Near real-time tropospheric products

The GOP routine near real-time zenith tropospheric delay (ZTD) product has contributed to the EU COST Action 716 (2001-2003) and the EC project TOUGH (2003-2005) since February 2001. Since 2005 the product has been distributed within the E-GVAP (EUMETNET GPS Water Vapor Programme). Tropospheric products are hourly updated and uploaded to the ftp server at the UK Met Office in COST-716 format (specifications can be found at www.oso.chalmers.se/~kge/cost716.html/ (working group 3 - data format spec). The files are also archived at ftp.pecny.cz. The BUFR format is generated based on COST-716 files at the UK Met Office and distributed within the meteorological community by the GTS network.

The availability of the GOP troposphere products Fig. 1 - The availability of the GOP troposphere products

The official solution is based on the IGS ultra-rapid orbits and processing double-difference GPS observables using the in network mode Bernese GPS software (BSW). The BSW V4.2 has been used since 2000 until March 2005 and the COST-716 format files has the acronym 'gope'. Only one constant ZTD value were estimated for each hour tagged by the mid-epoch. As of January 2005 the BSW V5.0 is used and the files has the acronym 'gop_' for official ambiguity-free solution and 'gopx' for testing ambiguity-fix solution. In this new solution, the ZTD were estimated as piece-wise linear function, thus ZTDs are reported at boundary of the valid interval (HR:00 and HR+1:00 epoch). Since COST-716 format does not allow duplicity, the latter (and less accurate) value 'HR+1:00' is tagged as HR:59 and in the following solution is in fact "replaced" by starting ZTD estimates with higher accuracy. An overlapping period of a few months (January - May in 2005) was provided for both products using different version of Bernese GPS software and modified analysing strategy. In January 2010 we have modified the strategy by increasing processing window to 4 hours and we have developed a first hourly global ZTD solution ('gopg','goph' acronyms). These are routinely provided to the Met Office UK database since August 2010. In April 2011 we have implemented a multi-GNSS solution (GPS+GLONASS) running in a paralel to the official solution. This is based on unofficial IGS ultra-rapid GPS+GLONASS orbits (igv).


Post-processing/off-line tropospheric products

The GOP post-processing (offline) tropospheric product are provided either within a specific processing campaigns for comparisons or they are provided within EUREF processing. These products are based on the IGS final orbits and processed on daily basis.


References

  • Dousa J, Bennitt GV (2013), Estimation and evaluation of hourly updated global GPS Zenith Total Delays over ten months, GPS Solut, Springer, 17:453–464, doi:10.1007/s10291-012-0291-7, (ISSN online:1521-1886 printed: 1080-5370)
  • Dousa J (2010), Precise near real-time GNSS analyses at Geodetic observatory Pecný - precise orbit determination and water vapour monitoring, Acta Geodyn. Geomater., Vol. 7, No. 1 (157), 1-11. http://www.irsm.cas.cz/materialy/acta_content/2010_01/2_Dousa.pdf
  • Dousa J (2009), The impact of errors in predicted GPS orbits on zenith troposphere delay estimation., GPS solutions (first-online), Springer Berlin/Heidelberg, Vol 13, No 3(2010), pp.229-239. doi: 10.1007/s10291-009-0138-z
  • Dousa J (2004), Precise Orbits for Ground-Based GPS Meteorology: Processing Strategy and Quality Assessment of the Orbits Determined at Geodetic Observatory Pecný, J Met Soc Japan, Vol. 82, pp. 371-380.
  • Dousa J (2003), Evaluation of tropospheric parameters estimated in various routine analysis, Physics and Chemistry of the Earth, 29/2-3, pp.167-175.
  • Dousa J (2003), On the Specific Aspects of Precise Tropospheric Path Delay Estimation in GPS Analysis, In: Vistas for Geodesy in the New Millenium, IAG Symposium, Adam, J. and K.-P. Schwarz (eds.), Springer-Verlag, Berlin Heidelberg, Vol. 125, pp. 285-290.
  • Dousa J (2001), The Impact of Ultra-Rapid Orbits on Precipitable Water Vapor Estimation using Ground GPS Network, Physics and Chemistry of the Earth, Part A, 26/6-8, pp. 393-398.