GIA QUAN HE

30(2), 161-169 Tap chl C A C KHOA HOC VJ T R A I BAT 6-2008

DANH GIA QUAN HE ^{G I C A} HAM Ll/dNG HOl Nl/dC KHI QUYEN VA D O CHINH XAC DINH VI TUYET DOI

BANG GPS 6 VIET NAM

LE HUY MINH, PHAM XUAN T H A N H , NGUYEN CHIEN THANG, TRAN THI LAN, R. FLEURY, P. LASSUDRIE DUCHESNE, A. BOURDILLON, C. AMORY-MAZAUDIER,

TRANNGQCNAM, HOANGTHAILAN I. MCi D A U

Tin hieu tmydn tit ckc vt tinh ciia he thdng dinh vj toan cdu (GPS) tdi mdt may thu tren mat ddt bj anh hudng dang kd bdi tdng dien ly va tdng kbi quydn. Mdi trudng dien ly (mdi trudng tan xa) tao nen sy trd khae nhau ddi vdi hai tdn sd f i va fj phu thuOc vao mat dd dien tii trong tdng dien ly. Vdi cdng nghe GPS hai tdn sd, viee sii dung eae sy trd nay ed thd tinh toan ndng do dien tii tdng cdng tdng dien ly, vi vay anh hudng cila tdng dien ly cd thd duge loai trir trong img dung GPS vdi mue dich djnh vj. Tdng ddi luu anh hudng tdi su tmydn tin bieu GPS phire tap ban, dd xu' ly anh hudng ndy, hien nay thudng dting eae phdn mdm ehuyen dung trong xii ly sd lieu GPS nhu phdn mdm Gamit [ 1,2,4], phdn mdm Beme.se, phdn mdm Gipsy- Oasis... Trong khudn khd hgp tac giiia Vien Vat ly Dia edu va Trudng Dai hgc Rennes 1, Trudng Vidn thdng Qude gia Bretagne (Cdng hda Phdp) ba Uam thu tin hieu ve tinh GPS lien tue duge dat tai Ha Ndi, Hud vd tbanb phd Hd Chi Minh ttr ddu nam 2005 va 2006. Viee sir dung sd lieu eiia cac Uam thu GPS lien tuc nay trong nghien eim ndng dO dien tu tdng cdng tdng dien ly da duge gidi thieu trong [9,10]. Bdi bao nay trinh bdy kdt qua danh gia mire dg anh hudng eua tdng khi quydn tdi dg ehinb xae eila sy dinh vi tuyet ddi bang ba may thu GPS da neu. Tren co sd so sanh eae phdn du ciia tga dd xac dinh bdng cac may thu GPS va ham lugng hoi nudc tdng cdng tinh duge ttr md hinh tai phan tieh sd lieu khi quydn d pham vi toan edu eho ba vi tri dat tram GPS ed thd thdy anh hudng quan trgng ciia tdng kbi quydn tdi viee djnh vj bang cdng nghe GPS d Viet Nam.

II. SO LIEU vA PHUONG P H A P P H A N TICH Sd lieu dting trong bai bao nay la sd lieu GPS lien tuc ciia ba tram thu GPS d nudc ta [9-11]. Ddy

la cac may thu GPS loai GSV4004 cila bang NovAtel.

Cac tham sd quan sat duge cua cae may thu GPS loai ndy la :C1,L1, Dl, SI, P2, L2, D2 vaS2.Trong dd Cl va P2 la cae gia khoang each ma C/A va ma Y, Ll va L2 la phep do pha, Dl va D2 la cac tdn sd Doppler, SI va S2 la eudng dd tin hieu d cac tdn sd GPS f ] vd f2 tuong img. Di kem vdi cac may thu nay ed phdn mdm cho phep xae djnh tga dd va dd cao cua vi tri quan sat tai timg thdi didm quan sat kidu xae djnh tga dd tuyet ddi bdng mdt may thu GPS.

Nhu trong [9] ehung ta thdy sd cac ve tinh it nha't ma 3 may thu GPS ciia chiing tOi quan sat duge thudng la 6, thdng thudng la 9 de'n 11 ve tinh, do dd ndi chung tai mgi thdi didm quan sat ddu cd thd xac dinh duge tga dd tuyet ddi cila cae tram. Tuy nhien ehung ta se thdy trong bdi bao, viec xac djnh tga dd tuyet ddi bang eae may thu GPS GSV4004 cd dd chinh xae tdi eo met. Ngdy nay ngudi ta cd thd tidn hanh cae phep do trdc dja bang cdng nghe GPS vdi dd ehinh xae ed milimet, dd la phuang phap GPS vi phdn duge iing dung vdi muc dich do dae djch chuydn eiia vd Trai Da't [6].

