MOT CACH Tl£P CAN MOn TRONG VIEC GIAI QUYET
B A I T O A N B I E N T A P THU*A DAT SU* DUNG CAU TRUCD f LIEU DANH SACH CANH LIEN K £ T KEP
ThS. PHAM TH^ HUYNH Tm-ang Dai hoc Mo Dia chSt Tom tat
Hien nay, khi bien tap mai hoac chinh iy ban dd dja chinh bing cac phSn mSm chuyen dung thi mSi quan he topo cua cac thi>a dit tr§n ban do khong duxyc quan tam Iwu tru: M6i khi CO su- thay dSi v§ thCea dit nhw them dinh, bat dlnti, gdp thCea, tach thCea thi quan h$
topo giOa cac thCra bj pha vd' ddng thai mit di su- Hen kit giira thong tin khong gian va thdng tin thuoc tinh da duuc xay dung. Bai bao nay nghien cuv xay di/ng cac chuv nang bien t$p chuyen dung, dan gian ma vin duy tri dwac mSi quan he topo cOa cac thu^ dit. C^c thuat toan va giai phap du^c tac gia xay dung ia ca s& di hoan thien quy trinh thanh iap ban dd dia chinh trong giai doan hien nay a Viet Nam.
1. Ma dau
Thuat toan tao mo hinh topo da du'p'c nghi§n ciju trong bai bao (Tran Thuy Du'O'ng (2006)). Cac thuat toan tao mo hinh topo da du-pc Lrng dung trong eac mo dun phan mem nhu" Picklot, Famis, TMV-Map, AcadMap, ArcTopo ...
Mo hinh du' lieu danh sach canh lien ket kep DCEL (Doubly Connected Edge List) du'p'c trinh bay ehi tiet trong (Mark de Berg va ctv (2000)), cac mo hinh topo khae du'gc mo ta trong cac tai lieu (Michael F. Worboys (1995)) va (Peter F. Dale va John D.
McLaughlin (1988)). De the hien m6i quan he topo cua cac thi>a d i t hien nay, chuan du' lieu dia chinh (Bo Tai nguyen va Moi tru'O'ng (2010)-dleu 9) da quy djnh chuan djnh dang dij- lieu va sieu dtj lieu theo ngon ngi> djnh dang GML, XML voi ca so la mo hinh dO lieu DCEL.
Tuy nhien, voi cac phan mem bien tap ban do dja chinh a Viet Nam hien nay chi tap trung tao m6 hinh topo ma ehu'a chu trpng den viec lu-u trO m6i quan he topo cua cac vung. Chinh vi v|y, m6i khi co sy bien dong ve thong tin khong gian cua vung can Ngu&i phan bipn: ThS. Nguyen Phi Son
phai xay dicng lai mo hinh topo vCra ton thai gian, vCra mat di cac thong tin thuoc tinh cua cac vung da co. Luc nay, ngu'O'i SLP dung phai gan them cac du' lieu thuoc tinh cho cac vCing phat sinh. Viec gan them cac du' lieu thuoc tinh thycrng kho kiem scat bdi cac vung bi^n dOng co the 6" nhieu noi tren ban ve. Chinh vi vay, ngu-di su- dung thong thuo-ng gan lai toan bp co' sa du- li$u thupe tinh tren ban ve khi co bllt ky mot bien dpng nao ve vung dii chi nhiing thay doi r i t nho.
Day la mpt trong nhOng cong viec rat t6n thai gian va de nham Ian, bo sot trong cong tac npi nghi^p.
De giai quy§t van de nay, can phai xay dyng mpt he thong bien tap chuyen dung vai mpt mo hinh cau trCic dO' lieu topo phu hpp dong thoi eo cac giai phap d^ quan 1;?
CCT sa 60? lipu khi co bi^n dpng ve vung m^
van dam bao moi quan he topo giO-a c6c vung.
2. Mo ta cau true du> lieu danh s^ch canh lien k i t kep
Gom CO 3 bang: Bang danh s^ch dtnti;
bang danh sach ni>a cgnh va bSng danh sach vung. M6t cgnh g6m hai nCpa cgnh c6
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hu-dng ngu-p-c nhau va niia canh nay la ni>a cgnh dao cua ni>a canh kia.
