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NGA/GPS 5 Minute Ephemeris SP3 Format Description


Effective date February 26, 2012




The SP3 Enhanced Format used by the NGA St. Louis GPS Division (Geodesy & Geophysics):

The SP3 format is presented here in both the position (P) mode and the velocity (V) mode.  
We will be using the format finalized by the National Geodetic Survey.  The SP3 format is 
precise to 1mm and 1 picosecond.  If velocity is included, its precision is 10E-4 mm/sec 
and 10E-4 picoseconds/s.

The following four modifications were made to the SP3 format upon completion of a one year 
open period for customer feedback.

1.  Version Identification:  
On line one, character two, there is now a single version identification character.  The 
first released version has been designated version 'a'.  Subsequent versions will use the 
lower case letters in alphabetical order.

2.  Position/Velocity Mode Flag:
The proposed formats did not accommodate velocity data on the theory that it can be derived 
from the positional data.  Although it is true that velocity data can be computed from positional 
data--accurate to a few microns per second or better--there are arguments why velocity will be 
needed, explicitly, in some situations.  On line one, character three, there is now a single flag 
to indicate if the SP3 file will comprise only positional data (P) or both position and velocity 
data (V).

III.  Position/Velocity Mode P:
In the proposal, the first character on the lines containing the x, y, z, and clock correction 
values was 'V' for "vehicle".  Now the first character will be 'P' for position.

IV.  Position/Velocity Mode V:
When the position/velocity mode flag is set to 'V' each position line for a given satellite is 
followed by a velocity line for the same satellite.  The velocity components are given in 
decimeters/s and have a precision of 10E-14 mm/sec.  The last column of a velocity line is the 
rate of change of clock correction given in units of 10E-4 microsec/s.  The precision of this 
parameter is 10E-16 s/s.


In addition to the above four changes, we have added a marker to designate the locations of clock 
events.  This marker is an 'E' located in column 75 of the position line for a satellite.  This 
field will normally be blank.

*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*

The following is the format for the "enhanced" SP3:


       123456789012345678901234567890123456789012345678901234567890

1      #aV2012 10  1  0  0  0.00000000     288 DD+AD WGS84 FIT  NGA
2      ## 1708  86400.00000000   300.00000000 56201 0.0000000000000
3      +   31     1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17
4      +         18 19 20 21 22 23 25 26 27 28 29 30 31 32  0  0  0
5      +          0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
6      +          0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
7      +          0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
8      ++         2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2
9      ++         2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  0  0
10     ++         0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
11     ++         0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
12     ++         0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
13     %c cc cc ccc ccc cccc cccc cccc cccc ccccc ccccc ccccc ccccc
14     %c cc cc ccc ccc cccc cccc cccc cccc ccccc ccccc ccccc ccccc
15     %f  0.0000000  0.000000000  0.00000000000  0.000000000000000
16     %f  0.0000000  0.000000000  0.00000000000  0.000000000000000
17     %i    0    0    0    0      0      0      0      0         0
18     %i    0    0    0    0      0      0      0      0         0
19     /*      NGA, ST. LOUIS,MO.                                  
20     /*   EPHEMERIS COMPUTED FROM  1 DAYS OF DATA
21     /*   EPOCHA SMOOTHER  
22     /* CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
23     *  2012 10  1  0  0  0.00000000                                                 
24     P  1  -1677.901589  16285.584053 -20920.350325    275.849218                    
25     V  1 -25096.728698   8665.572021   8818.525202      0.015870                    
26     P  2  20801.130436 -14268.541598   7587.240521    404.556632                    
27     V  2  10280.136019   -147.845949 -29536.235333      0.011634                    
28                .             .             .             .       
29                .             .             .             .
30                .             .             .             .
31                .             .             .             .
32                .             .             .             .
33                .             .             .             .
34     *  2012 10  1 23 55  0.00000000                                                 
35     P  1  -1545.870613  16240.292187 -20966.016107    275.985617                    
36     V  1 -25177.862925   8604.994335   8581.662169      0.015774                    
37                .             .             .             .
38                .             .             .             .
39                .             .             .             .
40                .             .             .             .
41                .             .             .             .
42                .             .             .             .
43     P 32   -143.412125  18718.631715 -18837.924362   -493.864143                    
44     V 32 -18157.215193 -16024.551820 -15137.882157     -0.039374                    
45     EOF

