBTime( utc );
    
             //
             // Get the MGS MOC Narrow angle camera (MGS_MOC_NA) 
             // field of view (FOV) parameters. 
             //
             // We'll store the camera-fixed frame in `dref', 
             // the camera boresight vector in `bsight', and the 
             // FOV corner vectors in the array `bounds'.
             //
             MOCNACFov = new FOV( camera );
    
             bsight    = MOCNACFov.getBoresight();
             bounds    = MOCNACFov.getBoundary();
             ncornr    = bounds.length;
             dref      = MOCNACFov.getReferenceFrame();
    
             System.out.format( "%n" +                          
                                "Surface Intercept Locations for Camera%n"  +
                                "FOV Boundary and Boresight Vectors%n"      +
                                "%n"                                        +
                                "   Instrument:             %s%n"           +
                                "   Epoch:                  %s%n"           +
                                "   Aberration correction:  %s%n"           +
                                "%n",
                                camera.getName(), utc, abcorr.toString()  ); 
             //
             // Now compute and display the surface intercepts for the 
             // boresight and all of the FOV boundary vectors. 
             //
             for( i = 0;  i <= ncornr;  i++ )
             {
                if ( i < ncornr )
                {
                   title = String.format( "Corner vector %d", (i+1) );
                   dvec  = bounds[i];
                }
                else
                {
                   title = "Boresight vector";
                   dvec  = bsight;
                }
    
                System.out.format( "%n" +
                                   "%s%n",
                                   title  );
    
                System.out.format( "%n" +
                                   "  Vector in %s frame = %n", dref.toString() );
    
                System.out.format( "   %18.10e %18.10e %18.10e%n", 
                                   dvec.getElt(0), dvec.getElt(1), dvec.getElt(2) );
    
                System.out.format( "%n" +
                                   "  Intercept:%n" );
                //
                // Compute the surface intercept point using
                // the specified aberration corrections. Loop
                // over the set of computation methods.
                //
                for ( j = 0;  j < NMETH;  j++ )
                {
                   surfx = 
    
                      new SurfaceIntercept ( methds[j], target, et,   fixref, 
                                             abcorr,    obsrvr, dref, dvec   );
    
                   if ( surfx.wasFound() )
                   {
                      //
                      // Compute range from observer to apparent intercept. 
                      //
                      srfvec = surfx.getSurfaceVector();                  
                      dist   = srfvec.norm();
    
                      //
                      // Convert rectangular coordinates of the intercept 
                      // point `surfx' to planetocentric latitude and longitude.
                      // Convert radians to degrees. 
                      //
                      latCoords = new LatitudinalCoordinates(surfx.getIntercept() );
    
                      lon       = latCoords.getLongitude() * DPR;
                      lat       = latCoords.getLatitude()  * DPR;
                      radius    = latCoords.getRadius();
    
                      //
                      // Display the results. 
                      //
                      System.out.format ( 
                               "%n" +
                               "    Surface representation: %s%n" +
                               "%n"                               +
                               "     Radius                   (km)  = %18.10f%n" +
                               "     Planetocentric Latitude  (deg) = %18.10f%n" +
                               "     Planetocentric Longitude (deg) = %18.10f%n" +
                               "     Range                    (km)  = %18.10f%n" +
                               "%n",
                               srftyp[j], radius,  lat,  lon,  dist               );
                   } 
                   else 
                   { 
                      System.out.format ( "%n" +
                                          "Intercept not found.%n" +
                                          "%n"                       );
                   } // End of intercept processing for current vector
    
                } // End of method loop
    
             } // End of vector loop
    
          } // End of try block
    
          catch ( SpiceException exc )
          {
             exc.printStackTrace();
          }
    
       } // End of main method 
    
    }
    
    

    When this program was executed on a PC/Linux/gcc/64-bit/java 1.5 platform, the output was:

    Surface Intercept Locations for Camera
    FOV Boundary and Boresight Vectors
    
       Instrument:             MGS_MOC_NA
       Epoch:                  2003 OCT 13 06:00:00 UTC
       Aberration correction:  CN+S
    
    
    Corner vector 1
    
      Vector in MGS_MOC_NA frame = 
         1.8571383810e-06  -3.8015622659e-03   9.9999277403e-01
    
      Intercept:
    
        Surface representation: Ellipsoid
    
         Radius                   (km)  =    3384.9411357607
         Planetocentric Latitude  (deg) =     -48.4774823672
         Planetocentric Longitude (deg) =    -123.4740748197
         Range                    (km)  =     388.9830822570
    
    
        Surface representation: MGS/MOLA topography, 4 pixel/deg
    
         Radius                   (km)  =    3387.6408267726
         Planetocentric Latitude  (deg) =     -48.4922595600
         Planetocentric Longitude (deg) =    -123.4754119350
         Range                    (km)  =     386.1451004041
    
    
    Corner vector 2
    
      Vector in MGS_MOC_NA frame = 
         1.8571383810e-06   3.8015622659e-03   9.9999277403e-01
    
      Intercept:
    
        Surface representation: Ellipsoid
    
         Radius                   (km)  =    3384.9396985743
         Planetocentric Latitude  (deg) =     -48.4816367789
         Planetocentric Longitude (deg) =    -123.3988187487
         Range                    (km)  =     388.9751000527
    
    
        Surface representation: MGS/MOLA topography, 4 pixel/deg
    
         Radius                   (km)  =    3387.6403704508
         Planetocentric Latitude  (deg) =     -48.4963866889
         Planetocentric Longitude (deg) =    -123.4007435481
         Range                    (km)  =     386.1361644332
    
    
    Corner vector 3
    
      Vector in MGS_MOC_NA frame = 
        -1.8571383810e-06   3.8015622659e-03   9.9999277403e-01
    
      Intercept:
    
        Surface representation: Ellipsoid
    
         Radius                   (km)  =    3384.9396897287
         Planetocentric Latitude  (deg) =     -48.4816623489
         Planetocentric Longitude (deg) =    -123.3988219550
         Range                    (km)  =     388.9746411355
    
    
        Surface representation: MGS/MOLA topography, 4 pixel/deg
    
         Radius                   (km)  =    3387.6403603146
         Planetocentric Latitude  (deg) =     -48.4964120424
         Planetocentric Longitude (deg) =    -123.4007467292
         Range                    (km)  =     386.1357106985
    
    
    Corner vector 4
    
      Vector in MGS_MOC_NA frame = 
        -1.8571383810e-06  -3.8015622659e-03   9.9999277403e-01
    
      Intercept:
    
        Surface representation: Ellipsoid
    
         Radius                   (km)  =    3384.9411269138
         Planetocentric Latitude  (deg) =     -48.4775079405
         Planetocentric Longitude (deg) =    -123.4740779752
         Range                    (km)  =     388.9826233195
    
    
        Surface representation: MGS/MOLA topography, 4 pixel/deg
    
         Radius                   (km)  =    3387.6408166345
         Planetocentric Latitude  (deg) =     -48.4922849169
         Planetocentric Longitude (deg) =    -123.4754150656
         Range                    (km)  =     386.1446466486
    
    
    Boresight vector
    
      Vector in MGS_MOC_NA frame = 
         0.0000000000e+00   0.0000000000e+00   1.0000000000e+00
    
      Intercept:
    
        Surface representation: Ellipsoid
    
         Radius                   (km)  =    3384.9404100069
         Planetocentric Latitude  (deg) =     -48.4795802622
         Planetocentric Longitude (deg) =    -123.4364497355
         Range                    (km)  =     388.9757144062
    
    
        Surface representation: MGS/MOLA topography, 4 pixel/deg
    
         Radius                   (km)  =    3387.6402755068
         Planetocentric Latitude  (deg) =     -48.4943418633
         Planetocentric Longitude (deg) =    -123.4380804236
         Range                    (km)  =     386.1376152656
    
    

Throws:
SpiceException
Method Detail

create

public static SurfaceIntercept[] create(boolean prioritized,
                                        Body target,
                                        Surface[] surfList,
                                        Time t,
                                        ReferenceFrame fixref,
                                        Vector3[] rayVertices,
                                        Vector3[] rayDirections)
                                 throws SpiceException
Vectorized SurfaceIntercept creation method.

Code Examples

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.

  1. Compute surface intercepts of rays emanating from a set of vertices distributed on a longitude-latitude grid. All vertices are outside the target body, and all rays point toward the target's center.

    Check intercepts against expected values. Indicate the number of errors, the number of computations, and the number of intercepts found.

    Use the meta-kernel shown below to load the required SPICE kernels.