Sir dung chuong trinh convert4 [II] trong phdn mdm 0EM4 PC di kem vdi cac may thu GSV4004 cd thd thu duge chudi sd lieu tga dd vd dd cao eiia vi tri dat eae anten thu (ndc nha Vien Vat ly Dja cdu, ndc Trudng Dai hgc khoa bgc Hud va ndc Dai quan sat dien ly Hdc Mdn) timg thdi die'm quan sat (tung phiit hoae tiing 30 giay ; dd'i vdi tram Ha Ndi cd sd lieu timg gidy, chiing tdi tinh sd lieu tga dd va dO cao eung cho timg phut mdt). Giao dien sii dung chuong trinh convert4 trinh bay tren hinh 1. Trong

"Selected" ed thd diing "Edit" lya chgn "BESTPOSA"

dd la'y ra tga dd va dd eao vi tri quan sat; tuong ty trong "Time" ed thd dung "Edit" dd lya chgn bude thdi gian la'y sd lieu. Sau khi thu duge chudi sd lieu

j£iNoyAtel 0EM4 Convert

EfejH

S o u i c e F i l e : | b : \ g p » _ d a i a \ h o c m o n \ 1 4 5 1 \ 1 4 5 1 _ 0 _ 0 0 _ H 0 C I flpen... | Deslinalion File: ' D : \ g p « _ < ) a l a \ h o c m o n V l 4 5 1 \ 1 4 5 1 _ t r ( ) ( ) _ H b c i S,ave A t . . . I

Noi04tel

l^~ Selected f Time

\EMZ ^{A S C I I}

Binary Rinex

£onver( File

RangeB Log Compiesiion RangeCmpB Log Expaniion

M\ !

SWT^WH^^ffl

AfTUUIIDHSrMUM (EiianraM

•(ITBnvtUt

•MtVOA tiiTxru o i x u i f r K H ' CUBMtWCIU

• U O A T M N U OtRIUlIAMM OMDCSU

^ ^

aMCDNnu ftMLH SKMLOM SKSMK cnsA epsti

i r g ^ i t^ J

«—,

ArrUCAKOHSKTUH

K i r v i u Kincva aocuioaiia aoaorrtEii OinDAIADtSCI OmilATAOlM

SSSOT CDMcxMna

_,^mJ-,*?—i

• - « i « ^ ° ~ ^ - - 0— •witi^'i •«>» • ^ • • • i - '

PuCkako t«l««l.K¥ZTd>M»«

Cbck llHiv [IA~« tU»ag>

•niKSC <kk« b*

aaOttMwtbg

" l!!^ ? i l Z . 7 r . ^ r T , .frn OM Pari C»fipidi_

n.JMfci>iniiir.i..ii<i-Mi<i 8W>hPmWa>tMnnii 1 nn

g j __J j

//m/i 7. Giao dien chuong trinh Convert4 ciia phdm mdm 0EM4 PC ciia cac thanh phdn tga dd ellip (vy dd (p va kinh dd

A,, tinh bang dd ; dd cao h, tinh bang m) cho tiing phiit hoae timg 30 giay, ehung tdi tinh eae gia trj trung binb ngay ciia toan bd tap hgp sd lieu quan sat duge trong hai nam 2005-2006 tai ba tram (tram Huded sd lieu ttr ngay 14-01-2006). Sau dd tinh cac gia trj tga dO ellip trung binb ciia toan bO chudi sd lieu trung binh ngay da thu duge va tinh phdn du ciia cac tga dg ellip (dep, d^, dh) bang each Id'y gia trj (cp, X, h) trung binb ngay quan sat duge trir di cac gia trj trung binh eila toan bd chudi sd lieu ; tidn hanh bidn ddi eae phdn du tga dd ellip (dep, dX, dh) sang phdn du tga dd vudng gde dja phuong (de, dn, du), trong dd de la phdn du eua thanh phdn Ddng (tinh bang met), dn la phdn du thanh phdn Bac (tinh bang met) va du la phdn du cua tbanb phdn thing dumg hudng len tren (tinh bdng met) [3, 6]. Tap hgp sd lieu cae phdn du (de, dn, du) timg ngay duge sir dung dd so sanh vdi chudi sd lieu gia trj tung ngay eila ham lugng boi nude kbi quydn tai 3 vj tri duge trinh bay dudi day. Luu y, phdn mdm 0EM4 PC khi tinh toan tga dd vj tri quan sat ttr sd lieu GPS chi' tinh tdi hieu chinh do tdng dien ly, chua dua vao hieu chinb cho tdng khi quydn.

Sdlieu ham lugng hoi nudc tdng cdng (integrated water vapour - iwv) trong bai bao nay la'y ttr eo so dii lieu tai phan tich ciia Trung tam Dy bao mdi trudng qud'c gia, Trung tam Nghien ciru khi quydn qud'c gia My NCEP/NCAR. Tren thyc td, co sd dii lieu nay tap hgp sd lieu khdng Id tit nhidu ngudn khdc nhau (quan sat tai mat da't, quan sat bang tdu bid'n, rada, bdng tham khdng, may bay, ve tinh...) bang mdt md hinh dy bao sd trj [7]; duge thdnh ldp cho quy md toan edu, tren nhidu mire, eho nhidu trudng khi quydn khae nhau, vdi bude thdi gian khae nhau (4 gia trj trong ngay, trung binh ngay, trung binh thang) bat ddu tii ngay 1-1-1948.

Co sd dQ lieu tai phan tich NCEP/DOE-II (R-2) la mOt bude cai tie'n ttr co sd dii lieu tai phan tieh NCEP/NCAR (R-1). Trong R-2 lugng mua md hinh duge thay the' bdi lugng mua quan sat (sd lieu ve tinh va .sd lieu mang do mua) [8]. So vdi R-1, R-2 duge eai thien hon vd dO dn dinh va sy cap nhat thudng xuyen eae thdng sd vat ly.

Sd lieu ham lugng nude tdng cdng trong khi quydn sir dung trong bai bao nay la'y ttr co sd dii lieu NCEP/DOE-II tren khu vyc Viet Nam vdi dd phan giai ngang 2,5*2,5 dd kinh vy ttr 1-1-2005 de'n 31-12-2006, tinh cu thd cho 3 vj tri Ha Ndi, Hud va Tp Hd Chi Minh. Ham lugng hoi nude tdng cdng d day dae trung cho ham lugng hoi nudc d cac pha khdc nhau (hoi nudc, nudc long vd nude da) trong toan bd cdt khi quydn tie't dien 1 m tren mdi didm quan sat vdi gia thie't toan bd tdng kbi quydn duge coi nhu mdt ldp duy nha't.

Dd xem xet mdi tuong quan gi&a cae phdn du tga do, phdn du dd eao vdi ham lugng hoi nude, ehung tdi sii dung eOng thirc tinh tuong quan eheo R giiia ehiing theo cdng thirc (vi du he sd tuong quan giiia phdn du thanh phdn thing diing hudng len tren du, va ham lugng hoi nudc tdng cdng):

R. clu-iw\'

5](C(M, -duj^wVi -(vvvj

/ = 1

X [dUj -dujY, ('wv,- - iwvf trong dd dui - phdn du thanh phdn thing dirng budng len tren tai ngay thur /, iwv; - ham lugng hoi nudc tdng cdng ngay thir i,du va Jwv la eae dai lucmg trung binh tuong iing.

III. KET QUA VA PHAN TICH Hinh 2, J vd 4 trinh bdy bidn ddi theo thai gian cua cae phdn du tga dd dja phuang {de, dn, du) ddi

