H THNG THNG TIN A L (GIS)

(Ch3 Cu trc d liu GIS)Phan Trng TinDepartment of Software Engineering Hanoi University of Agriculture Office location: 3rd floor, Administrative building Office phone: (04)38276346, Ext: 132 Website: http://fita.hua.edu.vn/pttien Email:ptgtien@hua.edu.vn or phantien84@gmail.com

Mc tiuGii thiu cc m hnh d liu trong GIS

Sau bi hc ny sinh vin c th: M t m hnh d liu Vector v cho v d M t m hnh d liu Raster v cho v d M t m hnh d liu TIN Gii thch topology M t cc nh dng chnh s dng trong GIS

Cc i tng ha Cc i tng hin th trn bn

c gi l cc i tng hahay cc i tng.

Cc i tng c th l t nhinhoc do con ngi to ra n.

Cc i tng ha Vectors Points or Nodes Lines or Arcs Polygons Images Digital Orthophotography

Raster Cells or Pixels

Cc loi d liu GIS Images Vector Raster (GRID) Attributes TIN (Triangulated Irregular Network) Annotation

Paul Bolstad, GIS Fundamentals

Cc loi d liu GIS

Paul Bolstad, GIS Fundamentals

D liu khng gian RASTER

VECTOR

Th gii thcSource: Defense Mapping School National Imagery and Mapping Agency

Cc bn in t hai nh dng Raster v Vector

Cc ngun d liu Rasternh my bay

nh v tinh Cc bn qut

nh s trc giao (Digital Orthophotography) Mt nh c qut, dng cc cng c ton hc sa, b i, dch chuyn c cc hiu qu mong mun l cc i tng lun hin th vung gc vi mt t. nh trc giao cho ta nh ging nh thc trng ca tri t.Image Copyright 1993 Nassau County, NY

Cc bn dng Raster (images) Thit lp bi mu sc ca cc pixel Cch n gin mt mng cc pixel c xp theo cc hng v cc ct Cc Pixel l c t mu, nhng khng miu t cc i tng mt cch r rng Rasters c th c gi tr i km.

Source: Defense Mapping School National Imagery and Mapping Agency

c im ca Raster Trng ging trang bn giy Gi thnh r v d sn xut Chy d dng trn PC

C sn mi ni. Nhc im: Mc tnh ton c hoc khng theo h ta WGS84 Khng cho php t ng loi b ch nn hay s tr gip phn tch ca my tnh. Lu tr khng hiu quSource: Defense Mapping School National Imagery and Mapping Agency

D liu dng VectorMt cch lu tr thng minh d liu GIS, cc i tng th gii thc c miu t bng cc im (Point), ng (Line) v vng (Polyline). Mt i tng c miu t bi cc thuc tnh v cc ta . V d: Cc bn s ha D liu GIS

Source: Defense Mapping School National Imagery and Mapping Agency

Lin kt cc thuc tnh v ha Trong GIS cha thng tin. GIS kt hp bn vi h qun tr c s d liu. V vy khi phn tch d liu khng gian ch cn click trn i tng a l v tm thng tin v n. Hoc c th tryu vn trong database tm thng tin v tt cc cc i tng tha mn iu kin lc. Thng tin v mt i tng GIS c gi l thuc tnh (attribute)

Lin kt cc thuc tnh vi ha Trong v d ny, ngi dng truy vn chn ra tt c cc thuc tnh m c phn loi cc gia nh = 210, v cc vng tm thy c mu

D liu Vector c phn lp1

5Lake

4 6

2

7

Features: Line Points: Connected Detached Area Text

Spatial Data Analysis

30 30 N 040 40 E

30 30 N 040 50 E

D liu GIS t ring bit trn cc theme Network AnalysisSource: Defense Mapping School National Imagery and Mapping Agency

S thay i v m hnhC th nhn thy s khc nhau gia bn giy v bn s (ph thuc vo phn mm) Database cho php truy vn v chn cc layer Phng to cc chi tit Phc tp, t tin v tn nhiu thi gian lm ra sn phmSource: Defense Mapping School National Imagery and Mapping Agency

Cc m hnh d liu Raster v Vector

Real World1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 G B G G B B BG G B G G B G BK B G B B B B600 500 400 Y-AXIS 300 200 River 100 100 200 300 400 500 X-AXIS 600 Trees

