EVA: GPS-based extended velocity and acceleration determination

The Journal of …, 2006

Satellite velocity determination using the broadcast ephemeris is discussed and it is pointed out that the conventional rotation matrix method involves a complicated process of com-putation. This paper proposes an alternative method using a simple differentiator to ...

2013

A scrutiny of the existing time differencing carrier phase (TDCP) velocity estimation algorithms has revealed several shortcomings which could be further improved. One of those is that the velocity estimation at epoch t would require the receiver positions at epoch t+Δt or more are available. Another one is the usage of satellite velocities in the calculations which would increase the receiver computational load and degrade the accuracy. In this paper, an improved TDCP velocity estimation approach has been proposed and tested. The new approach depends only on receiver position at epoch t and satellite positions at epoch t and t+Δt. Satellite velocities are not required in this calculation. This proposed algorithm has been validated using static and kinematic field test data, showing that equivalent velocity accuracy achievable by using differential GPS techniques can be made possible with the proposed standalone GPS method.

Journal of Navigation, 2011

A scrutiny of the existing time differencing carrier phase (TDCP) velocity estimation algorithms has revealed several shortcomings that could be further improved. One of these is that the velocity estimation at epoch t would require the receiver positions at epoch t+Δt or more are available. Another is the usage of satellite velocities in the calculations which would increase the receiver computational load and degrade the accuracy. In this paper, an improved TDCP velocity estimation approach has been proposed and tested. The new approach depends only on receiver position at epoch t and satellite positions at epoch t and t+Δt. Satellite velocities are not required in this calculation. This proposed algorithm has been validated using static and kinematic field test data, showing that equivalent velocity accuracy achievable by using differential GPS techniques can be made possible with the proposed standalone GPS method.

GPS Solutions, 2012

Since the Selective Availability was turned off, the velocity and acceleration can be determined accurately with a single GPS receiver using raw Doppler measurements. The carrier-phase-derived Doppler measurements are normally used to determine velocity and acceleration when there is no direct output of the raw Doppler observations in GPS receivers. Due to GPS receiver clock drifts, however, a GPS receiver clock jump occurs when the GPS receiver clock resets itself (typically with 1 ms increment/ decrement) to synchronize with the GPS time. The clock jump affects the corresponding relationship between measurements and their time tags, which results in non-equidistant measurement sampling in time or incorrect time tags. This in turn affects velocity and acceleration determined for a GPS receiver by the conventional method which needs equidistant carrier phases to construct the derived Doppler measurements. To overcome this problem, an improved method that takes into account, GPS receiver clock jumps are devised to generate non-equidistantderived Doppler observations based on non-equidistant carrier phases. Test results for static and kinematic receivers, which are obtained by using the conventional method without reconstructing the equidistant continuous carrier phases, show that receiver velocity and acceleration suffered significantly from clock jumps. An airborne kinematic experiment shows that the greatest impact on velocity and acceleration reaches up to 0.2 m/s, 0.1 m/s 2 for the horizontal component and 0.5 m/s, 0.25 m/s 2 for the vertical component. Therefore, it can be demonstrated that velocity and acceleration measurements by using a standalone GPS receiver can be immune to the influence of GPS receiver clock jumps with the proposed method.

Navigation, 2003

Journal of Geophysical Research, 2010

We describe how GPS time series are influenced by higher-order ionospheric effects over the last solar cycle (1995-2008) and examine implications for geophysical studies. Using 14 years of globally reprocessed solutions, we demonstrate the effect on the reference frame. Including second-and third-order ionospheric terms causes up to 10 mm difference in the smoothed transformation to the International Terrestrial Reference Frame (ITRF) 2005, with the Z translation term dominant. Scale is also slightly affected, with a change of up to ∼0.05 ppb. After transformation to ITRF2005, residual effects on vertical site velocities are as high as 0.34 mm yr −1. We assess the effect of the magnetic field model on the second-order term and find a time-varying difference of 0-2 mm in the Z translation. We also assess the effect of omitting the third-order term. We find that while the second-order term is responsible for almost all the Z translation effects, it is the combination of the second-and third-order terms that causes the effect on scale. Comparison of our GPS reprocessing with ITRF2005 suggests that GPS origin rates may vary with time period. For example, we find Z translation rates of −0.82 ± 0.17 mm yr −1

Proceedings of the …, 2003

It has been shown in the past that differential GPS carrier phase kinematic position accuracy tends to degrade as baseline length increases. This position solution degradation is due to several factors, primarily, errors attributed to the spatial variation of atmospheric delays (and secondly, errors in the satellite orbit). This paper endeavours to assess the magnitude of these effects on the position solutions using various base stations located at distances between 1 and 200+ km. away from the vessel. The assessment will be based on data collected on the Chesapeake Bay during July 1999, in three consecutive days. The data were collected by an Ashtech Z12 receiver mounted on the NOS S/V Bay Hydrographer. The baselines used in the assessment were processed using an ionospheric delay-free processing technique. A local truth trajectory was established while the vessel was close enough to base station TANG to employ integer fixed RTK. This procedure yielded results that agreed with the "truth" trajectory to the decimetre level in latitude, longitude and height.

GPS Solutions, 2010

Based on 40 years of radio-occultation (RO) experiments, it is now recognized that the phase acceleration of radio waves (equal to the time derivative of the Doppler shift), derived from analysis of high-stability Global Positioning System (GPS) RO signals, is as important as the Doppler frequency. The phase acceleration technique allows one to convert the phase and Doppler frequency changes into refractive attenuation variations. From such derived refractive attenuation and amplitude data, one can estimate the integral absorption of radio waves. This is important for future RO missions when measuring water vapor and minor atmospheric gas constituents, because the difficulty of removing the refractive attenuation effect from the amplitude data can be avoided. The phase acceleration technique can be applied also for determining the location and inclination of sharp layered plasma structures (including sporadic E s layers) in the ionosphere. The advantages of the phase acceleration technique are validated by analyzing RO data from the Challenging Minisatellite Payload (CHAMP) and the FORMOSA Satellite Constellation Observing Systems for Meteorology, Ionosphere, and Climate missions (FOR-MOSAT-3/COSMIC).

Your article is protected by copyright and all rights are held exclusively by Springer-Verlag Berlin Heidelberg. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".

2004

The GPS technology has given many opportunities for the geodetic applications. Although GPS has many important advantages, there are many error sources that affect on GPS observations. In this study, the effects of initial phase ambiguity at GPS and modeling of ionosphere on base components were researched. Pseudorange observations and phase observations were done in the test network. The solutions that are related to frequency and solutions, which are unrelated to ionosphere, were done by using these pseudorange and phase observations. Fixed solution and float solution have been done for initial phase ambiguity solution. Suggestions about the solution parameters are made at the stage of GPS data analysis from obtained results.