*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*

SP3(Enhanced) Format:

Line One:
  ('#aV',i4,4i3,f12.8,6x,'96 DD+AD WGS84 FIT  NGA')
Column1       Symbol                 #
      2       Version Identifier     a               
      3       Pos/Vel Mode Flag      P or V
      4-7     Year Start             2012
      8       Unused                 _
      9-10    Month Start            _10
      11      Unused                 _
      12-13   Day of Month Start     _ 1
      14      Unused                 _
      15-16   Hour Start             _0
      17      Unused                 _
      18-19   Minute Start           _0
      20      Unused                 _
      21-31   Second Start           _.00000000
      32      Unused                 _
      33-39   Number of Epochs       ____288
      40      Unused                 _
      41-45   Data Used              DD+AD
      46      Unused                 _
      47-51   Coordinate System      WGS84
      52      Unused                 _
      53-55   Orbit Type             FIT
      56      Unused                 _
      57-60   Agency                 NGA

Line Two:
  ('##',i5,f16.8,f15.8,i6,f16.13)
Column1-2     Symbols                ##
      3       Unused                 _
      4-7     GPS Week               _1708
      8       Unused                 _
      9-23    Seconds of Week        _.00000000
      24      Unused                 _
      25-38   Epoch Interval         __300.00000000
      39      Unused                 _ 
      40-44   Mod Julian Day Start   56201
      45      Unused                 _ 
      46-60   Fractional Day         _.0000000000000

Line Three:
  ('+',i5,3x,17i3)
Column1-2     Symbols                +_
      3-4     Unused                 __ 
      5-6     Number of Sats         31
      7-9     Unused                 ___ 
      10-12   Sat #1 Id              __1
      13-15   Sat #2 Id              __2
        *         *                   *
        *         *                   *
        *         *                   *
      58-60   Sat #17 Id             _18

Line Four:
  ('+',8x,17i3)
Column1-2     Symbols                +_
      3-9     Unused                 _______ 
      10-12   Sat #18 Id             _19
      13-15   Sat #19 Id             _20
        *         *                   *
      43-45   Sat #29 Id             _30
        *         *                   *
        *         *                   *
      58-60   Sat #34 Id             __0

Line Five:
   ('+',8x,17i3)
(Same as Line Four for Sats 35 to 51)

Line Six:
  ('+',8x,17i3)
(Same as Line Four for Sats 52 to 68)

Line Seven:
  ('+',8x,17i3)
(Same as Line Four for Sats 69 to 85)

Line Eight:
  ('++',7x,17i3)
Column1-2     Symbols                ++
      3-9     Unused                 _______ 
      10-12   Sat #1 Accuracy        __0
      13-15   Sat #2 Accuracy        __0
        *         *                   *
        *         *                   *
        *         *                   *
      58-60   Sat #17 Accuracy       __0

Line Nine:
  ('++',7x,17i3)
(Same as Line Eight for Sats 18 to 34)

Line Ten:
  ('++',7x,17i3)
(Same as Line Eight for Sats 35 to 51)

Line Eleven:
  ('++',7x,17i3)
(Same as Line Eight for Sats 52 to 68)

Line Twelve:
  ('++',7x,17i3)
(Same as Line Eight for Sats 69 to 85)