Trees House

Miu t Raster

Miu t VectorSource: Defense Mapping School National Imagery and Mapping Agency

M hnh d liu VectorD liu GIS c lu tr trong cc lp ring bit nh Point, Line, Polygon

Paul Bolstad, GIS Fundamentals

Cu trc d liu Vector C mi quan h gia cc kiu d liu vector. Mi kiu thng c lp trn mt kiu khc nhau. Khi miu t d liu GIS theo nh dng vector, d liu phi c lu tr: Points: l cc i tng v hng c v tr khng gian, miu t cc i tng GIS nh v tr, hoc cy Lines: miu t i tng mt chiu, c v tr, c chiu di nh ng, sng. Lines c to bi vic kt ni cc im vi nhau. Mt ng bt u v kt thc ti mt im gi l nt (node), v cc im to nn ng gi l nh (Vertices). Polygons/Area: miu t i tng hai chiu, c v tr, c chiu di, v c c chiu rng nh ng danh gii ca cnh ng, t ai, hoc h N c to bi vic kt ni cc ng, im bt u ca polygon cng l im kt thc

Point

Line

Polygon

Points Point l i tng v hng c v tr v thuc tnh thng tin nhng qu nh c biu din bng vng. T l bn quyt nh mt i tng l im hay khng.

ng dng kiu im Cc mu t Kiu PH Cht gy i nhim (Contaminants)

V tr cc ct n Cc v tr xy ra tai nn Cc trung tm Khi/on a ch Ch s hu

Cc ct n

Cc trung tm

Lines or Arcs Lines l cc i tng mt chiu, c v tr, c chiu di nhng khng c vng nh ng, sng. Lines c to bi vic kt ni cc im vi nhau. Mt ng bt u v kt thc ti mt im gi l nt (node), v cc im to nn ng gi l nh (Vertices).

ng dng Lines or Arcs ng ph Street Name Address Ranges

Sng sui Depth Quality Flow Rate

H thng nc Pipe size Pipe Material Date Installed

ng ph

PolygonsPolygons l itng hai chiu, c v tr, c chiu di, v c c chiu rng (hay c din tch)

ng dng Polygons Cc mnh t Parcel ID Number Dimensions and Area

ng danh gii Type Permeability

Vng l lt

Polygons

Polygons

M hnh d liu VectorKiu V tr

im ng

3,2 1,5; 3,5; 5,7; 8,8; 11,7

Vng 11,3;

5,3; 6,5; 7,4; 9,5; 8,2; 5,3

im: c th hin bng mt cp to ng: c th hin bng mt chui cc cp to Vng: c th hin bng mt chui cc cp to v cp to u v cp to cui trng nhau.

Cu trc d liu VectorKiu V tr

im ng

3,2 1,5; 3,5; 5,7; 8,8; 11,7

Vng 11,3;

5,3; 6,5; 7,4; 9,5; 8,2; 5,3

im: c th hin bng mt cp to ng: c th hin bng mt chui cc cp to Vng: c th hin bng mt chui cc cp to v cp to u v cp to cui trng nhau.

S th hin d liu dng VectorMi im c th hin bng 1 cp ta

Mi ng th hin bng 1 chui cc cp ta

Mi vng c th hin bng 1 chui cc cp ta , c cp ta u v cp ta cui trng nhau.

M HNH VECTOR D liu dng Vector c t chc 2 m hnh: M hnh Spagheti M hnh quan h khng gian Topology

M hnh d liu Vector Spaghetti

L m hnh d liu n gin, cc i tng ch c lu tr bng cc cp to . Thng tin v quan h khng gian. Thng tin thuc tnh.

M hnh d liu Vector Spaghetti Khng m t c mi quan h khng gian gia cc i tng, v th cc php phn tch, tnh ton khng gian u thc hin kh khn. D liu dng vng, ng ranh gii gia 2 vng c ghi nhn 2 ln, mi ln cho mt vng. u im ca m hnh l n gin, d trnh by, bin tp, in n...v vy vn c s dng rng ri thnh lp bn . Phn mm in hnh l Mapinfo.