    KPL/MK
    File: SurfaceInterceptCreateEx1.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
       ---------                        --------
       phobos512.bds                    DSK based on
                                        Gaskell ICQ Q=512
                                        plate model
    \begindata
    
       PATH_SYMBOLS    = 'GEN'
       PATH_VALUES     = '/ftp/pub/naif/generic_kernels/dsk'
    
       KERNELS_TO_LOAD = ( '$GEN/phobos/phobos512.bds' )
    
    \begintext
    
    
    

    Example code begins here.

    
    //
    // Program SurfaceInterceptCreateEx1
    //
    import java.util.ArrayList;
    import spice.basic.*;
    import static spice.basic.AngularUnits.*;
    
    //
    // 

    Multi-segment, vectorized spear program. // //

    This program computes surface intercepts of rays emanating from a set of // vertices distributed on a longitude-latitude grid. All // vertices are outside the target body, and all rays point // toward the target's center. // //

    The program checks intercepts against expected values. It reports the // number of errors, the number of computations, and the // number of intercepts found. // //

    This program expects all loaded DSKs // to represent the same body and surface. // //

    Syntax: java -Djava.library.path= // SurfaceInterceptCreateEx1 // public class SurfaceInterceptCreateEx1 { // // Load SPICE shared library. // static{ System.loadLibrary( "JNISpice" ); } public static void main( String[] args ) throws SpiceException { // // Local constants // final double DTOL = 1.0e-14; final double SML = 1.0e-12; final int MAXN = 100000; final int MAXSRF = 100; // // Local variables // Body target; DLADescriptor dladsc; DSK dsk; DSKDescriptor dskdsc; LatitudinalCoordinates vtxLatCoords; LatitudinalCoordinates xptLatCoords; LatitudinalCoordinates xxLatCoords; ReferenceFrame fixref; String DSKName; String meta; Surface[] srflst; SurfaceIntercept[] surfxArr; TDBTime et; Vector3[] dirArr; Vector3[] rayVertices; Vector3[] rayDirections; Vector3[] vtxArr; Vector3 xpt; Vector3 xxpt; boolean prioritized = false; double d; double lat; double latstp; double lon; double lonstp; double polmrg; double r; double[] timcov; double[] xptArr; double[] xhitArr; int bodyid; int framid; int i; int latix; int lonix; int nderr; int nhits; int nlat; int nlon; int nrays; int nstep; int nsurf; int nvals; int surfid; try { // // Get meta-kernel name. // if ( args.length != 1 ) { System.out.println( "Command syntax: " + "SurfaceInterceptCreateEx1 " ); return; } meta = args[0]; // // Load kernels. // KernelDatabase.load( meta ); // // Open the first (according to load order) loaded DSK, // then find the first segment and extract the body and // surface IDs. // DSKName = KernelDatabase.getFileName( 0, "DSK" ); dsk = DSK.openForRead( DSKName ); dladsc = dsk.beginForwardSearch(); dskdsc = dsk.getDSKDescriptor( dladsc ); bodyid = dskdsc.getCenterID(); target = new Body( bodyid ); surfid = dskdsc.getSurfaceID(); framid = dskdsc.getFrameID(); fixref = new ReferenceFrame( framid ); // // Set the DSK data look-up time to the midpoint of // the time coverage of the segment we just looked up. // timcov = dskdsc.getTimeBounds(); et = new TDBTime( ( timcov[0] + timcov[1] ) / 2 ); // // Set the magnitude of the ray vertices. Use a large // number to ensure the vertices are outside of // any realistic target. // r = 1.0e10; // // Spear the target with rays pointing toward // the origin. Use a grid of ray vertices // located on a sphere enclosing the target. // // The variable `polmrg' ("pole margin") can // be set to a small positive value to reduce // the number of intercepts done at the poles. // This may speed up the computation for // the multi-segment case, since rays parallel // to the Z axis will cause all segments converging // at the pole of interest to be tested for an // intersection. // polmrg = 0.5; latstp = 1.0; lonstp = 2.0; nlat = (int)( (180.0 + SML) / latstp ) + 1; nlon = (int)( (360.0 + SML) / lonstp ); nhits = 0; nderr = 0; lon = -180.0; lat = 90.0; lonix = 0; latix = 0; nrays = nlat * nlon; vtxArr = new Vector3[nrays]; dirArr = new Vector3[nrays]; // // Generate rays. // i = 0; while ( lonix < nlon ) { lon = lonix * lonstp; while ( latix < nlat ) { if ( lonix == 0 ) { lat = 90.0 - latix*latstp; } else { if ( latix == 0 ) { lat = 90.0 - polmrg; } else if ( latix == nlat-1 ) { lat = -90.0 + polmrg; } else { lat = 90.0 - latix*latstp; } } vtxLatCoords = new LatitudinalCoordinates( r, lon*RPD, lat*RPD ); vtxArr[i] = vtxLatCoords.toRectangular(); dirArr[i] = vtxArr[i].negate(); ++ i; ++ latix; } ++lonix; latix = 0; } // // Assign surface ID list. // // We assume all DSK files referenced in the // meta-kernel have the same body and surface IDs. // We could check this using the DSK coverage routines, // but for brevity, we won't do so here. We'll create // a trivial surface list containing the surface from // the first segment of the first loaded DSK file. // nsurf = 1; srflst = new Surface[nsurf]; srflst[0] = new Surface( surfid, target ); System.out.println ( "Computing intercepts..." ); surfxArr = SurfaceIntercept.create ( prioritized, target, srflst, et, fixref, vtxArr, dirArr ); System.out.println ( "Done." ); // // Check results. // for ( i = 0; i < nrays; i++ ) { // // Recover the vertex longitude and latitude. These // values will be used to generate diagnostic messages, // if necessary. // vtxLatCoords = new LatitudinalCoordinates( vtxArr[i] ); lon = vtxLatCoords.getLongitude() * DPR; lat = vtxLatCoords.getLatitude() * DPR; if ( surfxArr[i].wasFound() ) { // // Record the fact that a new intercept was found. // ++ nhits; // // Compute the latitude and longitude of // the intercept. Make sure these agree // well with those of the vertex. // xpt = surfxArr[i].getIntercept(); xptLatCoords = new LatitudinalCoordinates( xpt ); // // Recover the vertex longitude and latitude. Generate // a new point having these coordinates and radius equal // to that of xpt. // vtxLatCoords = new LatitudinalCoordinates( vtxArr[i] ); xxLatCoords = new LatitudinalCoordinates( xptLatCoords.getRadius(), vtxLatCoords.getLongitude(), vtxLatCoords.getLatitude() ); // // Compute the distance between the intercept and the // point having latitude and longitude of the ray's vertex, // and radius equal to the radius of the intercept. // xxpt = xxLatCoords.toRectangular(); d = xpt.dist( xxpt ); if ( d/r > DTOL ) { xptArr = xpt.toArray(); xhitArr = xxpt.toArray(); System.out.format ( "===========================%n" ); System.out.format ( "Lon = %f; Lat = %f%n", lon, lat ); System.out.format ( "Bad intercept%n" ); System.out.format ( "Distance error = %e%n", d ); System.out.format ( "xpt = (%e %e %e)%n", xptArr[0], xptArr[1], xptArr[2] ); System.out.format ( "xhitArr = (%e %e %e)%n", xhitArr[0], xhitArr[1], xhitArr[2] ); ++ nderr; } } else { // // Missing the target entirely is a fatal error. // // This is true only for this program, not in // general. For example, if the target shape is // a torus, many rays would miss the target. System.out.format ( "===========================%n" ); System.out.format ( "Lon = %f; Lat = %f%n", lon, lat ); System.out.format ( "No intercept%n" ); return; } } System.out.format( "nrays = %d%n", nrays ); System.out.format( "nhits = %d%n", nhits ); System.out.format( "nderr = %d%n", nderr ); } // End of try block catch ( SpiceException exc ) { exc.printStackTrace(); } } // End of main }

    When this program was executed on a PC/Linux/gcc/64-bit/java 1.5 platform, using the meta-kernel shown above, the output was:

    Computing intercepts...
    Done.
    nrays = 32580
    nhits = 32580
    nderr = 0
    

Throws:
SpiceException

wasFound

public boolean wasFound()
Indicate whether the intercept was found.


getIntercept

public Vector3 getIntercept()
                     throws PointNotFoundException,
                            SpiceException
Return the surface intercept.

Throws:
PointNotFoundException
SpiceException

getTargetEpoch

public TDBTime getTargetEpoch()
                       throws PointNotFoundException,
                              SpiceException
Return the target epoch.

Throws:
PointNotFoundException
SpiceException

getSurfaceVector

public Vector3 getSurfaceVector()
                         throws PointNotFoundException,
                                SpiceException
Return the observer to intercept vector.

Throws:
PointNotFoundException
SpiceException

JNISpice
version 2.0.0

JNISpice Alpha Test Version 2.0.0 28-JAN-2017 (NJB)