# Presentation: 238688

## Initial Ideas and Suggestions for a New IGS Orbit Format

**Steve Hilla**
**National Geodetic Survey, NOAA**

**IGS Analysis Center Workshop**
**2-6 June 2008, Miami Beach, Florida, USA**

## Outline  

**Brief History**
**List of New Features**
**Other Interesting Ideas**
**Some Examples**
**Summary and Future Plans**

## A Brief History

**SP3-a:  developed by Ben Remondi in 1991 and used by the IGS from 1994 to 2004.**
**SP3-b:  modifications by Gurtner/Rothacher in 1998 to provide a way to mix GPS and GLONASS satellites.**
**SP3-c:  additions made in 2002 to provide time dependent accuracies, XYZt correlations, and event flags. The IGS switched from      SP3-a/b to SP3-c in 2004.**

## An example SP3-c file, the GPS final orbit for May 7, 2008

**## 1478 259200.00000000   900.00000000 54593 0.0000000000000**
**+   31   G02G03G04G05G06G07G08G09G10G11G12G13G14G15G16G17G18**
**+        G19G20G21G22G23G24G25G26G27G28G29G30G31G32  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  0**
**++         2  2  3  2  2  2  2  3  2  2  3  3  3  3  3  3  3**
**++         3  3  3  3  3  3  3  2  3  3  3  2  3  3  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  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:IGS05_1473 OL/AL:FES2004  NONE     Y  ORB:CMB CLK:CMB**
***  2008  5  7  0  0  0.00000000**
**PG02  -8809.661438  13800.152093  20688.250986    200.145019 11  8 10 152**
**PG03   8783.028077 -23775.730485  -7563.365732    224.532353 12 10 10 135**

- _An example SP3-c file, the GPS final orbit for May 7, 2008_

## Main list of new features

**Unlimited number of satellites**
**Unlimited number of comments**
**Irregularly spaced epochs for LEOs**
**Variable number of SVs at each epoch**
**A more flexible, SINEX-like header**
**0.1 mm precision (for GRACE, LEO veloc.)**
**Attitude information (quaternions)**

## Other interesting ideas (1 of 2)

**Use white space delimited fields (any precision)**
**Put time tag on each line to easily extract one SV:**
** ****( POS G02 2008 05 22 23 45 30.12345678  X  Y  Z  t )**
**Instead of quaternions, use ITRF body-x unit vector**
**Have attitude information in a separate section after       the position/clock data**
**Make the format usable for real-time data**

## Other interesting ideas (2 of 2)

**Future mixed GNSS files should be in UTC or TAI**
**Allow the use of the format for inertial orbits**
**Include EOP information in the header**
**Include Maneuver information in the header**
**Allow additional records for acceleration**
**Provide User Range Accuracy (URA) values**
**Supply satellite DCBs in the header**

## Example

*****
**:START HEADER ==================================================================**
**+FILE/DESCRIPTION**
** ****DESCRIPTION         IGS FINAL GNSS ORBIT COMBINATION**
** ****CREATED BY          IGS Analysis Center Coordinator**
** ****CREATION DATE       2008  5 20 12  0  0**
** ****INPUT DATA          Weighted Average of: cod emr esa gfz grz jpl mit ngs sio**
** ****CONTACT             Jim.Ray@noaa.gov**
** ****SOFTWARE            Orbit Combination Software Version 2.03**
** ****START TIME          2008 05 07  0  0  0.000000000000000**
** ****END TIME            2008 05 07 23 45  0.000000000000000**
** ****EPOCH INTERVAL      900.0 SECONDS**
** ****COORD SYS           IGS05**
** ****TIME SYS            GPS**
** ****ORBIT TYPE          HLM**
** ****DATA USED           ORBIT**
** ****NUMBER OF SVS       47**
** ****NUM OF SV TYPES     2**
** ****LIST OF SV TYPES    G R**
** ****NUM OF REC TYPES    1**
** ****LIST OF REC TYPES   POS **
** ****OCEAN LOADING       FES2004 (Center-Of-Mass correction included: Yes)**
** ****ATMOS LOADING       NONE (Center-Of-Mass correction included: N/A)**
** ****CMC FOR ORBIT       CMB (CoN=CenterOfNetwork,CoM=CenterOfMass,CMB=Combination)**
** ****CMC FOR CLOCKS      CMB (CoN=CenterOfNetwork,CoM=CenterOfMass,CMB=Combination)**
** ****GPS WEEK/SECWK      1478 259200.000000000000000 (start time)**
**-FILE/DESCRIPTION**
***-------------------------------------------------------------------------------**
**+SATELLITE/NAMES_AND_STD_DEVS**
***SV_ COSPAR#__ SV_TYPE______ SVN_ STDP(mm) STDCLK(psec) #EPOCHS CHAN#**
** ****G02 2004-045A BLOCK_IIR-B   G061     31.0         42.7      96   N/A**
** ****G03 1996-019A BLOCK_IIA     G033     16.0         28.0      96   N/A**
** ****G04 1993-068A BLOCK_IIA     G034     33.0         68.2      96   N/A**
**  ****.**
**  ****.**
**  ****.**
** ****R19 2007-052C GLONASS-M     R720     28.0         58.2      96     3**
** ****R20 2007-052B GLONASS-M     R719     34.0         57.1      96     2  **
** ****R23 2005-050A GLONASS-M     R714     38.0         73.5      96     3  **
** ****R24 2005-050B GLONASS-M     R713     42.0         71.8      96     2**
**-SATELLITE/NAMES_AND_STD_DEVS**
**:END HEADER ====================================================================**
*****

