GPS from getting started to giving up (19), precise ephemeris (SP3 format)

At present GPS In the system , In addition to the broadcast ephemeris broadcast by satellite ,IGS organization （International GNSS Service） Also provide precision Higher satellite ephemeris , We call it Precise ephemeris .

Precise ephemeris can be used for higher precision positioning requirements , Reach centimeter level . Of course, there may be a corresponding delay , The accuracy of real-time positioning may be poor . The major IGS Analysis Center （MIT、SIO、GFZ etc. ） Will produce their own precision products, such as precision ephemeris 、 Precision clock error, etc , and IGS The data of all analysis centers will be summarized and weighted , obtain IGS The data of .

        from ftp service station  ftp://cddis.nasa.gov/gnss/products/  Can download IGS Precise ephemeris data provided . The data under this path is in GPS Weeks （GPS Week） Collate and place for directory names . Like looking for 2020 The precise ephemeris data of new year's day , Through calculation, we know that that day is GPS Zhou di 2086 Zhou , So to enter 2086 Download the corresponding data from the directory .

        at present IGS There are three main types of precise ephemeris ： The final precise ephemeris （IGS Final, The label is IGS）、 Fast and precise ephemeris （IGS Rapid, The label is IGR）、 And ultra fast and precise ephemeris （IGS Ultra-Rapid, The label is IGU）. There are also three corresponding precision clock errors . The ultra fast and precise ephemeris is divided into observation part and prediction part . Their delay 、 Accuracy and other indicators are shown in the table below . In practice , We can meet the time and accuracy requirements of the project , Select different types of files to use .

 

sp3 Format

IGS The precise ephemeris uses sp3 Format , The naming rule of its file name is ：AAAWWWWD.sp3. among AAA Indicates type identification （IGS、IGU、IGR） Or the abbreviation of Analysis Center （ Such as MIT、SIO、GFZ etc. ）,IGS The weighted average of products of all analysis centers will be integrated to get the final product （ The label is IGS、IGR、IGU）;WWWW Express GPS Weeks （GPS Week）;D What day of the week （ Range 0~6,0 Means Sunday ,1 It means Monday ）.

       sp3 The file is stored in ASCII text file , The contents include header information and file body , Every... In the file body 15 Minutes gives the position of the satellite , And sometimes the speed of the satellite . If you need the satellite position at other times , It can be obtained by interpolating the given satellite position . About sp3 The detailed description of the document can refer to the official documents ：ftp://igs.org/pub/data/format/sp3c.txt

        It is different from the broadcast ephemeris , Precise ephemeris is not given by Kepler parameters , But directly give the satellite in ITRF Coordinate values in the frame ITRF（International Terrestrial Reference Frame International Earth reference framework ） Framework is made up of IERS（ International Earth Rotation Service ） released ,ITRF The composition of is based on VLBI、LLR、SLR、GPS and DORIS Observation data of space geodetic Technology , from IERS The global station coordinates and velocity field obtained from the analysis of the Central Bureau . since 1988 From the year onwards ,IERS Has been released ITRF88、ITRF89、ITRF90、ITRF9 1、ITRF92、ITRF93、ITRF94、ITRF96、ITRF2000、ITRF2005、ITRF2008、ITRF2014 And other global reference frameworks .
 

Here's from igs20863.sp3 The first part intercepted in the file , A brief introduction ：

