Comparison of Ppp And Double Differencing Solutions Case Study Campaign Gps Stations in Tanzania

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Addis Ababa University


Satellite Positioning systems are world-wide precise positioning systems and very useful for geodetic surveys, crustal deformation studies, station coordinates, absolute and relative station velocities. Two techniques for GPS data processing to obtain station position coordinates exist. The two methods are Differencing of observations, and Zero differencing techniques, known as Precise Point Positioning. The main aim of this study was to assess the accuracy of PPP Solution, using the already known accurate Double differencing solution. The data used in this study are three episodes’ campaign GPS stations in Tanzania established in 2006, 2008 and 2010. The data sets are available in RINEX format from the UNAVCO website. Double differencing was done using GAMIT_GLOBK software, in this case, the campaign data were combined in a solution experiment with reference GPS data for IGS stations in Africa, active from 2006-2010. The PPP solution was obtained from APPS (online-GIPSY/OASIS). Other available online PPP solution services were also used for comparison purposes. The results from APPS PPP solution were compared with GAMIT/GLOB DGPS solution in order to assess the accuracy of PPP. From 330, 24hours epochs of observations the results show that the range of the difference between GAMIT/GLOBK and APPS PPP solution is -3.7 to 5.6cm in X component, -3.8 to 5.0cm in Y component and -1cm to 3.4cm in the Z component. The residuals of coordinates (δX, δY and δZ) from the two solutions have mean value of 5.9mm in X component, 1.2mm in Y component and 0.4mm in Z component. Also the standard deviations in δX, δY and δZ are 11mm, 10mm and 4mm respectively. From the results analysis it has been shown that in most cases, for the data set used, PPP solution is very close to DGPS solution. Key words: Precise Point Positioning (PPP) Differential GPS (DGPS)



Precise ;Point Positioning ;(PPP) Differential GPS (DGPS)