KY YEU -CAC 0£ TAl NGHIEN CUU KHOA HOC - CONG NGHg NGANH TAI NGUYEN VA MOI TRUONG GIAI DOAN 2002 - 2006"
DETAI: N G H I E N C U f U 0 N G D U N G C O N G N G H E D G P S T R O N G D O V E HIEN CHiNH BAN DO DIA CHINH, BAN DO CHUYEN NGANH DIA CHINH
• • • C a quan chu t r i : Cue Do dac vd Ban do
Chu nhiem de tai: ThS. Vu Tien Quang Cac thanh vien:
TS. Trin Bach Giang Cue Do Dac Ban Do.
KS. Thai Viet Dung Vien Nghien Cuv Dia Chinh KS. Trinh Ngoc Hung Vien Nghien Ciru Dia Chinh KS. Nguyin Huong Giang Vien Nghien Cuu Dia Chinh KS. Chau Hdng Van Vien Nghien Cuu Dia Chinh KS. Vu Duy Tan Vien Nghien Cuu Dia Chinh KS. Nguyin Trinh Son Vien Nghien Cuu Dia Chinh KS. Vu Dirc Thuan Chi Cue Kiem Lam Son La KS. Trinh Van Toan Vien Nghien Cuv Dia Chinh KS. Pham Van Vinh Trung Tam TD BD BiSn
ThS. Cao Tien Nam Trung tam DTQHDD Muc tieu cua de tai:
1. Xac dinh kha nang, danh gia do tin cay, do chinh xac thuc te ciia cong nghe DGPS trong dieu kien dja hinh da dang tren dat lidn vai khoang each khac nhau d Viet Nam.
2. Xac lap qui trinh cong nghe ap dung phuang phap DGPS trong do dac phuc vu
viec cap nhat bien dong, lam mdi noi dung cac ban do dia chinh va ban do hien trang sir dung dat ti le trung binh (1:10000) thong qua viec thuc nghiem do ve cap nhat bien dong ban do dia chinh, ban d6 hien trang sir dung dat 1 dan vi xa.
Cac noi dung nghien cixu chinh:
1. Nghien cuu ly thuye't su anh hudng cua dieu kien khong gian den ket qua do cai chinh phan sai DGPS.
2. Kiem dinh ve do chinh xac, tinh on dinh thuc te cua cdng nghe DGPS trong nhung dieu kien khac nhau tren cac khoang each khac nhau tren da't lien.
3. Nghien cuu giai phap sir dung cac nguon phat tin hieu cai chinh va cac thiet bi do DGPS hien co.
4. Phuang phap thanh lap va viec cap nhat bien dong ddi vdi cac ban d6 dia chinh ti le 1:10000 va ban do hien trang sir dung da't.
5. Nghien cuu xac lap quy trinh ap dung phuang phap DGPS trong viec do dac cap
nhat su bien dong, lam mdi ndi dung ban do dd dia chinh t i Id 1:10000 va ban do hien trang sir dung da't.
Cac ket qua nghien cu*u chinh da dat duac CHlfONG I: CO s6 LY THUYET VE CONG NGHE DGPS I. LY THUYET CHUNG VE HE THONG GPS
Khi cong nghe GPS ra ddi da thiet lap dugc mdt he quy chieu toan cau ve khdng
KY YEU XAC BE TAI NGHIEN CUU KHOA HOC - CONG NGHE NGANH TAI NGUYEN VA MOI TRUONG GIAI SPAN 2003 - 2006'
gian va ca thai gian, ma theo do tai mot v i t r i bat ky tren trai dat ,d mot thai diem bat ky vdi may thu GPS trong tay ta co ngay toa do diem danh dau v i t r i va thai diem dang dung.
K h i may thu GPS se di chuyen theo dia vat tren thuc dia de thu thap thong t i n dinh vi thi no hoat dong tuong t u nhu mot thiet bi so hoa (digitizer) ngay tai thuc dia. V a nhu vay cong nghe GPS da m d ra mdt kha nang ung dung thu thap thong t i n mo ta tu nhien mpt each khoa hoc, thuan tien, chinh xac. Do vay, viec nghien cuu ung dung cong nghe GPS trong cong tac thanh lap ban d6 la nghien cuu van de ddi m d i k y thuat do ve ban do truyen thdng.
1.1 Vai net ve lich su phat trien cong nghe GPS
Tit nhung nam 60 ciia the k y 20, Co quan Hang K h o n g va V u Tru ( N A S A ) cung vdi Quan dpi Hoa K y da tien hanh chuang trinh nghien cuu, phat tridn he thdng dan dudng va dinh v i chinh xac bang ve tinh nhan tao. He thdng dinh v i d i n dudng bang ve tinh the he d i u tien la he thdng T R A N S I T co 6 ve tinh. hoat dong theo nguyen ly Doppler, dupe sir dung trong thuang mai vao nam 1967.
Sau he thdngTRANSIT, he thdng dinh vi ve tinh the he thu hai ra ddi co ten la NAVSTAR-GPS (Navigtion Satellite T i m i n g A n d Ranging - Global Positioning System) gpi tat la GPS. He thdng nay ban dau bao gom 24 ve tinh trien khai tren 6 qui dao nghieng 55° so vdi mat phang xich dao trai da't vdi chu k y gan 12 g i d d dp cao xa'p x i 12.600 dam (
«20.200 km). So vdi he thdng T R A N S I T , dp chinh xac dinh vi bang he thdng nay duoc nang cao, thai gian quan trac ve tinh dupe rut ngan. Cho den nay da cd 32 ve tinh cua he thdng GPS dang hoat dong tren dao.
Cung co tinh nang tuong t u vdi he thdng GPS dang hoat dong con co he thdng GLONASS ciia Nga (nhung khdng thuang mai hoa rpng rai) va mpt he thd'ng tuang lai se canh thi trudng vdi he thd'ng GPS la he thdng G A L I L E O cua Cdng Ddng Chau A u .
6 Viet Nam, phuang phap dinh v i ve tinh da dupe ung dung tir nhung nam dau thap ky 90. V d i 5 may thu ve tinh loai Trimble ban dau, sau mdt thdi gian ngan da lap xong ludi khdng che d nhung viing dac biet khd khan ma tir trudc dd'n nay chua cd ludi khdng. Nhung nam sau dd cong nghe GPS da ddng vai trd quyet dinh trong viec do ludi ca'p "0" lap he quy chieu Qudc gia m d i cung nhu viec lap ludi dia chinh ca sd hang I I I phu trum lanh thd va nhieu ludi khdng che cho cac cdng trinh dan dung khac.
1.2 Ca'u t r u e he thd'ng GPS
Theo su phan bd khdng gian ngudi ta chia he thd'ng GPS thanh 3 phan gpi la Doan (Segment): Doan Khdng Gian (Space Segment); doan dieu khien (Control Segment); doan ngudi sir dung (User).