Lines Thirteen and Fourteen:
  ('%c cc cc ccc ccc cccc cccc cccc cccc ccccc ccccc ccccc ccccc')
Column1-2     Symbols                %c
      3       Unused                 _ 
      4-5     2 characters           cc
      6       Unused                 _ 
      7-8     2 characters           cc
      9       Unused                 _ 
      10-12   3 characters           ccc
      13      Unused                 _ 
      14-16   3 characters           ccc
      17      Unused                 _ 
      18-21   4 characters           cccc
      22      Unused                 _ 
      23-26   4 characters           cccc
      27      Unused                 _ 
      28-31   4 characters           cccc
      32      Unused                 _ 
      33-36   4 characters           cccc
      37      Unused                 _ 
      38-42   5 characters           ccccc
      43      Unused                 _ 
      44-48   5 characters           ccccc
      49      Unused                 _ 
      50-54   5 characters           ccccc
      55      Unused                 _ 
      56-60   5 characters           ccccc

Lines Fifteen and Sixteen:
  ('%f  0.0000000  0.000000000  0.00000000000  0.000000000000000')
Column1-2     Symbols                %f
      3       Unused                 _ 
      4-13    10 column float        _0.0000000
      14      Unused                 _ 
      15-26   12 column float        _0.000000000
      27      Unused                 _ 
      28-41   14 column float        _0.00000000000
      42      Unused                 _ 
      43-60   18 column float        _0.000000000000000

Lines Seventeen and Eighteen:
  ('%i    0    0    0    0      0      0      0      0         0')
Column1-2     Symbols                %i
      3       Unused                 _ 
      4-7     4 column integer       ___0
      8       Unused                 _ 
      9-12    4 column integer       ___0
      13      Unused                 _ 
      14-17   4 column integer       ___0
      18      Unused                 _ 
      19-22   4 column integer       ___0
      23      Unused                 _ 
      24-29   6 column integer       _____0
      30      Unused                 _ 
      31-36   6 column integer       _____0
      37      Unused                 _ 
      38-43   6 column integer       _____0
      44      Unused                 _ 
      45-50   6 column integer       _____0
      51      Unused                 _
      52-60   9 column integer       ________0

Lines Nineteen to Twenty-two:
  ('/* CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC')
Column1-2     Symbols                /*
      3       Unused                 _          
      4-60    Comments               CC...CC

Line Twenty-three (The Epoch Header Record):
  ('*',i6,4i3,f12.8)
Column1-2     Symbol                 *_
      3       Unused                 _        
      4-7     Year Start             2012
      8       Unused                 _        
      9-10    Month Start            _10
      11      Unused                 _        
      12-13   Day of Month Start     _ 1
      14      Unused                 _        
      15-16   Hour Start             _0
      17      Unused                 _        
      18-19   Minute Start           _0
      20      Unused                 _        
      21-31   Second Start           _.00000000

Line Twenty-four (The Position and Clock Record):
  ('P',i3,4f14.6)
Column1       Position               P
      2-4     Vehicle Id             __1
      5-18    x coordinate (km)      __-1577.901589
      19-32   y coordinate (km)      __16285.584053
      33-46   z coordinate (km)      _-20920.350325
      47-60   clock (microseconds)   ____275.849218

Line Twenty-five (The Velocity Record):
  ('V',i3,4f14.6)
Column1       Velocity               V
      2-4     Vehicle Id             __1
      5-18    x coordinate (dm/sec)  _-25096.728698
      19-32   y coordinate (dm/sec)  ___8665.572021
      33-46   z coordinate (dm/sec)  ___8818.525202
      47-60   Rate of change of      ______0.015870
               Clock Correction (0.0001 microsec/sec)


(Line Twenty-four will include an 'E' in column 75 to designate an Event in 
the Position and Clock Record.)  ('P',i3,4f14.6,14x,'E')

(Lines Twenty-four and Twenty-five repeat for each vehicle in the epoch.)

(Epoch Headers in Line Twenty-three repeat for each new epoch with vehicle 
position and velocity records following.)

(Last line in file)  EOF


Point of Contact: GPS Division
Phone Numbers:
  Com. (314)676-9140
  DSN 846-9140

Document last modified Monday, 05-May-2014 16:33:07 EDT