Tap chiKHKTMo - Bia chdt. sd30. 412010. tr.53-51<br />
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TRAC DIA - DIA CHINH - BAN DO (trang 53-93)<br />
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ANH HirONG KHUC XA T A N G DOI LlTU DEN K £ T QUA DINH VI<br />
TUYET DOI BANG KHOANG CACH GIA<br />
DANG NAM CHINH, NGUYEN GIA TRONG<br />
Truong Dgi hgc Md - Dia chdt<br />
Tdm tat: Theo cdc md hinh khi quyin cua Hopfield vd Saa.stamoinen cd thi tinh todn sd cai<br />
chinh anh huong cua tdng ddi liru din tin hiiu vi tinh GPS. Trong bdi bdo ndy, tdc gia gidi thiiu<br />
mdt .so kit qud thue nghiim tgi Hd Npi cho bdi todn dinh vi tuyet ddi bdng khodng cdch gia.<br />
\. Anh hu-dng ciia mdi tru-dng truyen sdng giam anh hudng ciia tang nay ddi vdi tri do.<br />
den chat lugng tin hieu ciia ve tinh GPS Mudn lam giam anh hudng ciia nd chung ta phai<br />
Anh hudng ciia mdi trudng truyen sdng tac diing cac md hinh hieu chinh thuc dung la ham<br />
ddng tdi tin hieu ciia ve tinh dugc biet tdi bdi 3 cua cac dai lugng dac trung cho mdi trudng la<br />
nguyen nhan dd la tang ddi luu, tang dien ly va nhiet do, ap suat va do am de tinh hieu chinh trj<br />
hieu ung da dudng dan. Trong ndi dung ciia bai do. Nhu vay, trong qua trinh thu tin hieu cua ve<br />
bao nay se khao sat anh hudng ciia tang dien ly tinh, can phai xac djnh dugc gia trj ciia cac tham<br />
va tang ddi luu ddi vdi trj do khoang each gia. sd dac trung cho mdi trudng khi quyen nhu da<br />
Anh hudng ciia tang dien ly ddi vdi trj do ndi d tren. Trong ndi dung ciia bai bao nay, tac<br />
khoang each gia phu thudc vao gia trj tdng gia se tinh toan sd hieu chinh ciia tang ddi luu ddi<br />
lugng dien tu dgc theo dudng truyen sdng tin vdi trj do dua tren mdt sd md hinh khac nhau.<br />
hieu tir ve tinh tdi may thu (TEC). Miic do anh 2. Cac mo hinh hieu chinh anh hu'dng ciia<br />
hudng ciia tang dien ly cd gia trj khac nhau ddi tang ddi luu<br />
vdi van tdc pha, van tdc nhdm va khi do khoang Cd rat nhieu cac tac gia da xay dung md<br />
each gia tren nhung tan sd khac nhau. Anh hinh hieu chinh anh hudng ciia tang ddi luu ddi<br />
hirdng ciia nd tdi khoang each gia dugc tinh vdi trj do GPS la ham ciia cac yeu td dac trung<br />
theo cdng thii'c: cho dieu kien khi tugng nhu nhiet do, ap suat,<br />
40 3 40 3 do am va gdc cao cua ve tinh trong he toa do<br />
C =--phTEC;A;:;: = ^ T E C . (1) dja dien chan trdi. Sau day xin gidi thieu mdt sd<br />
Gia trj cua TEC cd the dugc xac djnh bang md hinh do.<br />
each su dung may thu 2 tan sd, ndi suy tii' md 2.1. Mo hinh Saastamoinen<br />
hinh TEC da dugc xay dung san hoac su dung Md hinh nay dugc Saastamoinen xay dung<br />
cac he sd de tinh hieu chinh gia tri cua TEC vao nhung nam 1972 va 1973 de tinh anh<br />
dugc phat di trong tep thdng tin dao hang. hudng cua tang ddi luu nhu sau:<br />
Trong khudn khd bai bao, se xac dinh gia trj ciia 0,002277 1255<br />
Tro= P+ +0,05 e-13tan"Z ^ R . ( 3 )<br />
TEC bang viec sii' dung khoang each gia do cosZ T<br />
bang may thu 2 tan sd theo cdng thirc: Trong cdng thu'c tren:<br />
(P-Pi f'f- Z la khoang thien dinh ciia ve tinh;<br />
TEC=^ - '' J -, =9.51964(P,-P,). (2)<br />
40,3 (fr-f;) T la nhiet do tai diem quan sat (do Kelvin);<br />
Trong cdng thuc (2), TEC cd don vj la P la ap suat cua khi quyen (tinh theo don vj<br />
TECU ( I TECU=10'"dientLi'/in-) millibars - mb);<br />
Anh hudng ciia tang ddi luu ddi vdi tri do e la ap suat rieng phin cua hoi nude (mb).<br />
khoang each gia dugc chia lam 2 phan la anh vdi<br />
hudng cua phin khd va anh hu'd'ng ciia phan udt. e=R,exp(-37,2465+0,213166T-0,000256908T'). (4)<br />
Viec sir dung may thu 2 tan sd khdng the lam R,, la do am tuong ddi tinh theo %.<br />
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53<br />
B \a 5R ia cac sd hieu chinh phu thudc vao P la dp suit khi quy en tinh theo dr '^^^'•<br />
do cao cua diem quan sat va khoang thien dinh e la ap suat rieng phan cua h^ ^^'"^ ^^<br />
cua ve tinh. dugc xac dinh theo cdng thirc:<br />
