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TRNG I HC CN TH

KHOA NNG NGHIP V SINH HC NG DNG

B MN KHOA HC T V QUN L T AI

TRN VN TNH

ti:

NGHIN CU NG DNG NH VIN THM

WORLD VIEW 1 GII ON HIN TRNG RNG

KHU VC VN QUC GIA

U MINH H - C MAU

LUN VN TT NGHIP

NGNH QUN L T AI

CN TH, 04/2008

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TRNG I HC CN TH



LUN VN TT NGHIP ti:


WORLD VIEW 1 GII ON HIN TRNG RNG

KHU VC VN QUC GIA

U MINH H - C MAU

Gio vin hng dn: Sinh vin thc hin:

Ts. V QUANG MINH TRN VN TNH

Ths. HUNH TH THU H NG MSSV: 4043901

LP: QL K30A

KHA 30 (2004 2008)

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TRNG I HC CN TH



------------------NHN XT CA CQUAN THC TP

Chng nhn ca B mn Khoa Hc t v Qun L t ai

Chng nhn bo co lun vn tt nghip vi ti:


WORLD VIEW 1 GII ON HIN TRNG RNGKHU VC VN QUC GIA

U MINH H - C MAU

Do sinh vin Trn Vn Tnh, l p Qun L t ai K30A khoa Nng

Nghi p V Sinh Hc ng Dng trng i Hc Cn Th thc hin t ngy

01/01/2008 n ngy 15/04/2008 ti b mn Khoa Hc t v Qun L t ai

khoa Nng Nghip V Sinh Hc ng Dng trng i Hc Cn Th.

Nhn xt: .......................................................................................................

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Cn Th, ngy ...thng 05 nm 2008

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TRNG I HC CN TH



------------------NHN XT CA CN B HNG DN

Chng nhn chp thun bo co lun vn tt nghip

ngnh Qun L t ai vi ti:



U MINH H - C MAU

Do sinh vin Trn Vn Tnh, l p Qun L t ai K30A khoa Nng

Nghi p V Sinh Hc ng Dng trng i Hc Cn Th thc hin t ngy

01/01/2008 n ngy 15/04/2008 ti b mn Khoa Hc t v Qun L t ai

khoa Nng Nghip V Sinh Hc ng Dng trng i Hc Cn Th.

Nhn xt ca cn b hng dn:...................................................................

.......................................................................................................................

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Knh trnh hi ng chm lun vn tt nghip thng qua.


Cn b hng dn

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TRNG I HC CN TH



------------------NHN XT CA HI NG BO CO

Hi ng chm lun vn tt nghip chp thun bo co vi ti:



U MINH H - C MAU

Do sinh vin Trn Vn Tnh thc hin v bo co trc hi ng.

Ngy.thng 05 nm 2008

Bo co lun vn tt nghip c Hi ng nh gi mc:......................

kin Hi ng:...........................................................................................

.......................................................................................................................

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Ch tch Hi ng

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LCH SC NHN

--------------

H v tn: Trn Vn Tnh.Ngy sinh: 12/09/1981.

Ni sinh: Long Bnh Long M - Hu Giang.

H tn cha: Trn Vn Trung.

H tn m: Nguyn Th Cn.

Tt nghi p ph thng trung hc vo thng 6/2001 ti trng Ph thng

trung hc huyn Long M - tnh Hu Giang.

T thng 02/2002 n thng 01/2004 nhp ng ti n v Tiu on BB6,

Trung on BB20, Son 330, Qun khu IX.

Vo trng i Hc Cn Ththng 9/2004, hc ngnh Qun L t ai.

Tt nghip k s chuyn ngnh Qun L t ai nm 2008.

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LI CM T

--------------

Qua thi gian 4 nm hc tp v rn luyn ti trng i Hc Cn Th,

trong khong thi gian 4 thng (t 01/2008 04/2008) ca hc k II nm hc2007 2008 em tin hnh nghin cu ti lun vn tt nghip. c s gip

v hng dn tn tnh ca thy c hng dn n nay lun vn tt nghip ca

em cng hon thnh. t c kt qu nh ngy hm nay, tt c l nhvo

cng n ca qu thy c ca trng i Hc Cn Th. c bit l qu thy c

thuc khoa Nng Nghip V Sinh Hc ng Dng, tn tnh truyn t nhng

kin thc qu bo trong sut bn nm hc di my trng i Hc. y l

nhng vn sng v cng quan trng, l hnh trang tri thc gip em vng bc

trong qu trnh cng tc v sau.

Em xin chn thnh gi li cm n n:

Qu thy c thuc B mn Khoa Hc t v Qun L t ai, trng

i Hc Cn Th, nhng ngi trc tip ging dy v hng dn em trong

sut thi gian hc tp v rn luyn ti trng.

Em xin chn thnh by t lng bit n su sc n thy V Quang Minh,

thy Trn Vn Hng, c Hunh Th Thu Hng tn tnh ch bo em trong sut

thi gian em thc hin ti cng nh thi gian hc tp ti trng.

Cc c ch, anh ch thuc ban qun l d n Vn quc gia U Minh H,

STi Nguyn Mi Trng Tnh C Mau cung cp cho em nhiu ti liu qu

bo gip cho em hon thnh lun vn ny.

Con xin cm n Ba, M chu nhiu vt v to iu kin tt nht cho

con hc tp v t c kt qu nh ngy hm nay.Cm n tt c cc bn lp Qun L t ai K30 ng vin gip ti

trong qu trnh hc tp v thc hin lun vn.

Trn Vn Tnh

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DANH SCH BNG

Trang

Bng 3.1. Ta cc im khng ch trn nh c nn ............................................... 36

Bng 3.2. Bng m tc im cc i tng sau khi phn loi khng kim tra ..........40

Bng 3.3. S lng cc im kho st ............................................................................ 44

Bng 3.4. Bng th hin ta cc im kho st v hin trng rng ........................... 45

Bng 3.5. Bng cha kha gii on mt si tng trn nh vin thm ..................... 46

Bng 3.6. Bng th hin kt qu gii on khng kim tra v kt qu kim tra thc a 48

Bng 3.7. Cc thng s ca cc nhm kim tra (ROI) cho tng i tng gii on ....50

Bng 3.8. Bng th hin kt qu kho st thc a v kt qu gii on bng phng

php phn loi c kim tra .............................................................................................. ..61

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DANH SCH HNH

Trang

Hnh 1.1. S phn xi vi nc...................................................................................... 3

Hnh 1.2. S phn xi vi t ........................................................................................ 4

Hnh 1.3. S phn xi vi thc vt ................................................................................ 5

Hnh 1.4. V tinh vin thm c phn gii siu cao World View 1 .............................. 18

Hnh 1.5. Biu tng phn mm ENVI ............................................................................ 20

Hnh 1.6. Thanh menu chnh ca phn mm ENVI ......................................................... 22

Hnh 1.7. Danh sch cc knh phang lm vic (Available Bands List) ...................... 22

Hnh 1.8. Cc ca s hin th d liu nh trong ENVI .................................................... 23

Hnh 2.1. Lu cc bc gii on nh vin thm ........................................................ 26

Hnh 3.1. nh v tinh World View 1 khu vc U Minh h ............................................... 33

Hnh 3.2. nh khu vc vn quc gia U Minh h c che ...................................... 34

Hnh 3.3. nh vn quc gia U Minh h (cha nn) ....................................................... 34

Hnh 3.4. Bn khu vc U Minh h c s ho ..................................................... 34

Hnh 3.5. V tr cc im tng ng c chn. ......................................................... 35

Hnh 3.6. nh khu vc vn quc gia U Minh h trc khi nn .................................... 36

Hnh 3.7. nh khu vc vn quc gia U Minh h sau khi nn......................................... 36

Hnh 3.8. nh v biu Histogram trc khi bin i tng phn .......................... 37

Hnh 3.9. nh v biu Histogram sau khi bin i tng phn ............................. 37

Hnh 3.10. nh khu vc vn quc gia U Minh h sau khi lc ...................................... 39

Hnh 3.11. S thay i gi tr sng ca pixel trung tm............................................... 39

Hnh 3.12. Biu Histogram th hin s phn b cc i tng trn nh .................... 41

Hnh 3.13. Bn hin trng vn quc gia U Minh h - C Mau (Kt qu phn loi

khng kim tra) ................................................................................................................. 42

Hnh 3.14. nh 3D khu vc vn quc gia U Minh h - C Mau ................................... 43

Hnh 3.15. V tr cc im kho st c chn trn nh ............................................. 44

Hnh 3.16. Bn hin trng vn quc gia U Minh h th hin ta cc im kho

st (Phn loi khng kim tra) .......................................................................................... 47

Hnh 3.17. Kt qu chn nhm kim tra (ROI) ................................................................ 49

Hnh 3.18. S lng pixel c chn cho tng nhm kim tra ....................................... 50Hnh 3.19. S lng pixel c chn ca tng i tng ................................................ 50

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Hnh 3.20. S phn b gi tr cc pixel ca cc nhm kim tra ....................................... 51

Hnh 3.21. Thng k s phn b cc gi tr pixel ca cc nhm kim tra i din cho

i tng lau sy .............................................................................................................. 52

Hnh 3.22. Bn hin trng rng vn quc gia U Minh h - C Mau ........................ 53

Hnh 3.23. i tng c gii on l dn, choi ......................................................... 54

Hnh 3.24. i tng c gii on l lau, sy .............................................................. 54

Hnh 3.25. i tng c gii on l rng t 2 tui n di 3 tui .......................... 55

Hnh 3.26. i tng c gii on l rng t 3 tui trln ........................................ 55

Hnh 3.27. i tng c gii on l rng tha ngp nc ........................................ 56

Hnh 3.28. i tng c gii on l t trng ngp nc .......................................... 56

Hnh 3.29. Biu Histogram th hin s phn b cc i tng .................................. 57

Hnh 3.30. Biu th hin din tch ca cc i tng c gii on ......................... 58

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MC LC

Trang

DANH SCH BNG.......................................................................................................

DANH SCH HNH........................................................................................................

TM LC .....................................................................................................................

MU ..........................................................................................................................

CHNG I: LC KHO TI LIU.........................................................................1

1.1. GII THIU V VIN THM..............................................................................1

1.1.1. nh ngha v vin thm.......................................................................................1

1.1.2. H thng vin thm ..............................................................................................1

1.1.3. S ghi nhn ca cc s vt ln nh vin thm......................................................1

1.1.4. Chp nh t v tinh ..............................................................................................2

1.1.4.1. Thnh phn........................................................................................................2

1.1.4.2. Cc kiu chp nh .............................................................................................2

1.1.4.3. Cc thng skthut ca mt v tinh...............................................................2

1.1.4.4. Sphn x ca cc svt theo di sng......................................................3

1.1.5. Tng quan v vin thm .......................................................................................5

1.1.6.u im ca cng ngh vin thm.......................................................................71.1.7.ng dng ca vin thm.......................................................................................8

1.1.7.1. ng dng trn thgii ......................................................................................8

1.1.7.2. ng dng cng ngh vin thm gim st ti nguyn thin nhin v mi

trngVit Nam..........................................................................................................9

1.1.8. X l nh vin thm ...........................................................................................12

1.1.8.1. Gii on nh bng mt ..................................................................................12

1.1.8.2. Xl nh kthut s.......................................................................................13

1.2. GII THIU V H THNG THNG TIN A L (GIS)...............................15

1.2.1. nh ngha ..........................................................................................................15

1.2.2. Xu hng pht trin ca GIS..............................................................................16

1.2.3. ng dng H thng tin a l v Vin thm trong qun l mi trng v ti

nguyn Vit Nam.......................................................................................................17

1.3. GII THIU V V TINH WORLD VIEW ......................................................181.4. GII THIU PHN MM ENVI ........................................................................20

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CHNG 2: PHNG TIN PHNG PHP ....................................................25

2.1. PHNG TIN ....................................................................................................25

2.2. PHNG PHP...................................................................................................25

2.2.1. Thu thp d liu .................................................................................................25

2.2.2. Cc bc x l nh, bn ................................................................................25

2.2.3. Vit bo co .......................................................................................................26

CHNG 3: KT QU THO LUN .....................................................................27

3.1. GII THIU KHI QUT KHU VC VN QUC GIA U MINH H .......27

3.1.1. iu kin t nhin .............................................................................................27

3.1.1.1. V tra l, din tch tnhin........................................................................ 27

3.1.1.2. Ti nguyn thc vt v ng vt......................................................................29

3.1.1.3. Vti nguyn thu sn.....................................................................................29

3.1.1.4. Vcc gi tr sinh thi, nhn vn ...................................................................29

3.1.2. c im kinh t x hi .....................................................................................31

3.2. KT QU THC HIN CC BC XY DNG BN HIN TRNG.33

3.2.1. Chn nh ............................................................................................................33

3.2.2. Nn nh ..............................................................................................................34

3.2.3. Tng cng cht lng nh ...............................................................................363.2.4. Phn loi khng kim tra................................................................................... 39

3.2.5. Kim tra, kho st thc a ................................................................................43

3.2.6. Thnh lp bng cha kho gii on ..................................................................46

3.2.7. Phn loi c kim tra .........................................................................................47

3.2.8. nh gi cht lng nh v kh nng ng dng ca nh ..................................59

CHNG 4: KT LUT - KIN NGH ...................................................................62

4.1. Kt lun................................................................................................................. 62

4.2. Kin ngh ..............................................................................................................63

TI LIU THAM KHO............................................................................................64

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TM LC

Rng l ti nguyn v cng qu gi, l l phi xanh ca mi vng mi quc gia

v n th hin nhng c trng v mi trng sinh thi ca khu vc . V vy n cn

phi c bo v v khai thc mt cch hp l mi trng sng ca chng ta lun

c trong sch. c bit l khu vc rng trm trn t than bn Vn quc gia U

Minh h - C Mau c thnh lp trn csnng cp rng c dng V Di, rng vi

gi tr rt cao va dng sinh hc, cnh quan thin nhin, mi trng, vn ha v lch

s.

p ng c yu cu ngy cng cao ca con ngi nhiu cng ngh vi k

thut cao ra i t bit l cng ngh vin thm. Cng ngh vin thm c ng

dng trong nhiu lnh vc c bit trong thnh lp bn hin trng phc v qun l

theo di ti nguyn thin nhin nht l ti nguyn rng.

