Khoa hgc Ty nhien
Md hlnh quasigeoid qudc gia khdi dau VIGAC2014 - Cd sci de thanh lap cac mo hinh mat bien trung binh, cao nhat va thap nhat tren vung bien Viet Nam
Ha Minh Hoa' Vi^n Khoa hoc Do dac vd Bdn do
Ngay nhan bai 5.10.2015, ngay chuyln phan bien 9.10.2015, ngay nhan phan bi?n 14.12.2015, ngay chSp nhan dang 26 12 2015
Bai bao trinh bay cac Icet qua ngliien cuu ciia ih tai c4p nha nirdc "Nghien ciru danh gia cac mat chuan mirc nirtfc bien (mat " 0 " dfi s&u, trung binh va cao nh^t) theo cac phuong phap tr§c dia, hai van va kien tao hi^n dai phuc vu xay dirng c^c c6ng trinh va quy hoach doi bo* Viet Nam trong xu the bien doi khi hau", ma so KC09.19/11-15 lien quan den vi^c xay dung mo hinh quasigeoid quoc gia Idioi dau VIGAC2014 lam Ctf sdr de xac dinh cac d9 cao quoc gia cua cac mat bi§n trung binh, cao nhat, thap nhat tai cac tram nghidm trieu dirge bo tri tr€n cac dao xa bcr, nham xay dung cac mo hinh mat bien trung binh, cao nhat, thap nhat trgn viing biin Viet Nam.
Ngoai ra, bai bao ciing trinh bay cac phtrong phap va cac ket qua xay dung cac mo hinh dia hinh mat b i l n trung binh MDTVN, mat bien cao nhdt HSS2015 va mat biln thap nhat LSS2015 tren vung bien Viet Nam.
Tir khda: GPS, mat bien cao nhdt, mat bien thdp nhdt, mat bien trung binh, MDT, mat geoid cue bg, trgm nghidm trieu.
Chi so phdn loai 1.5
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Dat van dg
M6 hinh dia hinh dpng lire trung binh MDTVN (Local Mean Dynamic Topography of Viet Nam) tren vung bien Viet Nam thuc chat la mo hinh dia hinh mat bien trung binh cue bp duac sir dung de lam nen thong tin dia ly tren bien, quy chieu cac dp sau dia hinh day bien do dugc ve he dp cao quoc gia HP72 phuc vu viec thanh lap ban do dia hinh day bien va cac ban do chuyen de ve bien. Trong tai lieu [1] da trinh bay quy trinh xay dimg mo hinh MDTVN ciing voi do chinh xac cua mo hinh nay dua tren cac do cao chuan nha nuac cua cac mat bien trung binh cue bp dup'c tinh toan theo phuang phap hai van tai 9 tram nghiem trieu co dinh c6 tiioi gian do muc nuac bien 1cm hon 18,6 nam:
Co To, Hon Dau, Hon Ngu, Tien Sa (San Tra), Quy Nhon, Nha Trang, Phu Quoc, Viing Tau va Con Dao, trong do c6 cac tram nghiem trieu nam tren cae dao nhu Co To, Hon Ngu, Con Dao va Phu Quoe. Doi vai cac tram nghiem trieu nam dpc ba bien Viet Nam, viee truydn dp cao nha nuoc len cac mat bien trung binh cue bp dugc tinh toan theo cac cac so lieu do muc nuac Vm hon 18,6 nam dl dang dupc thuc hien nha do dan dp cao tir cac diem dp cao hang 1, II quoc gia vao eae
"0" tram cua cac tram nghiem trieu nay. Tuy nhien, van dS khoa hpc mau chot la truyen dp eao quoc gia len cac
mat bien trung binh tai cac tram nghiem trieu dugc bo tri tren cac dao. Npi dung chinh cua bai bao nay nham giai quyet van de Ichoa hpc neu tren.