* Bang danh sach dinh: So hi§u diem (so nguyen), tpa dp X (s6 thyc), tpa dp Y (so thyc)
* Bang danh sach nipa egnh: So hieu nu-a canh (so nguygn), so hipu dinh dau (so nguyen), s6 hi^u dinh cuoi (so nguyen), so hi$u vung ben phai cua niKa canh (so nguygn). co" bao hieu du-a no vao lich su" de lu-u trlj (16 gic), nCra canh tru'O'c (s6 nguyen), nu-a canh sau (s6 nguyen)
* Bang danh sach vung: So hieu vung (so nguyen), so hieu nOa canh Quang bao, danh sach so hieu nu-a canh cua cac vung ddo (vLing trong vung) tu'ang u'ng va co bao hipu du'a vCing vao lich si> de lu'u trO (16 gi'c).
Van de dat ra la lam the nao de khi bien tap thCfa dSt (vCtng) phai phat sinh dCJ' lieu de b^o toan c l u trCic nhu' tr§n.
3. Chpn VCing chinh su-a
Khi tach vung lien quan den 2 nCra canh Bj, Bj trong vOng vol cac diem phan tach m, n \kn \uat thupe e,, Oj. Noi cac diem m, n bling mpt du'6'ng noi (eo the la doan thang, du'6'ng cong hoac ket hgp nhieu dogn thang, du-o-ng cong) se phat sinh ra cac di^m mo-i, cac niia canh moi va cac viing mdi dup-c danh so hieu vung tang them tie t6ng so vung da co, dong tho-i du'a 2 niia cgnh Bj, e, va vung ben phai cua nu'a canh ej vSo Ijch SU" d^ tu-u tru*.
Khi gpp hai hay nhieu viing se lien quan din c^c canh chung eua eac vung, lue nay phdt sinh mOt vung moi la vung gpp cua cac vung c6 so hipu vung la so vung da co cpng th6m mpt.
Qud trinh cgp nhat ban do dia chinh voi nhi4u d<yn vj c^p nh^t khae nhau vao ban do t6ng the lu'u tri> trong he thong quan ly. Vgy cin XLP ly nhu- t h i nao de khong bi xung dpt vd c6 t h i c^p nh^t du-pc eac dif lieu da
6ufac bign tap len toan he thong.
Gia su" chung ta co mpt tap hgp cac thOa d§t lien thong du'gc lu'u trij theo cau true dO lieu Danh sach canh lien ket kep, dugc to chijc thanh ba co so du* lieu dinh Vi, canh El vd vung A^. Tap hgp cac thija ddt lien th6ng nay du'gc gpi la Ket ciiu dja chinh.
De bien tap ta can chpn mpt tap hgp cac thij-a dat lien th6ng thuoc Ket cau dja chinh du'a vao c h i dp chinh sCpa va gpi la Vung chinh sOa. Du'O'ng bao cua Vung chinh sCra c§n dugc xac djnh tCr danh sach s6 hieu thCpa da chon. Du'O'ng bao nay co vai tro quan trpng trong viec danh d i u cac thila dat kh6ng du'gc chpn giap vo'i Vung chinh st)a.
DLP lieu cua cac thu-a dat nay va VOng chinh st>a bi cam chinh sija cho tai khi Vung chinh sua du'gc chinh su'a xong va tra ve Ket cau dja chinh de tranh bi xung dot trong qua trinh cap nhat bien dong.
Cac nCra canh thupe du'O'ng bao Vung chinh SUB CO mpt tinh chat quan trpng la vung thuoc tinh cac nu'a canh dao cua Chung se khong nam trong danh sach so hieu thCca dat noi tren.
4. Bien tap thCra dat 4.1. Tach thi>a
Ta ky hieu eae dinh la v kem ehi so, vi du nhu' V|; cac nu'a canh co ki hieu la e, vi dy nhu' ej, cac vung ki hieu la a, vi du nhu" a^.
Mpt thCra d i t a| se bao gom mpt danh sach cac nu'a canh co thupe tfnh viing la a,. Cac nCpa canh dao cua cac nOa canh nay se c6 eac thupe tinh viing la cac vung giap voi a,.
Khi chinh sCra thCpa dat bang cac phep dyng hinh se phat sinh cac dinh va cac nCra canh mai ben trong. ThCra dit nay se du'gc chia nho thanh cac thCra dat mai nim bgn trong. Cac thCra dat mo-i se lat kin thua dat nay.