1.2.1 Doan khdng gian: Doan khdng gian bao gdm cac ve tinh nhan tao phat tin hieu bay tren 6 mat phang qui dao nghieng 55° so vdi mat phang xich dao trai da't, chu ky 718 phut. Quy dao ve tinh gan hinh trdn, d dp cao 12.600 dam, m d i mat phang quy dao cd 4 hoac 5 ve tinh,. M d i ve tinh cd trang bi ten lira day de dieu chinh quy dao, thdi han sir dung khoang 7.5 nam.
1.2.2 Doan dieu khien: Doan dieu khien la 5 tram mat dat phan bd deu quanh trai da't trong dd 1 tram chu (Master Station) va 4 tram theo ddi (Monitor Station). Cac tram nay cd nhiem vu thu so lieu ve tinh lien tuc, tinh toan va dieu chinh quy dao cac ve tinh.
KY YEU "CAC DE TAl NGHIEN CPU KHOA HOC - CONG NGHE NGANH TAI NGUYEN VA MOI TRUONG GIAI DOAN 2002 - 2006'
/. 2. 3 Doan ngudi su dung: Doan ngudi sir dung bao gom cac may thu tin hieu ve tinh va phan mdm sir l y tinh toan sd lieu. M a y thu tin hieu GPS cd the dat cd dinh tren mat dat hay gan tren cac phuang tien chuyen ddng.
1.3 Cac t r i Do GPS
Tri do GPS la nhung sd lieu ma may thu GPS nhan dugc t u tin hieu cua ve tinh truyen tdi dung cho viec tinh toa dd diem do, bao gom: tri do Code (Code measurement) va tri do pha (Phase measurement).
1.4. Nguyen ly d i n h v j GPS
Dinh vi la viec xac dinh vi t r i diem can do (vi t r i tam pha cua anten). Tuy thuoc vao dac diem cu the cua viec xac dinh toa do ngudi ta chia thanh 2 loai hinh dinh v i ca ban:
dinh vi tuyet ddi va dinh vi tuang ddi.
1.4.1 Dinh vi tuyet ddi (point positioning)
Khi dat may d diem bat ky thu tin hieu tir cac ve tinh, khoang each tuong ring tir may thu den cac ve tinh dugc xac dinh va toa dp ciia diem do dugc xac dinh. Day ia bai toan giao hpi nghich khong gian k h i biet toa dp ciia cac ve tinh va khoang each tuong ung den may thu.
1.4.2 Dinh vi tuong ddi (Relative Positioning)
Mpt phuang an dinh vi khac cho phep sir dung he thdng GPS trong do dac trac dia cd dp chinh xac cao do la dinh vi tuang ddi. Sir khac ciia phuang phap dinh vj nay la d d i d phai sir dung tdi thieu 2 may thu tin hieu ve tinh ddng thai va ket qua ciia phuong phap la cac thanh phan sd gia toa dp A X , A Y , A Z (hoac AB, A L , A H ) ciia 2 diem trong he toa dp khong gian. Dp chinh xac dinh vi tuong ddi dat cd cm va chu yeu ap dung trong lap ludi khdng che trac dia.
1.5 Cac nguon sai sd t r o n g do GPS
Cung nhu bat ky mpt phuang phap do dac khac, viec dinh vi bang he thdng GPS chiu anh hudng ciia nhieu yeu td khac nhau.
7.5.7 Sai sd quy dao ve tinh
Toa dp diem do GPS dupe tinh dua vao v i t r i da biet ciia ve tinh. Ngudi sir dung phai dua vao lich thong bao toa ve tinh ma theo lich toa dp ve tinh co the bi sai so. Do vay neu sir dung quy dao ve tinh chinh xac co the dat ket qua dinh vi tdt hon.
->
7. 5.2 Anh hudng cua tdng ion
Tang ion la lap chua cac hat tich dien trong bau k h i quyen d dp cao tir 50 - 1000 km, tang ion co tinh chat khuc xa ddi vdi song dien tu, chief, suat ciia tang ion ty le vdi tan so song dien tir truyen qua no. V d i may thu 2 tan sd anh hudng tang ion, tri do giai trir do do viec dinh vi co dp chinh xac cao han, nha't la ddi vdi viec do canh dai.
7.5.3 Anh hudng cua tang ddi luu
Tang ddi luu co dp cao den 8 k m so vdi mat dat la tang lam khuc xa ddi vdi tin hieu GPS do chiet sua't bien ddi. Chiet sua't ciia tang ddi luu sinh ra dp cham pha tin hieu. Do vay so cai chinh mo hinh k h i quyen phai dupe ap dung ddi vdi tri do cua may mpt tan so va ca mav hai tan sd.
p KY YEU "CAC SE TAl NGHIEN CUU KHOA HOC - CONG NGHg NGANH TAI NGUYEN VA MOl TRUONG GIAI SPAN 2002-2006-
1.5.4 Hien tugng da tuyen (Multipath)
Do la hien tuong k h i t i n hieu tu ve tinh khong den thang anten may thu ma dap vao be mat phan xa nao do xung quanh rdi m d i dd'n anten may thu. H i e n nay vdi cong nghe Everest, may thu loai dugc cac t r i do co anh hudng cua Multipath.
7.5.5 Su suy giant do chinh xac (DOPs) do do hinh cac ve tinh
Dinh v i GPS la viec giai bai toan giao hoi nghich khong gian dua vao diem goc la cac ve tinh va cac khoang each tuong ung den may thu. Trudng hgp t d i uu k h i thu tin hieu ve tinh GPS la ve tinh co su phan bd hinh hoc can ddi tren bau trdi xung quanh didm do.
Chi sd mo ta do hinh ve tinh gpi la chi sd phan tan do chinh xac DOP (Delution of Precision)
1.6 N h u n g k y t h u a t do gps 7.6.7 Do GPS tuyet ddi
La k y thuat xac dinh toa dp cua didm dat may thu t i n hieu ve tinh trong he toa do toan cau WGS-84 su dung nguyen l y dinh v i tuyet ddi. D o nhieu nguon sai sd nen dp chinh xac v i t r i didm thap (cd 10m), chu yeu cho viec d i n dudng, va cac muc dich dac co yeu cau dp chinh xac khong cao. D d i vdi phuong phap nay chi su dung 1 may thu tin hieu ve tinh.
7. 6.2 Do GPS tuang ddi (Carrier-phase-based Relative GPS)
Thuc chat cua phuong phap do la xac dinh hieu toa dp khong gian cua 2 didm do ddng thdi dat tren 2 dau cua khoang each can do (Baseline) sir dung nguyen ly dinh vi tuong ddi. Do ban chat cua phuong phap, can tdi thieu 2 may thu ve tinh trong 1 thdi didm do. Phu thuoc vao quan he cua cac tram do trong thdi gian do ma ngudi ta chia thanh cac dang do tuong ddi sau:
/ 6.2.1 Do GPS tmh (Static)
Day la phuang phap chinh xac nha't sir dung 2 hoac nhieu may thu dat c d dinh thu tin hieu GPS tai cac didm c i n do toa dp trong khoang thdi gian thdng thudng tu 1 gid trd len.
I. 6.2.2. Do GPS ddng (Kinematic GPS)
Phuang phap dua tren nguyen ly dinh v i tuang ddi, dupe tie'n hanh vdi 1 may dat cd dinh (base station) va mdt hoac nhieu cac may khac (rover stations) di ddng dd'n cac didm can do vdi thdi gian rat ngan, dp chinh xac cd cm.
Tuy thudc vao thdi didm x u ly so lieu do - x u l y ngay tai thuc dia hay trong phong sau k h i do, ngudi ta chia thanh 2 dang:
- Do GPS ddng thdi gian thuc (GPS R T K - Real Time Kinematic GPS)
Phuang phap cho phep thu dupe toa dp dung tai thuc dia trong he toa dp dia phuong bat ky vdi thdi gian do ngan (1 tri do - 1 giay).
- Do GPS ddng xir l y sau (Post Procesed Kinematic GPS)
Gidng nhu phuong phap GPS R T K , phuong phap nay do mdt loat didm vdi thdi gian do ngan 2 (tri do). Toa dp ciia cac didm do cd dupe sau k h i xir l y so lieu trong phong.
7. 6.3 Do cdi chinh phdn sai DGPS (Code-based Differential GPS)
KY YEU 'CAC BE TAl NGHIEN CUU KHOA HOC - CONG NGHE NGANH TAl NGUYEN VA MOl TRUflNG GIAI BOAN 2002-2006' ^
La phuang phap do GPS sir dung nguyen ly dinh vi tuyet doi sit dung tri do code va
ca tri do pha co do chinh xac do toa dp 1- 3m, sit dung 2 may thu tin hieu ve tinh trong do 1 tai tram goc (Base station) co toa dp biet trudc va 1 tram do tai cac diem can do toa dp (Rover station). Tren ca so dp lech vd toa dp do so vdi toa dp thuc ciia tram gdc dd hieu chinh vao ket qua do tai cac tram dong theo nguyen tac ddng anh hudng. Tdng hop ve cac phuang phap do GPSPS trong bang sau:
Kieu do Sd ve tinh tdi thieu
Thdi gian do tdi thieu
Dp chinh xac dat
dupe Cac dac trung khac Do tinh
(Static) 4 l g i d
-1 tan sd:
5mm+lppm -2 tin sd:
5mm+0.5ppm
- May 1 tan sd cho dcx tdt nhat <10km
- Khong han che khoang each vdi may 2 tan sd.
Do tinh nhanh (Fast static)
4 8'-30' 5-10mm+lppm phu thudc t.gian do
Cac thu tuc do nhu vdi do tinh.
Do dong xir ly ly sau (GPS - PPK)
4 2 tri do
l c m + l p p m
- Khoang each tdi da 50km.
- Can khdi do bang do tinh nhanh tren canh khdi do.
Do dong thoi gian thuc(GPS - R T K )
4 1 tri do
l c m + l p p m
- Khoang each do phu thupc vao RadioLink,
<10km
- Can khdi do tren diem biet toa dp hoac do tinh nhamh
Do DGPS xir ly sau (Post- Processed DGPS)
4 2 tri do
- 0.5m vdi may thu Everest, Maxwel. vdi 5VT, PDOP<4 - l - 3 m vdi may thu khac cung D K
- Khdng can thu lien tuc ve tinh, khdng can Radio truyen tin hieu cai chinh.
Do DGPS thdi gian thuc (Realtime - DGPS)
4 1 tri do
- 0.2m vdi may thu Everest, Maxwel. vdi 5VT, PDOP<4 - l - 3 m vdi may thu khac ciing D K
- Khong can thu ve tinh lien tuc, can Radio truyen tin hieu cai chinh,
Cac gia tri ghi trong bang dua tren ket qua mdi nhat thu dupe vdi thiet bi do cua hang Trimble
Bang tong hap ve cac phuang phap do GPS.
1.7 Toa dp va he q u i chieu
Ellipsoid dupe chon lam he toa dp dinh v i toan cau la GRS-80 (Geodetic Reference System 1980), mat quy chieu nay dupe he dinh v i GPS sir dung 1984 gpi la He Trac Dia The Gidi (WGS-84). He toa dp nay dung ellipsoid xac dinh bdi ban true ldn a=
6378137.0 m va nghich dao dp det 1/f = 298.257223563. Day la he toa dp dia tam cd 3
KY YEU "CAC DE TAI NGHIEN CUU KHOA HOC - CONG NGHE NGANH TAI NGUYEN VA MOl TRUONG GIAI DOAN 2002-2006"
true X Y Z trong do gdc toa dd la dia tam, true X nam trong mat phang X i c h Dao di qua kinh tuyen gdc va dia tam; true Y nam trong mat phang X i c h Dao va vudng gdc true X tai dia tam; true Z vuong gdc vdi mat phang X i c h Dao tai dia tam cd hudng Bac va di qua diem cue BacTrung binh. D o m 6 i qudc gia lua chon mdt he toa dd rieng nen khi do GPS ket qua do can dupe tinh chuydn ve he toa do dia phuong theo cac tham sd tinh chuyen rieng.
II. CO S6 LY THUYET VA CAC GIAI PHAP KY THUAT CAI CHINH PHAN SAI TRI DO GPS (DGPS)
I I . 1 C o sd ly thuyet cai c h i n h phan sai t r i do GPS (dgps)
DGPS la phuong phap kiem tra tin hieu ve tinh GPS va cung ca'p sd cai chinh phan sai cho may thu GPS (may dong) nham nang cao dp chinh xac dinh v i . Bang sau cho tha'y su anh hudng cua cac nguPn sai sd den ket qua dinh v i .
Nguon sai sd Do GPS tuyet ddi ( m ) D O D G P S (m)
Dong ho ve tinh 3.0 0
Sai so qui dao 2.7 0
Tang ion 8.2 0.4
Ting ddi luu 1.8 0.2
Dong ho may thu 0.3 0.3
Da tuyen 0.6 0.6
Viec cai chinh phan sai co the tien hanh theo hai phuong phap sau day:
- Phuong phap cai chinh toa dp: Theo phuong phap nay sd cai chinh phan sai la hieu sd toa dp (hieu kinh dp, v i dp va dp cao:AB, ALva A H ) da biet va toa dp tinh dupe theo tri do GPS tai tram Base.
- Phuong phap cai chinh cu ly: Sd cai chinh phan sai la hieu khoang each that tit ve tinh tdi tam diem anten cua may thu GPS tai tram Base va khoang
each tinh dupe tir cac t r i do tai tram Base tdi cac ve tinh.
Tuy theo thdi diem cai chinh (cai chinh toa dp hoac cai chinh cu l y ) , cd 2 phuong phap do DGPS nhu sau:
- Phuong phap DGPS xir ly sau (Post processed):
Theo phuong phap nay, sd lieu dong thdi thu tin hieu cac ve tinh gidng nhau, trong
cung mpt khoang thdi gian tai tram Base va tram Rover dupe luu lai va sd cai chinh phan sai cung vdi toa dp da dupe cai chinh cua tram Rover chi co dupe sau khi xir l y sd lieu do thuc dia trong phong.
- Phuong phap DGPS thdi gian thuc (Realtime DGPS):
Theo phuong phap nay, tai tram Base so cai chinh phan sai lien tuc dupe tinh toan
va dupe truyen tdi cac may Rover thong qua cac thiet bi truyen thdng. Cac may thu DPS Rover dong thdi thu t i n hieu tu ve tinh GPS va tin hieu cai chinh phan sai phat tit tram Base de tinh ra toa dp chinh xac (da dupe cai chinh phan sai).
KY YEU "CAC BE TAI NGHIEN CUU KHOA HOC - CONG NGHg NGANH TAl NGUYEN VA MOI TRUONG GIAI BOAN 2002-2006"
I L 2 . Cac phuong phap do DGPS
II.2.1 Phuong phap MSK - DGPS vdi cac tram GPS dan dudng (Beacon Control GPS Station)
De ling dung ky thuat DGPS tren mpt khu vuc, ngudi ta xay dung cac tram Reference DGPS cd dinh d cac vi nhat dinh dd d i n dudng va cung cap tin hieu cai chinh phan sai cho bat ky may dong nao nam trong pham v i phu song dupe thiet ke.
Cac tram nay dupe gpi la tram GPS d i n dudng (Beacon Control GPS Station). Nhidu tram Beacon Control GPS Station cung hoat dong dudi sir dieu khien chung, dupe gpi la Beacon Control GPS System. Cau hinh thiet b i cua cac tram Beacon Control rat linh dong va phu thuoc vao quy mo tram, quy mo cua he thdng cung nhu yeu cau cua ddi tupng phuc vu.Tin hieu cai chinh phan sai dupe phat vao khong gian qua he thdng anten phat.
77.2.2. Phuung phap DGPS dien rdng
Cac tram Beacon Control thudng chi co tam phu song khoang 500-1000km. De cd the hoat ddng tren khu vuc rdng ldn hon, ngudi ta ap dung phuang phap DGPS didn rpng - WADGPS (Wide Area Differenfial GPS). Ve nguyen ly phuang phap W A D G P S nhu phuang phap M K S - Beacon DGPS song phuang thuc truyen tin hieu cai chinh tdi cac may thu DGPS la truyen gian tiep thdng qua ve tinh truydn thdng (Communication Satellite). Cac may GPS ddng nam trong tam khdng che ciia ve tinh truyen thdng ddu nhan dupe tin hieu cai chinh phan sai. M d i he thdng WDGPS gom nhieu tram Reference, mdt vai Trung tam kiem tra va khoang 3 - 4 ve tinh truydn thdng. Hidn nay, cd 3 he thd'ng WDGPS: He thd'ng Omnistar va Starfix cua hang Fugro va he thd'ng Skyfix cua hang Racal.
II.2.3. Phuang phap DGPS xu ly sau (Post Processed DGPS)
Ve ban chat nguyen t i c x u l y so lieu cung gidng nhu cac phuang phap tren song su khac nhau ca ban d day la thdi diem x u ly sd lieu. V d i phuang phap nay so lieu do thuc dia ciia tram tinh va tram ddng dupe ghi lai va ket hop xir l y trong phong sau thuc dia vdi dp chinh xac tuang duang. M d t uu the quan trong cua phuang phap nay la kha ca dong do khdng phu thudc vao t i m phu sdng cai chinh cua tram gdc. Tam hoat ddng cua tram ddng so vdi tram gdc dd'n 500 k m so cai chinh v i n phu hop, v i n dam bao dat dp chinh xac CHUONG II: CAC NGUON PHAT VA CAC THIET BI THU DGPS, GlAl PHAP
SCf D U N G T R O N G D I E U K I E N V I E T N A M .
Muc dich cua phan nay la nghien cuu cac ngudn phat tin hieu cai chinh va cac thiet bi thu DGPS hien cd, t u dd phan tich tinh phu hop thuc te ciia cong nghe, thiet bi cho muc tieu ciia de tai dang quan tam, ddng thdi de xuat giai phap mang tinh thuc tidn ve sir dung cac ngudn phat va cac thiet bi thu dgps trong dieu kien Viet Nam.
I. MOT SO NGUON PHAT VA CAC THIET BI THU DGPS HIEN DANG SU" DUNG TAI VIET N A M PHUC V U CHO CONG TAC DO DAC
L I Ngudn phat va cac thiet b i t h u DGPS sir dung dai tan sd cao U H F tai Viet N a m . Cdng nghe phat/thu tin hieu DGPS sir dung tan so cao U H F la loai cdng nghe can dau tu tha'p, dan gian, dd sir dung, cho dp chinh xac tuong ddi cao. Cdng nghe nay dac biet phu hop vdi viec phat/ thu tin hieu cai chinh phuc vu cho viec do dia hinh day sdng, ven bien. hd va do ve mat cat long sdng, tam hoat dpng han che ( < 1 0 K m tren da't lien va
<50Km tren bien). dia hinh khu do can bang phang, khdng bj che khuat bdi cac dia vat nhu cay cao, nha cao v.v..
KY YEU -CAC D£ TAl NGHIEN CUU KHOA HOC - CONG NGHE NGANH TAI NGUYEN VA MOl TRUONG GIAI BOAN 2002-2006"
1.2. Nguon t i n hieu va cac thiet b i t h u DGPS su dung cong nghe M S K - B E A C O N System
De phuc vu cong tac do dac tren dien rdng hon ngudi ta sir dung cong nghe MSK- DGPS. Hien nay tai Viet N a m da xay dung dupe 3 tram phat song B E A C O N M S K tai Do Son, Cao bang, V u n g Tau. Trong nam 2003 va cac nam sau se xay dung va dua vao hoat dong cac tram B E A C O N khac tai Ha Giang, L a i Chau, Da Nang. Dac diem co ban cua cong nghe nay la cho phep phat va thu t i n hieu cai chinh DGPS trong pham v i rpng den 500Km tren bien vai dp chinh xac dinh v i den dan v i met. B E A C O N M S K SYSTEM la mpt he thd'ng da chuc nang dung cho muc dich do dac, d i n dudng, thu thap sd lieu do tinh. He thdng nay cd gia thanh tuang ddi cao, nen thudng do ngudn ngan sach nha nude dau tu.
1.3. Ngudn t i n hieu va cac thiet b i t h u DGPS O M N I S R T A R
Day la mpt ngudn tin hieu cai chinh mang tinh chat thuang mai toan cau do hang FUGRO cung cap dupe xay dung tu nam 1995. De dam bao cho viec truyen cac tin hieu cai chinh R T C M SC - 104 tren viing rdng khoang 2000Km dung den he thdng ve tinh dia tinh I M A S A T . Ngoai ra de dam bao dp chinh xac cai chinh ( ± 3 m ) F U G R O phai xay dung mdt he thdng cac tram mat dat va ndi chung thanh mang chuyen ve trung tam x u ly. Tai Viet Nam, F U G R O sit dung tram cai chinh mat da't dat tai V u n g tau, he thd'ng cham soc khach hang do Cdng ty I M E C O S U M dam nhan.
Viec sir dung he thd'ng nay tai Viet Nam (ca tren mat da't lan tren bien - trir vung dau khi) nhu sau :
Ban hoac cho thud thiet bi DGPS ddng chuyen dung,
Cho thue tin hieu cai chinh theo ngay, tuan, thang hoac nam, Cung ca'p tin hieu cai chinh R T C M SC -104 lien tuc 24gid/24 gid.
1.4 Nguon tin hieu va cac thiet bi thu DGPS-HP hai tan dien rpng dp chinh xac cao.
Ve ca ban he thd'ng cai chinh DGPS - HP didn rdng dp chinh xac cao cd ca'u true
gidng nhu he thd'ng DGPS thdng thudng. Sir khac biet la vide sir dung thiet bi dinh vi hai tan so cho phep xir ly va truydn den may thu cua ngudi sir dung so lidu cai chinh dam bao dp chinh xac do loai tru" dupe sai so do anh hudng cua tang I O N trong k h i quydn va sai sd do Multipath dd thu dupe toa dp didm do cd dp chinh xac cd deximet.
II. NHUNG DE XUAT VE SUDUNG CAC NGUON PHAT VA THIET BI THU DGPS.
Ddi vdi ngudn phat tin hieu cai chinh: Sir dung 2 ngudn phat, dd la:
- Ngudn tin hieu cai chinh DGPS sir dung tram B E A C O N mat da't:
- Nguon tin hieu cai chinh DGPS O M N I S T A R va O M N I S T A R - H P .
Sd d i de tai de nghi lua chon 2 ngudn cai chinh neu tren dd lam thuc nghiem la xuat phat tit cac ly do sau:
- Cac ngudn phat tin hieu cai chinh tren dupe dau t u ca ban:
- Cac tin hieu cai chinh dupe phat lien tuc, on dinh 24/24 g i d trong ngay va tat ca cac ngay trong nam, cho phep quan trac lien tuc.
- D d la cac he thdng sir dung cdng nghe hidn dai va da dupe ap dung tai nhidu qudc gia tren the gidi ciing khu vuc A S E A N , Bac a...
KY YEU "CAC fig TAl NGHIEN CUU KHOA HOC - CONG NGHg NGANH TAl NGUYEN VA MOl TRUONG GIAI BOAN 2002-2006° ^
- Cac may do dac dinh vi di dong su dung c6ng nghe cao, on dinh, nho gon, dd sur
dung va co do chinh xac thoa man yeu cau k y thuat do dac phuc vucdng tac do ve ban do den t i le trung binh (1:10.000).
III. DOI V O I THIET B I THU DGPS (THIET B I T R A M DONG)
Tuong thich vdi cac ngudn phat t i n hieu cai chinh DGPS da lua chon tren la cac thidt bi.
+ D d i vdi nguon tin hieu cai chinh DGPS B E A C O N R E F R E N C E S T A T I O N SYSTEM: co nhieu loai may thu DGPS tuong thich vdi ngudn nay nhung trong dieu kien do dac vung dat lam nghiep chi co the lua chon cac may thu gon, nhe (may cam tay), co anten co the keo dai trong dd co the sit dung cac may thu:
- Geoexplore 3 vdi bo thu t i n hieu cai chinh BoB.
- Geoexplore CE vdi bd thu t i n hieu cai chinh BoB.
+ D d i vdi nguon t i n hieu cai chinh DGPS dien rpng O M N I S T A R va O M N I S T A R - HP: Do dac trung cua dich vu nay, chi sir dung cac may thu chuyen dung do hang san xua't nhu may thu OmniStar 3000L hoac cac may thu m d i loai Omnistar-HP (2 tan sd).
Du lua chon phuong phap Real time DGPS nao t h i trong dieu kien dia hinh nui cao can sir dung ket hop vdi phuong phap DGPS xir l y sau t h i m d i dam bao dap ung d£y du, hieu qua k h i do dac thu thap sd lieu thuc dia.
CHLTONG III: KHAO SAT DIEU KIEN THUC TE VE KHA NANG CfNG DUNG
DGPS T R O N G D O V E C A P N H A T B A N D O B A N D O D I A C H I N H V U N G N 0 l V A B A N D O H I E N T R A N G SU" D U N G D A T T l L E 1:10.000
I. NHU CAU TlTVIEC QUAN LY DAT DAI KHU VUC DAT LAM NGHIEP.
Theo thdng ke cua Tdng Cue D i a Chinh nam 2000 t h i nude ta cd tdng dien tich la 32.924.346 ha trong do bao gom:
- Da't nong nghiep: 9.345.346 ha, - Da't lam nghiep cd rirng: 11.575.429 ha, - Da't chuyen dung: 1.532.843 ha, - Da't chua sit dung: 10.027.265 ha.
Dien tich dat lam nghiep chiem t i trong kha ldn trong co cau sit dung dat chung d nude ta. Do chua co ban dd ty le phu hop nen d p h i n l d n khu vuc dat lam nghiep, viec quan ly nha nude vd sir dung dat con kho khan b i t cap. Viec Tdng Cue D i a Chinh cho thanh lap ban do dia chinh co sd t i le 1:10.000 bang anh hang khdng d cac tinh mien nui (da dupe tridn khai d 17 tinh) la mot dong thai tich cue khac phuc tinh trang tren. Nhung viec lam m d i , chi tiet hoa noi dung tai lieu nay phuc vu cho viec quan l y dat, giao dat giao rung den hp dan d dia phuong con chua cd giai phap cong nghe hop l y , qui trinh cu thd.
Thuc td quan l y , sir dung dat vung dat lam nghiep cho thay viec thanh lap cac loai ban do dia chinh, ban dd hien trang sir dung dat, cap nhat su bidn dong sir dung da\ la m6t yeu cau ca'p thiet, lam co sd cho viec td chuc quan ly tdt viec sir dung dat d khu vuc vung nui.
I I . K H A O SAT DIEU K I E N UNG DUNG CONG NGHE H . l . Ve cong - nghe D G P S :
KY YEU 'CAC B£ TAI NGHIEN COU KHOA HOC - CONG NGHE NGANH TAI NGUYEN VA MOl TRUONG GIAI BOAN 2002-2006"
Ve co ban l y thuye't cong nghe DGPS da duoc nghien cuu k y tren the gidi. va da trd thanh cong nghe ung dung, dupe thuang mai hoa rpng rai. d Viet N a m , cong nghe DGPS ap dung cho Hnh vuc do dac dia hinh day bien da dupe nghien cuu kha chi tiet trong de tai
"Khai thac ung dung cong nghe M S K - DGPS trong do dac bien" chu bien T.S Le M i n h - Vien Nghien Cuu Dia, nam 2001; va de tai "Nghien cuu he thdng GPS do ve ban do va kha nang ung dung trong cong tac thanh lap ban dd dia hinh, ban dd dia chinh" do ky su Nguyen Trinh Son - V i e n Nghien Q r u D i a Chinh lam chu bien, nam 2000. Song, van de co ban can nghien cuu d day la dieu kien ung dung, dac biet la dia hinh tren da't lien, vung nui. c a n phai ung dung loai hinh cong nghe DGPS cu the trong didu kien cu thd 6i rut ra quy trinh ung dung thuc tien cho ngudi su dung. N h u da phan tich d phan tren co 3 phuang phap DGPS co the su dung, do la:
- Phuang phap Real time DGPS su dung cong nghe M S K - DGPS, phat tin hieu cai chinh tit tram Beacon mat da't.
- Phuang phap Real time DGPS su dung he thdng DGPS dien rpng Omnistar, - Phuang phap DGPS xir ly sau (Post processed DGPS).
I I . 2 . Ve con ngudi sir d u n g :
Cong nghe DGPS doi hoi ngudi sit dung ngoai chuyen m d n ve t r i e dia ban 66 con can phai dupe lam quen vdi viec do dac t u ddng, vdi ket qua dang sd. Hien nay, cac can bp k y thuat cua co sd san xuat trac dia ban do da dupe hoa nhap dupe v d i su phat tridn cua cong nghe thong tin v d i nhieu thiet b i phan cung manh, phan m e m dd hoa da dang, va ban do sd da la san pham quen thupc cho nen cdng nghe DGPS cd dupe m 6 i trudng thuan lpi 6i tham nhap va phat trien.
II.3. K h a o sat thiet b i do dung cho don v i san xuat
V d i tieu chi phuc vu cho viec do ve bd sung lam m d i ban do tren da't lien, dac biet la dia hinh vung nui t h i chi co nhung thiet b i thu tin hieu ve tinh nho, gon, cd thd cam tay dupe, do nhanh m d i thoa man yeu cau nay. Cac thiet b i DGPS cim tay da co hoac co thi tiep can dupe trong dieu kien d nude ta gom:
- H p may thu GPS Pathfinder GeoExplorer cua hang Trimble
La loai may thupc loai cam tay nho, nhe, dd sit dung, thu t r i do C/A-Code va co may thu dupe tri do pha L I dung cho do DGPS:
May GeoExplorer 2, M a y GeoExplorer 3, M a y GeoExplorer CE.
- M a y thu DGPS cua hang khac
Tuy chua dupe phd bien d Viet Nam nhung mdt so hang cung da dua ra thi trudng cac loai may thu dung cho do DGPS co tinh nang tuong t u nhu loai may DSNP cua Thales, cac may thu cua hang S O K K I A , L A I C A . . .
11.4. K h a o sat p h a n m e m xir ly sd lieu
Vdi mdi thiet bi do cua cac phuang phap do DGPS deu cd phin mem xu ly sd lidu
rieng biet. Phan mem d day lam cac nhiem vu nhan sd lieu do tit may thu DGPS (trut sd lidu); x u l y sd lieu, cai chinh t r i do cho cac didm do va chuydn vd he toa dp dia phuong (vdi phuang phap DGPS xir l y sau); xuat ket qua do dang f i l e toa dp didm ( X Y h ) hoac file dd hoa ( D X F file) dd cd the nhap vao cac cac file ban dd da cd dd thuc hien cac budc tiep theo. Cac phan mem hien cd gom: phan mem Trimble Pathfinder O f f i c e Vr2.5, Vr2.80, Vr2.91va cac phan mem khac nhu Trimble Total Control ( T T C ) . . .
KY YEU "CAC D£ TAl NGHIEN CUU KHOA HOC - CONG NGHg NGANH TAI NGUYEN VA MOI TRUONG GIAI DOAN 2002-2006" ^
CHLTONG IV: PHAN THUG NGHIEM
De lam rd kha nang ung dung cong nghe DGPS trong dieu kien thuc te cua Viet Nam, theo de cuong da dupe phe duyet, de tai co 3 thu nghiem chinh:
1: D o kiem tra dp chinh xac tren cac diem khdng chd,
2: Do DGPS phuc vu cho viec bd sung npi dung ban dd dia chinh co sd t i le 1:10.000 thanh lap ban do dia chinh phuc vu giao dat giao rung 1 xa mien nui,
3: D o DGPS bd sung lam m d i ban do hien trang sir dung dat t i le 1:10.000 tren 1 xa.
1.1. DO KIEM TRA TREN CAC D I E M KHONG CHE 1,1.1. L u a chon cong nghe
V d i muc thuc nghiem ung dung cong ngh6, dd tai tien hanh do kidm dinh dp chinh xac cua cac phuang phap DGPS tren cac didm cd toa dp chuan (toa dp Nha Nude) d cac khoang each khac nhau, dp cao khac nhau, dieu kien m o i trudng khac nhau, sir dung cac thiet bi loai cam tay hien co nham rut ra nhung ket luan mang tinh thuc tidn, giup cho viec dinh hudng sir dung cong nghe DGPS trong dieu kien dia hinh mien nui nude ta.
Cac phuong phap do DGPS dupe de tai kidm dinh bao gom:
- Phuang phap do Real Time DGPS sir dung tin hieu cai chinh tram Beacon MSK DGPS Do San:
- Phuang phap do Real Time DGPS sir dung tin hieu cai chinh O M N I S T A R cua hang FUGO thong qua dai dien hang d Viet Nam I M E C O S U M .
- Phuong phap do DGPS xir ly sau sir dung sd lieu tram gdc thu tai tram Beacon D o Son va 1 tram gdc m d i lap rieng cho dd tai.
De tai lap ke hoach lua chon cac didm khdng che Nha Nude co toa dp dupe do dac bang cong nghe GPS tinh (cac didm DCCS hang I I I , hang I I , cac didm Cap "0") phan bd tuong ddi deu dan d cu ly tu 0 den 500km so vdi tram gdc D o Son. Dong thdi dd tang tinh chat khach quan va cung dd kidm tra phuong phap DGPS da tram gdc, de tai lap them 1 tram gdc cho do DGPS xir ly sau, thu sd lieu song song vdi tram D o Son tai tran nha Vien Nghien Cuu Dia Chinh. D i d m nay dupe xac dinh toa dp bang phuang phap do GPS tinh, tuydnong duong hang I I I . Viec thuc nghiem duoc tien hanh thanh cac dot t u thang
12/2002 den thang 8/2003.
1.1.2. T d chirc t h i cong
- Cong tac do dac thuc dia: V d i phuong phap Real time DGPS sir
dung tin hieu tram Beacon D o Son tai 1 diem dupe do 4 lan vdi 1, 2, 5, 10 t r i do nham nghien cuu su bien thien vd dp chinh xac. D d i vdi phuong phap DGPS sir dung tin hieu O M N I S T A R tai m d i didm do dupe do 5 - 10 lan. Ph j o n g phap DGPS xir ly sau cung dupe do 4 l i n vdi 1, 2, 5, 10 t r i do. Trong qua trinh do, dd tai da chon them mpt sd didm kidm tra dd xem xet su chenh lech toa dp giua cac phuong phap do DGPS trong cung mpt dieu kien.
Tdng hop cac dot thuc nghiem dd tai da tien hanh do kidm tra tren 37 didm tren pham vi 25 tinh vdi didm vdi 450 t r i do tren cac khoang each tir 0 k m den 550km tir dp cao 0m den dp cao 650m (xem so do trang sau).
KY YEU "CAC flg TAI NGHIEN CUU KHOA HOC - CONG NGHE NGANH TAI NGUYEN VA MOl TRUONG GIAI BOAN 2002-2006"
Tren co so phan tich ket qua do cho thay:
a. Ve dp chinh xac so vdi diem toa dp Nha Nude:
- V d i do Beacon Real time DGPS, dp lech toa dp Ax,Ay (so vdi toa dp chinh xac) co gia tri bien dong tir 0.1 den 3.5m vdi -100% tri do; sai sd v i t r i mat bang trung binh M p = ± 2 . 3 m , ve dp cao M h = ± 6 . 7 m .
- V d i do O M N I S T A R Real time DGPS, dp lech toa dp Ax,Ay (so vdi toa dp chinh xac) co gia t r i bien dong tir O.lden 3.5m vdi * 95% t r i do; sai sd v i t r i mat bang trung binh M p ± 2 . 8 m , ve dp cao M h ± 4 . 7 m .
- V d i do DGPS xir l y sau, dp lech toa dp Ax,Ay (so vdi toa dp chinh xac) co gia tri bien dong t u 0.1 den 3.5m vdi « 100% sd tri do;
sai sd v i t r i mat bang trung binh M p = ± 2.1m, ve dp cao M h = ± 2.4m.
- Dp chinh xac toa dp didm do khdng phu thupc vao sd t r i do.
- Trong khoang 500km so vdi tram gdc, sai sd vi t r i diem do khong phu thupc ro ret vao khoang each so vdi tram gdc.
- Chi khi sd lupng ve tinh >5, gia tri PDOP<6 mdi cd chat lupng do tdt, sai sd nho.
b. Ve tam hoat ddng:
- V d i phuong phap Real time DGPS Beacon t i n hieu suy giam 7% tren 10km va phu den tam 140 k m (cudng dp tin hieu chi con 1 - 5 % ) trong dieu kien dat lien vdi may thu BoB +Geoexplorer 3.
Cudng dp tin hieu(%)
100 80 60 40 20 0 0
BIEU D O SUY GIAM CUCJNG D O TIN HIEU Tram do son tren dat lien (may thu BoB+GE03)
—•-
50km 100km 150km
Tuy nhien cudng dp tin hieu cai chinh thu dupe con phu thupc vao dp nhay cua anten may thu va dieu kien k h i tupng tai thdi didm do. Neu trong tam phu sdng nhung khua't sau cac vat che chan nhu nha, dam cay, doi, nui t h i cudng dp tinh hieu giam nhanh chdng den muc khdng sir dung dupe.
- V d i phuong phap Real time DGPS O M N I S T A R t i n hieu phu song rdng nhung van co nhung thdi didm khong on dinh lam, dan den ket qua do khong dupe tdt (>5m) tren mdt sd didm khdng che.
KY YEU "CAC Ot TAl NGHIEN CUU KHOA HOC - CONG NGHg NGANH TAl NGUYEN VA MOI TRUONG GIAI BOAN 2002-2006"
- V d i phuong phap DGPS x u ly sau trong khoang each 500km so vdi tram gdc, dd chinh xac ludn dat 1 - 3.5m vdi m o i v i t r i thu dupe tin hieu GPS tdt. K h i su dung ket hop 2 tram gdc (lay toa dd trung binh t u 2 toa dd tinh tur 2 tram gdc) thu duoc toa dp cd dp cd dp lec trung binh <1,5 ldn so vdi 1 tram do.
II.2. THUC NGHIEM DO DAC BO SUNG B A N DO
n.2.1 Do dac bo sung lam mdi ban do dia chinh co sd t i le 1:10000 tren dia ban 1 xa.
De tai da chon xa M u d n g Chanh huyen M a i Son tinh Son L a - mpt xa mien nui dp cao tir 800m den 1750m cd di6n tich 2924,2 ha trong dd dat lam nghiep la 1723 ha chiem 59% con lai la cac loai da't khac (da't nong nghiep, tho cu, xay dung...) lam khu thu:
nghiem. V d i su gia tang dan sd va viec thieu su quan ly chat che cho nen trong sd 1723 ha da't lam nghiep thi chi co 66ha la con rung (thupc loai rirng thd sinh da bi tac dpng) sd con lai la rung tai sinh va cay bui. K h i cd dupe ban do dia chinh co sd t i le 1:10.000 (lap bang cong nghe anh sd nam 2001) nhung de giao da't lam nghiep - giao rirng cho tdng hp, nhom hp chua sir dung dupe lieu nay. Can phai tien hanh do dac xac dinh cac goc thira k h i giao da't. Cong viec nay khong the tie'n hanh vdi cong nghe do truyen thd'ng.
- Lua chon cong nghe.
Tr6n co sd dieu kien dia ly, do khong phu song truyen tin hieu cai chinh cua cac tram Beacon va do chi phi thud tin hieu DGPS O M N I S T A R cao, de tai da chon cong nghe DGPS xit ly sau lam cong nghe chu dao trong do dac thu thap so lieu thuc dia xac dinh ranh gidi hp phuc vu cho viec giao da't - giao rung tren dia ban xa. Thiet bi do: sd dung chu yeu may thu Geoexplorer 2 - mpt loai may thu tin hieu ve tinh cam tay cua hang Trimble vdi 6 kenh thu, 256kb bp nhd trong. Phan mem x u l y so lieu chon phan mem Pathfinder Office V r 2.51 cua hang Trimble. Sau k h i ket thuc viec do dac, vide giao da't - giao rung tai thuc dia, ket qua thu dupe nhu sau:
- 18 ban co da't lam nghiep da dupe giao da't - giao rirng - Do mdi « 2000 diem do DGPS, lap mdi 649 thira, trong do:
+ Tdng dien tich toan xa: 29242492.1 m2, + Da't lam nghiep 625 thira 17230041.0 m2, + Da't nong nghiep 23 thira, 785291.1 m2, + Da't khac 11227160.0 m2.
- Da giao da't cho:
+ 289 hp gia dinh, + 15 cong dong ban, + 8 td chuc tap thd.
(Xem chi tiet trong phu luc 2, phu luc 3)
Qua cong trinh giao dat - giao rung xa M u d n g Chanh cho tha'y vdi su h6 trp cua cong nghe DGPS viec lam mdi ban do dia chinh co sd thanh lap bang cong nghe anh sd dupe tien hanh nhanh chong, thuan tien. Cong tac do dac thuc dia dupe giam nhe, nen can bp ky thuat cd dieu kien tap trung vao cac cong tac mang tinh xa hpi khac lam cho cdng tac giao da't - giao rirng tdt hon.
II.2.2 Do dac lam mdi ban do hien trang su dung dat
KY YEU XAC BE TAI NGHIEN CO) KHOA HOC - CONG NGHE NGANH TAI NGUYEN VA MOl TRUONG GIAI BOAN 2002-2006'
- Lira chon k h u thu nghiem: De tai da lua thi tran Bin Y e n Nhan huyen M y Hao tinh Hung Yen lam k h u thu nghiem v i day la khu vuc co su bien dong manh nha't ve hien trang su dung da't do cac k h u cong nghiep, khu che xuat hinh thanh tren dia ban trudc day la dia phuang ndn kinh te thuan nong; khu vuc nay nam trong vung phu tin hieu cai chinh cua tram Beacon D o Son, each tram khoang 70 k m va la khu vuc da co ban do hien trang su dung dat t i le 1:10.000 den cap xa, duoc thanh lap tir nam 2000.
- Lua chon phuong phap do DGPS: Do khu do nam trong vung phu cua tram phat tin hieu cai chinh D o Son nen cong nghe chu dao 6 day la dung phuong phap Real time DGPS ket hop vdi viec do DGPS sd lieu sau d vung khua't sdng. Thiet bi do su dung may thu Geoexplore 3 vdi bd thu tin hieu cai chinh BoB, may thu Geoexplore 2.
Tong hop ket qua do trong khu: do la 638 didm tren dien tich 398927.6m2. cac khu vuc bien dong ve sir dung da't tren dia ban T h j tran Ban Yen Nhan huyen M y Hao - Hung Yen da dupe cap nhat vao ban do hien trang sir dung da't gdc thanh lap tit nam 2000. (Xem phu luc 4 - ban dd hien trang sir dung dat).
Nhin chung, viec sir dung cong nghe DGPS cho llnh vuc nay kha dan gian do ddi tupng do bo sung khong nhieu, yeu cau khdng phuc tap. V d i muc dp bidn ddng nhu tren thi thdi gian thuc hien chi can 3 - 5 ngay cd the cho ra ket qua cudi cung.
CHUONG V: QUY TRINH CONG NGHE C/NG DUNG CONG NGHE DGPS
T R O N G D O V E B O S U N G B A N D O D I A C H I N H , B A N D O H I E N T R A N G SU" D U N G D A T
Qua phan tich cac phan tren cho tha'y trong dieu kien dia hinh rirng nui nen sir dung 3 phuong phap do DGPS chu yeu, dd la:
- Phuang phap Real time DGPS sit dung tin hieu tram Beacon mat da't, - Phuang phap Real time DGPS sir dung tin hieu O M N I S T A R .
- Phuang phap DGPS xir ly sau sir dung so lieu tram gdc Becon M S K .
Quy trinh d day cung chi de cap dd'n 3 phuong phap nay vdi cac thiet bi do tuang thich, phd bien d dieu kien Viet Nam. Quy trinh ciing chi can de cap dd'n cac thao tac vdi thiet bi do di dpng gom cac giai doan:
- Giai doan chuan b i ,
- Giai doan do dac thuc dia, - Giai doan xir ly sd lieu do, - Xua't du lieu, bien tap ban dd.
KY YEU "CAC DE TAl NGHIEN CUU KHOA HOC - CONG NGHg NGANH TAl NGUYEN VA MOI TRUONG GIAI DOAN 2002 - 2006"
Dudi day la so do quy trinh cong nghe ung dung cong nghe DGPS
Cong tac chuan bj
Lira chon cong nghe, dang ky sir dung tin hieu c.c
Thu thap tai lieu, danh gia mu'c dp bien ddng
Cai dat tham sd thu tin hieu, lap bang ma chuan
Thu so lieu thuc dia
Xu" ly sd lieu
May thu tram gdc (Base)
May thu tram ddng (Rover):
Geo 3, Geo CE ...
Md Project
Tao he thd'ng toa dp Nhap file tr. gdc, t.d gdc Nhap file do (Rover) Chon phuong an x.iy Cai chinh toa dd
Xua't du" lieu
Bien tap ban dd, xua't tai lieu
Xua't ra man hinh Tao file DXF, DGN Tao file ASCII
Nhap du" lieu vao b.d gdc Bien tap, chinh ly ban dd Tinh dien tich, lap hd so thira
K E T L U A N V A K I E N N G H I
Tren co sd co sd nghien curu ly thuye't va cac thuc nghiem trong dieu kien cu thd cua Viet Nam dd tai dua ra cac ket lu$n sau:
1. Cac phuong phap DGPS nhin chung cho dd chinh xac 1 dd'n 5 m vdi tan xua't 100% tri do thuc te.
KY YEU "CAC Qg TAI NGHIEN CUll KHOA HOC - CONG NGHg NGANH TAl NGUYEN VA MOl TRUONG GIAI BOAN 2002-2006"
2. Do chinh xac toa do didm do khong phu thuoc vao so tri do. Chi can do 2 tri do (lOgiay) la du.
3. Dp chinh xac khong phu thupc r5 ret vao khoang each trong khoang each 500km so vdi tram goc. Nhung cang xa tram goc sd didm co sai sd ldn xuat hidn vdi tin xua't ldn hon.
4. V d i phuong phap Real time DGPS dung tram Beacon tien dung khi do dac d dia hinh thoang (tren song, bidn) nhung k h i sir dung tren da't lien b i han che do vat che chan (vat kidn true, cay, doi, nui). Tam hoat ddng (cudng dp t i n hieu cai chinh) suy giam nhanh theo khoang each (khoang 7% tren 10 k m vdi may thu BoB -Beacon).
5. V d i phuong phap Real Time su dung thiet b i va t i n hieu cai chinh cua O M N I S T A R khong phu thupc vao tam hoat dong (mpi v i t r i d Viet Nam) nhung van co thdi didm khong do dupe do ma't tin hieu cai chinh hoac t i n hieu kem d i n den dp chinh xac do vao thdi diem do khong dn dinh.
6. Viec do DGPS x u ly sau phu hop vdi cac don v i nho do chi phi d l u tu tha'p, quy trinh do dac, x u ly sd lieu don gian, dam bao do dupe trong m p i thdi didm trir k h i sd lupng ve tinh <5 va gia tri PDOP vupt qua gidi han cho phep (PDOP>6).
7. Viec ket hop ca 2 phuong phap: Real time DGPS va DGPS x u ly sau la giai phap hop ly, cho hieu qua cao trong do dac bd sung lam mdi ban do ti le trung binh (1:10.000).
8. Tren co sd cac nghien cuu thu nghiem ung dung cPng nghd DGPS trong didu kien thuc tai cua Viet Nam dd tai dd nghi phuong an sit dung cong nghe nay nhu sau:
9. Nhanh chdng tao didu kien thuan l p i cho viec phd bien cac phuong phap do DGPS den cac co sd do ve ban dd.
Sit dung triet dd cac tram Beacon vdi cdng nghe Real time DGPS trong didu kien dia hinh thdng thoang.
10. Sir dung cdng nghe Real time DGPS O M N I S T A R va O M N I S T A R - H P khi didu kien kinh te cho phep.
11. Sir dung cdng nghd DGPS xir l y sau d cac dia phuong k h i khdng cd didu kidn ung dung 2 loai cdng nghe Real time neu tren. Dac biet, cdng nghe nay se la ri\ thuan tien, phat huy dupe hieu qua cua cac tram Beacon k h i chuydn f i l e do cua tram cac tram gdc nay len mdt dia chi tren mang Internet hang ngay de nhieu don v i cung sir dung.
12. Sir dung ket hop cdng nghe Real time (Beacon hoac O M N I S T A R ) vdi cdng nghe DGPS xir l y sau.
