[unav-data] ITRF2014/IGS14: GAGE GPS Data Analysis Transition Plan

[Announce] from the UNAVCO Data Archive unav-data at postal.unavco.org
Mon Feb 6 13:43:42 MST 2017


GAGE GPS Data Analysis Plan for Transitioning to ITRF2014/IGS14

On January 29, 2017 (GPS week 1934 day 0), the IGS switched its operational products to use the IGS14 system, replacing the current IGb08 system. There are two major changes associated with this switch: (1) A new set of coordinates, velocities and, for some stations, post-seismic deformation models are being adopted for the core set of IGS sites that define the IGS realization of the ITRF2014 system; and (2) the antenna phase center models are being changed for the GPS satellites and for some GPS ground antennas. These new values are contained in the igs14_wwww.atx ANTEX file where wwww is the GPS week of the release. The current file is igs14_1930.atx. The details of the expected effects on the IGS results are discussed in IGSMAIL- 7399 (see link below). The change in the reference frame realization should be small but the change in the antenna model will change the coordinates of some stations by up to 19 mm in height and 5 mm in horizontal coordinates. The immediate effect on the GAGE/PBO data products should be small because the GAGE/PBO analysis centers will not adopt the new IGS14 ANTEX file until a later date when GAGE has reprocessed the data prior to week 1934 with the new IGS14 ANTEX file. The IGS combined orbits based on the IGS14 system have already been generated and the GAGE network processing AC (NMT) can use these files now. The PPP AC (CWU) will start reprocessing when JPL orbits and clocks become available in the IGS14 system.

The current plan is to complete the reprocessing and then release the full set of time series in the NAM14 (IGS14 rotated to the North America Plate) and IGS14 reference frames when all reprocessing is complete. The operational processing will also switch at the time of the release so that there will be no artificial offsets in the time series. The reprocessing is expected to take several months and an announcement will be made when the time series products are to be updated. The frame-resolved and loose SINEX files will be updated during the reprocessing.

GAGE GPS reprocessing will start soon and is expected to be completed before the end of 2017. 

For additional information, including expected position offsets for different antenna types and locations, please refer to the full GAGE GPS Data Analysis Plan for Transitioning to ITRF2014/IGS14 document available here:
http://www.unavco.org/data/gps-gnss/derived-products/docs/GAGE_IGS14_transition_plan_20170203.pdf <http://www.unavco.org/data/gps-gnss/derived-products/docs/GAGE_IGS14_transition_plan_20170203.pdf>

Reprocessed IGS orbits aligned to the IGS14 system are available and described in IGSMAIL-7411:
https://igscb.jpl.nasa.gov/pipermail/igsmail/2017/008601.html 

Full details of the update to IGS14 can be found in IGSMAIL-7399:
https://igscb.jpl.nasa.gov/pipermail/igsmail/2016/008589.html





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