To assess the convergence time, precision of satellite orbits and clocks and integrity monitoring GNSS observations from different sites were processed under different conditions such as varying data arc (1, 6, 12 and 24 hours), C1|P2 and P1|P2 dual frequency observations and 24 hour data arcs from 2000.0014 to 2010.0014.

In agreement with Héroux et al., (2004) description of PPP convergence, it is dependent on several factors including: number and geometry of visible satellites, user environment and dynamics and observation quality. The varying convergence rate amongst for the sites ALBH, NRC1, STJO and YELL affected the time required to reach a required precision. All four PPP providers showed a decreasing exponential trend in their solution, as expected. The least accurate was at the 1 hour data arc and most accurate at 24 hour data arc. There was 1 mm to 4 mm improvement in the final solution from 12 to 24 hours for all providers except for GAPS at the sites ALBH and YELL implying the solution had converged fully after 12 hours.

Precise orbits and clock products are critical for PPP processing if they do not meet the required accuracy it would not be possible to obtain a PPP solution. The accuracy of the results was expected to be directly proportional with time. This was not reflected in the results. This could have been due to the orbits and clocks being reprocessed.

There are two ‘typical’ pairs of dual-frequency pseudorange observables, P1|P2 and C1|P2. The difference in the quality of the solution is predominantly seen within the 1 hour data arc; this occurs because the solution is still a pseudo-code solution, the solution hasn’t fully converged and the ambiguities for the carrier phases have not been fully been resolved. It was expected that the C1|P2 would introduce a code bias as well as extend the convergence period because the ionosphere would not have been modelled as efficiently. The bias was prominent when processed by magicGNSS. APPS illustrated this bias at ALBH and STJO. For ALBH, STJO and YELL CSRS-PPP showed the results of the 3D difference being smaller when the C1|P2 was used and at NRC1 the C1|P2 reproduced identical results as P1|P2.

It is important to have a reliable integrity monitor of the solution being produced. Of the 4 PPP processors, only CSRS-PPP and APPS returned a sigma value with their solution. CSRS-PPP showed a stronger correlation to the 3D sigma value presented than APPS. These outliers imply that APPS is being too optimistic in the sigma value provided. Also, it was noted with APPS had a consistent sigma value when the data arc was 24 hours, this suggests than the method used by APPS to generate the sigma value provided to the user is more dependent on to the length of the data arc than the post-fit residuals provided by their PPP solution.

PPP allows users of different professions such as surveyors, engineers and scientists to perform centimeter level positioning in both urban and rural areas. Within urban areas, network RTK may already exist and PPP may be used as an independent positioning service to monitor the integrity of the solution being provided by network RTK. PPP would prove to be an asset in rural areas because it would provide few-centimetre level positioning within the first hour of data without the need for any reference stations. Careful consideration should be taken by the user on their reliance on the provided sigma value as with some PPP providers it may not be given or accurately represent the error of the solution. Due to the promising benefits of PPP based on its performance its application may be extended to applications in different aspects by scientists such as ionospheric delay estimation, code multipath estimation, satellite code bias and satellite clock error estimation. PPP’s application has been extended to the commercial sector as well, in areas such as the agricultural industry for precision farming, marine applications (for sensor positioning in support of seafloor mapping and marine construction) and airborne mapping (Bisnath

In agreement with Héroux et al., (2004) description of PPP convergence, it is dependent on several factors including: number and geometry of visible satellites, user environment and dynamics and observation quality. The varying convergence rate amongst for the sites ALBH, NRC1, STJO and YELL affected the time required to reach a required precision. All four PPP providers showed a decreasing exponential trend in their solution, as expected. The least accurate was at the 1 hour data arc and most accurate at 24 hour data arc. There was 1 mm to 4 mm improvement in the final solution from 12 to 24 hours for all providers except for GAPS at the sites ALBH and YELL implying the solution had converged fully after 12 hours.

Precise orbits and clock products are critical for PPP processing if they do not meet the required accuracy it would not be possible to obtain a PPP solution. The accuracy of the results was expected to be directly proportional with time. This was not reflected in the results. This could have been due to the orbits and clocks being reprocessed.

There are two ‘typical’ pairs of dual-frequency pseudorange observables, P1|P2 and C1|P2. The difference in the quality of the solution is predominantly seen within the 1 hour data arc; this occurs because the solution is still a pseudo-code solution, the solution hasn’t fully converged and the ambiguities for the carrier phases have not been fully been resolved. It was expected that the C1|P2 would introduce a code bias as well as extend the convergence period because the ionosphere would not have been modelled as efficiently. The bias was prominent when processed by magicGNSS. APPS illustrated this bias at ALBH and STJO. For ALBH, STJO and YELL CSRS-PPP showed the results of the 3D difference being smaller when the C1|P2 was used and at NRC1 the C1|P2 reproduced identical results as P1|P2.

It is important to have a reliable integrity monitor of the solution being produced. Of the 4 PPP processors, only CSRS-PPP and APPS returned a sigma value with their solution. CSRS-PPP showed a stronger correlation to the 3D sigma value presented than APPS. These outliers imply that APPS is being too optimistic in the sigma value provided. Also, it was noted with APPS had a consistent sigma value when the data arc was 24 hours, this suggests than the method used by APPS to generate the sigma value provided to the user is more dependent on to the length of the data arc than the post-fit residuals provided by their PPP solution.

PPP allows users of different professions such as surveyors, engineers and scientists to perform centimeter level positioning in both urban and rural areas. Within urban areas, network RTK may already exist and PPP may be used as an independent positioning service to monitor the integrity of the solution being provided by network RTK. PPP would prove to be an asset in rural areas because it would provide few-centimetre level positioning within the first hour of data without the need for any reference stations. Careful consideration should be taken by the user on their reliance on the provided sigma value as with some PPP providers it may not be given or accurately represent the error of the solution. Due to the promising benefits of PPP based on its performance its application may be extended to applications in different aspects by scientists such as ionospheric delay estimation, code multipath estimation, satellite code bias and satellite clock error estimation. PPP’s application has been extended to the commercial sector as well, in areas such as the agricultural industry for precision farming, marine applications (for sensor positioning in support of seafloor mapping and marine construction) and airborne mapping (Bisnath

*et al.*, 2008).## References

Bisnath, S. and Y. Gao, (2008) 'Current state of precise point positioning and future prospects and limitations',

Collins, P., Y. Gao, F. Lahaye, P. Héroux, K. MacLeod, and K. Chen, (2005) 'Accessing and Processing Real-Time GPS Corrections for Precise Point Positioning – Some User Considerations',

Collins, J.P., F. Lahaye, P. Heroux, and S. Bisnath, (2008) 'Precise Point Positioning with ambiguity resolution using the decoupled clock model.',

Farmer, J. (2010)

GMV (2010)

Hofmann-Wellenhof, B., H.Lichtenegger, and J. Collins, (2001)

IGS (2009)

Kouba, J. (2009) 'A GUIDE TO USING INTERNATIONAL GNSS SERVICE (IGS) PRODUCTS'.

Kouba, J. and Pierre Héroux, (2001) 'Precise Point Positioning Using IGS Orbit and Clock Products',

Lachapelle, G., M.E. Cannon, C. Erickson, and W. Falkenberg, (1992) 'High Precision C/A Code Technology for Rapid Static DGPS Surveys',

Landau, H., X. Chen, S. Klose, R. Leandro, and U. Vollath, (2008) 'Trimble’s RTK and DGPS Solutions in Comparison with Precise Point Positioning',

Leandro, R.F., M.C. Santos, and R.B. Langley, (2007) 'GAPS: The GPS Analysis and Positioning Software – A Brief Overview',

NRCan (2010)

P. Héroux, Y.G., J. Kouba, F. Lahaye, Y. Mireault, P. Collins, K. Macleod1, P. Tétreault1, and K. Chen, (2004) 'Products and Applications for Precise Point Positioning - Moving Towards Real-Time', Proceedings of ION GNSS 2004, the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation, Long Beach, California.

Rho, H. and R.B. Langley, (2005) 'Dual-frequency GPS Precise Point Positioning with WADGPS Corrections',

Rocken, C., J.M. Johnson, and J.J. Braun, (2000) 'Improving GPS surveying with modeled ionospheric corrections',

SOPAC (2011)

UNAVCO (2010)

http://facility.unavco.org/software/teqc/teqc.html.

