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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
HNG DN SDNG PHN MM ENVI 4.3(Dnh cho cc ngnh khoa hc Tri t)
I. GII THIU PHN MM
ENVI (ENviroment
for Visualizing Images) l
mt phn mm x l t liuvin thm ca ResearchSystem Inc, M. Cc cng cca phn mm ny c khnng hin th v phn tch
nh s vi mt mi trng vgiao din thn thin vingi s dng, p ng ccthao tc thut ton v x lnh v tinh v nh my bay.
Ngi dng c th pht trin cc cng c ca phn mm ENVI vi ngn nglp trnh l IDL (Interactive Data Language).
ENVI 4.3 cn tch h p cng c hin th d liu nh s chuyn nghi p ENVIZoom 4.3:
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
II. H THNG CC TRNH N (MENU) CA ENVI
1. Menu File
2. Basic Tools
Mnh
Thng tin vnh
To nh kim traXem cu trc d liu nh
Lu nh nhiu nh dng
Lm vic vi ngn ng IDL
c cc d liu nh c lu trong cc tape
Kim tra th mc cha d liu ENVIXc lp th mc cha kt qu xut
Chn la cc thay i
Thot khi chng trnh
Thay i kch thc pixelCt nhXoay nhGhp cc knh nhChuyn i cch lu tr
Ni rng d liu
Thng kPht hin thay i
Cng co khong cch, din tchTng cng cho kh nng x l nh
To nh phn on tnh phn loi
Cc chc nng to vng muKhm
To
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
Tng cng cht lng nh
To nh t sPhn tch thnh phn chnh
Chuyn i h thng mu
Cng c gin nh
Ch s thc vtChuyn i cc nh Landsat (MSS, TM, ETM) (*)
Th vin ph
Ph cho vng ly muXoay MNF
Ch s pixel gcHin th n-chiuCc phng php lp bn
Phn tch ph
Tnh ton ph
Tng sc nt nh
3. Classification
4. Transform
5. Spectral
Phn loi gim nhPhn loi phi gim nhPhn loi theo cy quyt nh
X l sau phn loi
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
Md liu a hnh
M hnh ha a hnhc im a hnh
To nh Hill ShadeThay cc gi tr liRaster ha d liu imTo DEM tng ng mc
Hin th 3D
ng k ta nhHiu chnh trc giaoKhm
Hiu chnh hnh hc theo h quy chiu a l
Hiu chnh li chiuChuyn i li chiuTo d liu nh a knh t nhiu nh khc nhau
Tnh ton phChuyn i ta
Kt ni GPS
Md liu vector
To lp vector miTo lp bin
Danh sch d liu vector
Chuyn raster sang vector
Chuyn kt qu phn loi sang vectorRaster ha d liu imTo DEM tng ng mc
Chuyn ROI, ANN, EVF sang DXF
6. Map
7. Vector
8. Topographic
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
9. Radar
10. Window
l2. Help
Phn trgip
Nhng chc nng mi trong ENVI 4.0V ENVI
Md liu radarXc nh khu
Hiu chnh antenna
Slant-to-GroundGc ti
Lc
nh mu tng hp
Cc cng c x l nh radar
Tm kim qun l cc ca s
To ca s mi
Mca s danh sch
Cc thng tin b tr
Mln ca s hin thnhChc nng lin kt cc ca s
ng cc ca s
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
III. GIAO DIN LM VIC CA ENVI
Trong qu trnh lm vic vi d liu nh, ngi dng s lm vic trn 3 ca s:Main Image, Scroll v Zoom Window.
Ca s Main Image
Ca s Scroll Ca s Zoom
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
Trong , mi ca s s hin thnh vi gii hn khng gian v mc chi titnh khc nhau.
IV. CC THAO TC NH S CBN
1. Hin thnhTi giao din chnh ca ENVI, chn File \ Open Image File, khi ca sEnter
Data Filenames xut hin, tm v chn n tp tin nh cn hin th v clickOpen, casAvailable Bands List s xut hin nh sau:
Trong ca sAvailable Bands List, cho php hin th2 ch l Gray Scalev RGB Color. ch Gray Scale, cho php hin th mt knh nh, ch RGB cho
php hin th v t hp mu theo 3 knh nh theo 3 mu R(Red), G(Green) v B(Blue).
