Tap chi KHKT Mo Bia chdt, sd30, 4/2010, tr 63 69 CHUYEN DOI DÛ LIEU TlT RASTER SANG VECTOR DOI VOI DOI TirONG VUNG TRONG QUAN TRAC VET DAU TREN B I E N LE MINH HANG, Hgc viin Ky thudt qudn su > '''' NGU[.]
Trang 1Tap chi KHKT Mo - Bia chdt, sd30, 4/2010, tr.63-69
CHUYEN DOI DU^ LIEU TlT RASTER SANG VECTOR
DOI VOI DOI TirONG VUNG TRONG QUAN TRAC VET DAU TREN B I E N
LE MINH HANG, Hgc viin Ky thudt qudn su
> ' NGUYEN DINH DU'ONG, Viin Dia ly - Viin KHCN Viet Nam
Tdm tat: Chuyin ddi dir lieu tir raster sang vector hoac vector hda la mpt tdc nghiep trong
xu ly dir lieu viin thdm Muc dich cua tdc nghiep ndy nhdm giiip cho viec tich hgp dir lieu
giira GIS vd viin thdm dugc di ddng hon ciing nhu gdp phdn hd trg cdng tdc nhdn dgng vd
phdn tich hinh dgng ddi tirgng Cdc thong tin chiit tdch tir tu lieu viin thdm thirdng Id ddi
tirgng dgng viing, vi du nhu cdc dnh phdn logi ldp phii bi mat, thuy vuc hoge ldp phu rirng
Cdc thudt todn chuyin ddi da dugc nghiin ciru nhieu, tuy nhiin viec lira chgn mpt thudt
todn hgp ly cho mpt dp dung cu thi ludn Id can thiit vi se gdp phdn tdi ini cdng tdc lap trinh
ciing nhir tdc dp xu ly Trong bdi bdo ndy, cdc tdc gid gidi thiiu viec chgn lira thudt todn
chuyin ddi tir raster sang vector dp dung vdi ddi tirgng viing trin dnh nhi phdn vd mpt so
kit qud lap trinh thir nghiem ban ddu tren ngdn ngir lap trinh Matlab 7.0 Tu lieu thirc
nghiim Id dnh vi tinh siiu cao tdn ALOS PALSAR vdi cdc vit ddu da dugc phdt hien
\ Dat van de anh ve tinh sieu cao tan sau khi xu' ly va phan
Ciing vd'i su phat trien cua cdng nghe thdng tich se tao ra anh nhj phan, tren dd cd nhieu vet
tin va ky thuat xu ly anh, nhieu thuat toan den bao gdm vet dau va nhieu [1] Viec vector
chuyen ddi du lieu raster sang du' lieu vector da
dugc nghien cuu, phat trien va dugc trien khai
trong cac bd phan mem chuyen ddi du' lieu
Nhin chung, thuat toan chuyen ddi du' lieu tir
raster sang vector dugc chia lam hai loai, dd la
vector hda ddi tugng dudng va viing Vector
hda ddi tugng dang dudng thudng dugc su
dung de sd hda anh trong cac phan mem CAD
Trong khi dd, vector hda ddi tugng dang viing
thudng dugc sir dung de tach cac ddi tugng tii'
ket qua phan loai tir anh vien tham Chgn lira
mdt thuat toan tdi uu viia don gian tii' gdc do lap
trinh, vira nhanh va it ddi hdi tai nguyen may
tinh la mdt yeu cau dat ra ddi vdi mdt bai toan
img dung cu the C» day, cac tac gia nghien ciru
chgn lira thuat toan vector hoa cho cac vet dau
iren bien sau khi dugc phan loai tii' anh ve tinh
Dac diem ciia cac vet dau la nhung vimg cd
dien tich khdng Idn thudng cd phan bd dang
tuyen va dac biet khdng cd cac dao nhd ben
trong tuc la mdt viing ddng nhat vdi mdt dudng
bao duy nhat
Trong cdng tac giam sat va phat hien sdm d
nhiem diu tren bien, viec tu ddng nhan dang va
phan loai vlt diu tren bien tir tu lieu vien tham
sieu cao tin cd tim quan trgng dac biet Tu lieu