Wahr, J.M. (1981) 'The forced nutation of an elliptical, rotating, elastic, and oceanless Earth',

Zumberge, J.F., M.B. Heflin, D.C. Jefferson, and M.M. Watkins, (1997) 'Precise point positioning for the efficient and robust analysis of GPS data from large networks.”',

*International Association of Geodesy Symposia*, vol. 1333, pp. 615-623.Collins, P., Y. Gao, F. Lahaye, P. Héroux, K. MacLeod, and K. Chen, (2005) 'Accessing and Processing Real-Time GPS Corrections for Precise Point Positioning – Some User Considerations',

*ION GNSS 18th International Technical Meeting of the Satellite Division*, 13-16 September.Collins, J.P., F. Lahaye, P. Heroux, and S. Bisnath, (2008) 'Precise Point Positioning with ambiguity resolution using the decoupled clock model.',

*Proceedings of the Institute of Navigation International Technical Meeting ION GNSS*, 16-19 September, pp. 1315-1322.Farmer, J. (2010)

*Jet Propulsion Laboratory*, http://develop.larc.nasa.gov/Jet_Propulsion_Laboratory.html.GMV (2010)

*About GMV*, http://www.gmv.com/company/about_GMV/about_gmv.htm.Hofmann-Wellenhof, B., H.Lichtenegger, and J. Collins, (2001)

*GPS Theory and Practice*, New York: Springer Wien.IGS (2009)

*IGS Products*, http://igscb.jpl.nasa.gov/components/prods.html.Kouba, J. (2009) 'A GUIDE TO USING INTERNATIONAL GNSS SERVICE (IGS) PRODUCTS'.

Kouba, J. and Pierre Héroux, (2001) 'Precise Point Positioning Using IGS Orbit and Clock Products',

*GPS Solutions*, vol. 5, no. 2, pp. 12-28.Lachapelle, G., M.E. Cannon, C. Erickson, and W. Falkenberg, (1992) 'High Precision C/A Code Technology for Rapid Static DGPS Surveys',

*6th International Geodetic Symposium on Satellite Positioning*, pp. 17-20.Landau, H., X. Chen, S. Klose, R. Leandro, and U. Vollath, (2008) 'Trimble’s RTK and DGPS Solutions in Comparison with Precise Point Positioning',

*International Association of Geodesy Symposia*, vol. 133, no. 4, pp. 709-718.Leandro, R.F., M.C. Santos, and R.B. Langley, (2007) 'GAPS: The GPS Analysis and Positioning Software – A Brief Overview',

*ION GNSS 20th International Technical Meeting of the Satelite Division*.NRCan (2010)

*About Us*, http://www.nrcan-rncan.gc.ca/com/index-eng.php.P. Héroux, Y.G., J. Kouba, F. Lahaye, Y. Mireault, P. Collins, K. Macleod1, P. Tétreault1, and K. Chen, (2004) 'Products and Applications for Precise Point Positioning - Moving Towards Real-Time', Proceedings of ION GNSS 2004, the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation, Long Beach, California.

Rho, H. and R.B. Langley, (2005) 'Dual-frequency GPS Precise Point Positioning with WADGPS Corrections',

*Proceedings of ION GNSS*, vol. 1470-1482, no. 2005.Rocken, C., J.M. Johnson, and J.J. Braun, (2000) 'Improving GPS surveying with modeled ionospheric corrections',

*Geographical Survey Institute (GSI)*.SOPAC (2011)

*Scripps orbit and permanent array center*, http://sopac.ucsd.edu/cgi-bin/sector.cgi.UNAVCO (2010)

*TEQC — The Toolkit for GPS/GLONASS/Galileo/SBA*,http://facility.unavco.org/software/teqc/teqc.html.

Wahr, J.M. (1981) 'The forced nutation of an elliptical, rotating, elastic, and oceanless Earth',

*Geophysical Journal of Royal Astronomical Society*, vol. 64, no. 705-727.Zumberge, J.F., M.B. Heflin, D.C. Jefferson, and M.M. Watkins, (1997) 'Precise point positioning for the efficient and robust analysis of GPS data from large networks.”',

*Journal of Geophysical Research*, vol. 102, no. B3, pp. 5005-5018.