EIWACS 2010 – The 2nd ENRI International Workshop on ATM/CNS
10-12 November, 2010, Tokyo, Japan

Current GPS Monitoring Activities inThailand and Total Electron Content (TEC)
Study at Chumphon and Bangkok, Thailand
Sarawoot Rungraengwajiake1
Assoc.Prof. Dr. Pornchai Supnithi2
Dr. Takuya Tsugawa3(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

Acknowledgements• I would like to thank the EIWACS 2010 organizers andENRI 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

Outline

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

3

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

Some interesting locations near the equator

Introduction• The availability of TEC measurement data are required
for the development of ionospheric models such as theInternational Reference Ionosphere (IRI).
– (IRI 2007 website - http://ccmc.gsfc.nasa.gov/modelweb/models/
iri_vitmo.php )• Recent increase in availability of TEC data has largely
come from a rapid increase in the number of GlobalPosition System TEC data (GPS TEC) over land.
• At the EIA regions, TEC is enhanced and peaks aroundfrom the magnetic equator. For the equatorial region,differential TEC contributes to the plasma bubble study.

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

Objectives• Overview available GPS networks in Thailand• Study the diurnal and seasonal variations of total
electron content (TEC) for different seasons at theequatorial magnetic latitude at Chumphon and Bangkok,
Thailand during 2009.
• Both locations are near the magnetic equator.
• Analyze the slant TEC is converted into the delay interms of distance relevant to aeronautical applications.
8World GPS Networks

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

SouthEast Asia Low-latitude
SouthEast Asia IOnospheric Network (SEALION)
4 STATIONSStationGPS
Type of Interval RINEX
Receiver observation (s) Version

Chiangmai(CMU)
Bangkok(KMI)
Chumpon(CPN)
Phuket(PTC)

Javad TPS
LegacyJavad TPS
LegacyJavad TPS
LegacyJavad TPS
LegacyC1 P1 P2 L1L2 D1 D2C1 P1 P2 L1
L2 D1 D2C1 P1 P2 L1L2 D1 D2C1 P1 P2 L1L2 D1 D230

2.130

2.130

2.130

2.1

Department of Public Worksand Town & Country Planning (DPT), Thailand
11 STATIONSDepartment of Public Worksand Town & Country Planning (DPT)
StationGPS ReceiverType of observation

Interval (s)RINEX Version

Chiangmai (CHMA)

Leica GRX1200 Pro

C1 L1 P2 L25

2.11

Uttaradit (UTTD)

Leica GRX1200 Pro

C1 L1 P2 L25

2.11

Udonthani (UDON)

Leica GRX1200 Pro

C1 L1 P2 L252.11

Nakhonsawan (NKSW)

Leica GRX1200 Pro

C1 L1 P2 L25

2.11

Sisaket (SISK)

Leica GRX1200 Pro

C1 L1 P2 L252.11

Nakhonratchasima (NKRM)

Leica GRX1200 Pro

C1 L1 P2 L25

2.11

Bangkok (DPT9)

Leica GRX1200 Pro

C1 L1 P2 L252.11

Chanthaburi (CHAN)

Leica GRX1200 Pro

C1 L1 P2 L252.11

Prachuapkhirikhan (PJRK)

Leica GRX1200 Pro

C1 L1 P2 L25

2.11

Suratthani (SRTN)

Leica GRX1200 Pro

C1 L1 P2 L252.11

Songkla (SOKA)

Leica GRX1200 Pro

C1 L1 P2 L252.11*** Total = 11 stations

KMITL& CU Network
In collaboration with Kyoto University

6 STATIONSGPSType of Interval
RINEX Version
Receiver observation (s)NongkaiTrimble
L1 L2 P2 C112.15700
Srisamrong
TrimbleL1 L2 P2 C1
1
2.15700
Ubonratchathani Trimble
L1 L2 P2 C1
12.15700
PimaiTrimble
L1 L2 P2 C1
12.15700
Bangkok
ManualPhuket
ManualStation* CU = Chulalongkorn University

StationsPhuket

SukhothaiNongkhaiPhimaiTEC Basics

TEC

GPSSatellite

1 TECU = 1 x 1016 el/m2

Depending on place & time.

ReceiverTEC Basics
Time dependent
24 December 2007

Location dependent

Chumphon station
00h30LTSolar Cycle
Monthly
averages
11-year cycle

Current cycle: 24

Source: http://solarscience.mfc.nasa.gov/SunspotCycle.shtml

Slant TECSlant TEC can be computed from the pseudorange P1, P2or the carrier phase L1,L2 (Blewitt, 1990)
STEC 2  f1 f 2 kSTEC 222
f1 - f 2

2  f1 f 2 k P2 - P1 222
f1 - f 2

 L11 - L22 

Needcycle slip correction
for the ambiguity ofthe cycle number

Vertical TEC (VTEC)IPPVTEC STEC  cosROO.

hRO RE cos  where  =arcsin R+h E
where  = the zenith angle
RE = the mean radian of the Earth = the elevation angle of GPS
h = the height of the ionosphere19

Bias computation
I
Satellite andreceiver bias
is lumped intoone
The biases arecomputed byThe MMSE
methodII

Satellite bias andreceiver bias
are determinedfrom MMSE
methodIII
Satellite bias isdetermined

Receiver bias
is determinedfrom minimum
variance method

These techniques have been developed and verified for a network with manyreceiver stations

Receiver bias estimation
TEC=(STEC - bs - br ) × cos χbs - the satellite bias
br - the receiver bias

br = 0.5 ns

Minimum Variance Method
Select the receiver bias that gives
the minimum variance Slant TEC

21

Ionospheric Delay
The measured distance (in meters) can be expressed asd  d0  ion  tropos  c *t  w

d0 - an actual distanceion - ionospheric errors
tropos – tropospheric errors
t - hardware clock error
w - the noise.

The ionospheric delay ion 40.3
ATEC (m)2f

For the L1 frequency at 1.57542 GHz, 1 TECU is about 16 cm delay.

Data and Methodology
Chumphon (10.72 ºN, 99.37 ºE)
Bangkok (13.73 ºN, 100.78 ºESeasons• 20 March 2009 (March equinox)• 21 June 2009 (Summer solstice)• 8 October 2009 (Autumnal equinox)• 21 December 2009 (Winter solstice),

Observation Setup
Choke-ring
antenna

AmplifierGPS
ReceiverComputer
Unit

Rinex files
every 30 seconds

24

TEC Computation
RINEX OBSRNX2TECTEC2GRDGRID Data(Vertical TEC)

Orbit
File
TEC2GRD

Slant TEC
Include Bias

TEC , ROTI plot
TEC

TEC2BIAS

Time

Satellite
Bias

Bias
(Satellite + Receiver)plot

TEC MAP

ReceiverBias

T-B2ATEC

Absolute
Slant TEC

Orbit
Orbit

VTECDiurnal variation of VTEC at Chumphon
station25
Vernal Equinox
20

Summer Solstice

VTEC (TECU)

Autumnal Equinox
Winter Solstice15

10500.5

4.5

8.5

12.5
Time (UTC)

16.5

20.5

23.5

Diurnal variation of VTEC at Bangkok
station25

Vernal Equinox
Summer Solstice
Autumnal Equinox
Winter Solstice

VTEC (TECU)

20

15

105

00.5

4.5

8.5

12.5
Time (UTC)

16.5

20.5

23.5

Slant TEC of Bangkok station in 2009
60

80
STECmax

STECmax

STECmean70

STECmean

50

STEC (x1016 electron/m2 )STEC (x1016 electron/m 2 )60

5040304030202010100004812Time (UTC)

162024048(a) Vernal equinox

12Time (UTC)

1620(b) Summer Solstice

80

80
STECmax

70

STECmax

STECmean70

STECmean

60

STEC (x1016 electron/m2 )STEC (x1016 electron/m2 )

60
50
4030
2050
4030
20100

24

1004812Time (UTC)

1620(c) Autumnal equinox

24004812Time (UTC)

1620(d) Winter solstice24

Slant TEC of Chumphon station in 2009
80

60
STECmax

70

STECmax

STECmean

STECmean

50

STEC (x1016 electron/m2 )STEC (x1016 electron/m2 )60504030

4030

2020

1010004812Time (UTC)

162002404(a) Vernal equinox

812Time (UTC)

162024(b) Summer Solstice

8070
STECmax

70

STECmax

STECmean

STECmean

60

STEC (x1016 electron/m2 )STEC (x1016 electron/m2 )

60
50
4030
2050

40

3020(c)
1010004812Time (UTC)

1620(c) Autumnal equinox

24004812Time (UTC)

1620(d) Winter solstice24

Ionospheric delay time of Bangkok
station in 200914

dion,max9dion,max

dion,mean

128dion,mean

768dion (m)dion (m)1064543221004812Time (UTC)

162024004(a) Vernal equinox

812Time (UTC)

162024(b) Summer Solstice14

dion,maxdion,max

10

10886

dion,mean

12dion (m)dion (m)14

dion,mean

1264

4220004812Time (UTC)

1620(c) Autumnal equinox

04

812Time (UTC)

162024(d) Winter solstice24

Ionospheric delay time of Bangkok
station in 200914

9
dion,maxdion,maxdion,mean128

dion,mean

710dion (m)dion (m)6865434221004812Time (UTC)

1620024048(a) Vernal equinox

12Time (UTC)

162024(b) Summer Solstice12dion,max

12dion,maxdion,mean

10dion,mean

108dion (m)dion (m)8664422004812Time (UTC)

1620(c) Autumnal equinox

24004812Time (UTC)

1620(d) Winter solstice24

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 theupcoming solar maximum period.

Non-uniform ionospheric delay
distribution

Referencestation* Working Paper: CNS/MET SG/14 WP/43, 19-22 July 2010, Jakarta, Indonesia

Dual-frequency GPS Data Collection
7 km

HIGH SCHOOL

KMITL

3-4 kmAIRPORTThank You35BACKUP