- ORBEX
- Header

## Example ORBEX Data Epoch

*****
**## 2008  5  7  0  0  0.000000000000000  47**
***REC  SV_ ______X_(km)__ ______Y_(km)__ ______Z_(km)__ __SVCLK_(usec) __STD_X __STD_Y __STD_Z ____STD_CLK**
***                                                                        (mm)    (mm)    (mm)      (psec)**
** ****POS  G02  -8809.6614480  13800.1521030  20688.2509810    200.1561940    11.6     5.9     9.3        42.7 **
** ****POS  G03   8783.0280890 -23775.7304950  -7563.3657510    224.5436290    14.6     9.3     9.3        28.0**
** ****POS  G04 -20366.9183010   7751.4287030  15329.9240560    -61.6745610     9.3    11.6    14.6        68.2     M**
**  ****.**
**  ****.**
**  ****.**
** ****POS  R19 -15108.0638680  20059.3830880   4484.7639460    -58.1237860    11.8     5.9     9.3        58.1 E**
** ****POS  R20  -2774.8011210  16607.6942980  19201.9866650    -57.2753910    12.7     5.8     7.2        43.2**
** ****POS  R23  14982.6131490 -20030.9220740  -4887.6747570   -164.5623570    13.6     8.9    10.4        43.3**
** ****POS  R24   1343.5390390 -15564.1095240 -20114.5221140   -177.3452340    14.2     7.9     9.6        73.4**
*****
**## 2008  5  7  0 15  0.000000000000000  47**
** ****POS  G02 -11140.7631150  13404.3243040  19780.8448450    200.1606680    11.6     4.8     9.3        41.6**
**  ****.**
**  ****.**
**  ****.**
**:EOF**

## Example

***------------------------------------------------------------------------------**
**+FILE/REFERENCE                                                                **
***INFO_TYPE_________ INFO_______________________________________________________**
** ****DESCRIPTION        My agency/institute                                        **
** ****OUTPUT             One-session solution generated by RNX2SNX BPE              **
** ****CONTACT            My e-mail address                                          **
** ****SOFTWARE           Bernese GPS Software Version 5.1                           **
** ****HARDWARE           My computer                                                **
** ****INPUT              IGS/IGLOS GNSS tracking data                               **
** ****TIME SYSTEM        GPS**
** ****ORBIT TYPE         FIT**
**-FILE/REFERENCE                                                                **
***------------------------------------------------------------------------------**
**+INPUT/ACKNOWLEDGMENTS                                                         **
***AGY DESCRIPTION_______________________________________________________________**
** ****XYZ My agency/institute and its address                                       **
** ****IGS International GPS Service                                                 **
**-INPUT/ACKNOWLEDGMENTS                                                         **
***------------------------------------------------------------------------------**
***Orbits generated at Center for Orbit Determination in Europe (CODE)**
***GNSS: Middle day of a 3/day arc GPS/GLONASS solution**
***      Gravity field JGM3 12x12**
***------------------------------------------------------------------------------**
**+SATELLITE/ID**
***CODE PRN SVN_ COSPAR___ TYP NAME________________ COMMENT______________________ **
** ****G01  001   32 1992-079A GPS **
** ****G02  002   61 1992-079A                          **
** ****G03  003   32 1992-079A                   **
** ****L06           2000-039B LEO CHAMP      **
**-SATELLITE/ID**
***------------------------------------------------------------------------------**
**+ANTENNA/OFFSET**
***CODE ANTENNA_____________ FRQ X_OFFSET Y_OFFSET Z_OFFSET ANTEX________________**
** ****G01  BLOCK IIA            L1    279.00     0.00  2201.00 IGS05_1480.ATX**
** ****G01  BLOCK IIA            L2    279.00     0.00  2201.00 IGS05_1480.ATX**
** ****G02  BLOCK IIR-B          L1      0.00     0.00   614.00 IGS05_1480.ATX**
** ****G02  BLOCK IIR-B          L2      0.00     0.00   614.00 IGS05_1480.ATX       **
** ****G03  BLOCK IIA            L1    279.00     0.00  2201.00 IGS05_1480.ATX**
** ****G03  BLOCK IIA            L2    279.00     0.00  2201.00 IGS05_1480.ATX          **
** ****L06  SPENCER/CR           L1      0.60    -0.50    56.30 **
** ****L06  SPENCER/CR           L2     -0.10    -0.60    91.90 **
**-ANTENNA/OFFSET**
***------------------------------------------------------------------------------**

