Lambert Wanninger's research while affiliated with Technische Universität Dresden and other places

Publications (43)

Article
Full-text available
In 2020, Garmin released one of the first consumer devices with a dual-frequency GNSS chip and a quadrifilar helix antenna: GPSMAP 66sr. The device is intended to serve as a positioning and navigation device for outdoor recreation purposes with positioning accuracies on the few meter level. However, due to its highly accurate GNSS dual-frequency ca...
Article
Full-text available
For a few years now, GNSS multi-frequency quadrifilar helix antennas (QHA) are available to be used for precise GNSS applications. We performed test measurements with two types of multi-frequency QHA and compared them with a geodetic patch antenna. Although code and carrier phase noise and high-frequent multipath was determined to be larger as comp...
Article
Full-text available
GNSS satellite and receiving antennas exhibit group delay variations (GDV), which affect code pseudorange measurements. Like antenna phase center variations, which affect phase measurements, they are frequency-dependent and vary with the direction of the transmitted and received signal. GNSS code observations contain the combined contributions of s...
Article
Full-text available
Zusammenfassung: Seit einigen Jahren ist es leicht möglich, auf die GNSS-Beobachtungsdaten von Android-Smartphones zuzugreifen. In diesem Beitrag werden die Code- und Phasendaten von drei verschiedenen solchen Smartphones (Xiaomi Mi8, Huawei P30 und Samsung S20) hinsichtlich Verfügbarkeit und Qualität analysiert. Es wird gezeigt, dass für Anwendun...
Conference Paper
Full-text available
Nowadays, Android enables the access of GNSS raw data and, thus, an in-depth evaluation of smartphone GNSS observations. We analysed and compared GNSS code and phase observations and the achievable position accuracies of three Android devices: tablet Google Nexus 9, smartphones Xiaomi Mi8 and Huawei P30. Not all the phase observables of these devic...
Article
Full-text available
In 2016, an application programming interface was added to the Android operating systems, which enables the access of GNSS raw observations. Since then, an in-depth evaluation of the performance of smartphone GNSS chips is very much simplified. We analyzed the quality of the GNSS observations, especially the carrier phase observations, of the dual-...
Article
Full-text available
Similar to the antenna phase center corrections for phase measurements, group delay variations (GDV) of satellite and receiving GNSS antennas affect code pseudorange measurements. They are frequency-dependent and vary with the direction of signal transmission and reception. We present the first GDV estimates for all five Galileo and three GLONASS f...
Article
Full-text available
Presently, the global positioning system (GPS) satellite constellation consists of 40% older Block IIA and IIR space vehicles and 60% newer IIR-M and IIF satellites. Only newer GPS satellites are capable of transmitting the L2C signal which is in quadrature to the legacy L2P(Y) signal being broadcast by all satellites. The data format RINEX-2 is no...
Article
Full-text available
The code observable of global navigation satellite systems (GNSS) is influenced by group delay variations (GDV) of transmitter and receiver antennas. For the Global Positioning System (GPS), the variations can sum up to 1 m in the ionosphere-free linear combination and thus can significantly affect precise code applications. The contribution of the...
Article
Full-text available
GPS code pseudorange measurements exhibit group delay variations at the transmitting and the receiving antenna. We calibrated C1 and P2 delay variations with respect to dual-frequency carrier phase observations and obtained nadir-dependent corrections for 32 satellites of the GPS constellation in early 2015 as well as elevation-dependent correction...
Chapter
This chapter describes the concepts of differential global navigation satellite system (DGNSS ) positioning focusing on practical details given that the fundamental concepts have been covered in prior chapters. The chapter starts with a review of the general concepts of DGNSS, including a quantitative discussion on the biases in DGNSS measurements....
Article
Full-text available
Code pseudorange measurements of the Chinese GNSS BeiDou reveal variations which result in code–phase divergences of more than 1 m. We have analyzed these delay variations based on observation data of the International GNSS Service and its Multi-GNSS Experiment campaign. Our results confirm that these code variations are elevation-dependent when ob...
Article
Full-text available
The quality of real-time GPS positions based on the method of precise point positioning (PPP) heavily depends on the availability and accuracy of GPS satellite orbits and satellite clock corrections. Satellite-based augmentation systems (SBAS) provide such corrections but they are actually intended to be used for wide area differential GPS with pos...
Article
Satellite based Augmentation Systems (SBAS) provide a valuable source of GPS orbits and satellite clock corrections. Although these data streams are intended for code based meter accurate positioning, we used them for carrier-phase based Precise Point Positioning (PPP). All our results are based on static dual frequency observation data from sites...
Article
The frequency division multiplexing of the GLONASS signals causes inter-frequency biases in the receiving equipment. These biases vary considerably for receivers from different manufacturers and thus complicate or prevent carrier-phase ambiguity fixing. Complete and reliable ambiguity fixing requires a priori information of the carrier-phase inter-...
Article
BIOGRAPHIES Nico Reussner is a member of the GNSS research group at the Geodetic Institute of TU Dresden. He received his Dipl.-Ing. in geodesy from TU Dresden in 2009. Lambert Wanninger is a professor of geodesy at TU Dres-den. He has been involved in research on precise GNSS po-sitioning since 1990. He holds a Dr.-Ing. degree in geodesy from Univ...