M hnh d liu Vector Topology L mt m hnh phc tp, cc i tng c qun l khng ch bi to m cn bng c mi quan h khng gian gia cc i tng. M t trn vn cc thng tin ca cc i tng khng gian bao gm:

Thng tin v v tr khng gian (Spatial data): Thng tin c th hin theo m hnh vector, bng cc ta m t v tr, hnh dng, ng bin ca cc i tng. Thng tin v quan h khng gian (Relational Spatial data Topology). M hnh d liu Topology th hin QHKG di 3 kiu quan h l: Lin thng vi nhau: th hin di dng file ng im ni (Arc-Node topology) K nhau: th hin di dng file m t ng bao (Polygon-Arc topology) Nm trong nhau, ph nhau.

M hnh d liu Vector Topology

- Thng tin v v tr trong khng gian + D liu khng gian cc i tng vng l mt tp cc i tng ng nh ngha ng bao vng v mt im nhn. + im nhn nm trong i tng vng c ngha xc nh cho vng ny.

M hnh d liu Vector Topology-Thng tin v quan h khng gian + D liu khng gian cc i tng vng l mt tp cc i tng ng nh ngha ng bao vng v mt im nhn. + M hnh Topology dng cc quan h khng gian nh ngha cc c tnh khng gian ca cc i tng

Cc quan h khng gianMi mt ng (arc) c im bt u v kt thc ti im nt (node).Cc ng (arc) ni vi nhau ti cc im nt (node).

Cc c tnh khng gian di ca ng. Hng ng (Directionality).Tnh lin tc (Connectivity)

Cc ng (arc) ni vi nhau to thnh ng bao ca vng (polygon).Cc ng tham gia nh ngha vng c hai bn : phi v tri.

Tnh to vng (Din tch vng, chu vi vng)Tnh k nhau (Adjacency or contiguity)

M hnh d liu Vector Topology

u, cui giao ca ng

Tnh lin tc

Tnh k nhau

Tnh to vng

M hnh d liu Vector Topologyp dng m hnh topology khi xy dng CSDL khng gian - ng ranh gii to thnh ng bao tha t lun m bo tnh khp kn tuyt i v to .

Sai

Sai

ng

- Cc ng ranh gii tha khng c php giao nhau, phi lun ct nhau ti u hoc cui ng ( ti im nt NODE).

Sai

ng

D LIU KHNG GIAN CHUNC s d liu chun l d liu khng cn li nh: bt qu, bt cha ti, vng cha khp.

Sai

ng

Lin kt d liu thuc tnh

Bng d liu (Attributes) ESRI

D liu thuc tnhL thng tin cho php miu t mt thc th c trnh by i tng ha.

D liu thuc tnhThng tin v i tng ha Mi phn thng tin thuc tnh lin quan ti mt phn i tng ha Cc trng thuc kiu d liu truyn thng ca CSDL Images Photos Video

Lin kt cc thuc tnh

Courtesy Village of Garden City

M hnh d liu Raster D liu GIS c lu tr di dng

li cc (cells) hay pixelnh vin thm, nh qut (scanner) lun dng Raster

D liu Raster Tp d liu GIS V s dng t/ bao ph t Cc Ch s thc vt S n nh t

nh s nh v cc ta nh Khung cnh cc tai ha S thit hi ma v Cc hnh nh v s vn ng

nh trc giao Cc nh trn khng c chnh sa

D liu Raster L mt mng hai chiu cc (pixel). Mi c chiu cao v chiu rng c nh v cng kch thc, tri trn mt hnh ch nht.

Bng d liu thuc tnh

Rasters c gi tr s nguyn cc nh (s lng cc cng gi tr) c ghi trong bng d liu thuc tnh. Mi bn ghi thuc tnh l duy nht vi mi gi tr ca . Bn c th thm cc trng ti bng d liu

Cc kiu d liu miu t trong D liu c lu tr trong raster c th c phn loi mt trong cc loi sau: D liu tn (Nominal data): d liu c phn loi theo tn. D liu s th t (Ordinal data): d liu c phn loi theo tn v khong gi tr. Khong d liu (Interval data): sp xp theo th t s v c cc khong khc nhau c ngha. D liu t l (Ratio data)

Cc kiu d liu miu t trong

Cc kiu d liu miu t trong Kiu Nominal v Ordinal dng miu t theo cc phn loi khc nhau, l cch tt nht miu t cc d liu kiu integer. Kiu Interval v Ratio m t cc gi tr lin tip, dng vi cc d liu l kiu real.

PIXEL (PICTURE ELEMENT)PIXEL l n v nh nht trong nh. C s h thng GIS l raster, thng tin thuc tnh c th c khi gn ti mi pixel.