2. Lin kt ng v chng lp nh
ENVI cung c p cho ngi s
dng cng c lin kt cc nh (khihin th nhiu ca snh khc nhau)gip so snh trc ti p cc nh bngcch quan st nh ny chng ph lnnh kia.
* lin kt ca s nh: chn
Tools\Link\Link Displays. H p thoiLink Displays xut hin ra cho php
la chn cc ca snh cn lin kt (chn Yes/No).
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
3. ng k ta v nn chnh nh
T giao din chnh ca ENVI, chn Map\Registration\Select GCPs:
- Image to Image: Nu ly csta nn nh t mt nh s.
Hin th nh cn nn chnh v nh c s, tin hnh tm cc im khng chtng quan ti cc ca s lm vic khc nhau.
Sau khi hon tt bc chn im khng ch, tin hnh nn chnh nh. Qu trnhx l nn nh xong. Ti ca s Ground Control Points Selection chnOptions\Warp File ca sInput Warp Image m ra cho php chn nh nn.Xc nh ng dn lu nh sau khi nn.
- Image to Map: Nu ly csta nn nh t mt bn
Chn cc thng s h quy chiu ph hp vi nh cn ng k v click OK, casng k nh (Ground Control Points Selection) xut hin:
Sau khi hon tt bc chn im khng ch, tin hnh nn chnh nh. Qu trnh
nn nh xong. Ti ca s Ground Control Points Selection chn Options\Warp File
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
ca sInput Warp Image mra cho php chn nh nn. Xc nh ng dn lunh sau khi nn.
4. Tng cng kh nng hin thnh
ENVI cung c p cc cng c khhiu qu cho vic tng cng kh nnghin th cc thng tin trn nh nhEnhance tng cng v Filter - lc nh. thc hin cc chc nng ny ta lmnh sau:
T ca s nh c m, chnEnhance, mt danh sch s s ra cho ta
chn cc din tch c tng cng lca s Image, Zoom hay Scroll theo cc
phng php:
* Linear (Tuyn tnh): s dnggi tr nh nht v ln nht ca nh thc hin php gin tuyn tnh. Phng
php ny p dng ph hp cho nh c tgi tr.
* Linear 0-255 (Tuyn tnh 0-255): phng php ny s hin th cc gi trthc pixel ca nh theo gi tr hin th ca mn hnh t 0 n 255.
* Linear 2% (Tuyn tnh 2%):phng php tng cng tuyn tnh s ct bt2% ca 2 u d liu tng kh nng hin thnh.
* Gaussian: phng php ny tng cng nh s dng gi tr xm trungbnh l 127 v lch chun ca d liu l 3 tng cng.
* Equalization (Cn bng): phng php ny s ko gin cn bng th ca
d liu c hin th.
* Square Root (Cn bc hai): phng php ny s tnh cn bc hai ca thu vo sau mi thc hin gin tuyn tnh.
ENVI cn cho php tng cng nh da theo mt nh c tng cng sdng chc nng Histogram Matching hay t tng cng da trn th v theo cchm ton hc nh sn thng qua chc nng Interactive Stretching.
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
Ta cng c th tng cng, lc nh nh bng cch chn Enhance\Filtervchn cc phng php tng ng Sharpen, Smooth hay Median lm sc nt hoclm mn nh.
5. Phn loi i tng tnh s
Phn loi nh s l vic phn loi v sp xp cc pixel trn nh thnh nhngnhm khc nhau da trn mt sc im chung v gi tr xm, sng nht, mt, tone nh, C hai kiu phn loi chnh: phn loi c chn mu (c gim st -Supervised Classification) v phn loi khng chn mu (khng gim st -Unsupervised Classification).
a)Phng php phn loi khng gim st - Unsupervised ClassificationENVI cung cp hai phng php phn loi khng chn mu l Isodata v K-
Means. tin hnh phn loi nh khng gim st, t giao din chnh ca ENVI,chn Classification\Unsupervised\ v chn mt trong hai phng php phn loi trn,chn nh cn phn loi, nhn OK chp nhn. Vi 2 phng php phn loi ta u
pha a ra cc tham s gii hn my thc hin.
* Phng php phn loi Isodata:s phi la chn cc tham s sau tinhnh phn loi:
Number of classes: chn s lp ti thiu (min) v ti a (max) phnloi.
Maximum Iterations: S ln tnh ton lp li ti a. Vic phn loi sdng li khi t ti s ln lp ti a a ra.