Truac tien ta xet viec chia thi>a dat lam
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hai bang mot flu'crng chia. Du'O'ng ehia thCra hoa viec phan tieh ma l<hong m i t tinh tong nay co the co eac dau mut hoac la nam tren quat.
canh hoac la flinh cua thCta flat du'g'c chia. j^^l j^^j j ( ^,1^^, g-^^^ (,^,ia (-„ go, (JQ, lieu 4 . 1 1 Hal diu mut duung chia diu nim diem se dttac bo sung. Trong tm'ong hop tren canh ihCra nay hai diem ehia v,, V2 se du'gc thSm vao
Gia sCr t h t o a^ bj chia thanh hai thCra moi " ^ ^" "" '!«" "i*"™' bang mpt du'O'ng chia co hai dau mut nam
trgn nu'a canh e, va e^. Hinh 1 mo ta cac cac canh (Oj, e'j), (ej, e'j) va eac viing a^, a2, ag tru'oc khi viing 82 bi chia. Khi do e, va Cj co cung thupe tinh viing la 32 con cac nu'a canh dao e'j va e'j se co cac thuoc tinh viing tu'ang ifng la a^ va a^- (Xem hinh 1)
Tao viina a^^:
- xuit phat til' nCi-a canh chia e^ co diim dau la Vi, diem cuoi la V2, xac djnh ej2 co goc la diem cu6i V2 r6i tim nOa canh tiep theo cua ej2. Tim nipa canh t i l p theo cho d i n khi nCpa canh tiep theo la e^ co (Sim eu6i la Vi
- cap nhat thuoc tinh cho tat ca nu'a canh tren viing thanh a^
Hinh 1: Cac canh thCea dat tru^c khi chia Tai 2 diem chia tren 2 nu'a canh e,, ej, 2 nua canh e,, Oj va vung a2 se du'gc lu'u thanh lich su', d6ng tho'i phat sinh them eae nCra canh e^i, e,i, 6,2, ej2. Cac nipa canh dao e'j, e', cung dugc xir ly tu-ong ty [Hinh 2).
Se phat sinh cac nua canh e^, e\ va cac viing 84, 85. Cac thuoc tinh cua 0,1, 6,2 se l l y theo thupe eua niia canh e,; cac thuoc tfnh cua e'ii, e'j2 lay theo thuoc tinh cua nija cgnh dao e',; tu'ang ty, cac thuoc tinh ciia e,i, e,2 lay theo ntpa canh e^; con eac thuoc tinh cua e',i, e'j2 l l y theo nira canh e'j. Lue nay ca sa dii' lieu se du'gc luu trti' vo'i cac dinh, cac nu'a canh moi, dong tho'i phat sinh them cac viing lien quan. Viec xet du'O'ng chia bing mot canh (Q^^ e'^ lam dan gian
Hinh 2: Thu'a dit du^c chia b^ng dieang chia eif vai diim diu v^ nim tren canh e, va diim cu6i V2 nim tren canh e^
Tao vung a^.
- Lam tu'ang t y nhu- tren cho nu'a cgnh dao e\
4.1.2. Hai diu mut cOa du^ng chia la dinh thCfa. (Xem hinh 3)
N l u dau mut cua du-ang chia la dinh se cac nu'a canh mai va dinh mo'i du'gc tao ra chi nam tren du'O'ng chia e^. Gia sCr dyo'ng chia xuat phat tai dinh v^ la diem goc cua nipa canh e,+^ va la diem cuoi eua nCpa cgnh e,; du'O'ng chia e^ eo diem cuoi tai dinh V2 Id
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^111
diem g6c cOa ni>a canh ej+i vd Id diem cu6i cua nCpa cgnh &
33, 34 thanh thCra d i t ag. Cac nira canh net diit se bi loai bo do vung thuoc tinh cac nipa canh dao cua no ndm trong danh sach so hieu thipa dat b| gpp, ngu'gc lai cac nipa canh net liln hinh thdnh du'ang bao thija d i t mo'i ag. (Xem hinh 4)
Hinh 3: Hai dau mOt dutfng chia ia dinh thu'a Qud trinh tao eac viing a^ vd ag du-gc tien hdnh tu'ang ty nhu' mo ta 6' myc 4.1.1, vai vai tr6 eiia e-, gilng nhu e^•^, e, giong nhu ej2
; 61+1 giong nhu e|2, Oj+i gilng nhu Oj^
4.1.3. M0t diu mOt nim tr§n canh, mot diu mOt id dinh thCea
Doi v6'i tru'6'ng hgp ndy khi dau mut ciia dub'ng ehia nam tren egnh ta su* dyng each chia dugc m6 ta 6' 4.1.1, con doi vo'i dau milt CLia du'b'ng chia Id dinh thua ta su dung cdch ehia dugc m6 ta a 4.1.2.
