National Key Laboratory of Geo Information Engineering

Fengcheng, China

National Key Laboratory of Geo Information Engineering

Fengcheng, China
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Zeng A.,Zhengzhou University | Zeng A.,National Key Laboratory of Geo Information Engineering | Zeng A.,Xian Research Institute Of Surveying And Mapping | Yang Y.,National Key Laboratory of Geo Information Engineering | And 3 more authors.
GPS Solutions | Year: 2017

Navigation applications will benefit significantly from the improved reliability, availability, and accuracy offered by combining BeiDou Navigation Satellite System (BDS) and Global Positioning System (GPS). In the BDS/GPS navigation data fusion model, the effect of inter-system bias (ISB) must be considered. We present a detailed analysis of the pseudorange measurements for BDS and GPS and demonstrate the existence of code ISB in BDS/GPS measurements. The ISB mainly consists of the time system offset, the coordinate system difference, and the inter-system hardware delay bias. A method based on statistical hypothesis testing is proposed to assess the stability and difference of the BDS–GPS ISB. Real data from 18 stations equipped with six types of receivers are used to compute the ISB. The results illustrate that (a) receiver-dependent ISBs are evident and comparatively consistent, with the maximum ISB observed in our experiments being −1516 ns, (b) these receiver-dependent ISBs exhibit great stability in terms of their standard deviation and intra-day variation, and (c) the estimated ISBs for each BDS satellite type with respect to GPS are consistent. © 2017 Springer-Verlag Berlin Heidelberg


Yang Y.,National Key Laboratory of Geo Information Engineering | Yang Y.,Xian Institute of Surveying and Mapping
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2012

Uncertainty always exists in satellite navigation process and results, which includes random errors, systematic errors, outliers and colored noises etc. There are many different measures for evaluating the quality of the navigation results, such as precision, accuracy, reliability and uncertainty, and so on. In practice, the accuracy, precision and error itself are often confused by the users, so are the uncertainty and the uncertainty measures. Especially, the accuracy is often followed several times standard deviation or error percentage. For example, the user range accuracy (URA) index is often followed standard deviation. In this paper, the user range error (URE) is redefined based on the uncertainty concept. Then the URE and URA are distinguished and their relationship is obtained. The uncertainty is distinguished from the uncertainty measure. The often used reliability concept in geodetic adjustment is introduced and described. At last, several notes on the concept of error, precision, accuracy, URE and URA are given.


Wei Z.,Xian Research Institute of Surveying and Mapping | Wei Z.,National Key Laboratory of Geo Information Engineering
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2012

This paper is devoted to treating the permanent tide in geodesy. First the numerical expression of the permanent tide potential is derived, then formal expressions of three kinds of tidal values and transformations among them for six types of geodetic observables frequently encountered are given, and finally the characteristic and usage of the three tidal systems in geodesy are discussed.


Peng F.,Xian Institute of Surveying and Mapping | Peng F.,National Key Laboratory of Geo information Engineering | Chen S.,Zhengzhou University | Jin Q.,Xian Institute of Surveying and Mapping | Jin Q.,National Key Laboratory of Geo information Engineering
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2014

The influence of altimetry errors on marine geopotential recovery is studied, and the formulae for the altimetry stochastic errors transmission during the marine gravity anomalies recovery are presented. In the end, the predicted geopotential errors with several resolutions from 2 cm and 8 cm altimetry random errors are quantitative analysed, respectively. The results can propose some references for the Chinese altimetry satellite design in the future.


Yang Y.X.,National Key Laboratory of Geo Information Engineering | Li J.L.,Zhengzhou University | Wang A.B.,Beijing Satellite Navigation Center | Xu J.Y.,Zhengzhou University | And 4 more authors.
Science China Earth Sciences | Year: 2014

BeiDou regional navigation satellite system (BDS) also called BeiDou-2 has been in full operation since December 27, 2012. It consists of 14 satellites, including 5 satellites in Geostationary Orbit (GEO), 5 satellites in Inclined Geosynchronous Orbit (IGSO), and 4 satellites in Medium Earth Orbit (MEO). In this paper, its basic navigation and positioning performance are evaluated preliminarily by the real data collected in Beijing, including satellite visibility, Position Dilution of Precision (PDOP) value, the precision of code and carrier phase measurements, the accuracy of single point positioning and differential positioning and ambiguity resolution (AR) performance, which are also compared with those of GPS. It is shown that the precision of BDS code and carrier phase measurements are about 33 cm and 2 mm, respectively, which are comparable to those of GPS, and the accuracy of BDS single point positioning has satisfied the design requirement. The real-time kinematic positioning is also feasible by BDS alone in the opening condition, since its fixed rate and reliability of single-epoch dual-frequency AR is comparable to those of GPS. The accuracy of BDS carrier phase differential positioning is better than 1 cm for a very short baseline of 4.2 m and 3 cm for a short baseline of 8.2 km, which is on the same level with that of GPS. For the combined BDS and GPS, the fixed rate and reliability of single-epoch AR and the positioning accuracy are improved significantly. The accuracy of BDS/GPS carrier phase differential positioning is about 35 and 20 % better than that of GPS for two short baseline tests in this study. The accuracy of BDS code differential positioning is better than 2.5 m. However it is worse than that of GPS, which may result from large code multipath errors of BDS GEO satellite measurements. © 2013, Science China Press and Springer-Verlag Berlin Heidelberg.


