Processing Results
Single-Receiver Un-Differenced Carrier Phase Processing
This document compares results from two Precise Point Positioning (PPP) software packages when applied to a kinematic airborne data set with medium dynamics (maximum speed of about 190 mph). These software packages only make use of data collected from the receiver on board the aircraft, along with precise orbit and clock data. In this case, precise orbit and clock data was obtained from JPL, at a resolution of 15 minutes and 1 second, respectively.
The first software package is P3, developed in the Department of Geomatics Engineering at the University of Calgary. The second is GIPSY/OASIS II, developed by the Jet Propulsion Laboratory (JPL). In this document, the JPL solution is used as the reference, with respect to which the P3 solution is compared. The data and processing specifications are provided below.
Figures 1 to 5 show various plots associated with this data set, including the aircraft trajectory, the number of satellites used and PDOP, the aircraft height, as well as estimations of the receiver clock error and zenith tropospheric delay.All information presented in Figures 1 to 5 was obtained from the P3 software. Figures 6 and 7 show the position errors between the P3 and JPL solutions for the forward and backward pass.
Data SpecificationsP3Processing Specifications
DATA TYPE: Kinematic, airborneSatellite Orbit:JPL 15 minute
DATE: August 28, 2003Satellite Clock:JPL 1.0 second
TIME (GMT): 14:57:03 – 19:40:54Processing Interval (s):1.0
DURATION: 4:43:51Elevation Cut-Off (deg):10
DATA INTERVAL (s): 0.5GDOP Cut-Off: 20
GMT – LOCAL TIME (h): 4
reference data for an assessment of processed results:GIPSY/OASIS II is the only software package that we found in the marketthatcan do single-receiver un-differenced carrier phase processing. As such, we have used GIPSY/OASIS II solutions from JPL as the reference for error analysis.
Figure 1: Aircraft TrajectoryFigure 2: Number of Satellites and PDOP
Figure 3: Height ProfileFigure 4: Forward and Backward Estimation of Rx Clock Error
Figure 5: Forward Estimation of TroposphereFigure 6: P3 Forward Processing
Figure 7: P3 Backward Processing
Results
Position Errors (cm)Latitude / Longitude / Height
Mean / 1.7 / 1.4 / -4.3
Std. Dev. / 1.7 / 1.7 / 6.8
RMSE / 2.4 / 2.2 / 8.0
Based on Figures 6 and 7 and the statistics shown on the right, it can be seen that the P3 solution agrees very well with the solution from the GIPSY/OASIS II software package developed by the Jet Propulsion Laboratory (JPL). A small oscillatory effect still remains in height for the backward pass, although it cannot be determined which solution introduces this effect.
Dr. Yang Gao, Positioning and Mobile Information Systems Group, Department of Geomatics Engineering, University of Calgary, Calgary, Alberta, Canada T2N 1N4 Tel: 403-220-6174 Fax: 403-284-1980 E-mail: