huongdansudungphanmemenvi

8/6/2019 huongdansudungphanmemenvi

1/14

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:


2/14



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


3/14



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


4/14



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


5/14



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


6/14



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


7/14



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).


8/14



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


9/14



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.


10/14



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.


11/14



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.


12/14



- 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


13/14



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 .


14/14



7. Mt s website download nh vin thm min ph:

http://www.landsat.org/

http://www.usgs.gov/

http://www.spot.com/

Documents

huongdansudungphanmemenvi