Cac mat bien trung binh, cao nhat, thap nhat dugc xac dinh dua tren cac so lieu do muc nuac bien nhieu nam theo phuang phap hai van tai cac tram nghiem trieu CO quan he mat thiet vai nhau. Do do, khi da xac djnh dupc dp eao chuan eiia mat bien trung binh trong he do cao quoc gia HP72 tai mpt tram nghiem trieu, ehiing ta cung se xac dinh dugc eae dp eao ehuan ciia eae mat bien cao nhat, thap nhat trong he dp cao quoc gia tai tram nghiem trieu do. Dieu nay tao tien de de xay dung mo hinh mat bien cao nhat HSS2015 (Highest Sea Surface of 2015) tren viing bien Viet Nam phuc vu thiet ke, quy hoach cac cong trinh eong nghiep, dan su, an ninh - quoc phong, eae tuyen de bien dpc ven bien va ven cac dao thuoc lanh tho Viet Nam; xay dung mo hinh mat bien thap nhat LSS2015 (Lowest Sea Surface 2015) tren viing bien Viet Nam phuc vu viee lua chpn mat quy chieu hai do quoe gia, xac dinh cac duang eo sa cho eong tac phan djnh lanh hai,
Cac ket qua xay dung cac mo hinh MDTVN, HSS2015 va LSS2015 se dugc trinh bay trong bai bao nay.
*Email: [email protected]
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The preliminary national quasigeoid model VIGAC2014 • The basis for construction
ofthe mean sea surface, highest sea surface and lowest sea surface models on
territorial waters of Vietnam
Summary
This scientific article describes the research results ofthe national scientific and technological project "Estimative research of a standard surfaces ofthe sea level ("zero" depth, mean, and highest sea surfaces) by the methods of geodesy, oceanography and modern tectonics serving the construction of works and planning the coast of Vietnam in trend of climate changes" with the code KC09.19/11-15 related to the construction of the preliminary national quasigeoid model VIGAC2014 that creates the basis for the determination of national heights ofthe mean sea surface, highest sea surface, lowest sea surface at the tide gauges located on off-shore islands with the purpose of bulding the mean sea surface, highest sea surface, lowest sea surface models on the territorial waters of Vietnam.
Additionally, this paper introduces methods and results of constructing the mean sea surface model MDTVN, highest sea surface model HSS2015, lowest sea surface model LS$2015 on the territorial waters of Vietnam.
Keywords: GPS, highest sea surface, local geoid, lowest sea surface, MDT (Mean Dynamic Topography), mean sea surface, tide gauge station.
Classification number 1.5
Doi tirong va phirong phap nghien ciin Doi tugng can xac dinh la dp cao chuan nha nuac cua cae mat bien trung binh, cao nhat va thap nhat tren cac tram nghiem trieu dugc bo tri tren cac dao xa ba. Cac phuang phap dugc su dung la phuang phap xay dung mo hinh quasigeoid quoc gia khai dau (preliminary national quasigeoid) VIGAC2014 (VIGAC- Vietnam Institute of Geodesy and Cartography) tren toan bp lanh tho Viet Nam, phuang phap xac dinh dp cao trie
dia ciia diSm la hinh chieu ciia di^m GPS dugc b6 tri tai tram nghi?m triSu dya tren cong nghe GPS va phuang phap do thuy chuan. Ngoai ra, chiing ta phai chuyen cdc dai lugng trac dja nhu dp cao chuan, dg cao trac dia, di thuang dg cao ve hg trieu 0 theo quy dinh trong t^ili$u [2].
Mat geoid c\ic bp Hon Dau sat nhat vai mat biln trung binh nhieu nam tai tram nghi?m trieu Hon Diu la mat khdi tinh cho he dg cao quoc gia HP72. Trong nhiSu tai lieu nghien cuu [3-6] da cong bo cac k^t qua xac dinh the trpng truang W'g =62636847,2911 m^s~'^
cua mat geoid ciic bp Hon DSu va dp cao W -W
HQ = -^^—- = 0,890 m ciia mat geoid cue bo Y
Hon Dau so v6i mat geoid toan cau, them vao do dp cao HQ la khong doi tren toan bp lanh tho \^et Nam. 0 day iV^ = 62636Z56,0 m^.s~^ la th^ trgng tmcrag cua mat geoid toan cau [7], ^N la gia tri tnmg binh ciia gia t6c trgng tru6tig chuan tai diem N bat ky tren lanh tho Viet Nam.