•D 3

1.0 0.5 0.0 -0.5 -1.0

1.0 0.5

f

TJ

-0.5 -1.0

Ha Noil

60 120 180 2404- Ngay- 2005

Ha Ndi

180 240 i 30|p rjigay - 2006

T -t-

60 120 180 240 Ngay^- 2005

+

300 360 60

360

120 180 240 300 360 Ngay- 2006

60 120 180 240 300 360 60 120 180 240 300 360 Ngay - 2005 Ngay - 2006

Hinh 2. Cac phdn du tga dd de,dn,du trung binh ngay quan sat duge tai tram Ha Ndi vdi eae tram Ha Ndi, Hud va Tp Hd Chi Minh tuong

img trong khoang thdi gian 2 ndm 2005-2006 (tram Hud chl cd sd lieu ttr ddu nam 2006). Chung ta ed thd tha'y tai mdi tram, phdn du du hiin ddi lien Uie ttr ngay nay sang ngay khae vdi bien dO khoang 1- 2 m ddi khi ldn ban, eae phdn du dn va de eung vay nhung vdi bien dd khoang 0,5-1 m hoae han ; mirc do bidn ddi d tram Hud dudng nhu nhd nha't, edn ldn nhdt d tram Tp Hd Chi Minh. Trong mdi nam, sd lieu cac phdn du du ed mdt eye dai ro ret

vao khoang giiia nam (thdng 7) va eye tid'u vao cudi va ddu ndm (thang 12 va thang I). Toan bd chudi sd lieu trong hai nam phdn du hiin ddi phdn ldn trong khoang ±1 m, edn thdnh phdn de va dn hiin ddi trong khoang ±0,5 m. Nhu vay ed thd ndi do ebinh xac cua viee xae dinh tga dd tuyet ddi bang cac may thu GPS loai GSV4004 la co 1-2 m, ke't qua nay phu hgp kdt qua xac djnh tga dd tuyet dd'i bang cac loai may thu GPS 2 tdn sd khae |5|.

60 120 180 240 30|p 360

N ^ y - 2006

30p + *

60 120 180 240 300 360

N^y - 2006

1 O-r

60 120 180 240 300 360

Ngay-20(X.

Hinh 3. Cac phdn du tga dd de, dn, du trung binh ngay quan sat duge tai tram Hue'

Chudi sd lieu ham lugng hoi nude tdng cdng ttr md binb NCEP/DOE-II tinh eho ba vj tri Ha Ndi, Hud va Tp Hd Cbi Minh vdi dd phan giai thdi gian hang ngay duge trinh bdy tren hinh 5. Chiing ta tha'y ham lugng hoi nude tdng cdng ciing bie'n ddi tir ngay ng sang ngay kia, eung vdi mdt eye dai r5 ret vao khoang miia he (thang 6-7) va eye tidu vao mua ddng (thang 12-1). Nhu tren da neu dd xem xet md'i tuang quan giiia eae phdn du tga dd va phdn du dd cao vdi ham lugng hoi nude trong kbi quydn ehiing tdi da tinh tuong quan eheo giiia ehiing.

Bdng 1 trinh bdy he sd tuang quan giiia cac phdn du tga do va ham lugng hoi nude trong hai ndm 2005 va 2006 tai cac tram Ha Ndi, Hue' vd Tp Hd Chi Minh. Chiing ta tha'y ro rang tuong quan giQa

ham lugng hoi nudc va phdn du cua thdnh phdn Ddng vd thanh phdn Bdc Rje-iwy va Rdn-iwv la tuong quan am d ta't ca ba Uam. Rdciwv 6 ca ba Uam ddu CO -0,4 ddi vdi nam 2006 ; Rdc-iwv tai Uam Ha Ndi vd tram Tp H6 Chi Minh la kha nhd (-0,03 va - 0,04) ddi vdi nam 2005. Rdn-iwv 6 ca ba tram ddu ed gia trj nhd. Trai vdi hai thanh phdn da neu, phdn du cua thanh phdn hudng thing diing len tren du ed tuong quan rd't ro ret vdi ham lugng hoi nude tdng Cdng, cac gia trj Rdu-iwv ddu duong vd giam ttr Ha Ndi (Rdu-iwv = 0,74 - trung binh 2 nam) ddn Tp Hd Chi Minh (Rdu-iwv = 0,255 - trung binh 2 nam).

Hinh 6 trinh bdy sy thay ddi theo vy dd dia ly eua eae he sd tuong quan Rdu-iwv tir Tp Hd Chi Minh tdi Ha Ndi, nhu vay ro rang cang xa xich dao cac be sd tuong quan Rju-iwv cang ldn.

