12345673 of 14
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
GNSS hardware biases in code and carrier phase observables
KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning. Lantmäteriet.ORCID iD: 0000-0001-8871-2659
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

GNSS hardware biases appear in code and phase observations, and originates both from the receiver and satellite hardware. The presence of biases in GNSS observations might affect the accuracy in precise GNSS positioning applications, and might also be of relevance in other GNSS applications. They may also be a cause of incompatibility between different receiver types or GNSS constellations.

In this thesis, which is based on four papers, the biases in GNSS code and carrier phase observables are investigated. This is done by: characterizing and analyzing some selected biases; revealing some previously unknown biases; developing new methods to estimate some of the biases; and compiling and presenting information about biases in a new and comprehensive way.

Paper 1 gives a full review of how various kinds of biases affect various applications of precise GNSS positioning, including multi-GNSS positioning and ambiguity resolved PPP.

In Paper 2, two cases of relative phase biases, that potentially could degrade the positioning accuracy in precise positioning applications, are investigated. Fortunately, these biases turns out to be small in size with negligible effect on the positioning accuracy in both cases, which involves relative between-receivers biases for receivers of different type and between-signals biases for carrier phase observations of different signals associated with the same carrier frequency.

Paper 3 characterizes GNSS observations from a Nexus 9 Android tablet. By doing this, it reveals a number of earlier unknown biases. A drift between the code and phase observable of -3 and 2 mm/s is revealed for GPS and GLONASS, respectively. Additionally, an unexpected variation in the GLONASS phase observable, which seems to be dependent on the topocentric range rate of the satellite, is discovered.

In Paper 4, the existence of nadir dependent code biases is confirmed for GNSS observations from BeiDou-2 satellites of the BeiDou constellation by analyzing the residuals of 2-D and 3-D ionosphere modeling. This a new method to derive this kind of bias, independent of the earlier employed approach based on the multipath linear combination. The estimated effect is, however, too small to infer a similar nadir dependence for GPS and Galileo as well.

Abstract [sv]

Hårdvaru-relaterade GNSS biases uppträder i kod- och bärvågsobservationer som små avvikelser eller fel. Dessa är karaktäristiska för en viss typ av hårdvara och har sitt ursprung både i satellit och mottagare. Förekomsten av biases i GNSS-observationer har en potentiell negative påverkan för mätosäkerheten för tillämpningar av noggrann GNSS-positionering. Även i andra GNSS-tillämpningar kan biases i vissa fall vara relevanta. Förekomsten av biases kan också vara en orsak till kompatibilitetsproblem när GNSS-observationer från olika mottagartyper eller GNSS-konstellationer kombineras.

Denna avhandling, som är baserad på fyra artiklar, tittar närmare på biases som förekommer i kod- och bärvågsobservationer. Mer specifikt så involverar detta: karaktärisering och analys av några utvalda biases; avlöjande av vissa tidigare okända biases; utvecklande av nya metoder för estimering av biases; och sammanställning och presentation av biases på ett nytt och övergripande sätt.

Artikel 1 är en litteraturstudie som behandlar hur olika typer av biases påverkar tillämpningar för noggrann GNSS-positionering. Dessa tillämpingar innefattar bland annat GNSS-positionering som involverar flera GNSS-konstellationer och PPP med heltalslösning av periodobekanta.

Artikel 2 undersöker två typer av relativa biases för bärvågsobservationer. Dessa skulle potentiellt sett kunna ha en negativ inverkan på mätosäkerheten för noggranna GNSS-tillämpningar. De två typerna innefattar biases relativa mellan två mottagare, och biases relativa mellan två signaler. Lyckligtvis så visade det sig att dessa är så små att de endast har en försumbar effekt i de flesta GNSS-tillämpningar.

I artikel 3 karaktäriseras GNSS-observationerna från en surfplatta av modell Nexus 9 och med Android som operativsystem. Här avslöjas två tidigare okända biases: drift mellan kod- och bärvågsobservablerna motsvarande -3 och 2 mm/s för GPS och Glonass; samt en variation i Glonass bärvågsobservabel som verkar bero på den topocentriska hastigheten.