Vi ti Nghin cu ng dng nh vin thm World View 1 gii on

hin trng rng khu vc vn quc gia U Minh h - C Mau s dng nh vin

thm c chp t v tinh World View 1, cng ngh x l nh l phn mm ENVI 3.6

cng cc phn mm chuyn dng khc xy dng c bn hin trng khu vc

Vn quc gia U Minh h. Kt qu cho thy Vn quc gia U Minh h gm 3 cp

tui: Rng tha ngp 1 tui, rng trng t 2 di 3 tui, rng trng v rng t nhint 3 tui trln.

Vi kt qu ny cho thy kh nng ng dng nh vin thm World View 1

gii on v thnh lp bn hin trng l rt tt v chnh xc cao. Qua n s

gip cho vic qun l ti nguyn rng c cht ch v hp l.

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MU

nc ta hin nay, khoa hc cng nghang l nn tng v ng lc thc y

mnh m qu trnh cng nghip ha, hin i ha t nc. Trong khoa hc cng

ngh vin thm c nhim v nghin cu qun l ti nguyn thin nhin nh ti nguyn

t, nc, khong sn, rng v gim st mi trng, nhm gp phn quan trng vo s

nghip pht trin t nc mt cch bn vng.

Trong thi gian qua, cc ng dng cng ngh vin thm nc ta thu c

mt s kt qung k song cha nhiu, ch yu tp trung vo vic hiu chnh bn

a hnh, lp mt s bn chuyn , v mt s t lnh vc mi trng.

Ngy nay vi k thut vin thm ngy cng hin i hn gp phn to ln

trong vic thu thp, phn tch cc thng tin v pht hin s hin din cng nh s thay

i ca mi trng v ti nguyn thin nhin trn Tri t phc v cho nhiu mc

ch khc nhau. Ngnh vin thm pht trin gp mt vai tr ht sc quan trng, l

mt cng c phc v v h trc lc cho nhiu ngnh, nhiu lnh vc khc nhau.

Rng l mt trong nhng i tng cn c qun l mt cch cht ch. Vi

yu cu , chng ta cn phi bit c hin trng rng ca c khu vc qun l bao

gm: Cc i tng pht trin, tnh trng pht trin, tui ca tng i tng,.... V

vy, chng ta cn phi c nh ca khu vc qun l, vi cng ngh vin thm s gipcho chng ta c c nh ny.

nh vin thm c chp bi nhiu v tinh nh: V tinh Spot, Radasat, World

View 1v c ng dng trong nhiu lnh vc khc nhau. Cng ngh x l nh

c la chn l phn mm ENVI (The Enviroment for Visualizing Images) c

nhiu nh khoa hc nh gi l mt phn mm x l nh vin thm c nhiu tnh nng

u vit trong x l nh, v ENVI h trcho php x l nhng d liu khng phi l d

liu chun, hin th v phn tch nhng nh ln. N cng cho php mrng kh nng

phn tch d liu bi cc hm ca ngi dng.

Vi yu cu , ti: Nghin cu ng dng nh vin thm World View 1

gii on hin trng rng khu vc vn quc gia U Minh H - C Mau c

thc hin.

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CHNG 1

LC KHO TI LIU

1.1. GII THIU V VIN THM

1.1.1. nh ngha v vin thm

Theo V Quang Minh (1999), vin thm (Remote sensing) c nh ngha l

s thu thp v phn tch thng tin v cc i tng, s thu thp v phn tch ny c

thc hin t mt khong cch khng gian khng c s tip xc trc tip n cc vt

th.

Theo Thomos M.Lillesand v Ralph W.Kiefer (1996), vin thm l khoa hc v

cng ngh thu thp thng tin v mt vt th, mt vng hay mt hin tng thng qua

s phn tch ca d liu c c bi mt thit b m khng tip xc trc tip vi vt

th, vng hay hin tng nghin cu.

Theo L Nguyn (1999), k thut vin thm (m chng ta quen gi l vin

thm) l k thut nghin cu cc i tng mt cch gin tip thng qua m hnh ca

chng c chp hoc ghi t xa nht nh trong v tr, dng hnh nt ha hoc

dng s.

Theo Nguyn Xun Anh (2004), vin thm l mn khoa hc v ngh thut thu

nhn thng tin v cc vt, vng hay hin tng no qua vic x l s liu s dngthit b quan st t xa. t lu trong thin vn hc ngi ta dng knh thin vn, h

thng rada quan st cc hnh tinh trong h mt tri.

Phng php vin thm l phng php s dng bc xin t (nh x nhit,

sng cc ngn) nh mt phng tin iu tra v o c c tnh ca i tng.

My bay v v tinh l nhng vt mang ch yu cho quan trc trong vin thm,

(V Quang Minh, 1999).

1.1.2. H thng vin thm

Theo V Quang Minh (1996), c hai h thng vin thm l:

- H thng vin thm thng: l h thng ghi li nng lng c bc x t

nhin hay phn x t mt si tng.

- H thng vin thm chng: l h thng cung cp nng lng ring cho n

v chiu trc tip vo i tng nhm o c phn nng lng trv.

1.1.3. Sghi nhn ca cc svt ln nh vin thmTheo V Quang Minh (1996), s ghi nhn ca cc s vt ln nh vin thm l

1

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nh mu gi c cc c im sau:

- Nc trong t m cho mu xanh dng n en.

- t kh th mu xanh dng nht n trng.

- Thc vt mu xanh cho mu sng.

- Thc vt su bnh tn cng th cho mu hi hng, hi nu hay hi vng, ty

theo loi su bnh tn cng.

- Cc cy c ht chn vng th cho mu xanh l cy m pha ln vi mu vng

v trng.

1.1.4. Chp nh tv tinh

1.1.4.1. Thnh phn

M hnh chung ca vic chp nh t v tinh gm cc b phn sau:

- V tinh chp nh.

- V tinh nh v ton cu.

- V tinh chuyn tip.

- Trm thu.

1.1.4.2. Cc kiu chp nh

Theo V Quang Minh (1999), c hai kiu h thng chp nh v tinh l h

thng nh dng khung v h thng chp nh dng qut. H thng chp nh dng qutc 4 kiu bao gm: qut ngang, qut dc, qut vng v qut bn.

1.1.4.3. Cc thng skthut ca mt v tinh

Theo M. Lillesand v Ralph W. Kiefer (1994), mt v tinh thng thng c cc

thng s sau:

- Tn s hot ng.

- cao ca v tinh.

- S quo trong mt ngy.

- Thi gian hot ng.

- Ti liu lu v tinh.

- Cc h thng chp nh.

- Gc nhn.

- phn gii trn mt t.

- S detector trn mt band.

2

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1.1.4.4. Sphn x ca cc svt theo di sng

Theo L Quang Tr v ctv (1999), ty theo mi s vt m chng c s phn x

thay i nh sau:

- Sphn xi vi nc

Nc trong s hp thu mt s nng lng ln bc x trong khong nh sng

nhn thy c v s hp thu hon ton cc bc sng thuc ph hng ngoi. Nc

c c mang ph sa th c s phn x kh hn nc trong trong khong nh sng thy

c. Trong cc trng hp c bit, mt nc phng phn x t nh sng mt tri ln

my nh th s to mt nh sng (hot spot) trn nh.

Hnh 1.1. S phn xi vi nc

- Sphn xi vi t

Nhn tnh hng ln s phn xi vi t l m, cu trc t (c tnh

ct, tht v st), g gh, oxit st v cht hu c. Chng hn nhm trong t s

lm gim cng phn x, m ca t lm cho cu trc t th, t ct thot nc

tt, m trong t thp nn cng phn x cao. Trong trng hp khng c nc,

t c khuynh hng thay i cu trc t kh s c mu sm hn cu trc t mn,hai nhn t lm gim phn x ca t l b mt g gh v cha vt liu hu c, s

c mt ca oxit st trong t cng lm gim cng phn x trong bc sng nhn

thy, (Cole and Montgomery, 1987).

S phn x ca t da vo cc yu t sau y:

Tnh trng m ca b mt tri t. Thnh phn khong trong t. Hm lng hu ctrong t. phng ca b mt tri t.

3

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Hnh 1.2. S phn xi vi t

Thng thng th t m hp thu nh sng nhiu hn c bit l bc x hng

ngoi, t c cha thnh phn st nhiu cng h p thu mnh, t c cha nhiu

carbonare calcium hay nhiu ct th phn x mnh vi c nh sng nhn thy c v

nh sng hng ngoi. Mt t g gh to ra nhiu bng rm s lm gim s phn x

ca bc x nh sng thy c, t c nhiu cht hu c c sa cu mn s hp thu

nhiu nh sng, ngc li t c sa cu mn nhng khng c cht hu cth s pht x

nhiu hn.

- Sphn xi vi thc vt

Theo L Quang Tr v ctv (1999), thc vt xanh s h p thu mnh trong cc

band mu xanh l cy v mu nh sng thy c. S phn x chnh l qu

trnh quang tng hp ca dip lc t, qu trnh ny cng mnh th s hp thu nh sng

mt tri cng mnh. Do s phn x s km hn nhng n phn x rt mnh trongbc sng t 0.7 - 1.35m. Qu trnhphn x nydo cc khong trng ca cc t bo

thc vt. i vi nhng cy cn non cu trc ca nhng t bo cha pht trin hon

chnh cho nn n vn c tnh phn x mnh hn i vi nhng cy chn gi. i

vi nhng cy c l rng th s phn x mnh hn i vi nhng cy l kim. Cc thc

vt b cn trng hoc bnh tn cng, do cc dip lc t b ph hy lm tng khong

trng gia cc t bo nn lm cho bc x phn x khng ng u v n phn x cao

cc vng nh sng nhn thy c nhng li thp bc x hng ngoi.

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Hnh 1.3. S phn xi vi thc vt.

1.1.5. Tng quan v vin thm

S pht trin ca khoa hc cng nghnh hng trc tip n ng dng ca

vin thm. Vi vic pht trin k thut v tinh, vin thm tht s tr thnh mt cng

c khng th thiu phc v cuc sng con ngi, ng thi n cng l phng php

nghin cu rt hiu qu trong cc ngnh khoa hc, c bit l cc ngnh khoa hc tri

t. Hng lot cc chng trnh nghin cu s dng thit b vin thm trn v tinh

c thc hin nh LANDSAT, SPOT, IRS, REURS, SPIN, NOAA, GEOS,

SEASAT, EOS,Ty thuc vo mc ch, ngha ca vic nghin cu, cc h thng

thit b vin thm c cu to ph hp: phn gii t vi chc km n hng mt. S

liu m thit b vin thm thu nhn nhng dng rt khc nhau bao gm bin i v

lc (my o trng lc), sng m thanh, sng in t s dng trong dy tn s rng.