hoa tu ddng cac vet den dd se giiip cho cdng tac nhan dang vet dau dua tren cac tinh chat hinh hgc dugc thuc hien tu ddng va sau khi chdng ghep vdi cac thdng tin bd trg trong co' sd du' lieu viec xac djnh vet den nao la vet dau se dugc thuc hien hau nhu tu ddng vdi su can thiep ciia tac nghiep vien d muc tdi thieu
2 Noi dung nghien ciru
2.1 Cdu triic dir lieu raster vd dit lieu dnh nhi phdn
DO' lieu raster dugc hieu la du' lieu anh sd
Mdt anh sd dugc bieu dien bang tap hgp cac phan tu anh dugc ggi la pixel (pixel element) [2] Mdi mdt diem anh tuong ung vdi mdt pixel
va dugc md ta bang bam sd anh vdi cac bien tga
do diem anh (x,y) va gia trj do xam ciia nd (D) nhu sau:
f(x,y,D) (1) Trong trudng hgp neu cac gia trj do xam
thanh phan va cac bien tga do mat phang ciia diem anh dugc sd hda thanh cac tin hieu rdi rac thi anh sd la mdt tap hgp cac pi.xel theo mot ma tran gia trj do xam cd n cdt va m hang [2] Cac phan til' cua ma tran anh sd la nhung diem anh rdi rac vdi tga do ciia nd dugc xac dinh bina
Trang 2mdt sd nguyen duong nam giua (l^m) cdt va
(1-n) hang, tire la:
l<x<n I<}<m (2)
Ddi vdi anh nhi phan se bao gdm mdt tap
hgp cac pixel trong dd mdi gia trj pixel se cd
mdt trong hai gia trj 0 hoac 1
2.2 Cdu trdc dit lieu vector
Md hinh dir lieu vector la tap hgp cac ddi
tugng hinh hgc so' cap va cac ddi tugng phurc
hgp dua tren td hgp tii' cac ddi tugng so cap
Diem la thanh phan so' cap ciia du lieu vector
Dudng dugc djnh nghTa bdi tap hgp cac doan
thang ndi lai vdi nhau Mdi phan tu cua doan
thing dugc djnh nghTa bdi tga do diem dau ciia
vector, hudng va do Idn hoac chieu dai Viing
dugc djnh nghTa bdi tap hgp cac vector ndi lai
vdi nhau tao thanh mdt viing kin
Dti' lieu vector dugc xay dung dua tren
quan he khdng gian (topology) Quan he topo
cua vLing dugc xa} dung dua tren quan he topo
cua ddi tugng diem va ddi tugng dudng Mdt
viing se bao gdm chi sd (ID) cua viing, tap hop
cac dudng bao dugc sap xep theo chieu nhat
djnh (tham khao hinh 1) [5]
2.3 Thuat todn chuyen ddi dir lieu tir raster
sang vector dp dung vdi ddi tugng dgng vimg
Djnh nghTa mdt ddi tugng viing trong mdt
du lieu anh sd dugc xac djnh bdi dudng bao eua
viing Dudng bao mdt vimg se dugc xac dinh
bdi vi tri diem bat dau diem ket thiic va hudng
di chu}en tren cac pixel tren dudng bao a ddi tugng viing (hinh 2) [4]
Thuat toan chuyen ddi dir lieu raster sang vector bao gdm hai qua trinh chinh sau day: (1) Xac djnh cac chain-code (hay mdi quan
he gitra cac dilm tga do tren dudng bao) (2) Chu}en ddi cac chain-code sang md ta dang vector sii' dung thuat toan xac djnh dudng thang hoac thuat toan ddng viing
Thuat toan chuyin ddi tir dir lieu raster sang du' lieu vector dang vimg su dung thuat toan tim kilm dudng bao tbi cin phai xac djnh tga do quan he topology va djnh nghTa cac pixel ^nh tren dudng bao ciia ddi tugng vimg Tga do pixel la tga do ciia tam pixel anh [3] Mdi quan
he giua cac pixel thudc dudng bao ciia doi tugng vimg tren anh nhj phan dugc md ta nhir sau:
Qua trinh tim kiem se bat dau quet tirng ddng trong anh Qua trinh tim kiem se'bd qua pixel cd gia trj 0 tuong ung vdi gia trj ciia anh nin va diing lai khi gap mdt pixel dau tien c6 gia trj 1 tuong ung vdi gia trj cua vimg quan tam diu tien Qua trinh djnh hudng djch chuyen cua pixel sau pixel dau tien dugc bat dau theo quy tac Rook"s move (tuong irng vdi 4
