Wyniki wyszukiwania - BazTech

1

Validation of the accuracy of geodetic automated measurement system based on GNSS platform for continuous monitoring of surface movements in post-mining areas

Sokoła-Szewioła Violetta, Siejka Zbigniew

Reports on Geodesy and Geoinformatics

|

2021

|

Vol. 112

47--57

EN

The problem involving the monitoring of surface ground movements in post-mining areas is particularly important during the period of mine closures. During or after flooding of a mine, mechanical properties of the rock mass may be impaired, and this may trigger subsidence, surface landslides, uplift, sinkholes or seismic activity. It is, therefore, important to examine and select updating methods and plans for long-term monitoring of post-mining areas to mitigate seismic hazards or surface deformation during and after mine closure. The research assumed the implementation of continuous monitoring of surface movements using the Global Navigation Satellite System (GNSS) in the area of a closed hard coal mine ‘Kazimierz-Juliusz’, located in Poland. In order to ensure displacement measurement results with the accuracy of several millimetres, the accuracy of multi-GNSS observations carried out in real time as a combination of four global navigation systems, Global Positioning System (GPS), Globalnaja Navigacionnaja Sputnikova Sistema (GLONASS), Galileo and BeiDou, was determined. The article presents the results of empirical research conducted at four reference points. The test observations were made in variants comprising measurements based on: GPS, GPS and GLONASS systems, GPS, GLONASS and Galileo systems, GPS, GLONASS, Galileo and BeiDou systems. For each adopted solution, daily measurement sessions were performed using the RTK technique. The test results were subjected to accuracy analyses. Based on the obtained results, it was found that GNSS measurements should be carried out with the use of three navigation systems (GPS, GLONASS, Galileo), as an optimal solution for the needs of continuous geodetic monitoring in the area of the study.

2

Behavior of broadcast ionospheric-delay models from GPS, BeiDou, and Galileo systems

Farah Ashraf

Artificial Satellites : Journal of Planetary Geodesy

|

2020

|

Vol. 55, No. 2

61--76

EN

The GNSS observations suffer from different types of errors that could affect the achieved positioning accuracy based on the receiver type used. Single-frequency receivers are widely used worldwide because of its low cost. The ionospheric delay considers the most challenging error for single-frequency GNSS observations. All satellite navigation systems, except GLONASS, are advising their users to correct for the ionospheric delay using a certain model. Those models' coefficients are sent to users in the system's navigation message. These models are different in their accuracy and behavior based on its foundation theory as well as the updating rate of their coefficients. The GPS uses Klobuchar model for mitigating the ionospheric delay. BeiDou system (BDS-2) adopts a slightly modified Klobuchar model that resembles GPS ICA (Ionospheric Correction Algorithm) with eight correction parameters but is formulated in a geographic coordinate system with different coefficients in origin and updating rate. Galileo system uses a different model (NeQuick model). This article investigates the behavior of the three models in correcting the ionospheric delay for three stations at different latitudes during 3 months of different states of ionospheric activity, comparing with International GNSS Service-Global Ionospheric Maps (IGS-GIMs). It is advised from this research's outputs to use the GPS model for mitigating the ionospheric delay in low-latitude regions during the state of low-and medium-activity ionosphere. It is advised to use the BeiDou model for mitigating the ionospheric delay in mid-latitude regions during different states of ionospheric activity. It is advised to use the Galileo model for mitigating the ionospheric delay in high-latitude regions during different states of ionospheric activity. Also, the Galileo model is recommended for mitigating the ionospheric delay for low-latitude regions during the state of high-activity ionosphere.

3

Single-frequency ionospheric-delay correction from BeiDou & GPS systems for northern hemisphere

