The Multi-GNSS Experiment (MGEX) of the International GNSS Service (IGS) - Achievements, prospects and challenges

An initial characterization and performance assessment of the COMPASS/BeiDou-2 regional navigation system is presented. Code and carrier phase measurements on up to three frequencies have been collected in March 2012 with a small regional network of monitoring stations. The signal and measurement quality are analyzed and compared with the Japanese Quasi Zenith Satellite System. A high level of stability is demonstrated for the inter-frequency carrier phase biases, which will facilitate the application of triple-frequency undifferenced ambiguity resolution techniques in future precise point positioning applications. The performance of the onboard Rubidium frequency standards is evaluated in comparison to ground-based hydrogen masers and shown to be well competitive with other GNSS satellite clocks. Precise orbit and clock solutions obtained in post-processing are used to study the presently achievable point positioning accuracy in COMPASS/BeiDou-2-only navigation. Finally, the benefit of triple-frequency measurements and extra-wide-lane ambiguity resolution is illustrated for relative positioning on a short baseline.

Initial assessment of the COMPASS/BeiDou-2 regional navigation satellite system

On 17 April 2011, all analysis centers (ACs) of the International GNSS Service (IGS) adopted the reference frame realization IGS08 and the corresponding absolute antenna phase center model igs08.atx for their routine analyses. The latter consists of an updated set of receiver and satellite antenna phase center offsets and variations (PCOs and PCVs). An update of the model was necessary due to the difference of about 1 ppb in the terrestrial scale between two consecutive realizations of the International Terrestrial Reference Frame (ITRF2008 vs. ITRF2005), as that parameter is highly correlated with the GNSS satellite antenna PCO components in the radial direction. For the receiver antennas, more individual calibrations could be considered and GLONASS-specific correction values were added. For the satellite antennas, all correction values except for the GPS PCVs were newly estimated considering more data than for the former model. Satellite-specific PCOs for all GPS satellites active since 1994 could be derived from reprocessed solutions of five ACs generated within the scope of the first IGS reprocessing campaign. Two ACs separately derived a full set of corrections for all GLONASS satellites active since 2003. Ignoring scale-related biases, the accuracy of the satellite antenna PCOs is on the level of a few cm. With the new phase center model, orbit discontinuities at day boundaries can be reduced, and the consistency between GPS and GLONASS results is improved. To support the analysis of low Earth orbiter (LEO) data, igs08.atx was extended with LEO-derived PCV estimates for big nadir angles in June 2013.

Absolute IGS antenna phase center model igs08.atx: status and potential improvements

The Global Navigation Satellite System (GNSS) is the worldwide set of satellite navigation constellations, civil aviation augmentations, and user equipment. This paper reviews the current status and future plans of the elements of GNSS as it pertains to civil aviation. The paper addresses the following satellite navigation systems: the U.S. Global Positioning System (GPS), Russian GLONASS, European Galileo, Chinese Compass, Japanese Quasi Zenith Satellite System, and Indian Regional Navigation Satellite System. The paper also describes aviation augmentations including aircraft-based, satellite-based, ground-based, and ground-based regional augmentation systems defined by the International Civil Aviation Organization. Lastly, this paper details typical user equipment configurations and civil aviation applications of GNSS including navigation, automatic dependent surveillance, terrain awareness warning systems, and timing.

Evolution of the Global Navigation SatelliteSystem (GNSS)

This article describes the processing strategy and the validation results of CODE’s MGEX (COM) orbit and satellite clock solution, including the satellite systems GPS, GLONASS, Galileo, BeiDou, and QZSS. The validation with orbit misclosures and SLR residuals shows that the orbits of the new systems Galileo, BeiDou, and QZSS are affected by modelling deficiencies with impact on the orbit scale (e.g., antenna calibration, Earth albedo, and transmitter antenna thrust). Another weakness is the attitude and solar radiation pressure (SRP) modelling of satellites moving in the orbit normal mode—which is not yet correctly considered in the COM solution. Due to these issues, we consider the current state COM solution as preliminary. We, however, use the long-time series of COM products for identifying the challenges and for the assessment of model-improvements. The latter is demonstrated on the example of the solar radiation pressure (SRP) model, which has been replaced by a more generalized model. The SLR validation shows that the new SRP model significantly improves the orbit determination of Galileo and QZSS satellites at times when the satellite’s attitude is maintained by yaw-steering. The impact of this orbit improvement is also visible in the estimated satellite clocks—demonstrating the potential use of the new generation satellite clocks for orbit validation. Finally, we point out further challenges and open issues affecting multi-GNSS data processing that deserves dedicated studies.

