
	Contents of this file JUL20.TXT. This file contains RTCM
type 1 DGPS correction records. There are 4 main areas of this
document. Section 1 shows the record decoded and displayed by
the RTCMON program provided by DCI at their website. The 2nd
section is the ASCII "dumb terminal" display of the packet
received from a local station using the TAPR DGPS board.
The next area shows an HEX ASCII dump of the packet. The last
area shows how the DGPS data is extracted from the RTCM
record. The raw data used in this example is in "JUL20.DAT".
	Note that the RTCM message consists of a number of "words",
each word consisting of 5, 8-bit bytes. The upper 2 bits
of each byte must contain "01" to be a valid data record.
First, strip off the upper 2 bits, leaving 5, 6 bit words.
Next, reverse the bit order for each 6 bit group. These
30 bits form the data word in the RTCM message. The last
6 bits are the word parity, this leaves the 1st 24 bits
as the data area. The grouping of the 24 data bits into
data fields varies within the location of the message.
Also, if the last bit of the parity in the previous
word was set, you must bit invert this word's 24 data
bits, before parsing them.
	General notes: The sat no goes from 0 to 31,
representing sats 1 to 32. (add 1 to the no. decoded).
The SF flag determines whether the PRC is scaled by .02
or by .32, and PRRC scaled by .002 and .032 (the larger
factor if SF=1). The Z-Count is the GPS time scaled
by 0.6 sec. The message word count in word 2, is the
number of words remaining in this message. That is,
the total number of words in the message is this count+2.



RTCMON -- RTCM Data Monitor -- Ver. 3.4A (c) Copyright 1995 DCI      9600-8-N-1

---------------------------------------
Received Type  1 at  900.6 sec. (Len 12)
 SV  UDRE  IODE    PRC (m)    RRC (m/s)
 22    0     52     -5.02     -0.066
  1    0     94     10.14     -0.154
 25    0    147    -29.12     -0.448
  6    0      8      4.28      0.132
 29    0    194     -6.86      0.124
 16    0    115     27.68      0.036
 14    0    233    -19.20      0.384
---------------------------------------


 CLECOM>DGPS,CLECOM-1*,CLECOM-1:fAbxWt]cAmWBpW@{sB`eAbLEZF@rZAkMV`ApZRBAAnFUI
_s|^Wvi_[LdNB@w^p\YUv

000000  43 4C 45 43 4F 4D 3E 44  47 50 53 2C 43 4C 45 43    CLECOM>DGPS,CLEC
000010  4F 4D 2D 31 2A 2C 43 4C  45 43 4F 4D 2D 31 3A 66    OM-1*,CLECOM-1:f
000020  41 62 78 57 74 5D 63 41  6D 57 42 70 57 40 7B 73    AbxWt]cAmWBpW@{s
000030  42 60 65 7F 41 62 4C 7F  45 5A 46 40 72 5A 41 6B    B`e.AbL.EZF@rZAk
000040  4D 56 60 41 70 5A 52 42  41 41 6E 46 7F 55 49 5F    MV`ApZRBAAnF.UI_
000050  73 7C 5E 7F 57 76 69 5F  5B 4C 64 4E 42 40 77 5E    s|^.Wvi_[LdNB@w^
000060  70 5C 59 55 76 0D 0D 0A  0D 0A 0D 0D 0A 43 4C 45    p\YUv........CLE



000000  43 4C 45 43 4F 4D 3E 44  47 50 53 2C 43 4C 45 43    CLECOM>DGPS,CLEC
000010  4F 4D 2D 31 2A 2C 43 4C  45 43 4F 4D 2D 31 3A <66    OM-1*,CLECOM-1:f
           word 1       word 2              word 3
000020  41 62 78 57> <74 5D 63 41  6D> <57 42 70 57 40> <7B 73    AbxWt]cAmWBpW@{s
         word 4       word 5            word 6       word 7
000030  42 60 65> <7F 41 62 4C 7F>  <45 5A 46 40 72> <5A 41 6B    B`e.AbL.EZF@rZAk
                   word 8          word 9           word 10
000040  4D 56> <60 41 70 5A 52> <42  41 41 6E 46> <7F 55 49 5F    MV`ApZRBAAnF.UI_
                word 11         word 12           word 13
000050  73> <7C 5E 7F 57 76> <69 5F  5B 4C 64> <4E 42 40 77 5E>    s|^.Wvi_[LdNB@w^
           word 14
000060  <70 5C 59 55 76> 0D 0D 0A  0D 0A 0D 0D 0A 43 4C 45    p\YUv........CLE

============================================================================
  Word 1
 <66 41 62 78 57>