Nhk thut v tinh bng Laser (SRL) ngi ta c th xc nh c s dch chuyn

trn mt t c chnh xc ti vi cm hay nh hn ng dng trong nghin cu a

chn. V tinh TRIM c trang b cc thit b lm vic cc dy tn s khc nhau

chp my, chp st,V tinh ny c nhim vnh gi lng nc ma ti khu vcnhit i m ngi ta cho rng c th lin quan ti hin tng m dn ln trn ton

cu. Vin thm tht s m ra nhng chuyn vng ln v vic nh gi s tng tc

gia con ngi vi mi trng, (Nguyn Xun Anh, 2004).

Ngy nay, vi k thut GPS v GIS, vin thm ngy cng c rt nhiu ng dng

thc t trong nhiu lnh vc. Nhvin thm chng ta c th xc nh trng thi cy

trng, d bo thi tit, l lt, pht hin chy rng, phn vng quy hoch t ai,

nghin cu ng t, nghin cu v tr, nghin cu bin, nghin cu kh quyn, mi

trng, phc v vo mc ch qun s, (Nguyn Xun Anh, 2004).

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Theo Nguyn Vn Trung (1999), k thut vin thm lm cho cng tc thnh

lp v hiu chnh bn pht trin mnh m. nh vin thm em li ngun thng

tin mi, k thut mi v t tng nghin cu mi.

Theo L Nguyn (1999), nghin cu mt t th vin thm thng s dng

thng tin thu nhn c t v tr do cc v tinh nhn to chuyn dng nghin cu

ti nguyn mi trng thc hin, bay cao t 600 n 1000 km.

Theo Trn Minh v ctv (2003), t liu vin thm v cng a dng, c th tip

cn c bng nhiu ngun t nhiu ni trn th gii. Cng c v h thng thng tin

a l thc s s c nhiu hiu lc khi c ng dng rng ri trong cc gii chuyn

mn.

Nhc kh nng thu nhn nhnh, thu nhn lp li theo cc chu k khc nhau

trn phm vi rng ln nhng thng tin a dng v cc i tng, cc hin tng trn

t lin cng nh trn bin, cng ngh vin thm l cng c quan trng xy dng

mt phn c sd liu v c p nht nhng bin ng theo yu cu ca cng tc

qun l ven bin. Vi mc ch tng bc ng dng cng ngh vin thm phc v

cng tc qun l ven bin, trung tm vin thm tng cc a chnh s dng t liu

nh v tinh thnh lp b bn chuyn nh mt phn ca csd liu trn, (T

Quang Thnh v ctv, 2003).Cng ngh vin thm, mt trong nhng thnh tu khoa hc v tr t n

trnh cao v trthnh k thut ph bin c ng dng rng ri trong nhiu lnh

vc kinh t x hi nhiu nc trn th gii. Nhu cu ng dng cng ngh vin thm

trong lnh vc iu tra nghin cu, khai thc, s dng, qun l ti nguyn thin nhin

v mi trng ngy cng gia tng nhnh chng khng nhng trong phm vi Quc gia,

m c phm vi Quc t. Nhng kt qu thu c t cng ngh vin thm gip cc nh

khoa hc v cc nh hoch nh chnh sch cc phng n la chn c tnh chin lc

v s dng v qun l ti nguyn thin nhin v mi trng. V vy vin thm c s

dng nh l mt cng nghi u rt c u th hin nay, (Vin kh tng thy vn,

2006).

T nhng nm 60 ca th k 20 vi s xut hin ca v tinh nhn to u tin

th k thut khng gian c s pht trin vt bc. V tinh l cng c quan trng

trong nghin cu ca khoa hc hin i. K thut thm trc bng v tinh pht trinnhnh chng hnh thnh ln h thng quan trc kh tng v tinh ton cu. Quan trc

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tri t v quan trc khng gian bc sang mt giai on mi, lm phong ph thm

phm vi, ni dung quan trc. T quan trc mang tnh cc btng thp ca kh quyn

chuyn sng quan trc c h thng kh quyn. Rt nhiu nhng yu t, nhng v tr

trong kh quyn v trn tri t trc y rt kh quan trc th ngy nay vi v tinh kh

tng u c th thc hin c. Cng ngh vin thm cung cp rt nhiu s liu

cho cc lnh vc nh: thin vn, kh tng, a cht, a l, hi dng, nng nghip,

lm nghip, qun s, thng tin, hng khng, v tr..., (Vin kh tng thy vn, 2006).

Nc ta nhiu i ni, a hnh phc tp ( cao, dc, hng, khe sui thung

lng) iu kin kh tng, kh hu, thu vn din bin phc tp. Cng vi sm ln

ca kh hu ton cu cc hin tng thi tit bt thng nh: Hn hn, l lt ngy

cng gia tng v mc gy tn hi ngy cng ln, nhit tng cao kt hp vi hnhn dn ti nguy cchy rng, s pht sinh pht trin ca su bnh i vi ma mng

ngy cng trm trng. V vy vic s dng cc thng tin vin thm tch hp vi h

thng thng tin a l (GIS) v h thng nh v ton cu (GPS) cng vi cc quan trc

thu c t b mt sp ng khch quan v a dng cc thng tin cn thit phc v

cng tc nghin cu gim st v d bo kh tng thu vn, kh tng nng nghip v

mi trng m c bit l phc v cho cng tc gim st v cnh bo tc hi ca thin

tai c cc bin php phng trnh v ng cu k p thi, (Vin kh tng thy vn,2006).

nh vin thm c x l v tch hp trn cc phn mm hin i nh ENVI,

MATLAB, MAPINFO, ACVIEW... Cc sn phm c tnh ton thng qua cc thut

ton c ng dng nhiu nc trn th gii nh M, EU, Nht Bn, Trung

Quc... v c hiu chnh cho ph hp vi iu kin Vit Nam. Cc kt qu thu

c c tch hp vi h thng thng tin a l to ra cc bn chuyn .

Ngoi ra cc gi tr s ca cc sn phm vin thm cn c lu tr di dng nh

phn rt thun tin trong vic khai thc v s dng, (Vin kh tng thy vn, 2006).

1.1.6. u im ca cng ngh vin thm

Cng ngh vin thm l mt phn ca cng ngh v tr, tuy mi pht trin

nhng nhnh chng c p dng trong nhiu lnh vc v c ph bin rng ri

cc nc pht trin. Cng ngh vin thm trthnh phng tin cho cho cng

tc gim st ti nguyn thin nhin v mi trng cp tng nc, tng khu vc vtrong phm vi ton cu. Kh nng ng dng cng ngh vin thm ngy cng c

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nng cao, y l l do dn n tnh ph cp ca cng ngh ny. Vin thm l khoa hc

thu nhn, x l v suy gii cc hnh nh thu nhn t trn khng ca tri t nhn

bit c cc thng tin vi tng trn b mt tri t m khng cn tip xc n.

Nh vy, vin thm l phng php thu nhn thng tin khch quan v b mt tri t

v cc hin tng trong kh quyn nhcc my thu (sensor) c t trn my bay, v

tinh nhn to, tu v tr hoc t trn cc trm quo. Cng ngh vin thm c

nhng u vit cbn sau:

- ph trm khng gian ca t liu bao gm cc thng tin v ti nguyn, mi

trng trn din tch ln ca tri t gm c nhng khu vc rt kh n c nh rng

nguyn sinh, m ly v hi o;

- C kh nng gim st s bin i ca ti nguyn, mi trng tri t do chu

k quan trc lp v lin tc trn cng mt i tng trn mt t ca cc my thu vin

thm. Kh nng ny cho php cng ngh vin thm ghi li c cc bin i ca ti

nguyn, mi trung gip cng tc gim st, kim k ti nguyn thin nhin v mi

trng;

- S dng cc di phc bit khc nhau quan trc cc i tng (ghi nhn

i tng), nh kh nng ny m t liu vin thm c ng dng cho nhiu mc

ch, trong c nghin cu v kh hu, nhit ca tri t;- Cung cp nhnh cc t liu nh s c phn gii cao v siu cao, l d liu

cbn cho vic thnh lp v hiu chnh h thng bn quc gia v h thng CSDL

a l quc gia.

Vi nhng u im trn, cng ngh vin thm ang tr thnh cng ngh ch

o cho qun l, gim st ti nguyn thin nhin v mi trung nc ta hin nay.

1.1.7. ng dng ca vin thm

1.2.7.1. ng dng trn thgii

Theo V Quang Minh (1999), hin nay trn th gii vin thm c ng dng

trong mt s lnh vc sau:

- Nghin cu thin nhin, a cht, a mo.

- Tm kim khong sn.

- Theo di s suy thoi v bin ng rng.

- Nghin cu mi trng bin.- Thnh lp bn a hnh.

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- Xc nh v tr trong khng gian ca cc vt th bi cc php o trn nh.

- Phn loi t.

- Gii on cc mc ch c bit trong quc phng, an ninh, qun s,

- Nghin cu tnh hnh ngp nc.

- Theo di s ln chim ca sa mc.

- Theo di s di chuyn ca cc tng bng cc vng cc.

1.1.7.2. ng dng cng ngh vin thm gim st ti nguyn thin nhin

v mi trngVit Nam

ng v Nh nc ta khng nh pht trin khoa hc cng ngh l quc sch

hng u, l nn tng v ng lc y mnh cng nghip ho, hin i ho t nc.

y mnh cng nghip ho t nc l ni dung cbn ca qu trnh pht trin t

nc ta giai on 2005 - 2020 vi mc tiu c th l nc ta s tr thnh nc cng

nghip vo nm 2020. thc hin mc tiu trn, vn c tnh cht quyt nh l

y mnh ng dng v pht trin khoa hc cng ngh, a khoa hc cng ngh thc

s tr thnh nn tng v ng lc y mnh cng nghip ho, hin i ho t nc.

Pht trin khoa hc cng ngh ni chung v khoa hc cng ngh vin thm ni ring

phc v qun l ti nguyn thin nhin v mi trng ng vai tr quan trng cho s

nghip pht trin t nc ta hin nay, (L Minh, Nguyn Xun Lm v ctv, 2002).Theo L Minh, Nguyn Xun Lm v ctv (2002), nhu cu ng dng cng ngh

vin thm qun l ti nguyn thin nhin trc ht l ti nguyn t, ti nguyn

nc, ti nguyn khong sn, ti nguyn rng,...v gim st mi trng ngy cng tr

nn bc xc v trthnh mt trong cc nhim v cho ca ng dng v pht trin

cng ngh ca B Ti nguyn v Mi trng. Trong khi , vic ng dng cng ngh

vin thm gim st ti nguyn v mi trng nc ta trong thi gian qua tuy

thu c mt s kt qu song cn t, tn mn v trn thc t cha p ng c nhu

cu. Cc ng dng cng ngh vin thm ch yu mi tp trung vo lnh vc hiu chnh

bn a hnh, thnh lp mt s bn chuyn , bc u cp n ng dng

cng ngh vin thm phc v qun l t ai v mt s kha cnh ca mi trng.

Thc t i hi phi y mnh ng dng rng ri cng ngh vin thm phc v

qun l ti nguyn thin nhin v gim st mi trng. t c nhim v trn vic

u t cng ngh mi nhm xy dng ng b h thng thu nhn, x l d liu v pdng t liu nh v tr l yu cu cn thit v bc xc vi nc ta hin nay. Nm 2003

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Th tng Chnh ph ng cho s dng ngun vn ODA ca Cng ha Php

xy dng D n Xy dng H thng Gim st Ti nguyn thin nhin v Mi trng

Vit Nam v giao cho B Ti nguyn v Mi trng t chc thc hin. Trung tm

Vin thm - B Ti nguyn v Mi trng c giao ch tr thc hin. Thng 6 nm

2005 Trung tm Vin thm thuc B Ti nguyn v Mi trng c sy quyn ca

B trng B Ti nguyn v Mi trng k hp ng vi Cng ty Hng khng V

tr Chu u (EADS) tin hnh thc hin d n trong thi gian 3 nm. H thng gim

st Ti nguyn thin nhin v Mi trng bao gm 3 thnh phn:

- Trm thu mt t cho php thu trc tip t v tinh nh Spot 2, 4 v 5 (cc nh

c phn gii t 2,5m, 5m, 10m v 20m), nh Envisat ASAR (radar) phn gii

30m v nh MERIS phn gii thp 300m phc v cho nghin cu nhit v

mn nc bin;

- Trung tm D liu Quc gia c kh nng x l, phn tch, lu tr v phn

phi cc d liu thu nhn c;

- H thng ng dng d liu (gm 15 n v) cho php s dng cc d liu

c x l Trung tm d liu vo cc mc ch ring ca tng cquan, t chc.