#cP2020  1  1  0  0  0.00000000      96 ORBIT IGS14 HLM  IGS
## 2086 259200.00000000   900.00000000 58849 0.0000000000000
+   32   G01G02G03G04G05G06G07G08G09G10G11G12G13G14G15G16G17
+        G18G19G20G21G22G23G24G25G26G27G28G29G30G31G32  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  0  0  0  0
+          0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
++         2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2  2
++         2  2  2  2  2  2  2  2  3  2  2  2  2  2  2  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  0  0  0  0
++         0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
%c G  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  1.2500000  1.025000000  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
/* FINAL ORBIT COMBINATION FROM WEIGHTED AVERAGE OF:        
/* cod emr esa gfz grg jpl mit ngs sio                      
/* REFERENCED TO IGS TIME (IGST) AND TO WEIGHTED MEAN POLE:
/* PCV:IGS14_2086 OL/AL:FES2004  NONE     Y  ORB:CMB CLK:CMB
*  2020  1  1  0  0  0.00000000
PG01   9888.347661 -19617.637150 -14892.695413   -247.874423 12 10  5  71       
PG02 -21823.783543  13971.156772  -4920.780210   -377.229970 10  9  7  81       
PG03  -1601.529966 -16464.253025 -20857.441401    -63.370799  8  7 11 105       
PG04   1221.994671 -26086.976634  -4781.101677    -27.923755 12  4  5 109       
PG05 -19154.192243   5721.537965  17444.937173     -5.436142  7  8  6  88       
PG06 -21150.813850   2402.751626 -15853.420427   -169.653500  9  7  8 106       
PG07  -7307.639840 -13757.950583  21767.441209   -182.185020  6  6  5  99       
PG08   7039.047666 -21245.446842  14152.046835    -18.646350  8  5  7  94       
PG09  -6875.945629 -25134.252934   5050.629544   -121.818618  9  8  4 109       
PG10  24015.414289  11544.134960   1555.732288   -193.008701  8  8  8 103       
PG11   7282.297820 -25005.780611  -6416.591136   -403.117157  9  8  7  95       
PG12  -3612.078652  14754.643360 -22024.819114    167.238453  6  6  5 121       
PG13 -12822.251931  14077.120706  18359.989020    -22.958664  7  7  7  85       
PG14  15097.782136    719.539797 -21518.284406    -41.480187  8  9  3  98       
PG15  -5026.428258  22304.034935  12884.805910   -261.734981  8  6  5  83       
PG16  20065.806133  -2268.606859  17288.279253   -108.806027  7  8  6  98       
PG17 -13302.574437 -12501.633252 -18888.874080    190.733864  6  5  7  99       
PG18  15683.730129 -20086.062189  -7815.214505 999999.999999
PG19 -14744.295897  -4057.283573 -22007.637771   -218.643006  9  7  9 107       
PG20  18932.638979  14547.678555  11749.766535    527.763846 11 10 11  93       
PG21  10191.957706  12064.511376  22150.584734    -62.423168 10  8 11  69       
PG22   7023.579706 -14225.418680 -21077.053685   -780.142685  9  7  9  70       
PG23  -1206.975660 -26081.394867  -3218.011480   -145.988210 10  4  6 100       
PG24 -10589.076575  20789.036009 -12534.802874     -6.933769  9  7  4 109       
PG25  11115.892105  17563.783060 -16907.847503    -16.767205  8  8  6 106       
PG26  24809.687134   2652.030547   9387.846884    117.742691  8 10  8 116       
PG27  12654.914692 -10785.577586  20515.681941   -167.508526  8  5  8  92       
PG28 -22961.626731 -13197.537237    783.057544    747.765166  6  8  6  95       
PG29   4498.761624  25678.893062   4992.306129      4.083857 10 10  6  67       
PG30 -17217.300944  -5541.835900  19540.416589   -118.767102  6  7  7  87       
PG31  22625.699147  -4025.359523 -13738.508642    -13.516273  7  9  7  90       
PG32  14835.028318  11206.018688 -18957.170663    172.050190  9 10  5 104       
*  2020  1  1  0 15  0.00000000
PG01  11218.886280 -20435.428221 -12620.054414   -247.885427 11 10  5  55       
PG02 -21416.153632  13234.932709  -7652.201926   -377.236434  9  9  6  89       
PG03    658.942604 -15624.793321 -21537.118493    -63.377346  7  7 10  93       
PG04   1551.226922 -25415.284695  -7518.401629    -27.928395 11  5  6  93       
PG05 -20891.993883   4906.521003  15635.291423     -5.436689  7  8  5  80       
PG06 -19726.065274   1101.751537 -17715.564454   -169.663056  9  6  7 113
... ... ...