Bdng 1. He so tUdng quan glCra cde phSm dir toa do va ham lUdng hol nudc tdng cong tai cde tram

Tram HaNdi

Nam 2005

Rd R, dn-iwv Rd

-0,04 -0,15 0,71 Hud

1 p MdVl

2006 2006 2005 2006

-0,40 -0,44 -0,03 -0,37

-0,08 -0,16 -0,04 -0,20

0,77 0,68 0,32 0,19 Nhu tren da neu, cac phdn du tga dd va ham lugng boi nudc bie'n ddi theo chu ky 12 thang tuong ddi ro rang. Dd tha'y ro xu the'nay, ehiing tdi tinh eae gia trj trung binh thang cua eae phdn du tga do va gia trj trung binh thang cua ham lugng hoi nude, ke't qua duge bid'u didn tren hinh 7 va hinh 8. Tren cac hinh nay, mdi hinh nhd la bidn thien eua gia trj trung binh thang eiia mdt thanh phdn phdn du tga dd duge ve ciing vdi bidn thien ciia ham lugng hoi nudc trung binh thang. Bien dd hang nam eua phdn du du la ldn nha't c5 ±0,8m, cua phdn du thanh phdn de va dn c9 ±0,3m. Cac he sd tuong quan giiia cae dai lugng trung binh thang tuong ty duge trinh bdy d bdng 2. Rdu-iwv dat tdi xd'p XI 0,9 d ca ba tram trir nam 2006 d Tp Hd Chi Minh. Tuong quan Rdu-iwv = 0,29 ddi vdi Uam Tp Hd Chi Minh trong nam 2006 la do ttr ngay 15-06 (ngay 166) ddn ngay 25-6 (ngay 176), c6 mdt nguyen nhan nao dd chua ro rang lam cac gia Ui du xae dinh duge ldn tdi khoang 4 m, do dd gia tr:

trung binb thang ciia du thang 6 lech dang kd so vdi xu hudng chung tai Uam nay. He sd urang quan Rdu-iwv = 0,8 dd'i vdi Uam Tp Hd Chi Minh khi bd qua

c

E,

60 120 180 240 300 360 Ngay - 2005

60 120

IMgjy

30 240 306 -2006

360

360

60 120 180 240 300 360 60 120 180 240 300 360 Ngay - 2005 Ngay - 2006

Hinh 4. Ckc phdn du tga dd de,dn,du trung binh ngay quan sat duge tai tram Tp Hd Cbi Minh sd lieu thang 6-2006. He sd tuong quan Rdeiwv la

am va ed gia trj kha ldn (ed -0,6 ddn -0,9) trong nam 2006 d ca ba tram. He sd tuong quan Rdn-ivw dd'i vdi ca ba tram ddu am va ed gid Ui nhd hon (-0,2 ddn -0,5). Nhu vay ehiing ta tha'y khi Idy gia tri trung binh thang thi ta't ea ede he sd tuong quan ddu ldn ban so vdi he sd tuong quan dd'i vdi cac gia trj trung binb ngay. Didu nay cd thd hidu duge vi cac .sd lieu phdn du tga dd tinh ttr sd lieu GPS anh hudng bdi nhiing ydu td dja phuong ciia tdng

khi quydn gdn vj Ui quan sat, edn sd lieu bam lugng boi nudc tdng cdng tdng ddi luu da duge Uung binh hda Uong mdt khoang thdi gian dai va ehi cd y nghTa khu vye, nen viee la'y trung binh sd lieu Uong khoang thdi gian dai ban thi nhidu ydu td dja phuang se bj loai di va sy tuong quan giiia hai tap hgp sd lieu se cang td't hon.

Dd tha'y rd rang ban md'i tuong quan giiia bidn ddi ehu ky ngan eiia cac phdn du tga dO vdi bidn ddi tuong irng d bam lugng hoi nudc tdng cOng,

60 120 180 240 300 360 NgSy- 2005

120 180 240 300 360 NgSy -2006 E 70 3

B: 60 - o 5 0 : '§ 40 -

^ 30 '2 20 - -J 10

^ ^ ^ ^ ^ ^ '

Tp Ho Chf Minh ' I • I • I •

120 180 240 300 360 NgSy - 2005

' I ' I ' I • I • I 120 180 240 300 360 NgSy- 2006

Hinh 5. Ham lugng hoi nude tdng cdng tai Ha Ndi, Hud va Tp Hd Chi Minh

0.8

0.6

ce

0.2

12 14 16 18

Vy dp dja ly

20

Hinh 6. Sy thay ddi ciia cac he sd tuong quan Rdu-iwv theo vy dd

Bdng 2. Tuong quan giOra c5c gia tn trung binh thang cde phin dirtoa do va do cao v6l trung binh thdng

ham lugng hoi nudc

Tram HaNdi '