Conference Paper
Carrier phase multipath caused by reflections in the vicinity of GNSS stations is a major error source of precise differential positioning. Detection and mitigation of carrier phase multipath errors can be based on signal quality measurements, i.e. signal-to-noise ratio (S/N) or carrier-to-noise ratio (C/N), as provided by GNSS receivers. Variation...
Article
Antenna changes at GNSS reference stations frequently produce discontinuities in the coordinate time series. These apparent position shifts are mainly caused by changes of carrier-phase multipath effects and different errors in the antenna phase center corrections. A monitoring method was developed and successfully tested, which requires additional...
Article
The analysis of sea-level changes observed by tide-gauge measurements requires information of height changes of these gauges caused by vertical land movements. Such local, regional, or large-scale vertical land movements are monitored by geodetic observation techniques. In Germany precise geometric levelling campaigns have been performed for more t...
Article
Carrier phase multipath caused by signal reflections in the vicinity of GNSS stations is a ma-jor error source of precise differential positioning. Detection and mitigation of carrier phase multipath errors can be based on signal quality values (e. g. signal-to-noise ratio values) as provided by GNSS re-ceivers. These values are influenced by vario...
Article
Antenna changes at GNSS reference stations frequently produce discontinuities in their coordinate time series, especially in the height component. These coordinate shifts are mainly caused by changes of carrier-phase multipath effects and also, but usually to a smaller extend, by errors in the antenna phase center corrections. A monitoring method w...
Article
Full-text available
Precise Point Positioning (PPP) requires the availability of precise orbit and clock corrections for all satellites used. Unfortunately, only two Analysis Centers (AC) of the International GNSS Service (IGS) make GLONASS clock corrections available. Both products consist of tabular clock values with 5 minute intervals, which is not dense enough for...
Article
Antenna changes at GNSS reference stations often alter multipath errors which affect carrier-phase observations. As a result, apparent shifts of the antenna position occur. A monitoring method was developed and successfully tested with observation data from Rhineland-Palatinate, which allows modelling these alterations and correcting carrier-phase...
Article
Unlike GPS, GLONASS signals experience different hardware delays in the receiving equipment because each satellite transmits its own carrier frequency. The resulting interchannel biases may differ between receivers and they must be taken into account in carrier phase processing. A linear model to describe the frequency dependence of these biases pe...
Article
Precise (centimetre level) applications require code and carrier phase pseudoranges and differential positioning including carrier phase ambiguity resolution. Objective of this research work is to combine GPS with GLONASS and single-frequency SBAS ranging to gain improved availability, faster ambiguity resolution, and higher accu- racy. Although GL...
Article
The exchange of the antenna at a GNSS reference station may cause an apparent shift of the antenna position as determined from the GNSS observations. The reason for such a shift is found in station dependent observation errors, specifically multipath. The paper presents several examples for these effects, analyses their characteristics and suggests...
Article
Real-Time Kinematic (RTK) service providers compute RTK corrections based on the observations of networks of GNSS (Global Navigation Satellite Systems like GPS or GLON-ASS) reference stations with station distances of about 50 to 80 kilometres. This correction data enables Network RTK users to position themselves with centimetre accuracy in real-ti...
Article
Ionospheric disturbances may cause difficulties in single- base RTK and even in Network RTK positioning. Hence, index values providing statistical information on expected residual ionospheric biases are of great help to RTK users. One such indicator is the I95 ionospheric disturbance index which has been in continuous use in Central Europe since 19...
Article
Based on available GPS reference network observations, a procedure for estimating carrier-phase multipath corrections was developed, implemented, and tested. This procedure consists of three steps: detection and localization of multipath-affected satellite signals, daily estimation of multipath errors, and combination of these daily estimates to ob...
Article
GPS signal diffraction occurs whenever the direct GPS signal is obstructed but nevertheless a diffracted signal is received and processed. The longer propagation time of a diffracted signal causes carrier phase errors of up to several cm or even a few tens of cm. Diffraction effects are a common and often dominant error source in rapid static or ki...
Article
Summary GPS signal diffraction occurs whenever the direct GPS signal is obstructed but nevertheless a diffracted signal is received and processed. The longer propagation time of a diffracted signal causes carrier phase errors of up to several cm or even a few tens of cm. Diffraction effects are a common and often dominant error source in rapid stat...
Article
Positioning in regional networks of active GPS reference stations is performed by means of virtual reference stations. Their performance mainly depends on the quality of the models correcting for distance and direction dependent errors. In the presence of medium-scale ionospheric disturbances, most but not all ionospheric refraction errors are remo...
Chapter
Observations of several GPS reference receivers in a regional network enable two kinds of error modelling and reduction. The spatially correlated errors (orbit, ionosphere, troposphere) are modelled epoch-by-epoch and satellite-by-satellite by 2-D linear interpolation. Furthermore, multipath effects are mitigated by averaging correspondent observat...