Cac ket qua nghien cuu da dan den cong thiic chuyen doi di thuang do cao toan cau tir mo hinh trgng truong trai dat EGM2008 tuang umg vdi mat geoid toan cau ve mat geoid cue bg Hon Dau duoi d£ing sau:
^ ^ = f + 0,890 m + SC _ (1) 6 day f la gia tri di tihucmg do cao toan ciu tir mo
hmh trong truang trai dat EGM2008 tuang iing voi mat geoid toan cau, SC„-^ la so cai chinh chuyen di thuong dp cao toan cau tir he khong phu thu6c trieu ve he trieu 0 (xem trong [6]) va co dang:
^C^_^=(0,02871-0,08584.sin^S) <m>, con B la vT dp trac dja cua diem.
Dira tren cong thiic (1) da xay dung dugc mo hinh quasigeoid quoc gia khai dSu VIGAC2014 dua tren ca sa du lieu (CSDL) di thuong do cao toan cau cua mo hinh EGM2008 bao gom cac 6 chuan cua mang lu6i cac 6 vuong (grid) kich thuoc 2,5' x 2,5'. Cac dir lieu tren moi dinh ciia 6 chuan bao gom cac tga dp trac dia B,L tuong ling voi ellipsoid WGS84 quoc t6 va di
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thuang d6 cao toan cau ^ trong h6 khong phu thuOc trieu. Cac dinh cua cac 6 chuSn trong CSDL di thuang dg cao toan cau dupe sSp x6p theo thii ti^ tang dSn cua vT do trSc dia 5 theo cac vT tuydn va tren mgt vT tuyen cac kinh dp L dugc sap xep theo thir tu tang dSn. Phan lanh thd ViSt Nam, mpt phSn lanh th6 Trung Quoc, Lao, Campuchia, Thai Lan dugc sap xep Ian lugt tir vT dg trac dia 6" den 25'^ vai bude thay doi AS = 2',5 theo cac vT tuySn va trSn moi vi tuyen kinh dg i thay d6i tir lOO" d8n 118° vai buoc thay d6i AZ,-2',5.CSDL di thucmg dp cao toan cau ciia mo hinh EGM2008 dugc sir dung co tong so 65536 dinh ciia eae fl chuan hinh vuong kich thuac 2,5'x2,5'.
Cac ket qua danh gia tren 162 diem dp cao hang I quflc gia co do GPS va xu ly dii lieu do GPS trong Khung quy chieu trai 6.kx quflc te ITRF (International Terrestrial Reference Frame) tuang iing vai ellipsoid WGS84 cho thSy, di thuang do cao cue bp ^, eua diSm GPS dugc xac dinh tir mfl hinh VIGAC2014 eo do chinh xac a mirc ±1 cm [8]. Khi xir ly dii lieu do GPS trong ITRF vai viec sii dung lich ve tinh chinh xac a miic 2,5 cm va 5 cm, chung ta xac dinh dugc dp cao trac dia H^ ciia diem GPS vcri dp chinh xac a muc tir ± (1,4 - 2,8) cm. Dieu nay cho phep xac dinh dugc dp cao chuan qu6c gia Hi cua diem GPS theo cong thiic:
H^=H,+t, (2)
vai dp ehinh xac tucmg duang hang II.
Cong thiic (2) la ca sa de xac dinh cac dp cao chuan nha nuac cua cac mat bien trung binh tai cac tram nghiem tri6u dugc bo tri tren cac dao xa ba.
De kiem tra do tin cay cua mo hinh VIGAC20I4, dua tren nguyen tSe nho bo qua da xac dinh dugc tieu chi cua diem ca sa ciia mo hinh nay, theo do dp chenh ciia di thuang do cao cue bp dugc xae dinh tit mo hinh VIGAC2014 so vai di thuang dp cao GPS/thuy ehu§n khong vugt qua ± 1 cm. Tir tieu chi nay da xac djnh dugc 9 diem do cao hang I quoe gia la eac diem ea sa ciia mo hinh VIGAC2014 bao gflm I(HN-VL)6-l, I(HN-VL)28-1, I(HN-VL)64, I(HN-VL)72, I(VL-HT)98, I(VL-HT)158, 1(BH-HN)33, I(BH-TH)65,1(BH-TH)122A dugc phan bo tuang dfli
deu tren dat lien thupe lanh tho Viet Nam. Cac gia tri dp eao chuan H^, di thuang do cao cue bg ^^ (dugc xae dinh tir mo hinh VIGAC20I4), do cao trac dia H^ (dugc xae dinh tir eae k6t qua do va xir ly cae du lieu GPS trong ITRF tucmg iing vcri ellipsoid quoc te WGS84) trong he trieu 0 cua cac diem ca sa nay da dugc cong bfl trong tai lieu [6].
Tu 9 diem nay, chung ta kiem tra dp cao chuan cua diem j co do GPS duge xae dinh theo eong thirc (2) dua tren cflng thiie sau:
0 {HA
9 day
(3) do cao chuan
{H[ \ , {H, \ va if; la dp cao ehuan, dp eao trfie dia va di thuang do cao cue bp da biet cua diem ca sa thli i; \Hj)_ va ^j la do eao trfie dia va di thucmg dp cao cue bp eua diem kiem tra j .
Cac ket qua kiem tra tren hai diem trpng luc cfl do GPS tren cac dao Phii Quflc, Con Dao, va tren 26 diem GPS thuoc cac mang luai trac dia dia dpng luc mien Bac va dia dpng Iuc Dong bang song Cuu Long cho thay cac dp eao chuan (2) va (3) khflng chenh nhau qua 2 mm. Dieu nay khang dmh dp tin cay cua mfl hinh VIGAC2014.
Phuang phap xac dinh cac tpa dp trac dia B, L, H eua diem nam tren mat bien tmng binh va la hinh chieu cua diem do GPS dupe bo tri tren khu vue tram nghiem trieu da dugc trinh bay trong tai lieu [6]. Tren hinh 1, diem G la mflc tram thu tin hieu GPS, diem M la hinh chieu CLia diem G len mat bien trung binh cue bg duge xae dinh theo cac sfl lieu do mue nuoc bien nhieu nam tai tram nghiem trieu dugc bfl tri tren dao xa ba, them vao do mat bien trung binh cue bp eat thuac thiiy chi tai vach O. Chiing ta chpn tren thuac thuy ehi vach V bat ky co hinh anh ro rang. Tai vi tri gan moc G dat may do thuy chuan de xac dinh chenh eao c giira vach V tren thuac thiiy chi va moe G. Chenh eao c chinh la khoang each theo thuac thiiy chi giiia vach V va mat nam ngang di qua mflc G (hinh 1). Vai khoang each d
IIHQAHPC^ , 6(7)7.2016
Khoa hoc Ty nhien
giua mflc vach V va vach O tren thuac thuy chi da biet, chung ta se xac dinh dugc dp cao cua mflc G so voi diSm M theo cong thiic b = d-c. Voi dp cao anten a eua tam pha may thu GPS so voi moc G da dugc xae dinh, ehung ta xac dinh dp cao h ciia tam pha may thu GPS so vai mat bi8n trung binh theo eong thirc
h = a + b. Khi xir ly cac du lieu do GPS tai mflc G trong ITRF bang phan mem Bernese v. 5.2 vai "dp cao anten" h, theo nguyen ly xir ly cac dii lieu GPS (xem [6]), chiing ta se nheln dugc cac tga do trac dia
^ J W ' ^ M > ^ M ^^^ diSm M tren mat bien trung binh tai tram nghiem trieu.
Ket quA
Cac ket qua xac dinh dp cao chuSn quflc gia ciia cac mat bien trang binh, mat bi^n cao nhit va mat biSn thap nhat tai 9 tram nghidm trilu c6 dinh va 22 tram nghiem trieu tam thai (co thoi gian do mi^c nuac bien lien tuc trong 30 ngay dem) dugc trinh bay trong bang duoi day.
Tram thu GPS
Do cao trac dia H^^ dugc xac dinh trong ITRF tuang img vai he khong phu thupe trieu. D6 chuyen v6 he trieu 0 chiing ta sir dung eong thiic [6]:
(%)^=/f^+(0,062073-0,I85592.sin^5 ) <m>
Dp cao chuan quoc gia ciia mat bien trung binh tai tram nghiem trieu dugc xac dinh theo cflng thiie (2) va dugc kiem tra theo cflng thirc (3). Bang each nhu vay, chiing ta da xac dinh dugc eac do cao chuan quoc gia cua cac mat bien tmng binh tren cae tram nghiem trieu tai cac dao Cfl Tfl, Hon Ngu, Cfln Dao, Phii Quflc. Cac ket qua kiem tra cac do cao chuan quflc gia theo eong thiic (3) cho thay, eae dp cao ehuan quoe gia dugc xae dinh theo cflng thiic (2) va dugc kiem tra theo cflng thiic (3) khong chenh nhau qua 2 mm. Tir cac dp cao chuan quflc gia ciia eae mat bi8n trung binh, thflng qua quan he cua mat bien trung binh vdi cac mat bi^n cao nhat, thap nhat tai tram nghiem thku, chiing ta xac dinh dugc cac dp cao chuan quoc gia ciia cac mat bifln cao nhat, thap nhat tren cac tram nghiem trieu tai cac dao Co To, Hon Ngu, Cfln Dao, Phii Quflc.
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T t n I r i mc i c iDit b i i n Irung binh linmg iin|i vi>j gcnici cifc bi l U n D k (ID)
D# rmo c h o i n cAi c i c mfl blla c u l i b i t n n r n i ihig v«l geoid cvc b ( Hbu Dili (ID)
B4 O S cbolo b l ^ t h i p n b l l Immg teg tM gtDid C|iC bf B6n Diu (m) Cic l r | i n nghifm Irltu c6 I h ^ gian dn mirc DiHrc b i l n lAn b i n I 8 . i n i m 1
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0,085 0,103 0.076 0.050 -0,030 0.044 -0,098
2 2 1 0 0 0 1 352 MO 485 623 976 930 380 U 9 4 0.272
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• 1,635 -0,547 -0.894 -O.930 -2.550 -2.236 -0.618 Cic Irf Dl nghidm triiu If ID tbdi c6 thin g u n So m ^ n i n ^ 30 agiy Mm Hia t^
10 11 12 13 IA 15 16 17 l e 19 20 21 22 23 24 25 26 Z7 2S 19 3D 31
MUI Hgvc Bii Chiy B a L l l OaBiy Hoang Tan (Sim Scm)
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Canh Hao o.iis -0.008 0.189 0.290 0.007 0,179 -0,001 -0,216 -0,142 0,049 0.171 -n,is9 0,162 0,059 0,231 0 4 4 9 0,103 0,153 0,184 0,152 0,065 0,155
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1 945 492 479 240 897 439 809 444 438 759 on E21 232 149 2B1 009 923 SG3 024 932 885 825
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Bieu do mat cat cua cac mat bien trung binh, cao nhat va thap nhat dua tren 31 tram nghiem trilu dugc bo tri dge theo ven ba bien Viet Nam dugc trinh bay a hinh 2.
Hinh 2: bieu do mdl cat cua cdc mat bien trung binh. cao nhdt, thdp nhdt tren 31 tram nghidm triiu trong hf dd cao quae gia HP-72
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Tren ca sa cdc ket qua nghien ciiu trong tai h6u [ 1 ] da xay dung dugc CSDL cua mo hinh MDTVN dua trgn CSDL ciia mfl hinh DTUIO MDT. Dua tren cac dg cao chuan quoc gia ciia cac mat biSn trung binh tai 9 tram nghigm trieu co dinh da danh gia dugc dp chinh xac cua mo hinh MDTVN 6 miic ± 6,1 cm. Dua tren mo hinh MDTVN da tien hanh danh gia dugc dp chinh xac ciia cac dp cao chuan quoc gia cua cac mat bien trung binh tai 22 tram nghidm tri6u tam thoi 6 miic ± 0,142 m.
Dua tren cac dp cao chuan cua cac mat bien cao nhat, thSp nhat tai 31 tram nghiem trieu va phan mem ArcGIS da xay dung dugc cac CSDL ciia cac mo hinh HSS2015vaLSS2015.
Cac CSDL MDTVN, HSS2015 va LSS2015 cfl do phan giai 1' x 1' va c6 cac can tnic nhu nhau, eu the:
trong cac fl chuan (grid) cua CSDL, thong tm tai mgt dinh cua 6 chuan bao gom 3 so L (kinh dp, don vi dp), B (vT dp, dan vi dp), / / ( d a n vi met), 6 day
H = MDTVN dfli vdi mo hinh MDTVN, / / = H^^^
doi vdi mo hinh HSS2015, H = H^^^ doi voi mfl hinh LSS2015.
Cac dinh bat dau tir vT tuyen 24" thay dfli vai buo'c nhay A5 = I' cho den vT tuyen 8". Tai mpt vT tuyen xac dinh, cac dinh lai dugc bfl tri theo kinh tuyen bfit dau tli kinh tuyen 100" thay doi vai buac nhay AL = V cho den kinh tuyen 116". Cac dinh nam trong dat hen co gia tri MDTn bang 0. Trong pham vi vung bien Viet Nam CO tat ca 17.103 dmh cua cac fl chuan.
Ket luan
Mfl hinh quasigeoid quflc gia khai dau VIGAC2014 CO dp chinh xac cao a miic ± 7 cm, Tren ca sa mo hinh VIGAC2014 k6t hgp vdi cong nghe GPS, chung ta da giai quyet dugc bai toan chuyen cac mat bien trung binh, cao nhit, th4p nhSt dugc xae dinh theo phuang phap hai van tai cac tram nghiem trieu dugc bfl tri tren cac dao xa thuflc viing bien Viet Nam.
Cac mfl hinh MDTVN, HSS2015, LSS2015 do chinh xac cao duge xay dung tren co so cae phuang
phap khoa hpc chat che se dong gop tich cue cho cflng tac quy hoach, thiet ke cac cong trinh dan sir, eong nghiep va an ninh - quflc phong ven bien, xdc dinh duang CO sa phuc vu viec phan dinh lanh hai, xac dinh mat quy chieu hai do quoc gia phii hgp, thanh lap cac ban dfl chuyen de ve bien phuc vu phat trifln kinh tfl bien.
Ldi cdm ffn
Tdc gid trdn trong cdm on Chuang trinh KH&CN trpng diem cdp nhd nuac KC09/11-15 "Nghien ciiu KH&CNphiic v^ qudn ly bien, hdi ddo vd phdt trien kinh te bien " da ho tra ngi dung bdi bdo ndy.
Tai lieu tham khao
[1] Ha Minh Hoa (2015), "Cac ket qua xay dimg mo hinh dia hinh dpng lire trung binh cue bg sat nhat voi mat bien trung binh tren lanh hai Viet Nam", Tqp chi Khoa hoc vd Cong nghe Viet Nam, 3(10), tr 33-39
[2] International Association of Geodesy (lAG) (1984), lAG Resolutions adopted at the XVII! General Assembly of the lUGG m Hamburg, August 1983, Bulletin Geodetique. The Geodesist's handbook, p.321.
[3] Ha Mmh Hoa va nnk (2012), "Nghien CLTU ca so khoa hoc ciia viec hoan thi|n he dp cao gan lien voi vi?c xay dyng he toa do dgng lire quoc gia". Be tdi khoa hoc vd cong nghe cdp Bo Tdi nguyen vd Moi tneanggiai doan 2010-2012.
[4] Ha Minh Hoa (2013), "Esnmating the geopotentiaj value W,, ofthe local geoid based on data from local and global normal heights of GPS/Levehng points in Vietnam", Geodesy and Cartography.
39(3), pp 99-105
[5] Ha Minh Hoa (2014), "Phuong phap ehuyen do cao chuan nha nirdc len cac mat bien trung binh tai cac tram nghiem tneu tren cac dao xa", Kyyeu Hgi nghi khoa hoc trdc dia vd ban do vi hoi nhdp quoc te, Vien Khoa hgc Do dac va Ban do, Hoi Trac dia. Ban do va Viln tham Viet Nam, tr.2-15,
[6] Ha Minh Hoa (2014), £>'(/(«>'#; vd thuc lien cua trong luc trdc dia, NXB Khoa hpc va Ky thuat, 592 tr.
[7] Petit G, Luzum B (2010), lERS Conventions (2010), lERS Technical Note No 36, VerJag des Bimdesamts fur Kartographie und Geodasie, p, 179.
[8] Ha Minh Hoa (2014), "Danh gia dp chinh xac ciia mo hinh Quasigeoid EGM2008 tren lanh lh6 Viet Nam", Tap chi Khoa Iwc Do dac vdBdn do, No20, tr,l-13.
