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:[email protected] or
[email protected]
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