Farah Ashraf

Artificial Satellites : Journal of Planetary Geodesy

|

2019

|

Vol. 54, No. 1

1--15

EN

The range delay caused by the ionosphere layer is the major current source of error for GNSS users with single-frequency receivers. GNSS advice users to correct this type of error using ionospheric models whose coefficients are sent in their navigation messages. GPS-users use the Klobuchar model to correct this type of error. GPS navigation message contains the model’s eight coefficients which vary on the basis of seasonal ionospheric variations and average solar flux. The correction accuracy of Klobuchar model is about 50% (rms) of the ionospheric range delay. Beidou system calculates and broadcast 8 parameters of Klobuchar model based on continuous monitoring stations. BeiDou system updates the ionospheric coefficients every two hours. GPS-Klobuchar model uses completely different coefficients than BeiDou-Klobuchar model. This research demonstrates a comparison study between the Klobuchar model using the GPS broadcast coefficients and the same model using BeiDou-coefficients. The correction accuracy offered by the two models has been judged using the most accurate International GNSS Service-Global Ionospheric Maps (IGS-GIMs) for three different-latitude stations along northern hemisphere, one station in low-latitude region, the second station is in mid-latitude region and the third station is in high-latiude region to reflect models’ behaviour in different geographic regions. The study was applied over three different months of the year 2017 that each of them reflects a different activity state for the ionosphere layer. The study proves that BeiDou model is able to show the ionosphere’s day-to-day fluctuations while GPS model can’t. It can be concluded that GPS model offers better behaviour than BeiDou model in correcting range delay in low-latitude and high-latitude geographic regions under any activity state for the ionosphere. BeiDou model offers better correction accuracy than GPS model in mid-latitude under any activity state for the ionosphere.

4

Relevance of the relativistic effects in satellite navigation

Kulbiej E.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

|

2016

|

nr 47 (119)

85--90

EN

Position determination of Global Navigation Satellite Systems (GNSS) depends on the stability and accuracy of the measured time. However, since satellite vehicles (SVs) travel at velocities significantly larger than the receivers and, more importantly, the electromagnetic impulses propagate through changing gravitational potentials, enormous errors stemming from relativity-based clock offsets would cause a position error of about 11 km to be accumulated after one day. Based on the premise of the constancy of light, two major relativistic effects are described: time dilation and gravitational-frequency shift. Following the individual interests of the author, formulas of both are scrupulously derived from general- and special-relativity theory principles; moreover, in the penultimate section, the equations are used to calculate the author’s own numerical values of the studied parameters for various GNSSs and one Land Navigation Satellite System (LNSS).

5

BeiDou and Galileo, Two Global Satellite Navigation Systems in Final Phase of the Construction, Visibility and Geometry

Januszewski J.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

|

2016

|

Vol. 10, no. 3

381--387

EN

Spatial segment is one of three segments of each satellite navigation systems (SNS). Nowadays two SNSs, GPS and GLONASS, are fully operational, two next SNSs, BeiDou in China and Galileo in Europe, are in final phase of the construction. In the case of China system this segment will consist of 35 satellites with three types of orbits ? medium (MEO), geostationary (GEO) and inclined geosynchronous (IGSO). As GEO and IGSO satellites can be used in China and Asia-Pacific region only, BeiDou MEO constellation with 27 fully operational satellites will be taken into account in this paper. The orbital planes of the Galileo constellation will be divided in “slots” that contains at least one operational satellite. The Galileo reference constellation has 24 nominal orbital positions or operational slots in MEO homogeneously distributed in 3 orbital planes; i.e. 8 slots equally spaced per plane. As the error of user’s position obtained from both systems depends on geometry factor DOP (Dilution Of Precision) among other things the knowledge of the number of satellites visible by the user above given masking elevation angle Hmin and the distributions of DOP coefficient values, GDOP in particular, is very important. The lowest and the greatest number of satellites visible in open area by the observer at different latitudes for different Hmin, the percentage of satellites visible above angle H, distributions (in per cent) of satellites azimuths and GDOP coefficient values for different Hmin for BeiDou and Galileo systems at different latitudes are presented in the paper.

6

Multi-GNSS as a combination of GPS, GLONASS and BeiDou measurements carried out in real time

Siejka Z.

Artificial Satellites : Journal of Planetary Geodesy

|

2015

|

Vol. 50, No. 4

217--229

EN

In this paper the advantages of using combination of different GNSS including GPS, GLONASS and BeiDou with respect to singe GPS are presented. It was shown that an improvement of satellite conditions at the chosen measurement point due to increase of the number of visible satellites has an impact on RTK measurement errors. Additionally, it was shown that there are systematic errors in RTK measurements that can be eliminated to get more precise results of them, especially in the case of height determination.