hudng-di chuyen cua quan tdt) hoac thuat toan Queen's move (tuang iing vdi 8 hudng - di chuyen ciia quan hau) (tham khao hinh 3) [5]
Polygon
11-Chains 1,2.5
- 2 6 - 3
4 -5 3
Hinh 1 Quan he topology cua ddi tugng viing
0
0
0
0
0
0
0
1
0 1
1
0 I
0 0
(1
I
1
1
1 '
0
(1
0
1 '
1 '
0
0
u
u
(1
0
0
0
II 1)
0
0
0
0
(1 n
1 = 1 —
0 1
1 — 1
0 1 —
0 0
(j 0
1 I)
1 — 1
1 — 1
1 0
0 0
0
0
0
0
0
0 (a) (b)
Hinh 2 Quan he giua cac dilm tren dudng bao cua viing
Trang 3a) Four Directions Rook's move)
(b) Eight Directions (Queen's move)
/ ^
v_ /
«/> (c) Flow Directions
in Queen's move (2,3,4,4,4.3,2)
Hinh 3 Thuat toan dd tim dudng bien
Thuat toan tim kiem dudng bao va xac djnh cac hudng djch chuyen cua cac pixel sau diem dau tien tren dudng bao cua vimg sii' dung 4 hudng se so sanh vdi 6 trudng hgp (hinh 4a) [5] Trong trudng hgp ciia anh nhj phan chi bao gdm hai viing cd gia tri 0 va 1 nen viec xet cac nut giua cac viing trong 8 trudng hgp (hinh 4b) la khdng can thiet Dua tren cac trudng hgp neu tren, thuat toan tim kiem se tien hanh tim kiem cac pixel thda man va djch chuyen tren dudng bao ciia ddi tugng viing (tham khao hinh 5) [5]
r t
A
B
A
B
A
A
A
A
B
B
'
A
B
B
A
A
A
t
A
A
B
A
B
C
A
A
C
A
A
B
A
B
A
C
B
A
A
C
A
A
C
B
A
B
C
A
C
A
B
A
A
B
C
D
Hinh 4 Cac trudng hgp trong qua trinh tim kiem dudng bao (a) va cac nut giua cac viing (b)
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
C
C
A
A
C
C
C
C
B
B
C
C
C
C
B
B
B
C
C
C
B
B
B
B
C
C
B
B
B
B
C
C
A
A
A
A
A
A
C
C
A
A
C
C
c
B
B
C
c
B
B
C
C
B
B
C
C
B
C
C
(a) ^ (b) Hinh 5 Kit qua tim kilm dudng bao cua viing (a) va kit qua tim kilm nut giua cac viing (b)
Trang 4Sau khi qua} tro ve diem diu tien dudng
bao cua \iing dugc ddng kin va viing dugc tim
kiem se dugc xda di bing each gan gia tri 0 cho
toan \ iing Qua trinh tim kilm dudng bao cua
cac viing khac se dugc lap lai Quan he
topolog} giu'a hai viing kl nhau se dua tren
nhirng canh chung Mdt canh se dugc dinh
nghTa bdi viing ben trai va viing ben phai Mdt
trudng hgp dac biet mdt viing Idn cd the bao
gdm nhieu viing con Trong trudng hgp nay
nhung vimg ben trong dugc ggi la cac dao
{islands hoac holes) cdn viing ben ngoai dugc
ggi viing dudng bao ngoai {contour) Mdt dao
se dugc bieu dien bdi dudng bao ciia nd nhung
se dugc phan biet vdi dudng bao ciia viing
ngoai boi hudng Dudng bao viing ngoai se cd
hudng thuan chilu kim ddng hd cdn Av g bao
cua dao se cd hudng ngugc chilu kim ddng ho [4] ,
3 Ket qua lap trinh thii nghiem
3.1 Anh phdn logi tu tu lieu dnh vi tinh sieu cao tdn ALOS PALSAR
Trong bai bao na}' cac tac gia da thir nghiem tren tu lieu anh sieu cao tan ALOS PALSAR inu'c xu ly 4.2 ciia hang ERSDAC vdi
do phan giai khdng gian la 100m che do chup ScanSAR \a phan cue HH Thdi diem chup cua anh la 8/3/2007
Dir lieu anh ALOS PALSAR se dugc xir ly qua cac bude bao gdm:
- Dgc anh va Igc nhieu bang thuat toan loc Gamma vdi kich thudc cira sd la 5x5