4.2. Ggp thi>a
Thao tdc gpp thu-a trong Viing chinh sira cin phdi xdc djnh duang bao cua thipa dat gpp. Duyet theo cdc nua canh cua tipng thira d i t dugc chpn, n l u viing thuoc tfnh cdc nua cgnh dao eua no khong ndm trong danh sdeh s6 hipu thipa d i t bi gpp thi nipa cgnh ndy thuOc duo-ng bao thipa dat mo'i, thuOc tinh viing cua nua canh nay se dugc c^p nh$t; c6n neu nguge lai thi logi ca hai nipa cgnh ndy vd dua chung vao Ijch SLP IUU trO.
Trong hinh 4, Id vi dy gpp 3 thipa dat 82,
Hinh 4: Gap thij^
4.3. Them bat dinh
Truo'ng hgp tong quat khi canh (gom hai nupa canh e|^, e'l, dao nhau) dugc thay the bang mot duo-ng da tuyen co cilng chung diem dau va diem cuoi hoac ngugc lai. Ta nhgn thay cac canh ciia duo-ng da tuyen co thuoc tfnh giong vo'i (e^, e\), do do ta chi can sao chep thuoc tinh cua canh {e^, e\) cho tLPng canh eua da tuyen hoac ngugc lai va bo sung hoac loai bo cac diem, cac nipa c^nh can thiet.
5. Trpn VCing chinh sira vao Ket cau dja chinh
Sau khi chinh stpa chi cac yeu to phat sinh mai dugc cap nhgt vao cac ca sa dH lieu dinh V i , nipa canh Ei va viing Ai tuang Lpng.
Liie nay Vung chinh su'a se xoa bo c h i dp cam ehpn d l chinh sua va Vung chinh SLra da dugc trpn vao K i t c l u dja chinh.
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6. Ket luan
Bang each cap nhat mo hinh dO lieu DCEL nhy trinh bay a tren, viec bien tap thOa d i t trong Vung chinh sua co the dyge thyc hien de dang ma khong lam pha vg mo hinh cau true dy lieu topo.O
l A l LI6U THAM K H A O
[1], Tran Thuy Dyong (2006), "Mot giai phap xCr ly tru-ong hgp bien trong bai toan tao Topology", Tap chi KHKT Md-Dia chit, tap (14), trang 88-91.
[2]. Mark de Berg, Marc van Kreveld, Mark Overmars, Otfried Schwarzkopt, (2000), Computational Geometry, Algorithms and Applications, Springer-
Verlag, Berlin.
[3]. Christine Leslie and Chris Buscagiia (2008), Cadastral Editor Tutorial, ESRI, 380 New Yori< Street, Redlands, CA 92373- 8100, USA.
[4]. Bo Tai nguyen va Moi trycrng (2010), Thong Ivt sa 17/2010/TT-BTNMT - Quy djnh ky thuat v8 chuan dir lieu dja ehinh
[5]. Michael F. Worboys (1995), GIS : A Computing Perspective, Taylor & Francis, London.
[6]. Peter F. Dale and John D.
McLaughlin (1988), Land Information Management, Clarendon Press, Oxford.O
Summary
New method of parcel editing using data structure of doubly connected edges list MSc. Pham The Huynh
Hanoi University of Mining and Geology
When editting or modifying cadastral maps by special application nowadays, the main- tenance of topology wasn't be interested in. Each time having a change of parcel proper- ties, for example adding and deleting of parcel point, parcel merging or splitting then the topology is broken and the eonneetion bettwen spatial and attribute data is also lost. This article researchs to build the simple special editting functions but keeping this topology. The algorithms and solution introduced by author are basic of improving of cadastral mapping in Vietnam.O
Ngay nhan bai: 13/S/2014.
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