• Journal of Positioning, Navigation, and Timing
• /
• v.6 no.1
• /
• pp.35-41
• /
• 2017

Precise Point Positioning (PPP) method is based on dual-frequency data of Global Navigation Satellite Systems (GNSS). The recent multi-constellations GNSS (multi-GNSS) enable us to bring great opportunities for enhanced precise positioning, navigation, and timing. In the paper, the multi-GNSS PPP with a combination of four systems (GPS, GLONASS, Galileo, and BeiDou) is analyzed to evaluate the improvement on positioning accuracy and convergence time. GNSS observations obtained from DAEJ reference station in South Korea are processed with both the multi-GNSS PPP and the GPS-only PPP. The performance of multi-GNSS PPP is not dramatically improved when compared to that of GPS only PPP. Its performance could be affected by the orbit errors of BeiDou geostationary satellites. However, multi-GNSS PPP can significantly improve the convergence speed of GPS-only PPP in terms of position accuracy.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.1
• /
• pp.505-510
• /
• 2006

SVLBI (Space Very Long Baseline Interferometry) has some important potential applications in geodesy and geodynamics, for which one of the most difficult tasks is to precisely determine the orbit of SVLBI satellite. This paper studies several technologies which possibly will be able to determine the orbit of space VLBI satellite. And then, according to the sorts and characteristicsof satellite and the requirements for geodetic study and the geometry of GNSS (GPS, GALILEO) satellite to track the space VLBI satellite, the six Keplerian elements of SVLBI satellite (TEST-SVLBI) are determined. A program is designed to analyze the coverage area of the space of different heights by the stations of the network, with which the tracking network of TEST-SVLBI is designed. The efficiency of tracking TEST-SVLBI by the network is studied, and the results are presented.

• Journal of Astronomy and Space Sciences
• /
• v.26 no.4
• /
• pp.467-478
• /
• 2009

The super-geomagnetic storms called 2003 Halloween event globally occurred during the period of 29 through 31 which are the following days when the solar flares of X18 class exploded on 28 October 2003. The S4 index from GPS signal strength and the peak electron density ($NmF_2$) from GPS tomography method are analyzed according to the date. The occurrences of the cycle slip and scintillation in the GPS signals are 1,094 and 1,387 on 28 and 29 October, respectively and these values are higher than 604 and 897 on 30 and 31 October. These mean the ionospheric disturbances are not always generated by the period of geomagnetic storm. Therefore, GPS S4 index is useful to monitor the ionospheric disturbances. Behaviors of ionospheric electron density estimated from GPS tomography method are analyzed with the date. At UT = 18 hr, the maximum $NmF_2$ is shown on 28 October. It agrees with $NmF_2$ variation measured from Anyang ionosonde, and the GPS signal are better condition on 30 and 31 October than 28 October. In conclusion, GPS signal condition is relation with geomagnetic activities, and depend upon the variation of the electron density. We will study the long-term data to examine the relationship between the GPS signal quality and the electron density as the further works.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.38 no.5
• /
• pp.455-465
• /
• 2020

As cities continue to expand and additional underground structures are constructed, a policy is being planned to expand addresses, which are national framework data. In this study, the application scope of a proposed 3D (three-dimensional) mixed-use complex space for assigning 3D addresses was defined, based on past research on 3D address systems and by analyzing related laws. Underpass shopping malls, underground walkways (excluding underground shopping malls), and 3D mixed-use transfer centers with a gross floor area of 2,000㎡ or more are connected with each space by underground walkways or public paths. In addition, the detailed space corresponding to the public space of the 3D mixed-use complex space was presented and distinguished from the space to which the detailed address is assigned. The criteria for setting the road section were presented based on the intermediate space, which is a characteristic of 3D mixed-use complex spaces. The proposed criteria were applied to the Express Bus Terminal station (3D mixed-use transfer center) and COEX mall (underpass shopping malls). Thus, the road section was set for an unfamiliar 3D mixed-use complex space. However, by applying the proposed criteria to various 3D mixed-use complex spaces, additional and detailed criteria for different cases should be prepared.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.1
• /
• pp.501-503
• /
• 2006

We have processed the GPS data using several high quality GPS data processing softwares for last decade. Bernes and GIPSY II are some of them. Though these programs have different characteristics in terms of structures and processing philosophies, high quality results from these are still comparable. KASI Space Geodesy Research Division has developed several GNSS data processing softwares like the quasi real-time ionospheric parameter estimator, orbit propagator and estimator, and precision positioning estimator. However, we are currently in needs of our own comprehensive GNSS data processing software with the European Galileo system on the horizon. KASI team has worked on a preliminary pilot project for the software and is making block pieces for the software. The roadmap, the description, and brief results of KASIOPEA (KASI Orbit Propagator and EstimAtor) are presented in this paper.