Article
Distance-dependent errors due to ionospheric refraction complicate ambiguity resolution and limit the accuracy attainable in GPS baseline determination. This paper presents an approach for modelling these errors from the observations of several permanent GPS-stations surrounding the area of interest. Regional ionospheric correction models are produ...
Chapter
Severe ionospheric conditions, as e.g. scintillations or a very high electron content or large horizontal gradients of the electron content, can affect GPS observations in such a way that precise geodetic relative positioning becomes difficult or sometimes even impossible. A German-Brazilian joint project was established on the use of GPS in South...
Article
One of the major error sources in GPS positioning is ionospheric refraction which causes signal propagation delays. Due to the dispersive character of these delays, dual frequency phase measurements can effectively be used to gain ionospheric corrections.
Article
Zusammenfassung Für die cm-genaue Positionierung innerhalb regio-naler GPS-Netze aktiver Referenzstationen werden Beobachtungen virtueller Referenzstationen verwen-det. Deren Qualität hängt insbesondere von den Modellen für die entfernungs-und richtungsabhän-gigen Fehlereinflüsse ab. Beim Auftreten ionosphäri-scher Störungen mittlerer Größe kann di...

Citations

... The post-processing considers the GPS and Galileo L1 and L5 signal in PPP mode. For more details, please see Wanninger et al. (2022), who supported us in doing and evaluating the measurements. For the processing, the commercial WaPPP software was used. ...
... A great advantage of the GPSMAP 66sr in comparison with other consumer devices with dual-frequency GNSS chips, e.g., smartphones such as Xiaomi Mi8 or Huawei P30 [5], consists of its quadrifilar helix antenna (QHA). QHA produces a circularly polarized hemispherical radiation pattern and, thus, is able to mitigate multipath signals [6]. It proved to be a major advantage of the equipment that GNSS observations can be stored internally in RINEX 3.04 format [7] and that these files can be easily transferred to a computer for postprocessing. ...
... Based on these data, block-specific and frequency-specific phase center offsets for BDS-2 and BDS-3 satellites were included in the IGS antenna model starting with igs14_2069.atx. Direction-dependent group delay variations have been identified in various studies for the BDS-2 satellites (Lou et al., 2017;Wanninger & Beer, 2015), whereas BDS-3 satellites were shown to be essentially free of such variations (Beer et al., 2021;Hong et al., 2020). However, no common standard for the application of satellite GDVs exists and their consideration is presently left to the discretion of individual analysis centers and users. ...
... A study by Pensyna et al. [54] in 2014 showed that cm solutions are possible in principle, using smartphone antennas, and that the high Multipath sensitivity of smartphones can be overcome. Studies in recent years have shown that centimetre accuracies using smartphones are achievable under good conditions (open sky) [55][56][57], even with the same (Xiaomi Mi 8) or comparable (Huawei P30) smartphones as used in this study [58,59]. ...
... The recent development of smartphone GNSS chipsets, such as Broadcom BCM47755 embedded, makes precise code-based positioning [20], PPP [21], and instantaneous, centimeterlevel RTK positioning possible with Android-based smartphones [2,3,12,[22][23][24]. In this contribution, we assess the BIE positioning performance using Google Pixel 4 (GP4) smartphones and compare the performance to that of the ILS and float estimators. ...
... Tests have also been performed for various weather and environmental conditions [19] as well as regarding relative positioning [20]. Studies conducted using smartphones that record phase measurements offer the possibility of very high accuracy in static measurements: 1-4 cm [21] or even 2 cm for 60 min of measurement [22]. In addition, the use of external clock files and orbits allows the accuracy of the code solutions to be improved, and taking into account multi-tracking gives the possibility to achieve an accuracy of 2-3 m [23,24]. ...
... Based on these absolute receiver antenna GDV we are now able to estimate absolute multi-frequency GNSS satellite antenna GDV for GPS, GLONASS, Galileo, BeiDou, and QZSS. Since no such receiver antenna GDV corrections were available in earlier studies (Wanninger et al. 2017;Beer et al. 2020), the results for satellite antenna GDV differ from earlier estimations, especially at frequencies with large receiver antenna GDV. ...
... The published values agree on the level of 10 cm RMS for IF (Beer and Wanninger 2018). They improve precise applications of the code observable, like single-frequency precise point positioning (PPP), ambiguity-fixing with the Hatch-Melbourne-Wübbena linear combination, and the determination of total electron content. ...
... Even though the accuracy of code measurements is eminently worse than carrier-phase measurements, code measurements are, nowadays, primary in every GNSS receiver. While obtaining centimeter or even millimeter accuracy, the code measurements always support determining the exact coordinates, because the carrier-phase positioning performance relies on the code measurements [4]. For this reason, there is not much research performed on the efficiency of DGNSS positioning taking part in RTK phase measurements, even though the DGNSS technique may play a significant role in the course of time. ...
... Based on the assumption that code biases could be treated as a constant in the short term [29], RCBs are re-estimated every 24 h for convenience. Lately, an increasing number of experimental results point to the intra-day variation of RCBs [30,31], which is inconsistent with the former assumption. The magnitude of the receiver code is closely related to the receiver equipment, such as the receiver type, the antenna type, and the firmware version [32,33]. ...