Current GPS Monitoring Activities in Thailand and Total Electron Content (TEC) Study at Chumphon and Bangkok, Thailand

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1 EIWACS 2010 The 2nd ENRI International Workshop on ATM/CNS November, 2010, Tokyo, Japan Current GPS Monitoring Activities in Thailand and Total Electron Content (TEC) Study at Chumphon and Bangkok, Thailand Sarawoot Rungraengwajiake 1 Assoc.Prof. Dr. Pornchai Supnithi 2 Dr. Takuya Tsugawa 3 (1), (2) Faculty of Engineering, King Mongkut s Institute of Technology Ladkrabang, Thailand (3) Space Environment Group, National Institute of Information and Communications Technology, Japan

2 Acknowledgements I would like to thank the EIWACS 2010 organizers and ENRI for the invitation to attend this exciting workshop. In addition, acknowledgements to KMITL, Thailand CU (Chulalongkorn University), Thailand ENRI, Japan NICT, Japan Kyoto University Meteorology Department, Thailand Aeronautical Radio of Thailand City Planning Dapartment, Thailand Phuket Technical College, Thailand Talang Technical College, Thailand

3 Outline Introduction Current GPS networks in Thailand TEC Basics Data and analysis method Results and discussions Conclusions 3

4 Introduction Total electron content (TEC) is an important ionospheric parameter which directly affects the radio waves propagating through the ionosphere. It is well-known that at the low latitude regions, a characteristic of the ionosphere is symmetric peaks in electron density known as Equatorial Ionospheric Anomaly (EIA)

5 Some interesting locations near the equator

6 Introduction The availability of TEC measurement data are required for the development of ionospheric models such as the International Reference Ionosphere (IRI). (IRI 2007 website - iri_vitmo.php ) Recent increase in availability of TEC data has largely come from a rapid increase in the number of Global Position System TEC data (GPS TEC) over land. At the EIA regions, TEC is enhanced and peaks around from the magnetic equator. For the equatorial region, differential TEC contributes to the plasma bubble study.

7 Introduction Augmentations are necessary for the use of satellitebased navigation in aeronautical applications One of the important sources of positional error is due to the ionospheric effects on the navigational signals. The ionospheric conditions vary depending on locations, time of year, solar activity and others, hence, they need to be well studied. The International Civil Aviation Organization (ICAO) has realized the importance of ionospheric effects on the global navigation satellite system (GNSS).

8 Objectives Overview available GPS networks in Thailand Study the diurnal and seasonal variations of total electron content (TEC) for different seasons at the equatorial magnetic latitude at Chumphon and Bangkok, Thailand during Both locations are near the magnetic equator. Analyze the slant TEC is converted into the delay in terms of distance relevant to aeronautical applications. 8

9 World GPS Networks GPS Earth Observation Network (GEONET) International GPS Service (IGS) Continuously Operating Reference Stations (CORS)

10 SouthEast Asia Low-latitude SouthEast Asia IOnospheric Network (SEALION) 4 STATIONS Station Chiangmai (CMU) Bangkok (KMI) Chumpon (CPN) Phuket (PTC) GPS Receiver Javad TPS Legacy Javad TPS Legacy Javad TPS Legacy Javad TPS Legacy Type of observation C1 P1 P2 L1 L2 D1 D2 C1 P1 P2 L1 L2 D1 D2 C1 P1 P2 L1 L2 D1 D2 C1 P1 P2 L1 L2 D1 D2 Interval (s) RINEX Version

11 Department of Public Works and Town & Country Planning (DPT), Thailand 11 STATIONS

12 Department of Public Works and Town & Country Planning (DPT) Station GPS Receiver Type of observation Interval (s) RINEX Version Chiangmai (CHMA) Leica GRX1200 Pro C1 L1 P2 L Uttaradit (UTTD) Leica GRX1200 Pro C1 L1 P2 L Udonthani (UDON) Leica GRX1200 Pro C1 L1 P2 L Nakhonsawan (NKSW) Leica GRX1200 Pro C1 L1 P2 L Sisaket (SISK) Leica GRX1200 Pro C1 L1 P2 L Nakhonratchasima (NKRM) Leica GRX1200 Pro C1 L1 P2 L Bangkok (DPT9) Leica GRX1200 Pro C1 L1 P2 L Chanthaburi (CHAN) Leica GRX1200 Pro C1 L1 P2 L Prachuapkhirikhan (PJRK) Leica GRX1200 Pro C1 L1 P2 L Suratthani (SRTN) Leica GRX1200 Pro C1 L1 P2 L Songkla (SOKA) Leica GRX1200 Pro C1 L1 P2 L *** Total = 11 stations

13 KMITL& CU Network Nongkai Station Srisamrong Ubonratchathani Pimai Bangkok Phuket In collaboration with Kyoto University 6 STATIONS GPS Receiver Trimble 5700 Trimble 5700 Trimble 5700 Trimble 5700 Type of Interval RINEX Version observation (s) L1 L2 P2 C L1 L2 P2 C L1 L2 P2 C L1 L2 P2 C1 Manual Manual * CU = Chulalongkorn University 1 2.1