Artikel 4 bekräftar förekomsten av ett nadir-beroende för kod-biases för BeiDou-observationer gällande de satelliter som betecknas BeiDou-2. Detta resultat är härlett från jonosfärsmodellering i två och tre dimensioner genom analys av motsvarande residualer. Den presenterade metoden för denna härledning är ny, då metoden utnyttjad i tidigare studier istället använder sig av flervägsfelslinjärkombinationen av kod- och bärvågsobservationer.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2020. , p. 56
Series
TRITA-ABE-DLT ; 203
Keywords [en]
GNSS, GNSS positioning, hardware biases, phase biases, multi-GNSS, GPS, GLONASS, Galileo, BeiDou, satellite dependency, characterization, android, mass market, Group delay variations, nadir dependence, ionosphere modeling, ionospheric tomography
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Other Engineering and Technologies Geotechnical Engineering
Research subject
Geodesy and Geoinformatics; Geodesy and Geoinformatics, Geodesy
Identifiers
URN: urn:nbn:se:kth:diva-267044ISBN: 978-91-7873-454-2 (print)OAI: oai:DiVA.org:kth-267044DiVA, id: diva2:1390435
Public defence
2020-02-28, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20200104

Available from: 2020-02-04 Created: 2020-01-31 Last updated: 2020-02-04Bibliographically approved
List of papers
1. Review of code and phase biases in multi-GNSS positioning
Open this publication in new window or tab >>Review of code and phase biases in multi-GNSS positioning
2017 (English)In: GPS Solutions, ISSN 1080-5370, E-ISSN 1521-1886, Vol. 21, no 3, p. 849-860Article in journal (Refereed) Published
Abstract [en]

A review of the research conducted until present on the subject of Global Navigation Satellite System (GNSS) hardware-induced phase and code biases is here provided. Biases in GNSS positioning occur because of imperfections and/or physical limitations in the GNSS hardware. The biases are a result of small delays between events that ideally should be simultaneous in the transmission of the signal from a satellite or in the reception of the signal in a GNSS receiver. Consequently, these biases will also be present in the GNSS code and phase measurements and may there affect the accuracy of positions and other quantities derived from the observations. For instance, biases affect the ability to resolve the integer ambiguities in Precise Point Positioning (PPP), and in relative carrier phase positioning when measurements from multiple GNSSs are used. In addition, code biases affect ionospheric modeling when the Total Electron Content is estimated from GNSS measurements. The paper illustrates how satellite phase biases inhibit the resolution of the phase ambiguity to an integer in PPP, while receiver phase biases affect multi-GNSS positioning. It is also discussed how biases in the receiver channels affect relative GLONASS positioning with baselines of mixed receiver types. In addition, the importance of code biases between signals modulated onto different carriers as is required for modeling the ionosphere from GNSS measurements is discussed. The origin of biases is discussed along with their effect on GNSS positioning, and descriptions of how biases can be estimated or in other ways handled in the positioning process are provided.

Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2017
Keywords
Hardware biases, GNSS positioning, Multi-GNSS
National Category
Communication Systems Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Geodesy and Geoinformatics
Identifiers
urn:nbn:se:kth:diva-214726 (URN)10.1007/s10291-016-0572-7 (DOI)000403949500002 ()2-s2.0-84992052780 (Scopus ID)
Note

QC 20170922

Available from: 2017-09-20 Created: 2017-09-20 Last updated: 2020-01-31Bibliographically approved
2. Satellite dependency of GNSS phase biases between receivers and between signals
Open this publication in new window or tab >>Satellite dependency of GNSS phase biases between receivers and between signals
(English)In: Journal of Geodetic Science, ISSN 2081-9919, E-ISSN 2081-9943Article in journal (Refereed) Submitted
Abstract [en]

The existence of hardware induced phase biases might influence the accuracy in precise positioning if not handled properly. This is extra problematic if the biases are dependent on the satellite tracked, as these biases no longer will be common between the satellites and thus are not absorbed by the receiver clock term of the positioning solution. In this paper, we carried out two studies to investigate whether there exists a satellite dependency of the relative phase biases. Even though small in size, satellite dependent variations were found in both cases.

In the first case, relative receiver phase biases were studied, while the satellite dependency of relative phase biases between signals (e.g. between carrier phases from C/A-code and P-code tracking) was investigated in the second case. The biases in the first case had a size of 0.8 mm between the satellites with the largest and smallest values, and additionally showed temporal variations that were consistent over time. The corresponding size of the biases second case was 3.5 mm, and no temporal variations were found. 

