• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.1021-1023
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• 2003

Atmospheric water vapor is a key variable in numerical weather prediction (NWP) models, but it is a crucial factor to limit the accuracy of high-precision GPS positioning technique. For both issues, knowledge about the amount of water vapor is extremely important. In this study, we perform a simulation study to utilize GPS signals through a developed tomographic scheme to retrieve 3D structure of atmospheric wet refractivity, which may be assimilated into NWP models for advancing forecasting or position calculation for improving GPS positioning accuracy. For the purpose of knowing the absolute accuracy of the developed tomographic method, a well-defined temporal and spatial varying state of atmospheric profile is utilized. Under such circumstance, several factors that may influence the retrievals can be easily examined and their impacts may be clearly quantified. They include the values of the positional dilution of precision (PDOP) factors of the GPS signals, ... etc. Based upon the use of a variety spectrum of adjustable factors, many interesting findings are obtained. For example, the more is the number of the observed GPS signals the better becomes the retrievals as expected. Also, the smaller is the PDOP value the better becomes the retrievals.

• 대기
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• 제19권3호
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• pp.289-296
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• 2009

Measurements of the three-dimensional water vapor distribution in the atmosphere are important for forecast and analysis of meteorological phenomenon. In this study, two Global Positioning System (GPS) campaign networks were installed in Jeju Island and Kangwon-do to construct the vertical water vapor profile solely based on GPS measurements. We implemented a layer model to get the wet refractivity profile and compared the result with radiosonde measurements. The result showed that the vertical profiles from GPS and radiosonde agree well. The bias, root-mean-square error (RMSE) and standard deviation of GPS wet refractivities compared with radiosonde measurements were in the range of 6.6~11.1 mm $km^{-1}$, 11.9~13.9 mm $km^{-1}$, and 4.3~12.3 mm $km^{-1}$, respectively.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2078-2081
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• 2003

This paper presents the studies on prediction models of tropospheric scintillation. The prediction scintillation models are Karasawa and ITU-R , which can be improved for different locations and circumstances. In this paper, the investigation of average time between variance ${\sigma}_n\;^2$ and the wet part of refractivity $N_{wet}$ under various conditions of meteorological parameters have been carried out at King Mongkut’s Institute of Technology Lankrabang , Bangkok , Thailand , in the range of Ku-band (12.260 GHz) on high elevation angle from Thaicom2 satellite. From the studies results shows that average period of time of 30 days are best suitable for find out the relation between average time variance ${\sigma}_n\;^2$ and the wet part of refractivity $N_{wet}$ according to Karasawa model, the average time variance is express as ${\sigma}_n\;^2=(0.003N_{wet}-0.1313)^2$ , the appropriation model for occurrence of scintillation has been analyzed and experimental results are carried out.