Vic xy dng H thng Gim st Ti nguyn v Mi trng m ra thi k pht

trin mi ca cng ngh vin thm. Trc mt s thu nhn cc nh v tinh thng dng nu trn p ng rng ri, kp thi cc nhu cu cbn v t liu vin thm cho

cc ngnh. Sau mt thi gian ng dng s tin hnh nng cp thu cc v tinh i

mi c phn gii siu cao p ng nhu cu ngy cng cao trong nhiu lnh vc v

trong nhiu ngnh kinh t ca t nc.

Thc t i hi Trung tm Vin thm phi y mnh ng dng cng ngh

vin thm phc v qun l ti nguyn v gim st mi trng trn csphi hp cht

ch vi cc n v c lin quan trong v ngoi B, (L Minh, Nguyn Xun Lm v

ctv, 2002).

Hin nay, Vit Nam cc cquan ng dng vin thm s dng nhiu loi t

liu nh v tinh, trong s cc t liu va nu trn l ph bin. Cc t liu ny mi

c ng dng cho vic iu tra nghin cu cc i tng trn t lin nh hiu

chnh bn ti Trung tm Vin thm, lp bn a cht ti Cc a cht Vit Nam

v Vin nghin cu a cht v Khong sn, s dng trong qun l tng hp vng bCc Bo v Mi trng. Ti cc cquan ngoi B, cc t liu vin thm c s

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dng ti cc Vin nghin cu v mt s Trng i hc. Tuy nhin, vic ng dng

cc t liu ny ch yu cho vic quan st s dng t, mi trng, th. Cng c mt

s th nghim nh vin thm nghin cu v bin nhng l t, ch yu tp trung mt

sa im ven bnh Hi Phng, Qung Ninh, Nha Trang, Vng Tu. C mt s

ti nghin cu ng dng nh MODIS nghin cu cc thng s trng nhit , sng

th mi ch lm v d cha c kim chng nghim tc, (L Minh, Nguyn Xun

Lm v ctv, 2002).

Cc ng dng cng ngh vin thm trn t lin hin nay khng nh kh

nng ca cng ngh vin thm. Cc nghin cu ban u ng dng cng ngh vin

thm nghin cu bin trong thi gian qua Vit Nam cng vi kinh nghim s dng

cng ngh ny nc ngoi l cs la chn cng ngh vin thm nh mt trong

nhng gii php u tin quan trng trong vic xy dng h thng trm quan trc ti

nguyn mi trng v kh tng thy vn bin Vit Nam, (L Minh, Nguyn Xun

Lm v ctv, 2002).

Theo L Quang Tr v ctv (1999), ngnh vin thm ng vai tr ht sc quan

trng l cng c phc v v h trc lc cho cc ngnh khc nhau nh: Qun s,

quc phng an ninh, a cht, m, mi trng, bn , sn xut nng nghip v cc

ngnh khoa hc k thut khc.Ngoi ra, Vit Nam hin nay vin thm c ng dng trong cc lnh vc

khc nh:

- Nghin cu vng ni Ba V v Tam o v cu trc a cht trong khun

kh mt n vi Canada 1998.

- Cui nm 1996 nh Radarc chp t v tinh RADARSAT v ERS c s

dng nghin cu ngp lt, hin trng c cu cy trng ng Bng Sng Cu

Long.

- S dng nh SPOT nghin cu s thay i s dng t ai huyn Tn

Thnh tnh Long An, (L Quang Tr v ctv, 1996).

- S dng nh SPOT nghin cu s thay i s dng t ai huyn Vnh

Li tnh Minh Hi, (V Tng Anh, 1996).

- S dng nh Radara thi gian theo di din bin lng Bng Sng

Cu Long, (V Quang Minh, 1999).

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1.1.8. Xl nh vin thm

1.1.8.1. Giion nh bng mt

a.c im ca hnh nh

Theo V Quang Minh (1999), nh c cc c im sau:

- Bc nh l mt s th hin bng hnh nh khng kn bc sng hay thit b

to nh c s dng sn xut ra n.

- Nhng tnh cht thng thng ca mt bc nh gm: t l, sng, tone nh,

tng phn v phn gii.

+ T l: l t s gia hai i tng trn nh.

+ sng: l lng nh sng tc ng vo mt, l s nhy cm vi nh sng

ca ch th m ta c th xc nh mt cch tng i.

+ Tone nh: l s khc nhau v sng c th hiu chnh bng thang xm c

gi tr ten ti trng.

+ T s tng phn: l t s gia phn sng nht v phn ti nht.

+ phn gii: l kh nng phn bit hai i tng lin nhau gn hn gii hn

phn gii s xut hin nh mt i tng ng nht trn nh.

b. Cc c tnh khc

Theo Nguyn Ngc Thch v ctv (1997), khi gii on nh phi da vo ccdu hiu gii on nh sau:

- Cc yu tnh bao gm:

+ Tone nh: l tng hp lng nh sng c phn x t b mt i tng.

+ Cu trc nh (texture): l tn s lp li ca s thay i tone nh gy ra bi tp

hp ca nhiu c tnh rt r rng ca cc c th ring bit.

+ Kiu mu (pattern): l nhn t quan trng th hin s sp xp ca cc i

tng theo mt qui nh nht nh.

+ Hnh dng (shape): l nhng c trng bn ngoi tiu biu cho tng loi i

tng.

+ Kch thc (size): c xc nh theo t lnh v kch thc o c trn

nh.

+ Bng (shadow): nh v tinh thng chp t 9h30 n 10h, cn c vo bng

rmtrn nh ta c th xc nh cao tng i, t c th phn bit i tng trnnh.

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+ Mu (colour) mu ca i tng trn nh mu gi (FCC) gip cho ngi gii

on c th phn bit c nhiu i tng trn nh.

+ V tr (size): l du hiu quan trng phn bit i tng. Cng mt du

hiu nh, nu cc v tr khc nhau c th l cc i tng khc nhau.

- Cc yu ta kthut bao gm:

+ a hnh.

+ Thc vt.

+ Hin trng s dng t.

+ Mng li, giao thng, sng sui.

+ Cc khe nt ln v cc yu t dng tuyn.

+ T hp cc yu t.

1.1.8.2. Xlnh kthut s

Theo V Quang Minh (1999), nh thu c c cc c im sau:

- nh c ghi trn bng t my tnh chng c c v x l to nn hnh

nh.

- Cc nh bao gm cc phn t nh b c cng din tch (c gi l pixel).

- Cc pixel c sp xp theo hng, ct, v tr bc k no ca mt phn tnh

hay pixel u c xc nh ta XY.- Mi pixel c mt gi tr s tng ng vi cc gi tr phn x ph.

- Gi tr DN ghi li cng nng lng in t ri vo mt phn t phn gii

trn mt t m din tch c th bng 1 pixel.

- Cc s th t s ha t 0 n 255.

Theo V Quang Minh (1999), cc bc trong x l nh k thut s bao gm

a. Khi phc hnh nh

- Mc ch: Khc phc nhng sai st ca ti liu, hin tng nhiu v lch hnh

hc sinh ra trong qu trnh qut, ghi v truyn v.

- Ni dung:

+ Khi phc s sai lch hnh hc.

+ Khi phc s b st cc ng qut theo qui lut.

+ Khi phc cc ng chm ngt qung theo qui lut.

+ Hiu chnh s tn x ca kh quyn.b. Tng cng cht lngnh

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- Mc ch: Gip nng cao cht lng thng tin.

- Ni dung:

+ Tng cng tng phn.

+ To nh hn hp.

+ Lc nhiu s xut hin tn mn trn nh.

c. Phn loi nh

C 2 cch phn loi nh:

- Phn loi c kim sot (superviced classification)

+ L xc nh mt vng nh, l v tr kim tra (training site) hay mt im kim

tra. V tr kim tra th hin cho mt tiu chun a hnh hay mt lp a hnh. Cc gi

tr ph ca mi pixel trong v tr kim tra c dng xc nh cho cc khng gian

quy nh lp . Sau khi cc cm ca cc v tr kim tra c xc nh th da vo cc

ch tiu my tnh phn loi ton b cc pixel cn li trong hnh nh.

+ c im ca phn loi c kim sot l cc lp i tng c xc nh mt

cch r rng da vo cc tnh cht ca i tng xc nh trn cc v tr kim tra. Tuy

nhin trong thc t c nhiu i tng khc nhau nhng li th hin ph ging nhau.

Hay c nhiu du hiu ph khc nhau song nhng li thuc v mt i tng thay i

tn hiu ph tng pixel. V vy cn phi c s phn loi bng vic kt hp nhiu duhiu ph th hin mt lp i tng.

- Phn loi khng kim sot (unsuperviced classification)

+ Gi tr pixel trn mi hnh nh a s c th phn chia c 256 cp (t 0 n

255)

+ Da vo cc pixel (s dng histogram) ta c th tng ha phn chia hnh

nh ra nhiu lp i tng. Mi lp i tng tng ng vi khong gi tr sng

nht nh.

+ S phn loi ny ch cho thy s khc bit v gi tr sng gia cc nhm

pixel trn nh ch khng xc nh chnh xc bn cht hay tn gi ca chng.

+ Do s phn loi khng kim tra ch cho kt qu gi thuyt ban u.

d. Chuyn i nh

Ch s thc vt:

- Dng gi tr ngng thng qua gii on nh, phn tch biu tn s xuthin ca nh.

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- Pht hin cc vng bao ph trn nh theo ngng gii hn ly t pixel, cc

pixel gi tr nh hn ngng no gi l gi tr ngng.

- Phn tch s thay i ca mt lot nh theo thi gian:

+ Cc nh c s thay i cung cp thng tin v s bin i theo ma hoc cc

thay i khc. Cc thng tin ny c tch ra bng s so snh 2 hay nhiu nh ca mt

vng hay vic thu thp nh theo thi gian. Bc u tin phi xc nh ta hnh nh

ti mt thi im trn c s cc im kim tra mt t. Ti p theo s xc nh khi

lng l tr s lng cc pixel ca nh c nhn trc hoc sau thi im . Cc

gi tr sau khi tr c th dng, m hoc bng 0 (bng 0 l khng c s thay i).

+ Tip theo l nh du cc gi tr nh nh mt hnh nh vi xm trung

gian th hin bng 0. Mu en v mu trng l s thay i m cc i hoc dng cc

i. Phng php ko dn tng phn c s dng nhn mnh s khc bit .

Phng php ny rt c ch cho vic nghin cu cc qu trnh bin i, trn csphn

tch cc t liu vin thm nh: s bin i nhit, s bin i ma mng, bin i lng

ph sa ca cc dng sng, s thay i cc mng li sng sui, bin i din tch cc

n v s dng t.

1.2. GII THIU V H THNG THNG TIN A L (GIS)

1.2.1. nh nghaH thng thng tin a l (GIS) l mt k thut qun l thng tin da vo my

tnh c s dng bi con ngi vo mc ch lu tr, qun l v x l cc s liu

thuc v a l hoc khng gian nhm phc v cho cc mc ch khc nhau, (V

Quang Minh, 1999).

Ngoi ra h thng thng tin a l GIS cn c nh ngha nh mt h thng

dng x l s liu di dng s dng cho vic phn tch v qun l cc s liu

thuc va l, c kt hp vi cc h thng ph nhp v truy xut cc d liu, n

c kh nng nhp, lu tr, m t v khi phc hay biu th nhng s liu khng gian,

(V Quang Minh, 1999).

Theo Trn Vnh Phc (2003), h thng thng tin a l l mt h thng t

ng thu thp, lu tr, phn tch v hin th d liu vi tng, cc hin tng cc

s kin ca th gii thc theo khng gian v thi gian thc.

Theo B Ti nguyn v Mi trng (2004), h thng thng tin a l(Geographic Information System vit tt l GIS) l mt h thng bao gm cc d liu

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hnh hc v phi hnh hc c lin kt vi nhau th hin trn cc lp bn di dng

s, nh qut, cc bng ghi hoc cc bng biu nhm phc v cho vic nghin cu chi

tit v nh gi a hnh; lp k hoch v thit k cc cng trnh; m bo vic xy

dng v ci to cc im dn c, cc khu cng nghi p; lp t cc ng ng, cc

tuyn ng thng tin, cc ng dy ti in,phc v cho cng tc qun l nh

nc gp phn nng cao nng xut, cht lng v to nn mt ngun thng tin tch ly

rt cn thit. y l ngun thng tin rt quan trng a ra cc lun c khoa hc

phc v cng tc xy dng nh hng chin lc pht trin kinh t - x hi lu di

cho c vng.