ESRI, Modeling Our World

Cch biu din Raster Raster c th c mt hoc nhiu nhn. Gi tr ca mi c th mang cc gi tr khc nhau. C mt vi cch hin th raster vi gi tr ca . Hin th nhn n (single-band) Hin th nhn bi (multi-band)

Hin th nhn n

Hin th nhn bi

Cu trc d liu Raster Ma trn cc bng nhau

Vn v phn gii

WHEAT APPLES

WHEAT APPLES

HAY

HAY

Raster v Vector Phi c cn nhc k Tnh ri rc ca thc th ang m t ng dng mong i (Cc chc nng) Ngun d liu Quan tm s lu tr phn gii Mu sc

Mt cu hi t ra: nh dng no l tt nht m t cc i tng trong GIS, raster hay vector. Cu tr li l mt trong hai hoc c hai. l, dng mt trong hai m hnh d liu l tt nht Shoreline trong mi trng hp hoc c hai m hnh u thc hin cc vai tr nht nh trong GIS. Trong v d, ngun d liu vector miu Water t ng b bin xut hin c nhiu chi tit hn, v chnh xc ln hn. D Land liu Vector c th lu tr thng tin trong nhiu nh dang hn d liu Raster, v cng lm vic tt vi i tng thuc v chiu di nh lung cc mng. Tuy nhin, cc m hnh d liu Raster rt tt miu t thng tin lin tc trong Vector Shoreline t nhin nh nhit ni m gi tr Source: Defense Mapping School nhit c th khc vi ni lin k.National Imagery and Mapping Agency

M hnh Raster v Vector

Vector Nhng u im v nhc im Thun li Miu t tt thc t Gn kt nhiu cu trc d liu Topology c th c m t trong mng ha chnh xc

Nhc im Cu trc d liu phc tp M phng kh khn Mt vi phn tch khng gian l kh khn hoc khng th thi hnh.

Raster u im v nhc im u im Cu trc d liu n gin D ph ln nhau C nhiu kiu phn tch khng gian khc nhau Khng thay i kch thc v hnh dng Cng ngh r Nhc im S lng ln d liu Khng p Thay i h quy chiu l kh khn T l khc nhau gia cc lp c th l cn c mng C th mt thng tin nhng vng giao nhau

Cc chc nng Raster

Paul Bolstad, GIS Fundamentals

Cc phng php nn d liu Raster Mc ch: Gim kch thc lu tr. C cc phng php: Phng php (Chain Code) Phng php length code) Phng php Phng php code) nn theo ng bin vng

nn theo hng ct (Runnn theo khi (Block code) nn cy t phn (Quadtree

Phng php nn theo ng bin vng (Chain Code)0 3 1 2

Cc ng bin ca cc vng c th hin bng hng lin tc cc vect n v theo hng 4 phng, c qui c bng cc s: hng ng = 0, Bc = 1 Ty = 2 Nam = 3. V d trn nu ta bt u t cell ca hng 0 theo chiu kim ng h ta s c dy gi tr sau th hin bin ca vng theo m 1: 02,3,0,1 ,03,32,2,34,02,32,23,1,22,1,22,12,02,32,22,12

Phng php nn theo ng bin vng (Chain Code) u im: L phng php nn d liu raster hiu qu. D dng tin hnh tnh chu vi v din tch, nhn bit li lm, thay i hng t ngt.

Nhc im: Kh khn trong phn tch chng xp. D tha d liu v ng bin lu tr hai ln.

Phng php nn theo hng ct (Run-length code) Cc im trn mi nv bn c lu tr theo hng t tri qua phi t cell u n cell cui. Hng Hng 1: Hng 2: Hng 3: Hng 4: Hng 5 : Hng 6: Hng 7: Hng 8: Ct 2,3 2,7 4, 6 4, 6 2, 6 2, 6 4, 8 6, 8

5,7

Phng php nn theo hng ct (Run-length code) u im: Thch hp cho vic lu tr d liu trong my tnh c b nh t.

Nhc im: Kh khn trong qu trnh x l v phn tch d liu.

Phng php nn theo khi (Block code) V d trn c th vit di dng nn block code 2n x 2n nh sau: 7 block 1 n v vung 7 block 4 n v vung

Phng php ny c hiu qu vi cc vng c din tch ln vhnh dng cc ng bin n gin, c th kim tra s co gin v hnh dng ca vng.

