scholarly journals Double-epoch algorithm in rapid positioning using single frequency GPS receivers

2004 ◽  
Vol 7 (4) ◽  
pp. 284-289
Author(s):  
Wang Zhenjie ◽  
Ou Jikun ◽  
Liu Genyou ◽  
Ren Chao
Keyword(s):  
Single Frequency ◽  
Gps Receivers

GPS RECEIVERS TIMING DATA PROCESSING USING NEURAL NETWORKS: OPTIMAL ESTIMATION AND ERRORS MODELING

2007 ◽  
Vol 17 (05) ◽  
pp. 383-393 ◽  
Author(s):  
M. R. MOSAVI
Keyword(s):  
Neural Networks ◽  
Outdoor Recreation ◽  
Optimal Estimation ◽  
Single Frequency ◽  
Gps Receiver ◽  
Commercial Aviation ◽  
Gps Receivers ◽  
Before And After ◽  
Timing Data

The Global Positioning System (GPS) is a network of satellites, whose original purpose was to provide accurate navigation, guidance, and time transfer to military users. The past decade has also seen rapid concurrent growth in civilian GPS applications, including farming, mining, surveying, marine, and outdoor recreation. One of the most significant of these civilian applications is commercial aviation. A stand-alone civilian user enjoys an accuracy of 100 meters and 300 nanoseconds, 25 meters and 200 nanoseconds, before and after Selective Availability (SA) was turned off. In some applications, high accuracy is required. In this paper, five Neural Networks (NNs) are proposed for acceptable noise reduction of GPS receivers timing data. The paper uses from an actual data collection for evaluating the performance of the methods. An experimental test setup is designed and implemented for this purpose. The obtained experimental results from a Coarse Acquisition (C/A)-code single-frequency GPS receiver strongly support the potential of methods to give high accurate timing. Quality of the obtained results is very good, so that GPS timing RMS error reduce to less than 120 and 40 nanoseconds, with and without SA.

scholarly journals An Enhanced Method for Detecting and Repairing the Cycle Slips of Dual-Frequency Onboard GPS Receivers of LEO Satellites

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Zhouming Yang ◽  
Xin Liu ◽  
Jinyun Guo ◽  
Yaowei Xia ◽  
Xiaotao Chang
Keyword(s):  
Weighted Least Squares ◽  
Observation Equation ◽  
Single Frequency ◽  
Observation Data ◽  
Cycle Slip ◽  
Dual Frequency ◽  
Gps Receivers ◽  
Cycle Slips ◽  
Reference Satellite ◽  
Leo Satellites

Cycle slip detection and repair play important roles in the processing of data from dual-frequency GPS receivers onboard low-Earth orbit (LEO) satellites. To detect and repair cycle slips more comprehensively, an enhanced error method (EEM) is proposed. EEM combines single-frequency and narrow-lane carrier phase observations to construct special observations and observation equation groups. These special observations differ across time and satellite (ATS). ATS observations are constructed by three steps. The first step is differencing single-frequency and narrow-lane observations through a time difference (TD). The second step is to select a satellite as a reference satellite and other satellites as nonreference satellites. The third step is to difference the single-frequency TD observations from the reference satellite and the narrow-lane TD observations from the nonreference satellites by a satellite difference. If cycle slips occur at the reference satellite, the correction values for these ATS observations can be significantly enlarged. To process all satellites, the EEM selects each satellite as a reference satellite and builds the corresponding equation group. The EEM solves these observation equation groups according to the weighted least-squares adjustment (LSA) criterion and obtains the correction values; these correction values are then used to construct the χ 2 values corresponding to different equation groups, and the EEM subsequently carries out a chi-square distribution test for these χ 2 . The satellite corresponding to the maximum χ 2 will be marked. Then, the EEM iteratively processes the other satellites. Cycle slips can be estimated by rounding the float solutions of changes in the ambiguities of cycle slip satellites to the nearest integer. The simulation test results show that the EEM can be used to detect special cycle slip pairs such as (1, 1) and (9, 7). The EEM needs only observation data in two adjacent epochs and is still applicable to observation epochs with continuous cycle slips.

scholarly journals Stand-alone single-frequency GPS ice velocity observations on Nordenskiöldbreen, Svalbard

2010 ◽  
Vol 4 (4) ◽  
pp. 593-604 ◽  
Author(s):  
M. A. G. den Ouden ◽  
C. H. Reijmer ◽  
V. Pohjola ◽  
R. S. W. van de Wal ◽  
J. Oerlemans ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Temporal Resolution ◽  
Flow Line ◽  
Reference Station ◽  
Single Frequency ◽  
Maximum Speed ◽  
Gps Receivers ◽  
Ice Velocity ◽  
Using Data ◽  
Flow Velocities

Abstract. Precise measurements of ice-flow velocities are necessary for a proper understanding of the dynamics of glaciers and their response to climate change. We use stand-alone single-frequency GPS receivers for this purpose. They are designed to operate unattended for 1–3 years, allowing uninterrupted measurements for long periods with hourly temporal resolution. We present the system and illustrate its functioning using data from 9 GPS receivers deployed on Nordenskiöldbreen, Svalbard, for the period 2006–2009. The accuracy of the receivers is 1.62 m based on the standard deviation in the average location of a stationary reference station (NBRef). Both the location of NBRef and the observed flow velocities agree within one standard deviation with DGPS measurements. Periodicity (6, 8, 12, 24 h) in the NBRef data is largely explained by the atmospheric, mainly ionospheric, influence on the GPS signal. A (weighed) running-average on the observed locations significantly reduces the standard deviation and removes high frequency periodicities, but also reduces the temporal resolution. Results show annual average velocities varying between 40 and 55 m yr−1 at stations on the central flow-line. On weekly to monthly time-scales we observe a peak in the flow velocities (from 60 to 90 m yr−1) at the beginning of July related to increased melt-rates. No significant lag is observed between the timing of the maximum speed between different stations. This is likely due to the limited temporal resolution after averaging in combination with the relatively small distance (max. ±13 km) between the stations.

Performance Evaluation of USTEC Product for Single-Frequency Precise Point Positioning

GEOMATICA ◽  
2013 ◽  
Vol 67 (4) ◽  
pp. 253-257 ◽  
Author(s):  
Mahmoud Abd El-Rahman ◽  
Ahmed El-Rabbany
Keyword(s):  
Total Electron Content ◽  
Precise Point Positioning ◽  
Ionospheric Delay ◽  
Single Frequency ◽  
Electron Content ◽  
Dual Frequency ◽  
Total Electron ◽  
Gps Receivers ◽  
Mitigation Techniques ◽  
Point Positioning

Geodetic-grade dual-frequency GPS receivers are typically used for precise point positioning (PPP). Unfortunately, these receiver systems are expensive and may not provide a cost-effective solution in many instances. The use of low-cost single-frequency GPS receivers, on the other hand, are limited by the effect of ionospheric delay. A number of mitigation techniques have been proposed to account for the effect of ionospheric delay for single-frequency GPS users. Unfortunately, however, those mitigation techniques are not suitable for PPP. More recently, the U.S. Total Electron Content (USTEC) product has been developed by the National Oceanic and Atmospheric Administration (NOAA), which describes the ionospheric total electron content in high resolution over most of North America. This paper investigates the performance of USTEC and studies its effect on single-frequency PPP solution. A performance comparison with two widely-used ionospheric mitigation models is also presented.

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