Theo Godilano v Carangal (1991), GIS l h thng cc thng s, dng cho

vic phn tch v tnh ton cc d liu trong phm vi d liu a l, vi s kt hp vi

cc h thng ph cho vic s ha bn cho ngi s dng bit ni dung hon

thnh quyt nh. N tiu biu cho mt h thng, h thng ny l nn tng my tnh

cho vic qun l s liu thuc v khng gian v khng thuc v khng gian.

1.2.2. Xu hng pht trin ca GIS

Theo V Duy Mn (2002), trong thin nin k mi, c th khng nh GIS s

c chp nhn mt cch v cng rng ri trong x hi v trn ton th gii. Nhng

ngi dng GIS s c nhiu li th hn so vi nhng ngi khng dng. Cng nghGIS s pht trin ng nhp vi s tng trng v kh nng v gi ca cc thit b my

tnh, hiu hnh v ng truyn thng.

Tch hp chc nng GIS vo cc phn mm ng dng chun, th d nh bng

tnh in t. Cc nh cung cp GIS ph bin cc th vintin ch bn , cc bn

s ha v cc tp d liu a l mng cho nhng ngi vit chng trnh tch

hp c cc chc nng GIS vo cc phn mm ng dng. K thut GIS, GPS v nh

vin thm cng c a vo cc ng dng ph bin ca cng ngh thng tin, chng

khng cn l nhng th ring bit m hi nhp thnh mt th trng vi nhng h sn

phm cung cp mt cch rt tin li cc gii php cho ngi dng.

GIS c chc nng phn tch d liu khng gian, l tiu chun phn bit

chng vi cc h x l s liu khc. Phn tch d liu khng gian bao gm mt di cc

chc nng tn gin n phc tp.

Thin nin k mi s chng kin nhng tin bng k ca cc cng c qunl GIS to kh nng phn tch quy trnh lm vic, xc nh cc sn phm thng tin cn

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thit, m hnh ha v phn tch quy trnh d liu, ci t cc h thng thch hp vi

cc mc tiu chin lc ca t chc.

1.2.3. ng dng H thng tin a l v Vin thm trong qun l mi trng

v ti nguyn Vit Nam

Vic s dng kt hp Vin thm v GIS cho nhiu mc ch khc nhau tr

nn rt ph bin trn ton th gii trong khong 30 nm trli y. GIS bt u c

xy dng Canada t nhng nm su mi ca th k 20 v c ng dng rt

nhiu lnh vc khc nhau trn ton th gii. Sau khi v tinh quan st tri t Landsat

u tin c phng vo nm 1972, cc d liu vin thm c xem l ngun thng

tin u vo quan trng ca GIS nhnhng tin b v k thut ca n. Ngy nay, tri

t c nghin cu thng qua mt di quang ph rng vi nhiu bc sng khc

nhau t di sng nhn thy c n di sng hng ngoi nhit. Cc th h v tinh mi

c b sung thm cc tnh nng quan st tri t tt hn vi nhng quy m khng

gian khc nhau. V tinh cung cp mt lng thng tin khng l v phong ph v cc

phn ng quang ph ca cc hp phn ca tri t nh: t, nc, thc vt. Chnh cc

phn ng ny sau s phn nh bn cht sinh l ca tri t v cc hin tng din ra

trong t nhin bao gm c cc hot ng ca con ngi. Ch pht trin chnh ca

vin thm trong mt thi gian di chnh l mi trng v tm quan trng ca n tronglnh vc ny tng ln nhnh chng trong mt vi nm gn y, (Askne, 1995).

Trong khi mc tiu chnh ca vic s dng GIS l to ra nhng gi tr mi cho cc

thng tin hin c thng qua phn tch khng gian - thi gian v m hnh ho cc d

liu c ta . Nhkh nng phn tch khng gian - thi gian v m hnh ho, GIS cho

php to ra nhng thng tin c gi tr gia tng cho cc thng tin c trit xut t d

liu v tinh, (Burrough v cng s, 1998).

nh vin thm, nh hng khng l nhng t liu qu tm hiu s thay i s

dng t, che pht v s lng, v tr phn b trn mt khu vc trong nhng thi

im khc nhau, hay so snh gia 2 khu vc. Trn Th gii GIS c s dng ph

bin xy dng m hnh s dng t v quan trc, d bo cc thay i cc thm che

ph v a hnh (Elena v cng s, 2001; Kok v cng s, 2001; McDonalda v cng

s 2002; Stephenne v Lambin, 2001), so snh cc h sinh thi nng nghip (Stein v

Ettema, 2003), quan st cc s thay i v h thng canh tc theo a hnh (Nelson,2001; Schoorl v Veldkamp, 2001). c bit trong nhng nm gn y, nhiu nghin

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cu trong nc ng dng cng ngh GIS v vin thm trong nghin cu chin lc

ca ngi nng dn trong s thay i a dng ca h canh tc nng ry di cc tc

ng ca iu kin dn s, t ai, chnh sch v cc nhu cu v kinh t x hi ca

ngi dn, (L Trng Cc v Rambo, 2002; Jean-Christophe Castella v ng nh

Quang, 2002; Brabant P, Darracq S. and Nguyn Cm Vn (bin tp). 1999; Leisz v

cc cng tc vin, 2003).

tng tm hiu s thay i s dng t qua vic gii on nh vin thm, kt

hp GIS, v iu tra kho st thc a, l phng php mi trong p dng qun l

ngun ti nguyn c t thnh mc tiu ca ti v cng gip cho cc nghin cu

s c thm nhiu kinh nghim v hc hi thm c nhiu cng ngh mi, ng nh

mc ch ban u ca Din n Vng Cao (VUF) t ra, (Nguyn Vn C, 2002).

1.3. GII THIU V V TINH WORLD VIEW

Ngy 18/9/2007 mt v tinh vin thm i mi phn gii siu cao World

View 1 c phng ln quo bng tn la y Delta 2 t cn c khng qun

Vandenberg, California M.

Hnh 1.4. V tinh vin thm c phn gii siu cao World View 1.

V tinh World View 1 c quo cn cc, bay mt vng quanh Tri t mt 95

pht, l v tinh thng mi nh phn gii siu cao s cung cp cc nh v tinh c

phn gii mt t c50cm, m cha c v tinh dn s no cho ti ngy hm nay c th

cung cp c nh c phn gii cao ti nh vy.

Tn la y Delta 2 a v tinh World View 1 ln qu o.

Chnh ph M l khch hng tim nng ln nht cn nh World View 1 cho vic quan

st cc vng trng im v cho mc ch d thm. Ngoi ra hin nay cc nhu cu vcc loi nh nh vy cho mc ch gim st vic thc hin quy hoch th, nh gi

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bt ng sn, gim st mi trng v cc ngi s dng Google Earth ngy cng tng

cao.

Digital Globe, tr sng ti Longmont, Colorado vn hnh v tinh Quick

Bird gn 6 nm nay, nay vi s c mt ca World View 1 s cho php nng cao kh

nng thu chp nh v tinh phn gii siu cao ln gp 5 ln. Bi v 2 v tinh ny bay

ng thi trn quo cho php chp nh mt v tr bt k trn mt t hng ngy

thay v phi mt t 3 n 5 ngy nh trc kia mi chp lp li c.

Ngoi ra trn v tinh ny s dng mt loi h thng con quay iu khin nh vc

bit, ln u tin ng dng cho v tinh dn s, cho php v tinh nh vim chp nh

nhnh hn v tinh Quick Bird c gp 10 ln, nh m vic chp nh sc nhnh

hn, chp c nhiu nh hn trn quo. Digital Globe dnh s cng b bc nh

u tin ca World View 1 sau 1 thng, ng dip k nim 6 nm phng Quick Bird

cng bng tn la y Delta 2 t Vandenberg.

V tinh Quick Bird cung cp cc nh 0,6m v tinh World View 1 cho cc bc

nh c phn gii cao hn 0,5m. i vi vic khai thc thng tin nh, y l mt

bc tin mi v phn gii. Cc khch hng ca World View 1 s l Cc tnh bo.

nh v tinh phn gii siu cao cng sc s dng rng ri cho nhiu mc ch

khc trong c nhng ng dng mi nh lp bn sinh thi, theo di s bin isinh thi lin quan n i sng ca cc th vt ln c th nhn thy trn nh nh voi.

Digital Globe hy vng s vn hnh v tinh Quick Bird 2 nm na. V tinh World

View 1 c thit k tui th khong 7,5 nm. Cng ty Ball Aerospace ang tip tc

sn xut v tinh World View 2, d kin phng ln quo khong cui nm 2008.

V tinh World view 1 l sn phm ca s hp tc gia cng ty Ball Aerospace

v tp on cng ngh vi b phn cm bin hnh nh c cung cp bi tp on

ITT, n c tnh nng vt tri v h thng hnh nh ton sc cung cp cc nh c

phn gii 0.5m vi s ln quay chp li l 1.7 ngy. V tinh World view 1 c kh nng

thu chp nh ln ti 750,000 km2 (tng ng vi 290,000 dm vung) mi ngy vi

nh c phn gii 50cm. Tn s quay chp li cho php nng cao kh nng chp nh,

tng cng cc thit b d thm v gp phn h trcho vic cp nht bn . V tinh

ny cng cho php vic quay chp, lu tr v kt ni cc hnh nh ton cu mt cch

thng xuyn hn so vi bt c mt v tinh hnh nh thng mi no khc trong quo, ng thi cho php sao chp nh, lu tr v gi nh ti cc khch hng c yu

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cu gp v thi gian. World view 1 cng c kh nng p ng tnh chnh xc cao v v

tr a l v c tc nhnh nht t trc ti nay.

V tinhWorldview 1 l mt trong hai v tinh th h mi ca cng ty Digital

Globe c phng ln trong thi gian gn y. Vo cui nm 2008, cng ty Ball

Aerospace v tp on cng ngh phi hp cng tp on ITT s hon tt World view

2, nng tng s v tinh ca Digital Globe trn quo ln thnh ba v gip cng ty

ny c kh nng cung ng trc tip thit b quay chp nh ln n 1 triu km2 mt

ngy vi hnh nh c phn gii cao n khch hng trn ton th gii. Thm vo

World view 2 cng s cung cp nh a ph 8 knh vi mu sc trung thc v c ng

dng quang ph cao trong vic lp bn v gim st th trng.

1.4. GII THIU PHN MM ENVI

Hnh 1.5. Biu tng phn mm ENVI

ENVI l phn mm l tng trc quan ho, phn tch v biu din nh s.

ENVI c tt c cc tnh nng x l nh hon thin, bao gm: cng c sa cha hnh

hc; phn tch a hnh; phn tch raa; dng raster v vector ca GIS v c h trhnh nh t nhiu ngun khc nhau.

ENVI chuyn hin thnh, c kh nng phn tch a ph cho hnh nh qut ca

SPOT, TM. Ngoi ra ENVI cn c chc nng hin th vector.

Cc chc nng cbn ca ENVI:

- Hin thnh.

- Tch chit cc thng tin ph.

- To hnh nh chuyn ng.

- Hin th hnh nh vi mng li.

- Phn loi nh a ph.

- Cc chc nng phn loi theo Mask.

- Hiu chnh bc x.

- To lp cc th.

- To hnh nh nhiu chiu.- X l hnh nh Radar.

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- X l thng tin ph to cc nh ch s: chng xp cc band, to nh t s...

- Cc nh dng d liu: xy dng theo h thng ASCII, c th nhp v xut d

liu nh nh dng IMG v bng d liu nh dng GRD.

ENVI (The Enviroment for Visualizing) l mt phn mm x l nh kh mnh,

h thng ny c thit kp ng yu cu ca cc nh nghin cu c nhu cu s

dng d liu nh vin thm (Remote Sensing-RS), bao gm cc loi nh v tinh

(Satellite) v nh my bay (aircraft). ENVI hin th v phn tch nh vi nhiu kiu d

liu v kch cnh khc nhau, tt c trong mt mi trng giao din thn thin vi

ngi s dng, (Trn Nguyn nh, 2007).

ENVI c mt th vin kh y cc thut ton x l d liu nh cng vi

giao din ca s ho - Tng tc thn thin vi ngi s dng. Phn mm h tr

cc cng c thc hin mt s chc nng chnh nh: chuyn i d liu

(transforms), lc nh (filtering), phn loi nh (Classification), ng k h li chiu

(registration) v hiu chnh hnh hc (Geometric corections), cc cng c phn tch

ph, cc cng c s dng cho nh Radar, (Trn Nguyn nh, 2007).