    6    6     4    1     6    2     7    8     5    7
  0110 0110  0100 0001  0110 0010  0111 1000  0101 0111
    10 0110    00 0001    10 0010    11 1000    01 0111  drop top 2 bits
    0110 01    1000 00    0100 01    0001 11    1110 10  reverse bit order

     header       type       station id     parity
    0110 0110    00 0001   00 0100 0111    11 1010  re-group as 8, 6, 10, 6 bits
      6   6       0   1     0   4   7       3  a     STATION ID 71

============================================================================
  Word 2
 <74 5D 63 41 6D>

    7    4     5    D     6    3     4    1     6    D
  0111 0100  0101 1101  0110 0011  0100 0001  0110 1101
    11 0100    01 1101    10 0011    00 0001    10 1101
    0010 11    1011 10    1100 01    1000 00    1011 01

       Z COUNT         SEQ   COUNT   HEALTH   parity
    0 0101 1101 1101   100   0 1100   000    10 1101 (last bit set, invert next)
    0  5    D    D      4    0  C      0      2  D   SEQNO 4, WORD CNT 12
       Z-COUNT 05DD = 1501 * 0.6 = 900.6 SEC

============================================================================
  Word 3
<57 42 70 57 40>

    5    7     4    2     7    0     5    7     4    0
  0101 0111  0100 0010  0111 0000  0101 0111  0100 0000
    01 0111    00 0010    11 0000    01 0111    00 0000
    1110 10    0100 00    0000 11    1110 10    0000 00

   SF   RE   SATID           PRC            parity
    1   11   0 1001   0000 0000 1111 1010   00 0000
    0   00   1 0110   1111 1111 0000 0101   00 0000    INVERT DATA (NOT PARITY)
    0   0    1  6       F    F    0    5     0   0    SAT ID 16 (HEX) 22 (DEC)
      PRC CALC   FF05  =  -251 * .02  = - 5.02 m

============================================================================
  Word 4
<7B 73 42 60 65>

    7    B     7    3     4    2     6    0     6    5
  0111 1011  0111 0011  0100 0010  0110 0000  0110 0101
    11 1011    11 0011    00 0010    10 0000    10 0101
    1101 11    1100 11    0100 00    0000 01    1010 01

        PRCC     IODE    SF  RE  SATID   parity
    1101 1111  0011 0100  0  00  0 0001  10 1001 (last bit, invert next data)
      D    F     3    4   0   0  0   1    2   9   IODE 34(HEX) 52    SAT ID 1
      PRCC CALC   DF  =  -33 * .002  = - 0.066 m/SEC


============================================================================
  Word 5
 <7F 41 62 4C 7F> 

    7    F     4    1     6    2     4    C     7    F
  0111 1111  0100 0001  0110 0010  0100 1100  0111 1111
    11 1111    00 0001    10 0010    00 1100    11 1111
    1111 11    1000 00    0100 01    0011 00    1111 11

            PRC            PRCC     parity
    1111 1110 0000 0100  0100 1100  11 1111 (last bit, invert next data)
    0000 0001 1111 1011  1011 0011  11 1111   INVERT DATA
      0    1    F    B     B    3    3   F
       PRC CALC 01FB  = 507  * 0.02  10.14 M
      PRCC CALC   B3  =  -77 * .002  = - 0.154 m/SEC


============================================================================
  Word 6
 <45 5A 46 40 72> 

    4    5     5    A     4    6     4    0     7    2
  0100 0101  0101 1010  0100 0110  0100 0000  0111 0010
    00 0101    01 1010    00 0110    00 0000    11 0010
    1010 00    0101 10    0110 00    0000 00    0100 11

      IODE    SF  RE   SATID    PRC HI   parity
    1010 0001  0  11  0 0110  0000 0000  0100 11
    0101 1110  1  00  1 1001  1111 1111  01 0011 INVERT DATA
      5    E   1   0  1   9     F    F     2  C   SAT ID 25, IODE = 94


============================================================================
  Word 7
<5A 41 6B 4D 56> 

    5    A     4    1     6    B     4    D     5    6
  0101 1010  0100 0001  0110 1011  0100 1101  0101 0110
    01 1010    00 0001    10 1011    00 1101    01 0110
    0101 10    1000 00    1101 01    1011 00    0110 10

      PRC LO     PRCC       IODE     parity
    0101 1010  0000 1101  0110 1100  01 1010
    1010 0101  1111 0010  1001 0011  01 1010     INVERT DATA
      A    5     F    2     9    3    1   A       IODE 93(hex) 147(dec)
       PRC CALC FFA5  = -91  * 0.32  = -29.12 M  (sf was = 1)
      PRCC CALC   F2  =  -14 * .032  = - 0.448 m/SEC


