New versions of the BDS/GNSS zenith tropospheric delay model IGGtrop

The initial IGGtrop model proposed for Chinese BDS (BeiDou System) is not very suitable for BDS/GNSS research and application due to its large data volume while it shows a global mean accuracy of 4 cm. New versions of the global zenith tropospheric delay (ZTD) model IGGtrop are developed through further investigation on the spatial and temporal characteristics of global ZTD. From global GNSS ZTD observations and weather reanalysis data, new ZTD characteristics are found and discussed in this study including: small and inconsistent seasonal variation in ZTD between $$10^{\circ }\hbox {S}\, \mathrm{and}\, 10^{\circ }\hbox {N}$$10∘Sand10∘N and stable seasonal variation outside; weak zonal variation in ZTD at higher latitudes (north of $$60^{\circ }\hbox {N}$$60∘N and south of $$40^{\circ }\hbox {S}$$40∘S) and at heights above 6 km, etc. Based on these analyses, new versions of IGGtrop, named $$\hbox {IGGtrop}\_{r}_{{i}}\, ({i}=1, 2, 3)$$IGGtrop_ri(i=1,2,3), are established through employing corresponding strategies: using a simple algorithm for equatorial ZTD; generating an adaptive spatial grid with lower resolutions in regions where ZTD varies little; and creating a method for optimized storage of model parameters. Thus, the $$\hbox {IGGtrop}\_{r}_{{i}}\,({i}=1, 2, 3)$$IGGtrop_ri(i=1,2,3) models require much less parameters than the IGGtrop model, nearly 3.1–21.2 % of that for the IGGtrop model. The three new versions are validated  by five years of GNSS-derived ZTDs at 125 IGS sites, and it shows that: $$\hbox {IGGtrop}\_{r}_{1}$$IGGtrop_r1 demonstrates the highest ZTD correction performance, similar to IGGtrop; $$\hbox {IGGtrop}\_{r}_{3}$$IGGtrop_r3 requires the least model parameters; $$\hbox {IGGtrop}\_{r}_{2}$$IGGtrop_r2 is moderate in both zenith delay prediction performance and number of model parameters. For the $$\hbox {IGGtrop}\_{r}_{3}$$IGGtrop_r3 model, the biases at those IGS sites are between $$-6.4$$-6.4 and 4.3 cm with a mean value of $$-0.8~$$-0.8cm and RMS errors are between 2.1 and 8.5 cm with a mean value of 4.0 cm. Different BDS and other GNSS users can choose a suitable model according to their application and research requirements.

[1]  Y. Liou,et al.  Precipitable water observed by ground-based GPS receivers and microwave radiometry , 2000 .

[2]  Yuei-An Liou,et al.  Comparison of Precipitable Water Observations in the Near Tropics by GPS, Microwave Radiometer, and Radiosondes , 2001 .

[3]  Richard B. Langley,et al.  The residual tropospheric propagation delay: How bad can it get? , 1998 .

[4]  Richard B. Langley,et al.  A North America Wide Area Neutral Atmosphere Model for GNSS Applications , 2009 .

[5]  Steven Businger,et al.  GPS Meteorology: Direct Estimation of the Absolute Value of Precipitable Water , 1996 .

[6]  Yan Xu,et al.  GPS: Theory, Algorithms and Applications , 2003 .

[7]  Richard B. Langley,et al.  Assessment of Atmospheric Delay Correction Models for the Japanese MSAS , 2001 .

[8]  Alan Dodson,et al.  Assessment of EGNOS Tropospheric Correction Model , 1999 .

[9]  Yao Yi.  A new global zenith tropospheric delay model GZTD , 2013 .

[10]  J. Saastamoinen.  Atmospheric Correction for the Troposphere and Stratosphere in Radio Ranging Satellites , 2013 .

[11]  M. Kanamitsu,et al.  NCEP–DOE AMIP-II Reanalysis (R-2) , 2002 .

[12]  Richard B. Langley,et al.  UNB3m_pack: a neutral atmosphere delay package for radiometric space techniques , 2008 .

[13]  Robert Weber,et al.  Improved Troposphere Blind Models Based on Numerical Weather Data , 2013 .

[14]  R. Langley,et al.  UNB Neutral Atmosphere Models : Development and Performance , 2006 .

[15]  H. S. Hopfield.  Tropospheric Effect on Electromagnetically Measured Range: Prediction from Surface Weather Data , 1971 .

[16]  Torben Schüler,et al.  The TropGrid2 standard tropospheric correction model , 2013, GPS Solutions.

[17]  Chris Rizos,et al.  The International GNSS Service in a changing landscape of Global Navigation Satellite Systems , 2009 .

[18]  Yang Gao,et al.  Performance Analysis of Precise Point Positioning Using Rea-Time Orbit and Clock Products , 2004 .

[19]  T. Nilsson,et al.  GPT2: Empirical slant delay model for radio space geodetic techniques , 2013, Geophysical research letters.

[20]  Wei Li,et al.  A new global zenith tropospheric delay model IGGtrop for GNSS applications , 2012 .