/pdf/code-s-five-system-orbit-and-clock-solution-the-challenges-xgzeqm62ib.pdf

CODE’s five-system orbit and clock solution—the challenges of multi-GNSS data analysis

https://elib.dlr.de/97732/1/ASR_151015_GNSS_SatGeomAtt.pdf

GNSS Satellite Geometry and Attitude Models

It is intended to provide position information in a location where it is difficult for radio waves to penetrate. An indoor transmitter is capable of programmably changing a format of a transmitter signal. A process to be performed by a position information providing apparatus comprises the step (S610) of acquiring a received positioning signal, and the step (S612) of identifying an emission source of the positioning signal, wherein, if the emission source of the positioning signal is an outdoor source, the process further comprises the step (S622) of acquiring a navigation message included in the positioning signal, and the step (S624) of performing a processing for calculating a position based on the signal, or, if the emission source of the positioning signal is an indoor source, the process further comprises the step (S632) of acquiring message data from the positioning signal, the step (S634) of acquiring coordinate values from the data, and the step (S650) of displaying position information based on the coordinate values.

Position information providing system, indoor transmitter, and method for providing position information

Design concept of Quasi Zenith Satellite System

Our research goal is developing and deploying indoor and outdoor seamless Location-Based Service (LBS) that covers indoor and outdoor locations. The prime concern for GPS-based positioning systems such as car navigation are that they are not allowed to use ins ide building nor underground, where GPS signals are out of range. To increase flexibility for providing such se rvices, both indoor and outdoor seamlessly, we have developed a novel seamless positioning system with the followin g three steps. First, IMES (Indoor Messaging System), an innovative technology for seamless positioning that uses GPS chipset receiver was applied to realize indoor positioning. Any device that has a GPS chipset in t he receiver can detect IMES signal for positioning. Sec ond, the firmware on GPS chipset was modified in order to smoothly provide seamless location information both indoor and outdoor in accordance with the movement of the user. Third, Network-Assist GPS/IMES was developed to improve time to first fix and vertical positioning accuracy. The system will meet the needs of emergency where quick and accurate personal location information dramatically makes difference. The application may be extended to commercial activity as well for personal store navi gation. A prototype of system has been implemented and a shopping application has been investigated.

/pdf/indoor-and-outdoor-seamless-positioning-using-indoor-3lmw6vgn73.pdf

Indoor and Outdoor Seamless Positioning using Indoor Messaging System and GPS

Satellite-based navigation systems generate huge location
based service markets and it is expected that the market
will drastically increase in near future due to necessity of
GNSS enabled mobile phones for emergency services in
USA, Japan and many other countries. In order to realize
such huge growth, it is necessary to address the problems
of seamless navigation which are limited by the current
GNSS based applications alone. These systems are not
strong enough to provide navigation in indoor and deep
indoor environments with required resolutions. In order to
solve these problems and provide indoor position, we
have developed Indoor Messaging System (IMES).
The basic concept of the IMES is to transmit position data
and/or unique ID and/or other user defined data from the
transmitter while keeping the similar signal structure as of
QZSS/GPS signal. IMES has the same RF properties as
GPS/QZSS and PRN IDs from 173 to 182 are assigned
for IMES. The only difference is in the contents of
navigation message which can be set as per user’s
necessity and application fields. It is not necessary to
compute pseudorange, hence a single unit is enough for
position data.
We have developed prototype IMES device based on
QZSS-IS document. Experiments have been conducted
using software receiver and prototype IMES capable
mobile phone devices. The seamless navigation capability
has been demonstrated by using the IMES capable mobile
phone device. The mobile phone shows the user position
in seamless fashion when the user moves indoors and
outdoors. The interference analysis results showed that
with proper separation of other GNSS devices from IMES
transmitter, there is no harmful interference to the GNSS
user. Based on these experiments, minimum threshold
distance has been estimated, which is about 1.6m from the
IMES antenna at transmission power of -70dBm. This
paper discuss about IMES concept, signal structure,
prototype device, various experiments and their results.

http://gnss.co.jp/wp-content/uploads/2015/03/p63_E63.pdf

Satoshi Kogure

Papers

GNSS Satellite Geometry and Attitude Models

Position information providing system, indoor transmitter, and method for providing position information

Design concept of Quasi Zenith Satellite System

Indoor and Outdoor Seamless Positioning using Indoor Messaging System and GPS

Development of Ultimate Seamless Positioning System Based on QZSS IMES