============================================================================
  Word 8
 <60 41 70 5A 52> 

    6    0     4    1     7    0     5    A     5    2
  0110 0000  0100 0001  0111 0000  0101 1010  0101 0010
    10 0000    00 0001    11 0000    01 1010    01 0010
    0000 01    1000 00    0000 11    0101 10    0100 10


   SF   RE   SATID           PRC            parity
    0   00   0 0110   0000 0000 1101 0110   01 0010
    0   0    0  6       0    0    D    6     1   2    SAT ID  6 (HEX)  6 (DEC)
      PRC CALC   00D6  =   214 * .02  = 4.28 m


============================================================================
  Word 9
<42 41 41 6E 46>

    4    2     4    1     4    1     6    E     4    6
  0100 0010  0100 0001  0100 0001  0110 1110  0100 0110
    00 0010    00 0001    00 0001    10 1110    00 0110
    0100 00    1000 00    1000 00    0111 01    0110 00

        PRCC     IODE    SF  RE  SATID   parity
    0100 0010  0000 1000  0  00  1 1101  01 1000
      4    2     0    8   0   0  1   D    1   8   IODE 08(HEX)  8    SAT ID 29
      PRCC CALC   42  =   66 * .002  =   0.132 m/SEC


============================================================================
  Word 10
 <7F 55 49 5F 73> 

    7    F     5    5     4    9     5    F     7    3
  0111 1111  0101 0101  0100 1001  0101 1111  0111 0011
    11 1111    01 0101    00 1001    01 1111    11 0011
    1111 11    1010 10    1001 00    1111 10    1100 11

            PRC            PRCC     parity
    1111 1110 1010 1001  0011 1110  11 0011
      F    E    A    9     3    E    3   3
       PRC CALC FEA9  = -343  * 0.02 = -6.86 M
      PRCC CALC   3E  =  62 * .002  =  0.124 m/SEC


============================================================================
  Word 11
 <7C 5E 7F 57 76> 

    7    C     5    E     7    F     5    7     7    6
  0111 1100  0101 1110  0111 1111  0101 0111  0111 0110
    11 1100    01 1110    11 1111    01 0111    11 0110
    0011 11    0111 10    1111 11    1110 10    0110 11

      IODE    SF  RE   SATID    PRC HI   parity
    0011 1101  1  11  0 1111  1111 1010  0110 11
    1100 0010  0  00  1 0000  0000 0101  01 1011 INVERT DATA
      C    2   0   0  1   0     0    5    1   B   SAT ID 16  IODE 194


============================================================================
  Word 12
 <69 5F 5B 4C 64> 

    6    9     5    F     5    B     4    C     6    4
  0110 1001  0101 1111  0101 1011  0100 1100  0110 0100
    10 1001    01 1111    01 1011    00 1100    10 0100
    1001 01    1111 10    1101 10    0011 00    0010 01

      PRC LO     PRCC       IODE     parity
    1001 0111  1110 1101  1000 1100  00 1001
    0110 1000  0001 0010  0111 0011  00 1001  INVERT DATA
      6    8     1    2     7    3    0   9       IODE 73(hex) 115(dec)
       PRC CALC 0568  = 1384 * 0.02  =  27.68 M 
      PRCC CALC   12  =   18 * .002  =   0.036 m/SEC


============================================================================
  Word 13
<4E 42 40 77 5E> 

    4    E     4    2     4    0     7    7     5    E
  0100 1110  0100 0010  0100 0000  0111 0111  0101 1110
    00 1110    00 0010    00 0000    11 0111    01 1110
    0111 00    0100 00    0000 00    1110 11    0111 10


   SF   RE   SATID           PRC            parity
    0   11   1 0001   0000 0000 0011 1011   0111 10
    1   00   0 1110   1111 1111 1100 0100   01 1110  INVERT BITS
    1   0    0  E       F    F    C    4     1   E    SAT ID 0E (HEX) 14 (DEC)
      PRC CALC   FFC4  =  -60  * .32  =-19.2 m


============================================================================
  Word 14
<70 5C 59 55 76>

    7    0     5    C     5    9     5    5     7    6
  0111 0000  0101 1100  0101 1001  0101 0101  0111 0110
    11 0000    01 1100    01 1001    01 0101    11 0110
    0000 11    0011 10    1001 10    1010 10    0110 11

        PRCC     IODE    SF  RE  SATID   parity
    0000 1100  1110 1001  1  01  0 1010  01 1011
      0    C     E    9   1   1  0   A    1   B   IODE E9(HEX) 233   SAT ID 10
      PRCC CALC   0C  =   12 * .032 =   0.384 m/SEC