Hue Tp HCM

Nam 2005 2006 2006 2005 2006

'^de-iwv

-0,09 -0,87 -0,92 0,05 -0,64

Kdn-iwv

-0,28 -0,35 -0,25 -0,50 -0,22

^ d u - i w v

0,95 0,95 0,89 0,88 0,29

r 60

2 4 6 8 10 12 Thang - 2005

2 4 6 8 10 12 Thang - 2005

2 4 6 8 10 12 Thang - 2005

J^^f^

60 ^-^

E 50 "5.

- 40 ^ 30 X

_J

20 ^ 2 4 6 8 10 12

Thang - 2005

2 4 6 8 10 12 Thang - 2005

2 4 6 8 10 12 Thang - 2005

Hinh 7. Biin thien theo thdi gian eila cac gia trj trung binh thang trong nam 2005 cua cac phdn du tga dd {de, dn, du) {ckc hinh thoi) va cila ham lugng hoi nudc tdng cdng (cac hinh vudng)

chiing tdi xa'p xi' phdn dao ddng chu ky dai ciia cac dai lugng nay bang mdt da thirc bac cao. Sau khi thii nghiem ehung tdi diing da thire bae 15 va tha'y da thire xa'p xi nay ed thd bidu thj eae dao ddng ed chu ky ldn ban khoang 1 thdng {hinh 9).

Ld'y cac phdn du tga dd cQng nhu hdm lugng hoi nudc trir di cac dao ddng chu ky dai duge xdp xi' bang cac da thirc nhu da neu, chiing ta thu duge

phdn du cua cac phdn du tga dd {dde, ddn, ddu), va phdn du ciia ham lugng hoi nude (diwv). Vi du, hinh 10 bie'u thj ddu va diwv tai tram Ha Ndi trong thdi gian 2 nam 2005-2006. Chiing ta ed thd thdy cac dudng eong nay thd hien cae dao ddng tir ngay nay sang ngay khae tdi nhiing dao ddng chu ky ca vai chuc ngay va dudng nhu chiing cung cd sy tuang quan nha't djnh. Ke't qua tinh tuong quan giiia diwv

20 X 2 4 6 8 10 12

Ngay - 2006

2 4 6 8 10 12 Thang - 2006 0.8

^0.4

>0.0

3

-0.4 -0.8

0.8

^ 0.4

^0.0

^0.4 -0.8

U.B -|

0.4 -

^ 0 . 0 -c

TJ - 0 . 4 • - 0 . 8 •

r" i •

r

' i •

"

1-

- i - ^

r

i-

-^-

1"

i /

T 1

r 1

4- :

- 4 - ^

2 4 6 8 10 12 Thang - 2006

2 4 6 8 10 12 Thang - 2006

2 4 6 8 10 Thang - 2006

12

2 4 6 8 10 Thang - 2006

12

Tp Ho Chl Minh

• I ' I

2 4 6 8 10 12 Thang - 2006

2 4 6 8 10 12 Thang - 2006

2 4 B 8 10 Than* - 2006

Hinh 8. Biin thien theo thdi gian ciia cae gid tri trung binh thang trong nam 2006 ciia cae phdn du tga dd (ede hinh thoi) va eiia ham lugng hai nudc (cae binb vudng)

2.0 -1 1.0 -

I

0.0

-

3

a)

1 TJ t j iJ

-1.0 -

'

1

60

1 " 1 ~ " i n

1 ,

1 1 1 l l

120 180 240 300 N gay - 2006

- 1

1

1

360

70

^'^ 60

^ 50 H 40 S 30

^ 20 10

0 60 120 180 240 300 360 Ngay - 2006

Hinh 9. a) Phdn du du va xd'p xi bdng da thiic (dudng ddm), b) Ham lugng hoi nudc tdng cdng va xdp xi bang da thire (dudng dam) nam 2006 tai Hd Ndi

va eae phdn du dde, ddn, ddu tai cac tram Ha Ndi, Hud Tp Hd Chi Minh trong thdi gian 2005-2006 duge trinh bdy trong bdng 3. Mdt ldn niia chiing ta vdn tha'y eae gia trj tuong quan Rddu-diwv la duong va cung giam ttr Ha Ndi vdo Tp Hd Cbi Minh, dd'i vdi ca ba tram ehiing ddu nhd bon eae he sd tuong quan tuong img ddi vdi eae gia trj trung binb thang (bang 2). Cae he sd tuong quan Rddcdiwv va Rddn-diwv ddu ed gia trj tuong ddi nhd trong ea hai nam 2005 va 2006. Nhu tren da neu, viee djnh vi bang GPS bj anh hudng cila nhidu ye'u td cd tinh dja phuang (chua kd nhirng ydu td khdng cd ngudn gde khi

Bang 3. Tuong quan giCra cac phSn du cija phSn du toa do vdi phSn d u ham Jirong hoi nudc

Tram Nam Rd

HaNdi ²⁰⁰⁵ 0,01 -0,15 ^0.40 Hud

I p liL-M "

2006 2006 2005 2006

-0.03 0,03 0,07 -0.05

0.04 0.12 0.15 -0,01

0.58 0.43 0.28 0.19 quydn), Uong khi ham lugng hoi nude duge tinh tir md hinh ed tinh toan edu, do vay nhidu dae trung

60 120 180 240 300 Ngay - 2005 ;

360 60 120| 180 240 300 360 JNgSy- 2006

60 120 180 240 300 360 60 120 180 240 300 360 Ngay - 2005 Ngay - 2006

Hinh 10. a) Bidn thien theo thdi gian cila phdn du ham lugng boi nudc va b) Phdn du cila phdn du ddu tai tram Ha Ndi

dja phuong da bi trung binb hda, tuong quan giiia cae phdn du dde, ddn vdi diwv se khdng thd td't nhu tuong quan tuong img dd'i vdi eae gia uj trung binb thang.

KET LUAN

Cac kdt qua trong bai bao nay cho thdy viec xac djnh tga dd tuyet dd'i ciia eae vj tri quan sat bdng cac may thu GPS hai tdn sd eiia bang NovAtel ehi dat duge dd chinh xae eo 1 -2 m.

Dd chinh xac eiia cac phep xae djnh tga dd bang cdng nghe GPS phu thudc ra't rd ret vdo ham lugng hoi nudc ciia tdng khi quydn. Tuy nhien dd chinh xae eua mdi tbanb phdn tga dd xae dinh duge phu thudc khae nhau vao ham lugng hoi nudc tdng cdng.

Thanh phdn thing dting (hoae tuong ty dd eao) bj anh hudng bdi ham lugng hoi nudc ldn ban so vdi thanh phdn Bdc va tbanb phdn Ddng. Trong didu kien nude ta, vao mua ddng dd dm tha'p, anh hudng ciia tdng khi quydn tdi dd chinh xae ciia phep xae djnh tga dd bang GPS ciing thdp nha't. Do vay dd tdng do chinb xac ciia cac phep do trde dja bdng cdng nghe GPS phai tidn hanh vao mua kbO (eae thang 12 va thang 1).

Ke't qua trong bai bao cung cho thdy rang md binh khi quydn toan cdu ed thd ap dung tuong dd'i tdt ddi vdi vung vy dd trung binh (khu vyc ttr Hud trd ra), viee do dae Uac dja d vung vy dd thap (tir Hud ud vao) cd thd se dua de'n nhiing sai sd ldn ban, cac quy Uinb do dae se phai duge luu y chat ehe hon.

Ldi cam on : bai bao duge hoan thanh vdi sy trg giup kinh phi cila dd tai nghien eiru co ban "Xii ly sd lieu 3 tram thu GPS lien tuc dat tai Ha Ndi, Hud va Tp Hd Chi Minh vdi nhiing irng dung co ban trong nghien eOai ndng dd dien tii tdng cdng tdng dien ly d Viet Nam va chuydn ddng vd Trai Da't d cac vting quan sat", ma sd 711906.

TAI LIEU DAN

[ l i s . BASTIN et al, 2005 : On the use of GPS tomography to investigate water vapor variability during a Mistral/sea breeze event in southeastern France, Geophys. Res. Lett., 32, L05808, doi :10.1029/2004GL021907.