Cac gia trj dac trung cho dilu kien khi e=R„exp(-3 7.2465+0.213166T-0.000256908T-).<br />
quyen tinh theo cdng thu'c (3) la cac gia trj dugc<br />
Cac tham sd dac trung cho dieu kien khi<br />
xac djnh true tiep tai diem quan sat. Trong<br />
tugng trong trudng hop na} ciing la cac tham so<br />
trudng hgp khdng cd dieu kien do cac yeu td dd<br />
phai do true tilp tren thuc dja. Trong trudng<br />
tai diem quan sat. cd the xac djnh chiing thdng<br />
hgp ta khdng xac dinh dugc chimg trong qua<br />
qua mdi quan he nhu sau [5]:<br />
trinh thu tin bieu GPS thi ta cung cd the .xac<br />
P=P„(l-0.000226(H-H,))'"' , (5) dinh gian tilp chiing thdng qua cac cdng thirc<br />
(5).(6).(7).<br />
T=T,-0.0065 ( H - H j , (6)<br />
2.3. Hieu chinh theo md hinh Hopfield thuc<br />
R„=Ri„exp(-0.0006396(H-Hj); (7) dung<br />
vdi Ho = Om; Po = 1013.25 mbr; To = 18'^C va Md hinh nay la mdt hinh thirc bieu thj khac<br />
Rho = 50%. cua md hinh Hopfield va dugc bieu dien bdi cac<br />
2.2. Md hinh Hopfield cdng thuc nhu sau [5]:<br />
Md hinh Hopfield dugc xay dung vao cac + Anh hudng ciia phan khd<br />
nam 1969. 1970 va 1972. Theo md hinh nay. K,=1.55208*10^P((4OI36,O+148,72'nr)/(T+273,16)) .(22)<br />
Hopfield chia anh hudng cua tang ddi luu ddi + Anh hudng ciia phan udt<br />
vdi trj do GPS lam hai phan, la phan khd va phan<br />
K„ =-0.282*P/(T+274l6)+83072*P(T+27316)'.(23)<br />
udt. Anh hudng cua ca phan khd va phan udt<br />
dugc tinh toan theo he thdng cdng thiic sau [5]: Tdng hgp anh hudng cua ca phan khd va<br />
phan udt ddi vdi tin hieu cua mdt ve tinh co<br />
Tro=Tro,+Tro,^ (8)<br />
khoang thien dinh nhd hon 90" se la:<br />
va Trg = I O ' " N , ^ - ^ i - ' (i = d, w), (9) ^VE-+0.001904+ "*<br />
1=1 k 5R tiop :K,,/sin .(24)<br />
tronc dd: -0.084sinUE"+0,00068541<br />
r=^(R,+h,)"-R^sin-Z-R,cosZ; (10) 3. Ket qua tinh toan thuc nghiem<br />
fi, = l; f:,=4a,; (11) Sd lieu dimg de tinh toan thuc nghiem la so<br />
lieu dugc do bang may thu GB-1000 vao ngay<br />
l\,=6a;+4b,: f,,=4a, (a;+3b,); (12) 24 thang 7 nam 2009 tai Ha Ndi. Dua tren dii<br />
lieu do da chuyen sang dang Rinex, tien hanh<br />
t;,=a>12a;b,+6b-^f;,=4a,b,(a;+3b,);(13)<br />
tinh sd hieu chinh anh hudng ciia tang dien ly,<br />
f.,=b;(6a,-+4b,); f8,=4a,b;; (14) tang ddi luu tai mdt sd thdi diem, gia trj toa do<br />
thu dugc va do lech toa do tai cac thdi diem do<br />
t;,=b,^ (15) (do lech tuc thdi). Cung tii' kit qua do dd, da<br />
a,=-cosZ/h,;b,=-sin'Z/(2h,Rj ; (16) tinh gia trj do lech toa do cua diem xac djnh<br />
theo tat ca thdi gian do. Trong tinh toan da sir<br />
hj=40136+148.72(T-273,16)(m); (17) dung cac md hinh Saastamoinen va Hopfield<br />
h,, =11000(m); (18) thuc dung de xac djnh sd hieu chinh cho cac tri<br />
do khoang each gia.<br />
N,=77.64P/T(K/mb); (19)<br />
Gia trj do lech toa do d day la gia tri sai<br />
N„=-12.96e/T+371800e/T'; (20)<br />
khac cua toa do dang xet vdi toa do chinh xac<br />
RE=6378137m; (21) (cd 1cm) cua diem dd, dugc xac dinh bing each<br />
vdi: Z la gdc thien dinh cua ve tinh; lay sd lieu do xir ly chung vdi sd lieu cua mot<br />
T la nhiet do ciia diem quan sat tinh theo do sd tram thudng xuyen trong mang ludi IGS khu<br />
Kelvin; vuc gin Viet Nam bang phan mim Ik-rnese 5.0.<br />
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Sd hieu chinh cua ting dien ly ddi vdi trj do khoang each gia<br />
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Sd hieu chinh vao khoang each gia (m)<br />
STT Ten ve tinh<br />
23h47m30s 23h48m00s<br />
1 1 15,8165 17,5655<br />
2 9 13.3698 10,4478<br />
3 12 15,8310 16.9922<br />
4 14 11,4740 15,3972<br />
5 18 14,2335 13.5692<br />
6 21 13,7388 14.6180<br />
7 22 14,9663 13.6689<br />
8 24 16,9279 16.5766<br />
9 26 13.2304 12,3750<br />
10 27 13,4416 15,5753<br />
11 30 17,2402 12,6886<br />
* Sd hieu chinh ciia tang ddi luu tinh theo cac md hinh khac nhau<br />
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Ten ve Gdc cao Sd hieu chinh (m)<br />
STT<br />
tinh (
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