SP3 Ephemeris File

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The SP3Ephemeris object provides functionalities for reading and writing SP3 Ephemeris data to and from a SP3 Ephemeris file. This is an ASCII file of Precise Ephemeris SP3 files conforming to the Ephemeris SP3 standard.

 

SP3 ephemeris files (also known as "Precise Ephemeris") contain data records for the orbit and clock states for the entire GPS constellation. There are two versions of the format, Version A and Version C. FreeFlyer has the ability to read and write both versions. The data records are nominally provided at 15 minute intervals, the time system of the file is GPS time, and the reference frame for the orbit data is Earth-Centered-Earth-Fixed (ECEF). FreeFlyer automatically converts between ECEF and MJ2000 when reading and writing SP3EphemerisFiles.

 

More information on the SP3 format can be found in several locations. Two example references are provided below:

 

http://earth-info.nga.mil/GandG/sathtml/sp3format.html

ftp://igscb.jpl.nasa.gov/pub/data/format/sp3c.txt

 

Additionally, historical SP3EphemerisFiles can be downloaded from multiple sources; two examples are provided below:

 

ftp://ftp.nga.mil/pub2/gps/

http://sopac.ucsd.edu/cgi-bin/dbDataByDate.cgi

 

The NGA site provides position and velocity data in Version A of the SP3 format. There are two separate sets of SP3 files provided on the NGA site; one for the center of mass of the vehicle, and one set for the Antenna Phase Center of the vehicle. The SOPAC site provides position-only data in Version C of the SP3 format under the "Products" Data Type.

 

An example of the format of a SP3 file (Version C) is given below.

 

#cP2012  7 23  0  0  0.00000000      96 ORBIT IGS08 BHN ESOC                  

## 1698  86400.00000000   900.00000000 56131 0.0000000000000                  

+   53   G32G26G27G03G04G30G06G08G09G10G14G13G28G21G11G22G20                  

+        G18G16G19G23G02G31G17G12G15G29G07G05G25G01R10R11R13                  

+        R14R15R18R21R02R08R01R06R05R22R24R23R09R12R16R04R03                  

+        R07R17  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0                  

+          0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0                  

++         5  5  5  6  5  5  5  5  5  5  5  5  5  5  5  5  5                  

++         5  5  5  5  6  5  5  5  5  5  4  6  5  5  6  7  6                  

++         7  5  6  7  6  7  7  6  6  7  6  6  6  6  6  6  6                  

++         6  7  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0                  

++         0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0                  

%c M  cc GPS ccc cccc cccc cccc cccc ccccc ccccc ccccc ccccc                  

%c cc cc ccc ccc cccc cccc cccc cccc ccccc ccccc ccccc ccccc                  

%f  0.0000000  0.000000000  0.00000000000  0.000000000000000                  

%f  0.0000000  0.000000000  0.00000000000  0.000000000000000                  

%i    0    0    0    0      0      0      0      0         0                  

%i    0    0    0    0      0      0      0      0         0                  

/* CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC                  

/* CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC                  

/* CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC                  

/* PCV:IGS08_1639 OL/AL:FES2004  NONE     YN ORB:CoN CLK:CoN                  

*  2012  7 23  0  0  0.00000000                                                

PG32  12325.934180   9871.773008  21597.348206   -468.143926                  

PG26 -11524.612440 -13089.258464 -20758.629578   -338.364556                  

PG27 -20091.525648 -16906.001482   6133.481603    412.051561                  

PG03  10941.207500  12979.312053 -20960.632113     78.728606                  

PG04   -786.357125 -20369.466503  16606.408729    251.824776                  

PG30  -1357.934648  25469.211310  -7788.366927   -314.787781                  

PG06   5566.952736  14738.732620 -21287.154700      3.173907                  

PG08   6667.580049 -14550.233395 -20987.824305      1.803402                  

PG09 -19910.625009 -14488.939395   9319.689768    173.545748                  

PG10   8667.283478 -24817.183998  -1924.768640    -45.689269                  

PG14 -12748.473446  13864.900621  18848.216550    207.742907                  

PG13  25262.002878  -5713.873341  -6280.826742    192.898985                  

PG28  11924.789360 -23460.438373  -1983.963628    167.636111                  

PG21 -14452.128908   6694.327782 -20802.840877   -238.317149                  

PG11  23360.121655  12015.198364   4519.915825   -284.472282                  

PG22  -9660.565704  24664.983494    240.401060    145.793865                  

PG20  16510.542479   -808.760716  20622.109989     65.107989                  

PG18 -16417.476070  16232.900086 -12430.336526    206.511949                  

PG16   3432.495291  20151.137593 -16785.304984   -241.796448                  

PG19  20942.918992   8613.320518 -14254.426370   -287.228090                  

PG23  26117.697972    448.557841   5879.628136    182.718535                  

PG02 -12468.819241 -22774.986213   6882.403768    397.620522                  

PG31   2640.032890  20991.521550  16090.409999    262.200592              

 

 

See Also


SP3EphemerisFile Properties and Methods