(^) , - (b) Hinh 6 (a) Du' lieu anh gdc; (b) Anh sau khi da Igc nhieu bang thuat toan Gamma
- Phan ngudng phat hien cac vet den tren anh sau khi Igc nhieu va luu dudi dinh dang file Tiff/GeoTiff dang anh nhj phan
Hinh 7 Phan ngudng cac vlt den
Trang 53.2 So dd thudt todn chuyin ddi die lieu raster sang vector dp dung vdi ddi tuong dgng vung tren
tu lieu dnh nhj phdn
DH lieu anh nhi phan
"
Doc tirng hang anh (i =1 - nl.ines)
"
Pi.xel ( 1 ) ^ 0
Dung
1 '
•*-Sai
Xac dinh huang cua cac Pi.xel tren duang bao
1 r
- Toa do diem tren duang bao ciia viing
- Chain-code cac diem tren duang bao ciia viing
' r
DK dong \ iing
' '
- Toa do diem tren duang bao
- Chain-code cac diem tren duong bao cua \'ung
'
' '
Ve duang bao cua doi tugng viing
' '
XcSa vung hien thoi (gan gia tri pi.xel trong \ img la 0)
Sai
'
'
^ '
Luu ducmg bao cua \ iing dugc xac dinh
'
i == nLines
' , Diing
KC't thiic qua trinh tim kiem
1 r
, 1 -
1, ju Kci qua uu J l Qinn aan e rue v ecior
Hinh 8 So dd thuat toan chuyen ddi du lieu raster sang vector vdi ddi tugng viing tren anh nhi phan
Trang 6Tren hinh 8 la so dd khdi viec chuyin ddi
dtr lieu tir raster sang vector ap dung cho mdt
viing Tren anh phan loai vlt diu chi cd hai ddi
tugng dd la nen anh vdi gia trj pixel la 0 va vlt
den vdi gia trj bang 1 Do do, thuat toan tim
kiem dudng bien chi can don gian vdi dd tim
theo bdn hudng Viec tim kiem dugc thuc hien
bat dau tir ddng anh dau tien Khi gap mdt pixel
dau tien cd gia trj bang 1, chuong trinh se bit
dau vector hoa viing do Sau khi ket thuc viing
thir nhat bang viec ddng vimg hay chuong trinh
da trd lai pixel diu tien, viec tim kiem se lai thuc hien lai tir diu anh diu tien Qua trinh vector boa dugc coi la kit thiic khi ddng anh tim kilm diu tien chinh la ddng anh cudi ciing trong anh
3.3 Kit qud thuc nghiem
Du lieu anh diu vao dugc luu d dang anh nhj phan \'di hai gia tri 0 va gia trj 1 tuong irng vdi mau trang va mau den Ket qua thuc nghiem khi thuc hien lenh chuyen ddi tir du lieu raster sang vector ap dung vdi ddi tugng vimg
%
Hinh 9 Ket qua thuc nghiem hien thj trong mdi trudng Matlab Trong chuong trinh chuyen ddi du' lieu tii' raster sang vector, tac gia cd tien hanh so sanh mdt so
dieu kien khi ap dung thuat toan chuyen ddi du' lieu tii' raster sang vector ap dung vdi ddi tugng
dang viing tren anh nhj phan Ket qua du lieu khi ap dung thuat toan su dung tim kiem theo 4 hudng
va tim kiem theo 8 hudng dugc the hien trong hinh 10 [6]
(a) , (b) ; Hinh 10 Ket qua sir dung thuat toan tim kiem theo 4 hudng (a)
Ket qua sir dung thuat toan tim kiem theo 8 hudng (b) Ngoai ra trong modul chuyen ddi cd xet den hai trudng hgp thudng xay ra khi chuyin ddi
tir du lieu dang raster sang vector, dd la trudng hgp cd dao ben trong viing xet va trudng hgp khdng
cd dao ben trong vimg xet Kit qua thuc nghiem dugc thi hien trong hinh 11 [6]
(a) (b) Hinh 11 Trudng hgp khdng xet dao ben trong vimg (a) va trudng hgp xet dao ben trong vimg (b)
Trang 74 Ket luan
Qua qua trinh nghien ciru tim hieu thuat