14 Stations Phuket Sukhothai Nongkhai Phimai

15 TEC Basics TEC GPS Satellite 1 TECU = 1 x el/m 2 Depending on place & time. Receiver

16 TEC Basics Time dependent 24 December 2007 Location dependent Chumphon station 00h30LT

17 Solar Cycle Monthly averages 11-year cycle Current cycle: 24 Source:

18 Slant TEC Slant TEC can be computed from the pseudorange P1, P2 or the carrier phase L1,L2 (Blewitt, 1990) 2 ff STEC - k f f P P ff STEC - k f f L L Need cycle slip correction for the ambiguity of the cycle number

19 19 Vertical TEC (VTEC) IPP VTEC STEC cos RO O. hro where =arcsin R E R cos E + h where = the zenith angle R E = the mean radian of the Earth = the elevation angle of GPS h = the height of the ionosphere

20 Bias computation I II III Satellite and receiver bias is lumped into one The biases are computed by The MMSE method Satellite bias and receiver bias are determined from MMSE method Satellite bias is determined Receiver bias is determined from minimum variance method These techniques have been developed and verified for a network with many receiver stations

21 21 Receiver bias estimation TEC=(STEC - b - b ) cos χ s r b s - the satellite bias b r - the receiver bias b r = 0.5 ns Minimum Variance Method Select the receiver bias that gives the minimum variance Slant TEC

22 Ionospheric Delay The measured distance (in meters) can be expressed as d d c w 0 ion tropos * t The ionospheric delay d 0 - an actual distance ion - ionospheric errors tropos tropospheric errors t - hardware clock error w - the noise. ion f ATEC (m) For the L1 frequency at GHz, 1 TECU is about 16 cm delay.

23 Data and Methodology Chumphon (10.72 ºN, ºE) Bangkok (13.73 ºN, ºE Seasons 20 March 2009 (March equinox) 21 June 2009 (Summer solstice) 8 October 2009 (Autumnal equinox) 21 December 2009 (Winter solstice),

24 24 Observation Setup Choke-ring antenna Amplifier GPS Receiver Computer Unit Rinex files every 30 seconds

25 TEC Computation RINEX OBS RNX2TEC TEC2GRD Orbit File Slant TEC Include Bias TEC, ROTI plot TEC GRID Data (Vertical TEC) TEC2GRD TEC2BIAS Time Satellite Bias plot Bias (Satellite + Receiver) Receiver Bias TEC MAP T-B2ATEC Orbit Absolute Slant TEC Orbit VTEC

26 Diurnal variation of VTEC at Chumphon station VTEC (TECU) 25 Vernal Equinox 20 Summer Solstice 15 Autumnal Equinox Winter Solstice Time (UTC)

27 VTEC (TECU) Diurnal variation of VTEC at Bangkok station Vernal Equinox Summer Solstice Autumnal Equinox Winter Solstice Time (UTC)

28 STEC (x10 16 electron/m 2 ) STEC (x10 16 electron/m 2 ) STEC (x10 16 electron/m 2 ) STEC (x10 16 electron/m 2 ) Slant TEC of Bangkok station in STEC max STEC max 70 STEC mean 50 STEC mean Time (UTC) (a) Vernal equinox Time (UTC) (b) Summer Solstice STEC max STEC max 70 STEC mean 70 STEC mean Time (UTC) (c) Autumnal equinox Time (UTC) (d) Winter solstice

29 STEC (x10 16 electron/m 2 ) STEC (x10 16 electron/m 2 ) STEC (x10 16 electron/m 2 ) STEC (x10 16 electron/m 2 ) Slant TEC of Chumphon station in STEC max STEC max 70 STEC mean 50 STEC mean Time (UTC) 80 (a) Vernal equinox Time (UTC) 70 (b) Summer Solstice STEC max STEC max 70 STEC mean 60 STEC mean (c) Time (UTC) (c) Autumnal equinox Time (UTC) (d) Winter solstice

30 d ion (m) d ion (m) Ionospheric delay time of Bangkok station in 2009 d ion (m) d ion (m) 14 d ion,max 9 12 d ion,mean 8 d ion,max d ion,mean Time (UTC) 14 (a) Vernal equinox d ion,max Time (UTC) 14 (b) Summer Solstice 12 d ion,mean 12 d ion,max d ion,mean Time (UTC) Time (UTC) (c) Autumnal equinox (d) Winter solstice

31 d ion (m) Ionospheric delay time of Bangkok station in 2009 d ion (m) d ion (m) d ion (m) 14 9 d ion,max 12 d ion,mean 8 d ion,max d ion,mean Time (UTC) Time (UTC) (a) Vernal equinox (b) Summer Solstice 12 d ion,max d ion,mean 10 d ion,max d ion,mean Time (UTC) (c) Autumnal equinox Time (UTC) (d) Winter solstice

32 Future works TEC Gradient investigation around Suvarnabhumi airport Partners: KMITL, ENRI, Aeronautical Thailand Co. Cooperation on the data collection and analysis in the low-latitude and equatorial regions for the upcoming solar maximum period.

33 Non-uniform ionospheric delay distribution Reference station * Working Paper: CNS/MET SG/14 WP/43, July 2010, Jakarta, Indonesia

34 Dual-frequency GPS Data Collection 7 km HIGH SCHOOL KMITL 3-4 km AIRPORT

35 Thank You 35

36 BACKUP

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