[2J C. CHAMPOLUON et al, 2004 : GPS monito- ring of the tropospheric water vapor disUibution

and variation during the 9 September 2002 torrential . precipitation episode in the Cevennes (southem France), J. Geophys. Res., 109, D24I02, doi :

1029/2004JD004897.

[3] S.P. DRAKE, 2002 : Converting GPS coor- dinates ((pA-b) to navigation coordinates (ENU), DSTO-TN-0432.

[4] I. DUAN et al, 1996 : GPS Meteorology : Direct estimation of the Absolute Value of Preci- pitable Water, J. Appl. Meteo., 35, 830.

[5] VI QUOC HAI, TRAN DINH TO, DUONG CHI CONG, 2004 : Xac djnh tga dd tuyet ddi bang GPS, Tap chl Cac Khoa hgc vd Trai Ddt, T. 2 6 , 1 , 76-81.

[6] B. HOFTMANN-WELLENHOF, H. UCH- TENEGGER and J. COLLINS, 2001 : GPS Theory and Practice, Springer.

[71 E. KALNAY et al, 1996 : The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor.

Soc, 77, 437-462.

[8] M. KANAMITSU et al, 2002 : NCEP-DOE AMIP-II Reanalysis (R-2). Bull. Amer. Meteor.

Soc, 83, 7657-7642.

[9] LE HUY MINH, A. BOURDILLON, R LASSU- DRIE-DIXMESNE, R. FLEURY, NGUYEN CHIEN THANG, TRAN THI LAN, NGO VAN QUAN, LE TRUdNG THANH, TRAN NGOC NAM, HOANG THAI LAN, 2006 : Xae djnh ndng dd dien tii tdng cdng tdng dien ly d Viet Nam qua sd lieu cac tram thu tin hieu ve tinh GPS, Tap ehi Dja ehdt, A 296,54-62.

[10] LE HUY MINH, NGUYfiN CHIE'N T H A N G , TRAN THI LAN, R. FLEURY, P. LASSUDRIE-DITHES- NE, A. BOURDILLON, C. AMORY-MAZAUDIER, TRAN NGOC NAM, H O A N G THAI LAN, 2007 : Anh hudng cila bao ttr tdi ndng dd dien tiir tdng cgng vting di thudng dien ly xich dao Ddng Nam A quan sat duge ttr sd lieu GPS, Tc CKHvTD, T. 29, 2, 104-772.

[11] NOVATEL 2003 : 0 E M 4 family of receivers, USER manual.

SUMMARY

Estimation of the relation between the total tropospheric water vapour and the precision of the

absolute positioning by GPS in Vietnam This paper presents the determining results of the residual time variation of the daily mean navigation coordinates (de.dn.du) collected from three GSV4004 GPS continuous stations in Hanoi, Hue and Ho Chi Minh city, and their correlations to the daily mean Integrated water vapour of the atmosphere at the same positions. It Is found that the residuals du vary day-to-day In the range of about 1-2 m and around the annual period general tendency which Is maximum In summer (June or July) and minimum in winter (December or January) and whose amplitude of about +0.8 m.

The annual variation of the integrated water vapour is maximum in summer and minimum in winter also. It is found that the different coordinates have different corelations with respect to the total tropospheric water vapour The residual du has highest correlation with respect to the Integrated water vapour, their correlation coefficient are about 0,74 for the Hanoi station ; 0.66 for Hue and 0.255 for Ho Chl Minh city. The residual de has the negative correlation with respect to the integrated water vapour, their correlation coefficient are about -0.4 for three stations. The residual dn has smallest correlation with respect to the integrated water vapour, about -0.2 or smaller for all three stations.

Correlation coefficients of the monthly mean residuals du and the monthly mean integrated water vapor are of 0.95 in Hanoi. 0.89 in Hue and 0.58 in Ho Chi Minh city. These results in this paper show that it is necessary to carry out the repeated GPS measurements for the tectonic studies in Vietnam in winter (dry season) in order to limit the effect of the atmosphere.

Ngdy nhdn bdi: 15-01-2008 Vien Vdt ly Dia cdu,

Trudng Vien thong Qudc gia Bretagne (Phdp) Trudng Dgi hgc Rennes 1 (Phdp) Trung tdm Nghien cdu Moi trudng Trdi Dd't vd

Cde hdnh tinh (Phdp) Trudng Dgi hgc Khoa hgc Hue Phdn Vien Vdt ly tP Ho Chi Minh