Change Threshold: Ngng thay i sau mi ln tnh ton lp li. Vicphn loi cng s dng li khi sau mi ln tnh lp li, s phn trm binng ca cc lp nh hn ngng bin ng c xc nh.
Minimum pixel in class: s pixel nh nht c th c ca mt lp.
Maximum class Stdv: ngng lch chun ti a ca mt lp. Nu lch chun ca mt lp ln hn ngng ny th lp s b chia ra lm hai.
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
Minimum class Distance: Khong cch ti thiu gia cc gi tr trungbnh ca cc lp. Nu khong cch gia cc gi tr trung bnh ca cc lpnh hn gi tr nhp vo th cc lp sc gp vo.
Maximum Merge Pairs: s ti a cc cp lp c gp.
Maximum Stdev From Mean: Khong cch lch chun ti a t gitr trung bnh ca lp.
Maximum Distance Error:khong sai s ti a cho php xungquanh gi tr trung bnh ca lp.
Maximum Merge Pairs: s cccp lp ti a c thc gp.
* Phng php phn loi K-Means:
tng t nh phng php phn loi IsoData, tacng phi chn cc tham s tng ng trc khitin hnh phn loi. Sau khi cc tham s c la chn ph h p, ta chn ng dn lu kt qu v nhn OK tin hnh phn loi.
b) Phng php phn loi c gim st - Supervised Classification
Phn loi c gim st l phng php phn loi nh s da trn cc pixel mu
c chn sn bi ngi thc hin cng tc phn loi. Bng cch chn mu, ngiphn loi ch ra gip phn mm xc nh nhng pixel c cng mt sc trng i
tng v ph phn x - nh ngha chung mt i tng.
* Chn mu phn loi
- Hin thnh cn phn loi
- T thc n chnh, chnBasic Tools\ Region Of Interest\ROI
tooltrn mn hnh s mra hp thoiROI Tool cho php thao tc chnmu.
- Chn vo mt trong cc Image, Scroll, Zoom chn mu
phn loi trong ca snh tng nghoc chn Off tm thi tt chcnng chn mu. Chn New Region
to mu cho i tng khc.
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
- t tn lp i tng v chn mu cho mu phn loi.
Lu : Mi mt i tng c th chn nhiu vng mu phn loi.
- Lu kt qu chn mu: Trn ca s ROI Tool, chn File\Save ROIs
* Phn loi: ENVI cung cp kh nhiu thut ton phn loi c gim st, baogm: Parallelepiped, Minimum Distance, Mahalanobis Distance, MaximumLikelihood, Spectral Angle Mapper, Binary Encoding v Neural Net. Trong bit p ny s trnh by phng php phn loi theo thut ton Maximum Likelihood,y l thut ton phn loi c gim st c s dng rt nhiu.
Ti thc n chnhca ENVI, chnClassification\Supervised\
Maximum Likelihood.Chn nh cn phn loitrong ca s ClassificationInput File ri nhn OK, cas Maximum LikelihoodParameters xut hin:
- Select Classes from
Regions: chn cc b mu
phn loi (Select AllItems)
- Output Results (of Class Filename) to File/Memory: Lu kt qu phn loi
- Output Rule Images: No
- OK
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
Kt qu phn loi
6. Chuyn i kt qu phn loi sang dliu vector
Ti thc n chnh ca ENVI, chn Vector/Classification to vector.
- Chn nh phn loi cn chuyn i, OK
- Ch
n cc Class cn chuy
n
i (Select All Items)- Xc nh ng dn v lu kt qu chuyn i, OK
- Sau khi qu trnh x l chuyn i hon tt, ca sAvailble Vectors list xuthin. Chn file vector v Load Selected. File d liu vector hin th.
- Chuyn i nh dang file vector ca ENVI (*.evf) sang nh dng file caphn mm GIS (shapefile *.shp). Ti ca s hin th d liu vector, chn File\ExportActive Layer to Shapefile.
- S dng phn mm GIS hin th v bin tp kt qu bn .
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Hng dn s dng phn mm x l t liu vin thm
Nguyen Quang TuanGeoSciences Faculty, Hue College of SciencesE-mail: [email protected]
7. Mt s website download nh vin thm min ph:
http://www.landsat.org/
http://www.usgs.gov/
http://www.spot.com/
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