EVA: GPS-based extended velocity and acceleration determination

Abstract

In this work, a new GPS carrier phase-based\ud velocity and acceleration determination method is presented\ud that extends the effective range of previous techniques. The\ud method is named ‘EVA’, and may find applications in fields\ud such as airborne gravimetry when rough terrain orwater bodies\ud make difficult or impractical to set up nearby GPS reference\ud receivers. The EVA method is similar to methods such\ud as Kennedy (Precise acceleration determination from carrier\ud phase measurements. In: Proceedings of the 15th international\ud technical meeting of the satellite division of the Institute\ud of Navigation. ION GPS 2002, Portland pp 962–972,\ud 2002b) since it uses L1 carrier phase observables for velocity\ud and acceleration determination. However, it introduces\ud a wide network of stations and it is independent of precise\ud clock information because it estimates satellite clock\ud drifts and drift rates ‘on-the-fly’, requiring only orbit data\ud of sufficient quality. Moreover, with EVA the solution rate\ud is only limited by data rate, and not by the available precise\ud satellite clocks data rate. The results obtained are more\ud robust for long baselines than the results obtained with the\ud reference Kennedy method. An advantage of being independent\ud of precise clock information is that, beside IGS Final\ud products, also the Rapid, Ultra-Rapid (observed) and Ultra-\ud Rapid (predicted) products may be used. Moreover, the EVA\ud technique may also use the undifferenced ionosphere-free\ud carrier phase combination (LC), overcoming baseline limitations\ud in cases where ionosphere gradients may be an issue\ud and very low biases are required. During the development of\ud this work, some problems were found in the velocity estimation\ud process of the Kennedy method. The sources of the problems were identified, and an improved version of the\ud Kennedy method was used for this research work. An experiment\ud was performed using a light aircraft flying over the Pyrenees,\ud showing that both EVA and the improved Kennedy\ud methods are able to cope with the dynamics of mountainous\ud flight. A RTK-derived solution was also generated, and\ud when comparing the three methods to a known zero-velocity\ud reference the results yielded similar performance. The EVA\ud and the improved-Kennedy methods outperformed the RTK\ud solutions, and the EVA method provided the best results in\ud this experiment. Finally, both the improved version of the\ud Kennedy method and the EVA method were applied to a network\ud in equatorial South America with baselines of more\ud than 1,770 km, and during local noon. Under this tough scenario,\ud the EVAmethod showed a clear advantage for all components\ud of velocity and acceleration, yielding better and more\ud robust results.Peer ReviewedPostprint (published version

Gravity Field Model Determination Based on GOCE Satellite Point-Wise Accelerations Estimated from Onboard Carrier Phase Observations

“…The ionosphere-free carrier phase combination observation between the GPS satellite and LEO satellite receiver is given as follows [21]:…”

“…The most commonly used method is performed by double time-differentiating successive trajectories of the moving satellite, also known as the orbit differentiation algorithm. A major drawback to this method is that the accuracy of the differentiated accelerations is strongly dependent on the position precision; an increase or decrease in the number of visible satellites can lead to discontinuities [21]. Another method is the Doppler measurement, which can be used afterward to obtain the satellite's velocity before the satellite accelerations are computed by the first-order derivative of the satellite's velocity.…”

On Precision Kinematic Accelerations for Airborne Gravimetry

“…It is also noted that the Parks-McClellan/Remez method is an iterative process that may not always converge and may have other instabilities. The central difference method is very stable and is the method of differentiation often used for GPS kinematic accelerations (e.g., Kennedy et al, 2001, Salazar et al 2011). …”

High accuracy acceleration determination by using multiple GNSS reference stations

“…One of the most important advantages is the increase in reliability and availability of the service. Salazar et al used multiple reference stations to determine the carrier phase based velocity and acceleration, however, un-difference algorithm was used in their paper, and the accuracy cannot match the high accuracy applications [10].…”