GPS-TEC and S4 variations of equatorial latitude stations in Thailand and their relationship with GPS positioning error | |
| Author | Kasidit Taechasan |
| Call Number | AIT Thesis no.RS-15-07 |
| Subject(s) | Global Positioning System Ionosphere |
| Note | A thesis submitted in partial fulfillment of the requirement s for the degree of Master of Science in Remote Sensing and Geographic Information Systems |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. RS-15-07 |
| Abstract | Nowadays, high precision positioning through Global Navigation Satellite System (GNSS) , has become a vital tool in various field s such as mapping, navigation and surveying. Ionosphere is key factor that plays as an impediment in achieving high positioning accuracies in GNSS system. This research study aims to understand the phenomenon of ionospheric scintillation s and Total Electron Content (TEC), through GPS signals and to determine the relation ship between the se two phenomena and GPS positioning error. This research study h as been classified into three objective s , the first objective was to determine TEC (total electron content) and S 4 (Scintillation index) at Bangkok and Phuket GPS - SCINDA stations by using raw GPS data and analyzing daily , monthly and annual variations of TEC and S 4 . From the observe d diurnal, monthly and annual variation in GPS - TEC , we found that, TEC value is highest during 50 0 0 UT - 1000 UT whereas S 4 value is found to be high during 13 00 UT - 17 00 UT . In addition to this , TEC value s were observed to be higher, particularly, in two times of the year, March to May and October to December, S 4 value s also, exhibited the similar trend . T he se months with higher TEC and S 4 value s coincided with months of equinox and whereas with less TEC and S 4 values during solstice months. The second objective was to compare TEC and S 4 data from Bangkok and Phuket station s and to find the correlation between them. Post - processing of GPS raw data has been performed by GPS Application Software and further, Matlab scripting has been used to analyze and correlate data between the stations. It has been observed that GPS - TEC values at Bangkok are higher than at Phuket station in every month. Also, S 4 value at Phuket is usually higher than Bangkok, but in April and September, Bangkok is higher than Phuket. Maximum difference between the two stations found to be ~ 20 TECU. In May 2014, the highest values of TEC exhibited by Bangkok and Phuket stations were 82 TECU and 63 TECU respectively. Minimum difference between the two stations found to be ~ 1 TECU. In April 2014 , the highest values of TEC exhibited by Bangkok and Phuket stations were 86 TECU and 85 TECU respectively . While, Maximum difference S 4 value between the two stations found to be ~ 0.09. In April 2014, the highest values of S 4 exhibited by Bangkok and Phuket stations were 0.392 and 0.306 respectively. In conclusion, TEC values at Bangkok were higher than that of Phuket, but S 4 value at Phuket is higher than Bangkok, especially during equinox time, April and September months. The last objective was to determine the correlation between GPS positioning error and GPS - TEC & S 4 values . N avigation files and observation files were used to analyze GPS positioning error; it was found that , there is a positive correlation be tween TEC value and GPS error, the R 2 value is about 0.7 . When GPS - TEC value s were increasing , the GPS Positioning error also observed to be increasing . In contrast, S 4 value s has shown negative correlation coeffienct of - 0.3, thus, there is very low correlation between S 4 and GPS positioning error. In conclusion, TEC value has greater impact on GPS postioning error than S 4 value. |
| Year | 2015 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. RS-15-07 |
| Type | Thesis |
| School | School of Engineering and Technology |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Remote Sensing (RS) |
| Chairperson(s) | Tripathi, Nitin Kumar;Shinichi Nakamura |
| Examination Committee(s) | Taravudch Tipdecho;Sarawut Ninsawat |
| Scholarship Donor(s) | Greater Mekong Subregion (GMS) |
| Degree | Thesis (M. Sc.) - Asian Institute of Technology, 2015 |