ENVI h trcho php x l nhng d liu khng phi l d liu chun, hin th

v phn tch nhng nh ln, v cng cho php mrng kh nng phn tch d liu bi

cc hm ca ngi dng, (Trn Nguyn nh, 2007).Ngoi ra, ENVI cho php lm vic vi tng knh ph ring l hoc ton bnh.

Khi mt file nh c m, mi knh ph ca nh c thc thao tc vi tt c cc

chc nng hin c ca h thng. Vi nhiu file nh c m, ta c th d dng la

chn cc knh t cc file nh x l cng nhau, (Trn Nguyn nh, 2007).

Theo Trn Nguyn nh (2007), ENVI c cc cng c chit tch ph, s dng

th vin ph, v cc chc nng chuyn cho phn tch nh phn gii ph cao (High

resolution imges). ENVI c thit k da trn ngn ng lp trnh IDL (Interactive

Data Language). IDL l ngn ng lp trnh c cu trc v cung cp kh nng thch hp

gia x l nh v kh nng hin th vi giao din ha d s dng. Tnh linh hot v

mm do ca ENVI phn ln nhvo kh nng ca IDL. Cc dng d liu ca ENVI:

- D liu nh (d liu Raster):

+ ENVI cho php s dng hng lot loi nh khc nhau (nh Landsat, nh Spot,

nh Ikonos, nh NOAA, nh Radar...). Theo nhiu khun dng d liu khc nhau nh(tiff, geotiff. Jpeg, bmp...). D liu nh ENVI thng c lu thnh file *.img, km

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theo mi file nh l mt file lu thng tin chung v nh *.hdf.

ENVI c th lm vic vi cc file d liu y hoc ch l tp con ca chng. Phn

mm c cc cng c x l cc nh ton sc (panchromatic images), AVHRR, d

liu Landsat MSS, d liu Landsat TM, d liu ca h thng SAR. Cc cng c

AVHRR cho php hin th cc d liu thin vn, hiu chnh d liu, nn chnh hnh

hc v tnh ton nhit b mt. Cc hm x l nh Landsat cho php kh nghing

(de-skewing) v chnh sa t l co (aspect ratios) cho d liu MSS, bc tch v chnh

sa nhiu kh quyn, xc nh h s phn x. Cc cng c hiu chnh d liu hng

ngoi nhit cng c pht trin trong ENVI.

+ Mt khc, ENVI cng h trx l cc d liu nh c nh dng chun nh:

ASCII, BMP, JPEG,TIFF/GeoTIFF, HDF, PDS, PNG, SRF, vv

- D liu ho ( d liu Vector):

+ ENVI c kh nng tch hp v lm vic vi d liu ho t cc khun dng

khc nhau nh: ArcView Shape file, Arc/Info, Mapinfo, Microstation, AutoCADD

liu ho cu ENVI thng c lu thnh file *.evf.

Hnh 1.6. Thanh menu chnh ca phn mm ENVI

+ ENVI cung cp kh nng truy cp vo cc file nh hay tng knh ph ca file

nh. Ca s Available Bands List (Hnh 1.7) lit k cc knh ph ca tt c cc file

nh ang c mtrong ENVI. Ngi s dng c th chn tng knh ph hin th

cng nh la chn ch hin thnh cp xm hay nh mu.

Hnh 1.7. Danh sch cc knh phang lm vic (Available Bands List)

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Scroll Window (Hnh 1.8b): Trong trng hp ton b tm nh khng hinth ht trn ca s Main Image, ca s Scroll c mra hin th ton b

bc nh vi phn gii thp hn. Khung mu trn ca s Scroll xc

nh vng nh c hin th trn ca s Main Image.

Zoom Window (Hnh 1.8c): Hin th mt phn c phng i ca nh. Hs phng i c hin th trong ngoc trn thanh tiu ca Zoom

Window. Vng c phng i c xc nh bng hnh vung trn

Image Window.

Cc u im ca ENVI c th hin cch tip cn trong cng tc x l nh,

l vic kt hp cc k thut da trn knh ph v k thut da trn tp tin. Khi d

liu c m, cc knh phc lu vo danh sch chx l ca chng trnh, hoc

khi cc tp tin c m, cc knh ph ca cc tp tin c x l nh mt nhm. ENVI

c tt c cc chc nng x l nh cbn, trong ch tng tc vi ngi s dng v

ha. c bit trong khi x l, ENVI khng c gii hn v knh phc x l

ng thi do vy cc d liu nh siu ph cng c th dc x l v phn tch bng

ENVI. Hin nay, ENVI phin bn mi c nhiu ci tin hn so vi phin bn trc, c

thm nhiu chc nng v c bit l tc c v x l d liu nhnh hn nhiu so

vi phin bn trc, (L Vn Trung v ctv, 2006).

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CHNG 2

PHNG TIN PHNG PHP

2.1. PHNG TIN

My vi tnh.

My in mu.

My GPS.

Phn mm: Microsoft World, Microsoft Exel, Microsoft PowerPoint, Microsoft

Paint, Envi 3.6, Mapinfo.

nh v tinh World View 1 khu vc Vn quc gia U Minh h - C Mau c

chp ngy 21 thng 01 nm 2008 vi phn gii l 30m x 30m v y l nh trng

en.

2.2. PHNG PHP

Phng php thc hin ti l s dng phn mm ENVI gii on nh vin

thm khu vc vn quc gia U Minh h - C Mau c chp t v tinh World View 1

2.2.1. Thu thp dliu

- Thu thp nh vin thm: nh v tinh World View 1 c chp ngy 21 thng

01 nm 2008 khu vc vn quc gia U Minh h - C Mau.

- Thu thp bn v vng nghin cu nh: Bn khu vc rng trm tnh CMau ( B Mn Khoa Hc t & QL).

- Cc s liu, ti liu v din tch, dn s, iu kin t nhin, kinh t x

hi,...ca vng nghin cu c tham kho t cc ti liu do UBND tnh C Mau cung

cp.

2.2.2. Cc bc xl nh, bn

nh vin thm c phn tch trn phn mm ENVI vi cc bc:

- c th tin hnh vic gii on nh th nh phi c x l nh: Che nh,

nn nh, tng cng cht lng nh: Tng cng tng phn, lc nh.

- Gii on hin trng rng khu vc vn quc gia U Minh h theo phng

php phn loi khng kim tra.

- Kt h p gia kt qu nh c gii on bng phng php phn loi

khng kim tra v nh ban u (nh cha gii on) chn im iu tra kho st

(da vo t im v sng ca cc i tng trn nh).- Tin hnh i kho st thc a vi cc v tr c chn kim tra v ghi nhn

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li hin trng ti im kim tra.

- Kt hp vi kt quiu tra kho st thc a tin hnh phn loi nh theo

phng php phn loi c kim tra.

- Thnh lp bn hin trng rng khu vc vn quc gia U Minh h vi kt

qu phn loi c kim tra.

2.2.3. Vit bo co

Hon chnh 02 bn hin trng rng khu vc vn quc gia U Minh h nm

2008 vi kt qu phn loi nh khng kim tra v phn loi nh c kim tra.

Vit bo co, thuyt minh.

Cc bc gii on nh vin thm:

S ha bn

Bn hin trng

Phn loi khng kim sot

Kho st, kim tra thc a

Thnh lp bng cha kha gii on

Phn loi c kim sot

X l nh, bn

Nn nh

Tng cng cht

lng nh

Hon chnh bn

Chn nh

Thu thp d liu

Hnh 2.1. Lu cc bc gii on nh vin thm.

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CHNG 3

KT QU THO LUN

3.1. GII THIU KHI QUT KHU VC VN QUC GIA U MINH H

3.1.1. iu kin tnhin

Vn quc gia U Minh h l mt vn quc gia ti tnh C Mau. c thnh

lp theo quyt nh s 112/Q-TTg ngy 20 thng 1 nm 2006 ca Th tng chnh

ph nc Cng ha X hi Ch ngha Vit Nam, trn csnng cp khu bo tn thin

nhin V Di nm trong h thng cc khu rng c dng ca Vit Nam. y l khu

vc c hng thc vt c trng vng t ngp nc trn lp than bn do xc thc

vt tch t lu nm to thnh. Thc vt c hu y l cc loi: Trm, s, vt, c,

mm... ng vt c trng l: Ra, rn, trn, c thi li, cc loi c nc ngt, chim,

cn trng... y l khu rng li ca Vit Nam, ton b vn rng U Minh hc bo

v kh nghim ngt nhm bo tn cc loi ng thc vt rng trn t than bn, phc

v cng tc nghin cu khoa hc; gi gn cnh quan mi trng... y l mt trong

hai vn quc gia ti tnh C Mau, (Trnh Vn Ln, 2006).

3.1.1.1. Vtra l, din tch tnhin

Theo kt qu thng k ca y ban nhn dn tnh C Mau (2007), Vn quc

gia U Minh h nm cch Thnh ph C Mau vo khong 30 km v pha Bc, gmvng li khu bo tn thin nhin V Di (c) v mt phn ca cc Lm ng trng U

Minh III v Lm ng trng Trn Vn Thi.

Vn quc gia U Minh h c tng din tch t nhin l 8.527.8 ha.

V ranh gii hnh chnh, Vn quc gia U Minh h nm trn a bn cc x

Khnh Lm, Khnh An, Nguyn Phch thuc huyn U Minh v cc x Trn Hi,

Khnh Bnh Ty Bc thuc huyn Trn Vn Thi.

V v tr ca Vn quc gia U Minh hc xc nh bi toa l v ranh

gii nh sau:

- Ta a l: T 91230 ti 91741 vbc v 1045411 ti 1045916

kinh ng.

- Ranh gii:

+ Ranh gii pha Bc l knh s 27, t knh T90 n knh T100;

+ Ranh gii pha Nam l knh 600 (on t knh 19 n knh gia), knh 500v knh 1200 (on t knh gia n knh ng trong);

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+ Ranh gii pha Ty l knh s 90 (on t knh 27 n knh 21); knh ng

trong (on t knh 1200 n knh 21);

+ Ranh gii pha ng l knh s 100 (on t knh 27 n knh 21); v knh

T19 (on t knh 21 n knh 600).

Theo Trnh Vn Ln (2006), Vn quc gia U Minh h c ba phn khu chnh

gm:

- Khu bo tn h sinh thi rng trn t than bn: 2.570 ha (l vng li ca Khu

bo tn thin nhin V Di hin nay). Chc nng ch yu l: Bo v nghim ngt h

sinh thi rng trn t than bn, sa dng v cnh quan t nhin v ti nguyn ng,

thc vt; bo v v ti to ni c tr, kim n v sinh sn ca cc loi ng vt hoang

d, c bit l cc loi chim nc; to ni c tr thch hp cho cc loi thy sn v

cung cp ngun ging thy sn t nhin; phc v cng tc nghin cu khoa hc v

rng ngp nc, t than bn, bo tn a dng sinh hc, cnh quan thin nhin v mi

trng ca vng t ngp nc U Minh h.

- Phn khu phc hi v s dng bn vng h sinh thi rng ngp nc c din

tch 4.961 ha (thuc Tiu khu 059, 061, 063 ca Lm Ng Trng Trn Vn Thi v

Tiu khu 069, 070, 072, 073, 075, 076 ca Lm Ng Trng U Minh III hin nay), c

chc nng ch yu l: Khi phc rng trm v h sinh thi t ngp nc; bo tnngun gen sinh vt qu him, ni sinh sng v kim n ca cc loi ng vt hoang

d, c bit l cc loi chim nc, ti to hng, thc vt bn a; bo v nhng cnh

quan thin nhin c th ca h sinh thi rng ngp nc, pht trin du lch sinh thi

v cc phng thc bo tn gn vi s dng bn vng cc loi ti nguyn ca h sinh

thi t ngp nc.

- Phn khu dch v hnh chnh c din tch 755 ha (din tch ca Phn tri K3

c thuc Tri giam K1 Ci Tu) c chc nng ch yu: L trung tm qun l v iu

hnh mi hot ng ca Vn quc gia U Minh H; l ni xy dng cc cng trnh:

Nh lm vic ca Vn quc gia, nh din gii mi trng, trung tm iu hnh du

lch sinh thi, nh khch cng v v cc hng mc cng trnh xy dng khc; L a

im xy dng mt h cha nc vi din tch t 200 300 ha, nhm mc ch phc

v phng, chng chy rng v cung cp nc ngt cho nhn dn vng ln cn.