- ORBEX
- File
- (1 of 2)

- (Courtesy of Urs Hugentobler)

## Example

***CODE AC Accuracy  Ecl Unh**
** ****G01   2      3.8   -   -**
** ****G02   5     31.2   E   U**
** ****G03   3      7.1   -   -**
**-ACCURACY/CODE**
***------------------------------------------------------------------------------**
**+CENTER/DEFINITION**
***DATA__ CENTER_______________**
** ****ORBITS CENTER OF NETWORK      **
** ****CLOCKS CENTER OF NETWORK                **
**-CENTER/DEFINITION**
***------------------------------------------------------------------------------**
**+CENTER_OF_MASS/INFO**
***CORRECTION ON MODEL_______________**
** ****OTL        Y  FES2004**
** ****ATL        N                            **
**-CENTER_OF_MASS/INFO**
***------------------------------------------------------------------------------**
**+ORBIT/INFO**
***CODE PLANE SLOT **
** ****G01      A    1 **
** ****G02      B    2                          **
** ****G03      C    3                   **
** ****L06     **
**-ORBIT/INFO**
***------------------------------------------------------------------------------**
**+MANEUVER/INFO**
***CODE MANV_START__ MANV_END____ DV_RADIA DV_ALONG DV_CROSS**
** ****G01  08:020:45367 08:020:45389     1.23   324.50  -10.234                  **
**-ORBIT/INFO**
***------------------------------------------------------------------------------**
**+EPHEMERIS/DATA**
**> 2008 01 06 00 00  0.0000000 10**
**POS G01 -14784237.0620   -3230043.6852  -21615673.5353 **
**VEL G01      1234.0000        123.0000          1.0000**
**CLK G01       176.303984**
**COV G01 ...**
**ATT G01 ...**
**POS G02  22264336.8400  -10011598.2350  -10248988.2470    **
**VEL G02      1234.0000        123.0000          1.0000**
**POS G03  22264336.8400  -10011598.2350  -10248988.2470    **
**VEL G03      1234.0000        123.0000          1.0000**
**POS L06     13273.1421      14323.3948     323421.3423**

- ORBEX
- File
- (2 of 2)

- (Courtesy of Urs Hugentobler)

## Summary and Future Plans

**There are several valid reasons to move to a new format.**
**These changes will benefit both LEO and GNSS users.**

**Next step: with the ACs, create a draft format document.**
**Solicit comments via IGS Mail.**
**Work with the other services (ILRS, IDS, etc.).**
**After final acceptance, the IGS will need to support both SP3-c and ORBEX (for one year, or maybe longer).**
**Tools will be needed later to convert ORBEX to SP3-c .**

- Steve.Hilla@noaa.gov

## Thank You.

- Questions?  Comments?

## Acknowledgements  

**The author would like to thank the following individuals who offered their initial ideas and suggestions about what might be needed in a future IGS orbit format:**
**Willy Bertiger, Yehuda Bock, Henno Boomkamp, Oscar Columbo, Rolf Dach, Mark Davis, Gerd Gendt, Clyde Goad, Jake Griffiths, Heinz Habrich, Urs Hugentobler, Jan Kouba, Gerry Mader, Michael Meindl, Oliver Montenbruck, Erricos Pavlis, Jim Ray, Benjamin Remondi, Ignacio Romero, Eun Hwan Shin, Mark Schenewerk, Tim Springer, and Robert Weber.**

## http://www.gsfc.nasa.gov/sp3c_satlist.html

**http://www.gsfc.nasa.gov/sp3c_satlist.html**