Keywords
GNSS, hardware delays, phase biases, satellite dependency
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Geodesy and Geoinformatics
Identifiers
urn:nbn:se:kth:diva-214842 (URN)
Note

QC 20170925

Available from: 2017-09-22 Created: 2017-09-22 Last updated: 2020-01-31Bibliographically approved
3. Characterization of GNSS observations from a Nexus 9 Android tablet
Open this publication in new window or tab >>Characterization of GNSS observations from a Nexus 9 Android tablet
2019 (English)In: GPS Solutions, ISSN 1080-5370, E-ISSN 1521-1886, Vol. 23, no 1, article id UNSP 21Article in journal (Refereed) Published
Abstract [en]

Global navigation satellite system (GNSS) raw data were made available in the application programming interface (API) starting from version 7.0 of the Android operating system. This opens possibilities for precise positioning with Android devices, as externally generated GNSS corrections can now be included in the positioning estimation in a convenient way. The Nexus 9 tablet is a good candidate for an early assessment of the raw GNSS observables and the corresponding derived precise positions, as it also supports many of the optional features and observation types presented by the API, including carrier phase observations which play an important role in many precise positioning techniques. It is known from the previous studies that poor handling of multipath in smartphones and tablets is a big challenge when it comes to precise GNSS positioning with these kinds of devices. Hence, this study assesses the raw GNSS observations and the calculated precise positions of the Nexus 9 tablet in two experimental setups with different multipath impacts. In addition, various biases of the observations are determined, some of which is not present on high-grade geodetic receivers. The analysis is done for GPS and GLONASS, which are supported by the Nexus 9 tablet. The study shows that multipath plays an important role for the expected accuracy of the calculated precise positions, both due to the induced error on the measurements, and due to loss of lock of the GNSS signals, which significantly affects precise positioning from carrier-phase measurements. Position accuracy ranges from just below 1m to a few decimeters between the experimental setups with moderate and low levels of multipath respectively, for positioning based on carrier-phase observations. It is, furthermore, demonstrated that consideration of code inter-system biases and code inter-frequency biases of the Nexus 9 tablet are crucial for differential GNSS with multiple GNSS systems and when GLONASS observations are used in the positioning solutions. Besides these expected biases, also other less expected behaviors were discovered in the Nexus 9 GNSS observations, including various drifts for the code and phase observations. This study also proposes some strategies to handle these.

Place, publisher, year, edition, pages
SPRINGER HEIDELBERG, 2019
Keywords
GNSS positioning, Characterization, Biases, Android, Mass market, GPS, GLONASS
National Category
Human Geography
Identifiers
urn:nbn:se:kth:diva-241187 (URN)10.1007/s10291-018-0818-7 (DOI)000454562800001 ()2-s2.0-85059346560 (Scopus ID)
Note

QC 20190121

Available from: 2019-01-21 Created: 2019-01-21 Last updated: 2020-01-31Bibliographically approved
4. Nadir dependent GNSS code biases and their effect on 2D and 3D ionosphere modeling
Open this publication in new window or tab >>Nadir dependent GNSS code biases and their effect on 2D and 3D ionosphere modeling
2020 (English)In: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292Article in journal (Refereed) Submitted
Abstract [en]

Recent publications have shown that group delay variations are present in the code observables of the BeiDou system, as well as to a lesser degree in the code observables of the GPS. These variations could potentially affect precise point positioning, integer ambiguity resolution by the Hatch-Melbourne-Wübbena linear combination, as well as total electron content estimation for ionosphere modeling from GNSS observations. The latter is an important characteristic of the ionosphere and a prerequisite in some applications of precise positioning. By analyzing the residuals from total electron content estimation, the existence of group delay variations is in this study confirmed by a method independent of methods previously used. It also provides knowledge of the effects of group delay variations on ionosphere modeling. These biases are confirmed both for 2-dimesional ionosphere modeling by the thin shell model, as well as for 3-dimensional ionosphere modeling using tomographic inversion. BeiDou group delay variations are prominent and consistent in the residuals for both the 2-dimensional and 3-dimensional case of ionosphere modeling, while GPS group delay variations are smaller and cannot be confirmed due to the accuracy limitations of the ionospheric models. Group delay variations are to a larger extent absorbed by the ionospheric model when 3-dimensional ionospheric tomography is performed in comparison with 2-dimensional modeling.

Place, publisher, year, edition, pages
MDPI, 2020
Keywords
GNSS, Group delay variations, Biases, Nadir dependence, Ionosphere modeling, Ionospheric tomography
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-267043 (URN)
Note

QC 20200203

Available from: 2020-01-31 Created: 2020-01-31 Last updated: 2020-02-03Bibliographically approved

Open Access in DiVA

thesis(6114 kB)23 downloads
File information
File name FULLTEXT01.pdfFile size 6114 kBChecksum SHA-512
4e14f399b34be91d398a59799c07b1f8ae77ad0e0704c3125db7920dbce6176adc0f19be00ade8b992d17f1527b1e52befa9f0442d2e9931abd35dfb4f8a7fb1
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Håkansson, Martin
By organisation
Geodesy and Satellite Positioning
Electrical Engineering, Electronic Engineering, Information EngineeringOther Engineering and TechnologiesGeotechnical Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 23 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 169 hits
12345673 of 14
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf