Tong Hop Bai Giang

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bai giang trac dia

Text of Tong Hop Bai Giang

  • TRC A

    (GEODESY)

    GV: o Hu S

    Khoa Xy dng

    daohuusi@hcmuarc.edu.vn

  • TRC A

    (GEODESY)

    GV: o Hu S

    Khoa Xy dng

    daohuusi@hcmuarc.edu.vn

    xb11arch@googlegroups.com

    Huy 0909559196

  • NI DUNG CC CHNG MC:

    Chng 1. Tri t v cch biu th mt t Chng 2. Sai s trong o c Chng 3. Dng c v cc phng php o trong trc a

    Chng 4. Li khng ch trc a Chng 5. o v s dng bn a hnh Chng 6. B tr cng trnh Chng 7. Quan trc cng trnh

    Kim tra, bi tp

    Thi cui k

  • TI LIU THAM KHO:

    Trc a i cng Tc gi: Nguyn Tn Lc- NXB: i hc Quc gia Tp.HCM

    Trc a xy dng thc hnh Tc gi: V Thng NXB: Xy dng.

    TCXDVN 309 2004 Cng tc trc a trong xy dng Yu cu chung

    K hiu bn a hnh ca Tng cc a chnh (Nay l B Ti nguyn v Mi Trng),

    Internet

  • Trc a (Geodesy) l mt ngnh khoa hc chuyn

    nghin cu v hnh dng, kch thc v b mt t nhin ca

    Tri t.

    Bn (Map) l hnh nh thu nh ca b mt tri t

    c biu din ln mt phng theo mt quy lut ton hc

    nht nh.

    1. KHI NIM

  • Trc a: - Thut ng trc a hm phn chia t ai

    - Ngnh khoa hc trc a c t lu i, n sinh ra do nhu

    cu ca i sng x hi loi ngi: nh vic i li, qun

    l t ai, giao thng bun bn, thm him, qun s... - Trong qu trnh pht trin, Trc a c phn ra

    lm nhiu phn ngnh chuyn mn hp nh: + Trc a cao cp + Trc a nh + Trc a cng trnh + Bn hc . . .

    2. LCH S PHT TRIN

  • Trc a, bn c vai tr quan trng trong cc ngnh

    kinh t quc dn nh:

    Nng - lm nghip,

    Giao thng vn ti, thy li,

    Quy hoch - Xy dng,

    Quc phng (bn l con mt ca qun i)

    Trc a cn thit trong tt c cc giai on: quy hoch,

    kho st, thit k, thi cng, nghim thu qun l v s dng

    cng trnh.

    3. VAI TR

  • Ngy nay nh cng ngh pht trin m trc a

    pht trin ln tm cao mi:

    - Cng ngh nh vin thm, cho php con ngi c

    th xc nh nhng v tr, thnh lp bn nhng khu

    vc nguy him hoc khu vc khng th tip cn

    - Cng ngh nh v ton cu GPS (NAVigation

    System with Time And Ranging Global Positioning

    System) vic xc nh v tr nhanh chng v cho kt qu

    vi chnh xc cao

  • LCH S GPS:

    n c hnh thnh vo u thp nin 60

    V tinh u tin c phng vo qu o nm 1973

    c B Quc phng M vn hnh v khai thc.

    Hin ti c tng cng 30 v tinh ang hot ng

  • CU TRC GPS:

  • S lng v tinh GPS quan st c

  • GV: o Hu S

    Khoa Xy dng

    Chng 1:

    TRI T V CCH BIU TH

    MT T

  • NI DUNG CHNG 1

    Hnh dng - kch thc tri t v cch biu th

    mt t

    Cc h ta - cao

    Khi nim v bn

    Phn mnh v nh s hiu bn

  • 1.1 HNH DNG V KCH THC

    TRI T 1.1.1 Hnh dng

    B mt tri t c din tch S 510,2 triu km2. Trong

    : i dng chim 71%

    Lc a chim 29%

    L mt g gh, li lm; ch cao nht +8882m (nh

    Hymalaya), ch thp nht -11032m (h Marian Thi

    Bnh Dng, gn Philippines)

    u th k 20 (Listinger c), a ra khi nim

    mt Geoid v dng mt ny biu th b mt tri t

    Mt Geoid : l mt nc bin trung bnh yn tnh, ko

    di xuyn sut qua cc lc a hi o to thnh mt mt

    cong khp kn (Mt Geoid cn c gi l mt thy

    chun lc a, hay mt nc gc tri t)

  • Hnh nh tri t chp t v tinh

  • Mt Geoid c dng lm mt quy chiu ca h thng

    cao

    Mt Geoid c c tnh:

    + Mt Geoid khng phi l mt ton hc

    + Ti mi im trn mt Geoid u vung gc vi

    phng ca ng dy di ti im .

  • 1.1.2 Kch thc.

    Do mt Geoid khng phi l mt ton hc, nn khi

    tnh ton - biu din kch thc Tri t chng ta phi

    dng b mt khc gn trng vi Geoid v phi l mt

    ton hc, l mt Ellipsoid tri t (Gi tt l

    Ellipsoid), cn tho mn:

    - Tm Ellipsoid trng vi tm Geoid

    - Mt phng xch o Ellipsoid trng vi mt phng

    xch o Geoid

    - Th tch Ellipsoid tri t = th tch Geoid

    - Tng bnh phng chnh cao t mt Ellipsoid ti

    mt Geoid l nh nht ([h2] =min)

  • c im ca Ellipsoid:

    - Ellipsoid l mt mt biu din c bng phng

    trnh ton hc v hu ht mi tnh ton Trc a thc

    hin trn mt ny (gi l Mt quy chiu)

    - Ti mi im, b mt Ellipsoid lun vung gc vi

    phng php tuyn.

  • c trng cho Ellipsoid

    + Bn trc ln (bn knh ln): a

    + Bn trc nh (bn knh nh): b

    + dt a

    ba

    2 2 2

    2 2 2

    Ph.trnh:

    1.X Y Z

    a a b

    Geoid

    Ellipsoid

    O

    b a

  • Tc gi

    (Ellipsoid)

    Quc

    gia

    Nm Bn trc ln a (m)

    Bn trc nh b (m)

    dt

    Delambre Php 1800 6.375.653 6.356.564 1:334,0

    Everest Anh 1830 6.377.276 6.356.075 1:300,8

    Bessel c 1841 6.377.397 6.356.079 1:299,2

    Clark Anh 1980 6.378.249 6.356.515 1:293,5

    Krasovski Nga 1940 6.378.388 6.356.863 1:298,3

    WGS84 M 1984 6.378.137 6.356.752,3 1:298,257

    Mt s Ellipsoid tri t

  • 1.2.1 Khi nim

    Trong trc a,

    tin cho vic thit k

    k thut, ngi ta

    tm cch biu din b

    mt tri t ln mt

    phng. Phng php

    ny cho php chng

    ta thu nh b mt tri

    t vi chnh xc

    cn thit.

    1.2 CCH BIU TH MT T

  • V b mt tri t l b mt t nhin v cng phc

    tp, v vy biu din ln mt phng ta phi chiu b

    mt tri t ln mt Ellipsoid hoc mt cu ri thu nh

    mt cu tri t theo t l mong mun. Bng php chiu

    xuyn tm ngi ta tip tc chiu hnh cu tri t ln

    mt tr, mt nn, theo cc phng php khc nhau.

    Sau ct mt tr, mt nn, theo mt ng sinh c

    chn trc v tri ra mt phng.

    Phng php chiu ny lm cho b mt qu t b

    bin dng. S bin dng ph thuc vo im chiu v cc

    im trn mt t cng nh phng php chiu.

  • 1.2.2 nh v cc im trn mt t

    V tr khng gian cc im trn mt t c xc nh

    bng 2 yu t:

    1. To a l (, ) hoc to vung gc phng (x, y) trn mt quy chiu Ellipsoid

    2. cao ca im so vi mt Geoid

    xc nh v tr cc im A,B,C trong khng gian ta

    chiu chng xung mt Geoid theo phng dy di ta

    c cc im a, b, c.

  • Trong trng hp biu din b mt tri t trong mt

    phm vi khng ln, vi yu cu chnh xc khng cao

    chng ta coi b mt tri t c chiu trc tip ln mt

    phng

    B

    A

    C

    c

    b

    a

    P

  • 1.3 H TO A L Trong ton hc cng nh trong trc a, xc nh to

    ca mt im, chng ta cn xc nh quan h gia im

    vi mt h trc c chn lm gc.

    P

    P1

    O M

    M

    Q Q1

  • xc nh to a l ca mt im trn b mt

    tri t, Gi s phng php tuyn trng vi phng dy

    di v mt Geoid trng vi mt Ellipsoid trn xoay ca

    tri t.

    Cc yu t c chn lm gc trong h to a l

    nh sau:

    - Tm O ca tri t c chn lm gc to

    - Hai mt phng gc l mt phng kinh tuyn gc v mt

    phng xch o

    T hnh v:

    - P, P1: l cc Bc v cc Nam ca tri t

    - PP1: trc xoay ca tri t

    - Q, Q1: l cc Ty v cc ng ca tri t

    - G (Greenwich): V tr i thin vn Greenwich ngoi

    Lun n

  • hiu r h to a l, chng ta c mt s khi

    nim sau:

    - Mt phng kinh tuyn l mt phng i qua trc xoay PP1

    ca tri t

    - Mt phng v tuyn l mt phng vung gc vi trc xoay

    PP1

    - ng kinh tuyn l giao tuyn ca mt phng kinh tuyn

    vi mt cu tri t

    - ng v tuyn l giao tuyn ca mt phng v tuyn vi

    mt cu tri t

    - Mt phng kinh tuyn gc l mt phng kinh tuyn i qua

    G (Mt phng kinh tuyn gc chia tri t ra lm hai na

    ng bn cu v Nam bn cu)

    - Mt phng xch o l mt phng v tuyn i qua tm O

    ca tri t

  • To a l ca im M(M ,M)

    M (v ): l gc hp bi mt phng xch o v ng

    dy di qua M

    M (kinh ): l gc hp bi mt phng kinh tuyn gc v

    mt phng kinh tuyn i qua im M

    Trn xch o =0, trn kinh tuyn gc =0

    Thng quy c:

    M t xch o ln gi l v Bc (00 900)

    M t xch o xung gi l gi l v Nam (00 900)

    M t kinh tuyn gc G sang ng gi l kinh ng (00

    1800)

    M t kinh tuyn gc G sang Ty gi l kinh Ty (00

    1800)

  • 1.4 H TO VUNG GC KHNG GIAN

    OXYZ (H T. A TM)

  • H ta vung gc khng gian: l h thng gm

    im gc to v 3 trc to X, Y, Z xc nh

    trong khng gian Euclide 3 chiu: h quy chiu ny

    c s dng trong o c v tinh v nhng bi ton

    trc a ton cu.

  • 1.5 H TO VUNG GC PHNG Trong trc a h to vung gc phng ngc vi h

    to vung gc cc; trc X theo phng ng, trc

    Y theo phng ngang

    Qua nhiu thi k khc nhau th c nhng h to cng

    khc nhau (ngay c Vit nam cng nh th gii)

    y

    x

    O

  • th hin mt khu vc trn b mt tri t ln mt

    phng ngi ta phi s dng cc php bn . Thng qua

    cc php chiu bn nh ngha cc h ta vung gc trc a

    Cc li chiu bn thng dng:

    - Hnh tr ngang,

    - Hnh tr ng,

    - Hnh nn,

    - Phng v,

  • 1.5.1 Php chiu Gauss, H to vung gc phng

    Gauss Kruger

    Php chiu ny s dng Ellipsoid Krasovski vi cc

    thng s

    a= 6.378.245 m , b= 6.356.863 m, = 1/298,3

    Php chiu Gauss l php chiu hnh tr ngang ng gc.

    Trong php chiu ny tri t c chia thnh 60 mi

    chiu 60 v c nh s tng ng t 1 60 bt u t

    kinh tuyn gc Greenwich (00) sang ng vng qua Ty

    ri tr v knh tuyn gc.

  • Mi mi chiu c gii hn bi kinh tuyn ty - bn

    tri v kinh tuyn ng - bn phi (2 kinh tuyn bin). V

    kinh tuyn gia ca mi chiu c gi l kinh tuyn

    trc, i xng vi 2 kinh tuyn bin.

    T=60(n-1), G=6

    0.n-30, P=60 .n

    Vi n l s th t ca mi chiu

  • GP'

    O

    P

    Sau khi chia ra tng mi chiu v xc nh kinh tuyn

    trc ca mi mi chng ta cho qu cu tri t tip