RTCMON -- RTCM Data Monitor -- Ver. 3.4A (c) Copyright 1995 DCI      9600-8-N-1

---------------------------------------
Received Type  1 at  906.0 sec. (Len 12)
 SV  UDRE  IODE    PRC (m)    RRC (m/s)
 22    0     52     -5.48      0.020
  1    0     94      9.30     -0.186
 25    0    147    -30.72     -0.352
  6    0      8      4.76     -0.032
 29    0    194     -6.06      0.088
 16    0    115     27.66      0.080
 14    0    233    -17.60      0.384
---------------------------------------


 CLECOM>DGPS,CLECOM-1*,CLECOM-1:Y~]GMtsjAYh}w]NPqB`bQgN@zeyME|ZrC`Ap]FO@AnYmH
MHCa@hIfSasRq}d}Ocfjl

000060  70 5C 59 55 76 0D 0D 0A  0D 0A 0D 0D 0A 43 4C 45    p\YUv........CLE
000070  43 4F 4D 3E 44 47 50 53  2C 43 4C 45 43 4F 4D 2D    COM>DGPS,CLECOM-
000080  31 2A 2C 43 4C 45 43 4F  4D 2D 31 3A 59 7E 5D 47    1*,CLECOM-1:Y~]G
000090  4D 74 73 6A 41 59 68 7D  77 5D 4E 50 71 42 60 62    MtsjAYh}w]NPqB`b
0000A0  7F 51 67 4E 40 7A 65 79  7F 4D 45 7C 5A 72 43 60    .QgN@zey.ME|ZrC`
0000B0  41 70 5D 46 4F 40 41 6E  59 7F 6D 48 4D 48 43 61    Ap]FO@AnY.mHMHCa
0000C0  40 68 49 66 53 61 73 52  71 7D 7F 64 7D 4F 63 66    @hIfSasRq}.d}Ocf
0000D0  6A 6C 0D 0D 0A 0D 0A 0D  0D 0A 43 4C 45 43 4F 4D    jl........CLECOM


RTCMON -- RTCM Data Monitor -- Ver. 3.4A (c) Copyright 1995 DCI      9600-8-N-1

---------------------------------------
Received Type  1 at  910.8 sec. (Len 12)
 SV  UDRE  IODE    PRC (m)    RRC (m/s)
 22    0     52     -5.76     -0.038
  1    0     94      8.44     -0.202
 25    0    147    -32.32     -0.256
  6    0      8      5.18      0.066
 29    0    194     -5.20      0.100
 16    0    115     27.56     -0.036
 14    0    233    -16.00      0.352
---------------------------------------


 CLECOM>DGPS,CLECOM-1*,CLECOM-1:Y~]GhKDY~Ph}wAIwrB`J@VVvCzeyMYQrQ`AHpODBAne@B|
lr|^WvybXLRq}\RP_YUw



RTCMON -- RTCM Data Monitor -- Ver. 3.4A (c) Copyright 1995 DCI      9600-8-N-1

---------------------------------------
Received Type  1 at  915.6 sec. (Len 12)
 SV  UDRE  IODE    PRC (m)    RRC (m/s)
 22    0     52     -6.12     -0.032
  1    0     94      7.56     -0.134
 25    0    147    -33.92     -0.320
  6    0      8      5.44     -0.084
 29    0    194     -4.36      0.130
 16    0    115     27.38      0.028
 14    0    233    -14.08      0.416
---------------------------------------


 CLECOM>DGPS,CLECOM-1*,CLECOM-1:Y~]GMtwnA_h}w\hpO}_tEjPyEZF@rVBiMJ`AHB|T~~Q|@lY
_GCa@hIZBgsyNB@uvOafj@



RTCMON -- RTCM Data Monitor -- Ver. 3.4A (c) Copyright 1995 DCI      9600-8-N-1

---------------------------------------
Received Type  1 at  921.0 sec. (Len 12)
 SV  UDRE  IODE    PRC (m)    RRC (m/s)
 22    0     52     -6.48     -0.062
  1    0     94      6.66     -0.192
 25    0    147    -35.34     -0.172
  6    0      8      5.60      0.048
 29    0    194     -3.48      0.116
 16    0    115     27.08     -0.078
 14    0    233    -12.48      0.352
---------------------------------------


 CLECOM>DGPS,CLECOM-1*,CLECOM-1:fAbxrK@^~Ch}WO\GrB`iud~TzaygMXVUrZ`AHFCX@AnMkD
WKCa@hIRmis~NB@Yjo`fjH