Phng php nn cy t phn (Quadtree code)

Phng php nn cy t phn (Quadtree code)Th hin s chia lin tc ca dng ma trn 2n x 2n thnh dng cy 4 nhnh u im ca phng php nn hnh cy: - D tnh ton din tch chu vi ca cc vng c hnh dng chun - C th giam bt s lu tr vi cc phn gii khc nhau Nhc im : - Kh khn cho vic chn cc m hnh, gii php - Mt vng c th chia thnh rt nhiu phn gy kh khn cho vic truy nhp DL

TIN(Triangulated Irregular Network) TIN l mt m hnh d liu c s dng miu t cc i tng ba chiu. Cc im miu t bi cc gi tr x,y,z. Dng cc phng thc tnh ton hnh hc, cc im c kt ni vo nhau gi l php c tam gic. Cc ng ca cc tam gic gi l cc cng v min pha trong gi l b mt (facet)

TIN(Triangulated Irregular Network) M hnh TIN c mt vi im phc tp hn dng Point, Line, Polygon trong m hnh Vector, hay m hnh Raster, n thc s hu ch miu t cao. V d th hin li ch ca TIN:

Li Raster c th th hin ton b b mt ca min a l. Nu chng ta mun hin th chi tit th ta phi chia li ny thnh cc nh hn -> nhng vi mt b mt tng i bng phng -> tn b nh Vi TIN chng ta khng phi dng nhiu im trn min bng phng, nhng cng c th thm nhiu im vng dc ni chng ta mun hin th nhiu chi tit hn.

Cu trc d liu TIN Cu trc d liu TIN da trn hai phn t c bn: Cc im vi gi tr x,y,z Cc cung ni cc im ny.

Php c tam gic TIN tha mn theo tiu chun Delaunay

Tiu chun DelaunayVng trn ngoi tip khng cha mt nt ca bt k phn t no khc. Vng trn ngoi tip ca mt tam gic l vng trn i qua cc nh.

Cc thnh phn TIN TIN l mt tp hp cc tam gic lin k, khng b chng nhau. ArcGIS h tr c hai m hnh cao: TIN and lattice (li).

Nodes Edges Triangles Hull Topology

Cc thnh phn TIN Nodes: l c s xy dng cc khi ca TIN. Cc nt bt u t cc im v cc nh cung cha t cc ngun d liu nhp vo. Edges: Mi nt c ni vi nt gn nht theo tiu chun Delaunay. Mi cung c hai nt nhng mt nt c th c hai hoc nhiu cung. Triangles: Mi b mt tam gic miu t mt phn ca b mt TIN Hull (bao): c hnh thnh bi mt hoc nhiu polygon bao gm ton b tp d liu cc im s dng xy dng nn TIN. Cc Polygon Hull nh ngha vng ni suy ca TIN Topology: l cu trc hnh hc ca TIN nh ngha mi quan h gia cc nt, cc cung v mi quan h gia cc tam gic lin k.

Trong ARC/INFO, TIN c lu tr trong mt th mc gm cc file. Tuy nhin, TIN khng bao cha v khng kt hp vi file thng tin (INFO). Th mc TIN cha 7 file bao gm thng tin v b mt TIN. Cc file ny c m ha theo dng nh phn v khng c c ch hin th vn bn.

ESRI, Modeling Our World

ESRI, Modeling Our World

Ch gii (Annotation)L vn bn (text) hoc nhn (labels)

v trn bn m miu t hoc nhn din mt i tng hoc thm thng tin khc ti bn

Ch gii (Annotation) Text Thng tin c t trn bn cung cp thm thng tin v mt i tng ha.

K hiu (Symbols) L cch thc m cc i tng ha hin th trong GIS

K hiu (Symbols)Cc k hiu gip nhn din cc c im v cung cp thng tin v chng.

qc,PX

Annotation, Symbology, and Text

Courtesy Village of Garden City

Vn v t l trong i tng m t Ph thuc vo t l m t, mt i tng c th nhn nhiu mu khc nhau Buildings V cng trnh cng cng building outline USGS Quad Sheet point location City USGS Quad Sheet Polygon of city boundary Rand McNally Map Point representing city location

TopologyTp hp d liu s miu t r rng cc i tng lin k, cha trong nhau v tnh lin tc gia cc i tng bn m c th lu tr v thao tc trn my tnh.

Topology

Paul Bolstad, GIS Fundamentals