toan chuyen ddi tir dtr lieu raster sang dti: lieu
vector ap dung vdi ddi tugng dang viing su
dung tu lieu anh nhi phan, lap trinh modul thir
nghiem bang ngdn ngu lap trinh Matlab va cac
ket qua nghien cuu thu nghiem da dat dugc, tac
gia cd mdt sd ket luan nhu sau:
- Thuat toan tim dudng bao cua ddi tugng
dugc nghien ciru trong de tai gidi ban pham vi
ap dung vdi kich thudc anh va sd lugng ddi
tugng viing han che
- Thuat toan tim dudng bao khi su dung 8
hudng de djnh hudng cho ket qua dudng bao
min hon khi su dung 4 hudng de djnh hudng
- Khi thuc hien chuyen ddi tir dti' lieu raster
sang du' lieu vector trong nghien cuu phat hien
va phan loai vet dau tren bien dua tren tu lieu
vien tham sieu cao tan, viec xac djnh cac vj tri
dao ben trong vung dang xet la khdng can thiet
Do dd, trong qua trinh tim kiem neu xac djnh
cac viing la vimg con ciia mdt viing to thi cd the
bd qua
Trong thdi gian tiep theo, tac gia se tien
hanh nghien cuu tiep phuong phap tdi uu thuat
toan de nang cao kha nang xii' ly vdi kich thudc
anh Idn va giam thdi gian chuyen ddi du' lieu tii'
raster sang vector cung nhu trien khai lap trinh trong mdi trudng khdng phu thudc vao thu \ ien tinh toan ciia MathLab
TAI LIEU THAM KHAO
[1] Nguyen Dinh Duong, 2007 Thuyet minh de tai " 6 nhilm dau tren viing bien Viet Nam va Biln Ddng", Masd KC.09.22/06-10 Ha Ndi
[2] Truong Anh Kiet, 2000 Phuong phap do anh giai tich va do anh sd, Trudng Dai hgc Md -Dja chat Ha Ndi
[3] Junhua Teng et al, 2008 An eficient algorithm for Raster-to-Vector Data, The International Association of Chinese Professionals in Geographic Information Science (CPGIS), 54 -62
[4] ANGELA Y WU, 1989 PARALLEL PROCESSING OF REGION BOUNDARIES Pattern Recognition, Vol 22, No 2, pp 165 172, 1989
[5] JICA - Net Mutimedia Content, Remote Sensing Course and GIS course Prof Shunji Murai, Professor Emeritus of The University of Tokyo, President of Japan Society of Photogrammetry and Remotes Sensing
[6] User's Guide, Image Processing Toolbox'
6, Matlab
,TM
SUMMARY Raster to vector data conversion with polygon applied for detecting oil spills
Le Minh Hang, Mililaiy Technical Academy Nguyen Dinh Duong, Institute of Geography
Raster to vector data conversion or vectorization is a key function in geographical information systems (GIS) and remote sensing (RS) image processing for data intergration between
RS and GIS In general, there are two types of Raster to vector algorithm, namely line vectorization and polygon vectorization Polygon vectorization is often used in extracting geographical features from RS imagery classification resutls Therefore, there is a need of development of raster to vector data conversion algorithm for polygon features from imagery classification results In this paper, the authors present a algorithm of polygon vectorization applied by binary image and the result of an experiment modul in Matlab 7.0 language programme The experiment data is imagery classification of ALOS PALSAR data
Ngudi phan bien: Doan Thi Xudn Huong