I am working on some IDL to code to read in GMS imagery in the McIDAS
format. There is one section that I am having difficult understanding -
the orbital element section. I know how to use the numbers in the
navigation model, but how do I extract the values from this section?
From what I can understand, the nav section is a character string and
the character values are converted into a bit, then converted into a
real. There is some FORTRAN code at the bottom that maybe of some help.
I would appreciate any suggestions anyone may have to help me to use IDL
to convert this character string into a real number.
Kelly
=============FORTRAN Code ==========================
SUBROUTINE DECODE_OA_BLOCK( COBAT, FORM )
C*********************************************************** *************
C ORBIT AND ATTITUDE DATA PROCESSING ROUTINE
C*********************************************************** *************
C
implicit none
INTEGER MAP(672,4)
integer i,j
CHARACTER COBAT*3200, FORM*5
REAL R4DMY,RESLIN(4),RESELM(4),RLIC(4),RELMFC(4),SENSSU(4)
REAL VMIS(3),ELMIS(3,3),RLINE(4),RELMNT(4)
real SUBLAT,SUBLON
DOUBLE PRECISION R8DMY,DSPIN,DTIMS,ATIT(10,10),
& ORBT1(35,8)
C
COMMON /MMAP1/MAP
COMMON /NAV1/SUBLAT, SUBLON
C
EQUIVALENCE (MAP( 5,1),DTIMS), (MAP( 7,1),RESLIN(1))
EQUIVALENCE (MAP(11,1),RESELM(1)),(MAP(15,1),RLIC(1))
EQUIVALENCE (MAP(19,1),RELMFC(1)),(MAP(27,1),SENSSU(1))
EQUIVALENCE (MAP(31,1),RLINE(1)), (MAP(35,1),RELMNT(1))
EQUIVALENCE (MAP(39,1),VMIS(1)), (MAP(42,1),ELMIS)
EQUIVALENCE (MAP(131,1),DSPIN)
EQUIVALENCE (MAP(13,3),ORBT1(1,1)),(MAP(13,2),ATIT(1,1))
C
C=========================================================== ==============
C
DO 1000 I=1,4
DO 1100 J=1,672
MAP(J,I) = 0
1100 CONTINUE
1000 CONTINUE
C
CALL SV0100( 6, 8, COBAT( 1: 6), R4DMY , DTIMS )
CALL SV0100( 4, 8, COBAT( 7: 10), RESLIN(1), R8DMY )
CALL SV0100( 4, 8, COBAT( 11: 14), RESLIN(2), R8DMY )
CALL SV0100( 4, 8, COBAT( 11: 14), RESLIN(3), R8DMY )
CALL SV0100( 4, 8, COBAT( 11: 14), RESLIN(4), R8DMY )
CALL SV0100( 4,10, COBAT( 15: 18), RESELM(1), R8DMY )
CALL SV0100( 4,10, COBAT( 19: 22), RESELM(2), R8DMY )
CALL SV0100( 4,10, COBAT( 19: 22), RESELM(3), R8DMY )
CALL SV0100( 4,10, COBAT( 19: 22), RESELM(4), R8DMY )
CALL SV0100( 4, 4, COBAT( 23: 26), RLIC(1) , R8DMY )
CALL SV0100( 4, 4, COBAT( 27: 30), RLIC(2) , R8DMY )
....
....
....
....
.... if the rest of the code is needed, let me know.
SUBROUTINE SV0100( IWORD, IPOS, C, R4DAT, R8DAT)
C*********************************************************** *
C TYPE CONVERT ROUTINE ( R-TYPE )
C*********************************************************** *
C
implicit none
INTEGER IWORD,IPOS,IDATA1
CHARACTER C(*)*1
REAL R4DAT
DOUBLE PRECISION R8DAT
C
C=========================================================== ==
C
R4DAT = 0.0
R8DAT = 0.D0
IF(IWORD.EQ.4) THEN
IDATA1 = ICHAR( C(1)(1:1) )/128
R8DAT = DFLOAT( MOD(ICHAR(C(1)(1:1)),128))*2.D0**(8*3)+
* DFLOAT( ICHAR(C(2)(1:1)) )*2.D0**(8*2)+
* DFLOAT( ICHAR(C(3)(1:1)) )*2.D0**(8*1)+
* DFLOAT( ICHAR(C(4)(1:1)) )
R8DAT = R8DAT/10.D0**IPOS
IF(IDATA1.EQ.1) R8DAT = -R8DAT
R4DAT = SNGL(R8DAT)
ELSEIF(IWORD.EQ.6) THEN
IDATA1 = ICHAR( C(1)(1:1) )/128
R8DAT = DFLOAT( MOD(ICHAR(C(1)(1:1)),128))*2.D0**(8*5)+
* DFLOAT( ICHAR(C(2)(1:1)) )*2.D0**(8*4)+
* DFLOAT( ICHAR(C(3)(1:1)) )*2.D0**(8*3)+
* DFLOAT( ICHAR(C(4)(1:1)) )*2.D0**(8*2)+
* DFLOAT( ICHAR(C(5)(1:1)) )*2.D0**(8*1)+
* DFLOAT( ICHAR(C(6)(1:1)) )
R8DAT = R8DAT/10.D0**IPOS
IF(IDATA1.EQ.1) R8DAT =-R8DAT
R4DAT = SNGL(R8DAT)
ENDIF
RETURN
END
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