Li J.,Zhengzhou University | Yang Y.,National Key Laboratory of Geo Information Engineering | Xu J.,Zhengzhou University | He H.,Beijing Satellite Navigation Center | And 2 more authors.
Lecture Notes in Electrical Engineering | Year: 2013

The initial performance of the BeiDou single-epoch dual-frequency RTK is evaluated. The success rate and reliability of single-epoch dual-frequency ambiguity resolution (AR) by BeiDou or BeiDou/GPS are analyzed, which are also compared with those by GPS alone. The results show that the BeiDou-only dual-frequency RTK is already feasible, whose single-epoch AR performance and positioning accuracy are compared to those of GPS alone. Furthermore, the success rate and reliability of BeiDou/GPS single-epoch AR are improved when compared to GPS, in particular under high cut-off elevation situations. It is also observed that the improvement of positioning accuracy reach to 31 % for the very short baseline of 4.2 m and is 2.9 % for the short baseline of 8.2 km. © 2013 Springer-Verlag Berlin Heidelberg.


Li J.,Zhengzhou University | Yang Y.,National Key Laboratory of Geo Information Engineering | Xu J.,Zhengzhou University | He H.,Beijing Satellite Navigation Center | Guo H.,Beijing Satellite Navigation Center
GPS Solutions | Year: 2013

The regional constellation of BeiDou navigation satellite system (BDS) has been officially in operation since December 27, 2012, and real-time kinematic positioning using BDS and GPS multi-frequency observations is feasible. A heavy computational problem arises when resolving ambiguities in the case of multi-system with multi-frequency observations. A multi-carrier fast partial ambiguity resolution strategy is developed with the property that the extra-wide-lane and wide-lane ambiguities in the multi-frequency case can be resolved reliably in advance. Consequently, the technique resolves ambiguities sequentially instead of the usual batch ambiguity resolution (AR) mode so as to improve the computational efficiency of AR significantly. The strategy is demonstrated with real BDS/GPS dual- and triple-frequency observations. The results have shown that the probability of correct AR by the proposed method is comparable to that of the batch AR. Experimentally, the new method is about 2.5 times as fast as the batch AR in the dual-frequency case, 3 times in the mixed dual- and triple-frequency case and 3.5 times in the triple-frequency case. © 2013, Springer-Verlag Berlin Heidelberg.


Wang R.,National Key Laboratory of Geo Information Engineering | Wang R.,Xian Institute of Surveying and Mapping | Hu X.,National Key Laboratory of Geo Information Engineering | Hu X.,Xian Institute of Surveying and Mapping | And 3 more authors.
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2013

The key technologies employed in the photogrammetry of Mapping Satellite-1 without ground control points are introduced, including camera on-orbit calibration, equivalent frame photo (EFP) multi-functional bundle adjustment, error compensation of attitude angle with low frequency, drift angle (yawing) effect processing etc. The processing results provided by the production unit with EFP multi-functional bundle adjustment software are also presented in the paper. All these results show that the accuracies of positioning without ground control points have met the requirements of engineering technical indexes, coming up to the level of SRTM of United States. Additionally, several results of positioning with ground control points are listed and compared as well.


Huang G.,Chang'an University | Huang G.,National Key Laboratory of Geo Information Engineering | Zhang Q.,Chang'an University | Fu W.,Chang'an University | Guo H.,Beijing Satellite Navigation Center
Advances in Space Research | Year: 2015

A new strategy is proposed to monitor GPS/GLONASS time offsets for common navigation users using a combined GPS/GLONASS Precise Point Positioning (PPP) method based on the orbit and clock products of different time scales. The results of the inter-system GPS/GLONASS time offset, the user time offset and the inter-system device delay difference were obtained using the proposed method. The properties of these results were analyzed in terms of the stability, precision and variation characteristics. Moreover, the practicality of the time offset results in an actual navigation application was tested and demonstrated. The results indicate that the monitoring and prediction of the user time offset, but not the inter-system time offset, has important values for navigation users. © 2015 COSPAR.


He H.,Beijing Satellite Navigation Center | Li J.,Zhengzhou University | Yang Y.,National Key Laboratory of Geo Information Engineering | Xu J.,Zhengzhou University | And 2 more authors.
GPS Solutions | Year: 2014

The first results of the short baseline single-epoch kinematic positioning based on dual-frequency real BeiDou/GPS data are presented. The performance of the BeiDou/GPS single-epoch positioning is demonstrated in both static and kinematic modes and compared with corresponding GPS-only performance. It is shown that the availability and reliability of the single-frequency BeiDou/GPS and dual-frequency BeiDou single-epoch kinematic positioning are comparable to those of the dual-frequency GPS. The fixed rate and reliability of ambiguity resolution for the single- and dual-frequency BeiDou/GPS are remarkably improved as compared to that of GPS-only, especially in case of high cutoff elevations. For positioning accuracy with fixed ambiguities, the BeiDou/GPS single-epoch solutions are improved by 23 and 4 % relative to the GPS-only case for two short baseline tests of 8 km, respectively. These results reveal that dual-frequency BeiDou real-time kinematic (RTK) is already applicable in Asia-Pacific areas and that single-frequency BeiDou/GPS RTK is also achievable but only with initialization of several seconds. More promisingly, the dual-frequency BeiDou/GPS RTK can overcome the difficulties with GPS-only RTK under the challenging conditions assuming, of course, that the additional BeiDou satellites are visible. © 2013 Springer-Verlag Berlin Heidelberg.

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