Ngoi ra, Vn quc gia U Minh h cn c vng m vi din tch 25.013 ha,thuc phm vi Lm Ng Trng U Minh III, Lm Ng Trng Trn Vn Thi, Lm

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Ng Trng U Minh I, Trung tm ging huyn U Minh, Phn tri K3 mi thuc Tri

giam K1 Ci Tu v Trung tm nghin cu ng dng k thut rng ng p Minh Hi

(ngoi din tch quy hoch cho Vn quc gia U Minh H). (Trnh Vn Ln, 2006).

Tri qua bao th h con ngi i khai hoang, m t, nhng vn rng vn

khng mt i, rng vn c bo tn v pht trin, (Ngc Qun, 2007).

3.1.1.2. Ti nguyn thc vt v ng vt

V ti nguyn thin nhin, rng trm trn t than bn ca vng U Minh h c

tnh a dng sinh hc cao, c nhiu loi ng, thc vt qu him. U Minh h nm

trong vng bn o C Mau l mt vng t tr, tri qua qu trnh a mo hng ngn

nm hnh thnh y mt h sinh thi t ngp nc vi nhng ti nguyn ng,

thc vt c th ca Vit Nam. Rng trm U Minh h l mt kiu rng hn hp trn

t than bn, tiu biu cho kiu rng m ly, vi 79 loi cy c t nhin thuc 65 chi,

39 h thc vt khc nhau nh: trm, bi, mp, trm kh, b bi, mt ct, V c tng

dy leo pha di nh choi, dn, V hng vt rng, do c thm thc vt ngp

nc to ni c tr thun li cho nhiu loi ng vt hoang d, gm 32 loi th

thuc 13 h trong 8 b v 74 loi chim; c bit c hng chc loi chim, th qu him

c ghi vo Sch ca T chc Bo tn thin nhin Quc t (IUCN), nh: t t, ri

c lng mi, cy ging, cy hng, mo rng, di ch tai ngn, di nga ln, (TrnhVn Ln, 2006).

3.1.1.3. V ti nguyn thu sn

Rng trm U Minh h l ni sinh sng ca nhiu loi c nc ngt nh c lc,

c r, c tr, c tht lt, c sc rn,Nhng kt qu kho st cho thy thnh phn thy

sn Vn quc gia U Minh h c khong 37 loi c thuc 19 h. Trong c 9 loi

c kinh t l cc loi c: C r ng, tht lt, lc, dy, lc bong, tr vng, tr trng, sc

rn, sc bm. Trong cc loi c trn c 2 loi c xp vp sch ng Vt Vit

Nam gm c tr trng, c Cm. Mc e da cc loi ni trn bc T (be da), do

cn c bin php bo vi tng c ny, (y ban nhn dn tnh C Mau, 2007).

3.1.1.4. V cc gi trsinh thi, nhn vn

Rng U Minh l mt vng a l c khc su trong tim thc v tnh cm

ca ng bo Nam B ni ring, ca ngi Vit Nam ni chung, vi nhng hnh nh

rt thn quen ca rng trm, c thm cy dng x dy c, bt ngn, c t than bn,nc v rt nhiu sn vt tr ph, qu him. Rng U Minh h l vng cn ca

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cch mng ca Nam B trong sut hai thi k khng chin chng thc dn Php v

quc M, c ngha rt ln trong lch su tranh ho hng ca dn tc, gn lin vi

cc di tch lch s cch mng, l nhng gi tr tinh thn v cng qu gi ca vng t

U Minh kin cng, bt khut, (Trnh Vn Ln, 2006).

Theo Trnh Vn Ln (2006), chnh v nhng gi tr to ln ca rng U Minh h,

nn Th tng Chnh ph ban hnh Quyt nh v vic chuyn Khu bo tn thin

nhin V Di thnh Vn quc gia U Minh h, vi nhng mc tiu v nhim v sau:

- Mt l, bo tn v ti to cc gi tr v cnh quan thin nhin, mi trng sinh

thi v a dng sinh hc ca h sinh thi ngp nc c th, rng trm trn t than

bn. Bo tn v ti to ngun gen ca cc loi ng thc vt qu him, cung cp

ngun ging sinh vt t nhin cho ton vng.

- Hai l, s dng bn vng ti nguyn rng, ti nguyn thu sn v cc sn

phm khc ca h sinh thi t ngp nc phc v cho nhu cu pht trin kinh t

x hi ca a phng v ca vng.

- Ba l, bo tn cc gi tr vn ho, tinh thn, cc di tch lch s, gp phn gio

dc truyn thng u tranh chng gic ngoi xm ca th h cha ng cho cc th h

mai sau.

- Bn l, phc v cng tc nghin cu khoa hc, tham quan, pht trin du lchsinh thi v cc hot ng pht trin cng ng nng thn.

trin khai thc hin Quyt nh s 112/Q-TTg ca Th tng Chnh ph,

UBND tnh ang cho cc s, ngnh chc nng xy dng n v t chc b my,

lp d n u t xy dng Vn quc gia U Minh h, d n u t xy dng vng

m ca Vn quc gia U Minh h v D n pht trin du lch sinh thi ca Vn

quc gia. Vi cc d n u t nu trn v vi cc chng trnh hot ng ca Vn

quc gia U Minh h, nh: chng trnh qun l bo v rng v phng, chng chy

rng; chng trnh bo tn a dng sinh hc; chng trnh khi phc h sinh thi t

ngp nc v s dng bn vng ti nguyn t ngp nc v t than bn; chng

trnh nghin cu khoa hc; chng trnh pht trin du lch sinh thi; chng trnh qun

l rng trm v t ngp nc c s tham gia ca cng ng v cc bn lin quan;

chng trnh o to pht trin ngun nhn lc v bo tn a dng sinh hc, qun l

v s dng bn vng t ngp nc theo cch tip cn h sinh thi; chng trnh hptc quc t, tin chc rng rng U Minh h sc bo tn v pht trin bn vng trong

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tng lai, (Trnh Vn Ln, 2006).

Theo ti liu khoa hc, rng trm U Minh h - C Mau in hnh cho vic bo

v, n nh mi trng sinh thi cho vng Bn o C Mau, ngi ta cn v n l "l

phi xanh" cho c Nam B. Gi tr v tm quan trng ca n c ghi nhn trong

th mc rng cc nc vng chu .

Rng ngp y vi nt c sc ring c t than bn kh dy, nc ; l ni

tr ng ca nhiu ng, thc vt qu him; ni cung cp lm sn, gieo trng la, trng

cc loi cy n qu, nui trng, nh bt thy sn; l ni sinh sng ca cc cng ng

dn ca phng.

Vi ngha v nt c th ny, thi gian gn y, tnh C Mau dn sc u

t nhiu tng xy dng c sh tng, trc ht l xy dng trn 100 km ng

lng nha, ri ...i su v chy vng vo di tn cc cnh rng va phc v phng,

chng chy rng va to thun li cho c dn vng rng sinh hot, i li thng thong

cho khch tham quan du lch.

T vng t heo ht, giy trn vng t Vn quc gia U Minh h mi ngy

nhn nhp hn bi cc cng trnh quc gia: Cm cng nghip kh - in - m, Khu

cng nghip Khnh An v nhiu cng trnh phc v dn sinh khc v ang tip tc

c u t xy dng ngy cng nhiu, gp phn lm i thay vng t ngho kh UMinh.

bo v v lm giu vn rng Vn quc gia U Minh H, tnh C Mau

trin khai mt s nhim v, chng trnh hot ng c th: qun l bo va dng

sinh hc v ti nguyn thin nhin, cnh quan; pht trin v gi vn rng hin c,

trng rng mi, xc tin ti sinh rng; xy dng v ci thin c sh tng phc v

cng tc qun l, bo v; lp d n mi gi, h tru t pht trin du lch sinh thi

trn vng m ca Vn quc gia.

Vi bc i v cch lm kh c th, Vn quc gia U Minh h khng ch l ni

bo tn ton b nhng gi tr h sinh thi ca rng trm m ni y, trong tng lai

khng xa s l im tham quan, du lch sinh thi l th ti C Mau.

3.1.2. c im kinh t x hi

Theo qui hoch mi th trong phm vi Vn quc gia U Minh h khng c dn

c sinh sng. Ton bt nng nghip sc chuyn thnh vng m, (y ban nhndn tnh C Mau, 2007).

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Theo y ban nhn dn tnh C Mau (2007), vng m ca Vn quc g U

Minh h thuc phm vi 5 x nm trong hai huyn Trn Vn Thi v U Minh. l cc

x: x Khnh Lm, Khnh An, Nguyn Phch thuc huyn U Minh v cc x Trn

Hi, Khnh Bnh Ty Bc thuc huyn Trn Vn Thi.

Tng s h gia nh ca 5 x vng m l: 17.637 h, vi 82.552 khu. S h

gia nh nm trong vng m l: 4.077 h (chim 23.1% vi 18.823 khu). Nh vy

mc bnh qun nhn khu trong vng m tng ng vi mc bnh qun nhn khu

trn ton quc 4.7 ngi/h v mc bnh qun nhn khu ca vng (vng 7: vng

ng bng sng M Kng) l 5 ngi/h. Phn ln dn c t p trung trn cc tuyn

knh o , nh knh xng Minh H, knh 29, knh 33,cha hnh thnh cc cm dn

c. Dn cy l cc h ngho n t cc huyn U Minh, Trn Vn Thi, Ci

Nc,c giao t khon rng, (y ban nhn dn tnh C Mau, 2007).

Thnh phn dn tc: Vng m U Minh h l ni nh c ca dn tc kinh v

dn tc khme, trong ch yu l dn tc kinh (chim 95,6%), (y ban nhn dn

tnh C Mau, 2007).

Lao ng: Ch yu l lao ng nng nghip. Tng s lao ng l 11.792 ngi,

trong lao ng chnh l 6.449 ngi (chim 54.7%), lao ng ph l 5.343 ngi

(chim 45.3%) v ngoi lao ng l 441 ngi. (y ban nhn dn tnh C Mau, 2007).Ccu thu nhp ca cc h dn (81.5%) thu nhp t ngh nng lm ng

nghip. Thu nhp t lm thu cng chim t l kh cao (11.6%), cho thy ngi dn

y cn ngho, cuc sng cha n nh. Phn thu nhp t dch v, lng v cc ngnh

ngh khc chim t l nh (7%), (y ban nhn dn tnh C Mau, 2007).

Tnh trng nh , c khong 5% s h c nh trong tnh trng kh tt, 25% s

h c nh cht lng trung bnh, cn li l cht lng thp v khng c nh , (y

ban nhn dn tnh C Mau, 2007).

Nhn chung, ngi dn sng trn vng m U Minh h ch yu l nhng ngi

ngho, khng c vn sn xut nn khng chng trong sn xut. Cc m hnh Trm

La C l m hnh sn xut chnh ca ngi dn y, nhng cha c hnh thc t

chc qun l hp l, nhiu h dn cn quen vi hnh thi c canh cy la nn d b

ri ro mt ma. Phn ln cc ch h thiu kin thc v th trng, kh nng tiu th

sn phm. Th trng tiu th rng trm hin nay cha c u ra. H thng knh xphn ra bin cn cha hon thin, (y ban nhn dn tnh C Mau, 2007).

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3.2. KT QU THC HIN CC BC XY DNG BN HIN

TRNG

3.2.1. Chn nh

Khu vc nghin cu c chp bi v tinh World View 1 (nh trng en), c

chp bc sng t 0.4 0.9 m , nh c chp vo ngy 21 thng 01 nm 2008 v

y cng l nh c phn gii cao vi phn gii l 30m x 30m. nh khu vc U

Minh hc th hin qua hnh 3.1

Vng m

Vng m Vng m

Khu vc vn quc gia UMinh h

Hnh 3.1. nh v tinh World View 1 khu vc vn quc gia U Minh h.

y l nh th hin ton cnh khu vc vn quc gia U Minh h bao gm c

vng m ca vn quc gia U Minh h, khu vc U Minh h l phn bn trong ca

ng k mu xanh, phn bn ngoi ng k l vng m. Nhng i tng m

chng ta cn quan tm y ch l hin trng rng ca vn quc gia U Minh h. V

vy kt qu gii on c tt v tp trung th cn phi tch khu vc vn quc gia

U Minh h ra khi vng m . thc hin c vic ny th ta s dng phng php

che nh (Masking). Kt qu che nh c th hin hnh 3.2.

Sau nh c che i phn vng m gip cho chng ta d quan st c i

tng, to iu kin thun li cho chng ta khi phn bit cc i tng.

Nhng vi kt qu che nh, chng ta ch c th xc nh mt cch tng i v

ranh gii gia vn quc gia so vi vng m bao quanh khu vc vn quc gia U

Minh h (da vo h thng knh ca khu vc vn quc gia), iu ny snh hngn vic tnh din tch ca vn quc gia so vi din tch thc t c xc nh.