• Bulletin of the Korean Space Science Society
• /
• 2008.10a
• /
• pp.31.3-31.3
• /
• 2008

Satellite laser ranging (SLR) system which measures the round trip time of laser to satellites is one of the important techniques in space geodesy. SLR system gives a powerful tool to determine the precise orbit of satellites, the center of mass of the Earth, and etc because it provides instantaneous range measurements of millimeter level precision. China Transportable Ranging Observation System (TROS) was built in 1999 and other four SLR stations were founded in China. TROS has been upgraded to the new electronic system capable of KHz ranging since last year, and succeeded in KHz SLR technology. TROS has been operated in KASI headquarter for research of space geodesy since August 2008, which will be operated for 12 months by August 2009. Now ISCEA and KASI keep strong relationship in SLR field.

• Journal of the Korean earth science society
• /
• v.30 no.3
• /
• pp.381-397
• /
• 2009

The Modem Geodesy monitors physical and geometrical shape and motion of the Earth and, more importantly, its temporal variations with unprecedented precision. It provides accurate and stable reference frames for Earth observations in the Space era. Furthermore, with an aid of interdisciplinary approaches, it also traces the causes of the variations in shape and motion of the Earth and eventually contributes to a better understanding of the Earth system. The International Association of Geodesy (IAG) has established the Global Geodetic Observing System (GGOS) to integrate the multitude of geodetic tools and tried to contribute to the management of global environmental changes as a partner of the Global Earth Observation System of Systems (GEOSS). Here we introduce the contribution of geodesy to the various fields of Earth Science by focusing on GGOS and encourage interdisciplinary researches.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2007.04a
• /
• pp.301-306
• /
• 2007

Because the cost of road management is increasing proportional to road construction, there are needs to build general and systematic road management system. To solving such problems, Ministry of Construction and Transportation started research and development of Highway Management System(HMS), and established a foundation for systematic road management system. But, the implementation of HMS has some limitations because it is just converting roads of physical space to roads of electronic space and managing roads of electronic space. Although HMS offers many conveniences compared to old system which was based hard-copy and paper maps or unit operations, it can not overcome the problem of inefficency of road management due to the separation of operation between outer field and inner office. Therefore, to overcome such inefficency, this study focused on Road Disaster Management System development based on Ubiquotous.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
• /
• v.23 no.1
• /
• pp.12-17
• /
• 1995

Space explorations by spacecraft have detected the solar wind and the interplanetary magnetic field (IMF), whose existences had been suggested to explain the narrow comet plasma tail formation before the space age. Thereafter, a global magnetic structure seperating the opposite polarity regions of IMF in the heliosphere was discovered (Wilcox and Ness, 1965). It is called helispheric current sheet (HCS). Comets have been proved as the useful heliospheric probes. Recently, another capability of comet as a probe of HCS was suggested by Yi (1994). In the process of comet plasma tail disconnection events (EDs) showing the ray folding and main tail severance between the folding rays (Brandt, 1982), the folding rays preceding DE might be the visualization of HCS draped around comet, In order to test this new idea, the association of comet Halley 16 DEs with comet crossings of HCS confirmed by spacecraft observations at the time of comet Halley apparition 1985~1986 was investigated.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.5 no.2
• /
• pp.47-55
• /
• 1987

In this paper, the direct linear transformation is described in which a inner and exterior orientation parameters are treated as unknown for non-iterative direct space resection, and the computer program was developed to obtain object space coordinates. Image coordinates measurements are conducted with analogue stereo-plotter and digitizer. To prove the appropriateness of the two image coordinate measurement devices and the DLT method, the standard errors of object space coordinates are compared with semi-analytical method.