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Vng m c che

Vn quc giaU Minh h

Hnh 3.2. nh khu vc vn quc gia U Minh h c che.3.2.2. Nn nh

Nn nh l hiu chnh s mo hnh hc nhm loi tr sai s hnh hc do nh b

nghing gy ra v lm cho nh trvng ta thc ca n.

c th nn nh th cn phi c file nh ging nhnh cn c nn v c

ta hoc bn c ta ca khu vc c th hin trn nh. Vi ti ny,

s dng bn c s ha t bn giy bng phn mm Mapinfo ca khu vc th

hin trn nh v sau c lu li vi phn ui l .MIF xut sang ENVI.

Hnh 3.3. nh khu vc vn quc

gia U Minh h (cha nn).

Hnh 3.4. Bn khu vc U Minh

h c s ho.

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Bn khu vc vn quc gia U Minh h c s ha t bn rng trm

tnh C Mau c thnh lp nm 2005, th hin h thng knh ca vn quc gia. nh

khu vc vn quc gia U Minh hc chp vo nm 2008. Qua ta c th thy,

gia bn v nh khng c s khc bit nhau ln, y l iu kin thun li chn v

tr ging nhau gia nh v bn khi thc hin vic nn nh.

tin hnh vic nn nh ta cn hin thnh cn nn v xut bn c s

ha t phn mm MAPINFO, sau chn cc v tr tng ng (ging nhau) gia nh

v bn ri tin hnh nn nh. Vic chn im khng chc th hin qua hnh

3.5.

Hnh 3.5. V tr cc im tng ng c chn.

c th nn c nh thta phi chn t nht l 4 im khng ch ti cc v

tr tng ng gia nh v bn , khi nh c s khng b mo. nh c nn

c chnh xc cao th vic chn im khng ch phi tht chnh xc. i vi nh

nn, chn c 6 im ging nhau gia nh v bn . Sau khi v tr cc im c

chn gia nh v bn th ta ti v tr cc im c chn trn bn s tng

gn cho v tr cc im c chn tng ng trn nh khi ta tin hnh nn nh. Ta

ti v tr im th nht trn bn s tng gn cho v tr im th nht trn nh v

c nh vy ta v tr cc im c chn trn bn sc gn cho v tr cc

im c chn trn nh khi ta thc hin thao tc nn nh. Ta cc im khng ch

ca nh c nn c th hin bng 3.1. Kt qu ca vic nn nh c th hin hnh 3.7.

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Bng 3.1. Ta cc im khng ch trn nh c nn.

Ta khng chSTT

X Y1 489196 1027856

2 489346 1021796

3 491086 1018286

4 498796 1017806

5 499066 1021766

6 498586 1027646

Hnh 3.6. nh khu vc vn quc gia

U Minh h trc khi nn

Hnh 3.7. nh khu vc vn quc gia

U Minh h sau khi nn

Qua kt qu nn nh cho ta thy, nh trc khi nn v sau khi nn khng c s

khc bit nhau ln, iu ny l do nh c chp gc gn ng vi v tr ta

thc ca n nn sau khi nn nh khng c s thay i ln. Trn nh sau khi nn, tt ccc im trn nh u c ta tng ng c ni suy t 6 im khng ch.

3.2.3. Tng cng cht lng nh

Tng cng cht lng nh c thc nh ngha nh mt thao tc lm ni

bt hnh nh sao cho ngi gii on dc, d nhn bit ni dung trn nh hn so vi

nh gc. Phng php cbn thng c s dng l bin i cp xm, chuyn

i histogram, t hp mu,(L Vn Trung, 2005).

Vi s thay i ln ca cng phn xng vi nhiu knh ph do sadng ca vt th trn b mt tri t (t, nc, rng,) nn khng c thut ton hiu

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chnh bc x tng qut no c thc xem l ti u v cng khng c gii php

chung cho vic hin th ti u v sng cng nh mc tng phn thch hp cho tt

c cc i tng trong nh. Do ty vo tng trng hp ng dng c th v ty vo

tng loi nh v tinh cng vi nhng c im ca tng knh nh, ngi gii on cn

phi iu chnh sng v mc tng phn thch h p, (L Vn Trung, 2005).

nh c s dng gii on l nh trng en v c gi tr DN t 0 173. Do

vy cc i tng trn nh s c phn x gn ging nhau hay cc i tng tp

trung ti cc pixel c gi tr sng gn nhau. Trn nh s dng th cc i tng tp

trung ch yu cc pixel c gi tr sng trong khong 58 129. Kt qu l nh th

hin khng r rng cc i tng ( tng phn thp).

khc phc c hn ch trn chng ta cn phi bin cp xm ca nh

bng phng php ko gin tng phn tuyn tnh trn biu Histogram. y l k

thut tng cng cht lng nh n gin. Kt qu m chng ta c c l nh mi

c tng phn c tng cng v nh sau khi bin i trnn r rng hn.

Hnh 3.8. nh v biu Histogram Hnh 3.9. nh v biu Histogram

trc khi bin i tng phn. sau khi bin i tng phn.

Qua kt qu sau khi tng cng tng phn cho ta thy, cc i tng c

tng phn kh r rng, lm ni bt ln i tng cn quan tm. Trn biu Histogram ca nh trc khi tng cng tng phn th ta thy cc i tng trn

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nh c gi tr DN trong khong t 0 173 v cc i tng c gi tr DN tp trung

nhiu nht trong khong t 58 129 (Input Histogram), khi ta thc hin ko gin

tuyn tnh trn biu Histogram vi gi tr DN trong khong 58 129 th kt qu s

cho chng ta gi tr DN thay i t 0 255 (Output Histogram). Theo L Vn Trung

(2005) th gi tr sng ca pixel bt k trn nh c bin i c tnh theo

cng thc: minminminmax

minmax )( yxxxx

yyy +

=

Vi: - gi tr sng nh nht ca nh gc.minx

- gi tr sng ln nht ca nh gc.maxx

- gi tr sng nh nht ca nh bin i.miny

- gi tr sng ln nht ca nh bin i.maxyy l gi tr sng ca pixel bc k trn nh c bin i.

Kt qu trn biu Histogram ca nh sau khi tng cng tng phn

cc i tng trn nh c gi tr DN trong khong 0 255 (Input Histogram) v c

ngha: gi tr 0 = en, 50 = xm m, 150 = xm trung bnh, 200 = xm nht v 255

= trng. Khi nh ca chng ta trnn r rng hn, gip cho ta d dng phn bit

cc i tng.

Tuy nhin vi kt qu nh vy th chng ta ch c th phn bit c cc i

tng m chng ta lm ni bc hn so vi cc i tng khc, c th l c mu

sng hn hoc ti hn so vi cc i tng khc tu thuc gi tr DN c thay i.

V vy, khi chng ta cn quan tm n i tng no, xc nh c khong gi tr

DN ca i tng trn nh th ta t p trung ko gin tuyn tnh trn biu

Histogram vi gi tr DN trong khong th chng ta s nhn c kt qu l i

tng ca chng ta cn quan tm sc ni bt hn cc i tng khc. Vi kt qunh vy s gip cho chng ta d dng xc nh c i tng khi phn loi.

Lc nh cng l mt cch nhm tng cng cht lng nh. Lc nh nhm mc

ch hn ch hin tng mui v tiu trn nh phn loi, hoc lm m sinh ra trn

nh do sai s pht sinh ra trong qu trnh truyn d liu hoc b gin on tm thi.

Vi nh hng ny, mt s pixel trn nh c gi tr sng ln hn hay nh hn rt

nhiu so vi cc pixel xung quanh. Kt qu to ra cc im sng trng hay sm en

trn nh, lm nh hng n vic tch thng tin tnh. V vy trc khi phn loichng ta nn lc nh. ti ny s dng kiu lc median vi ca s 3x3, vi kiu

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lc ny th gi tr ca pixel trung tm s mang gi tr trung bnh ca cc pixel xung

quanh.

Hnh 3.10. nh khu vc vn quc gia U Minh h sau khi lc

nh sau khi lc trnn mn hn. Vi kiu lc Median ca s 3x3 th gi tr

ca pixel trung tm s mang gi tr trung bnh ca cc pixel xung quanh. Chng ta c

th thy r qua v d sau:

Input Output

16 12 2013 9 152 7 12

12

Pixel trung tm sau khi bin iPixel trung tm trc khi bin i

Hnh 3.11. S thay i gi tr sng ca pixel trung tm.

Tng t nh vy tt c cc pixel trn nh s ln lt c thay i, khi s

chnh lch v gi tr sng ca cc pixel lin k sc hn ch. Vi kt qu ny sgip cho chng ta c c kt qu gii on cc i tng tp trung hn.

3.2.4. Phn loi khng kim tra.

Mi pixel trn nh c c trng bi du hiu ph v n c gi tr sng

tng ng. Qu trnh phn loi l qu trnh x l cc du hiu ph ri qui nh thnh

cc ch tiu hay i tng.

Phng php phn loi khng kim tra ch yu da vo gi tr sng ca cc

pixel m my c th tng phn chia nh thnh nhiu i tng khc nhau. ng vimi i tng l nhng khong gi tr sng nht nh tng ng vi mt mu trn

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nh.

Sau khi nh c x l th tin hnh phn loi khng kim tra. ti ny

chn kiu phn loi IsoData, vi kiu phn loi ny cc nhm i tng c phn

loi da trn qui lut phn b v tn s xut hin ca cc pixel trn nh. S lng cc

nhm i tng c phn loi cng c th tng hoc gim ty theo yu cu ca

ngi gii on t ra. Ngoi ra ngi gii on cn c tht ra nhng ch tiu khc

nh: s ln lp li, s phn tnh ti thiu trong mt nhm,khi tin hnh phn loi

nh. Kt qu phn loi khng kim tra c th hin trn bn hin trng khu vc

vn quc gia U Minh h - C Mau (Hnh 3.13).

Kt qu phn loi khng kim tra c thc hin bi s gom nhm i tng

v c 4 i tng c gii on tng ng vi cc khong gi tr DN c th

hin qua bng 3.2.

Vi kt qu nh trn, nhm i tng 1 c gi tr DN cao t 82 173, y c

th l rng non bi v rng non th cu trc t bo ca l cy cha hon chnh v cht

dip lc t trong l cy rt t nn phn x li nhiu bc x mt tri v vy trn nh c

mu sng. i vi nhm i tng 2 c gi tr DN t 64 81 th y c th l rng lu

nm nn l cy cha nhiu dip lc tiu ny lm cho l hp thu phn ln cc bc x

mt tri b nn kt qu trn nh c mu ti. i vi nhm 3 v nhm 4 c gi tr DNthp t 0 63, y c th l vng rng tha, b ngp nc nn hp thu phn ln cc

bc x mt tri v vy i tng ny c gi tr DN thp, kt qu trn nh c mu nu

en n en. Kt qu phn loi khng kim tra c m t chi tit qua bng 3.2.

Bng 3.2. Bng m tc im cc i tng sau khi phn loi khng kim tra.

c im trn nh gcNhm itng

Mu trn nh phn loikhng kim tra

Sa cu Tonenh

Sc Gi trDN

Din tch(ha)

i tng 1 Mn Sng T xm n trng 82 173 7187,13i tng 2 Th Ti Nu 64 81 1189,89i tng 3 Hi th Ti Nu en 41 63 143,64i tng 4 Mn Ti en 0 40 30,24

Vi kt qu ny gip cho chng ta c c cchnhn khi qut v vn quc

gia U Minh h. Qua ta thy c phn ln din tch ca vn quc gia c gii

on l i tng rng cn non vi din tch l 7187,13 ha v sau l i tng rng

gi vi din tch l 1189,89 ha, cc i tng ny c phn b theo tng khu vc v

cng kh tp trung, cc i tng khc th chim din tch rt nh v khng c tptrung. Tuy nhin y ch l kt qu chng ta tham kho, s ph hp ca cc i

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tng cn phi c kim tra li. V v vy vic kim tra thc a c tin hnh.

336 1596

13221

79857

0

10000

20000

30000

40000

50000

60000

70000

80000

0 - 40 41 - 63 64 - 81 82 - 173

BIU TH HIN SPHN B CCI TNGS LNG PIXEL I TNG 1

I TNG 2

I TNG 3

I TNG 4

GI TR DN

Hnh 3.12. Biu Histogram th hin s phn b cc i tng trn nh.

Qua biu trn cho thy phn ln s lng pixel c gii on cho i

tng 1 vi gi tr DN t 82 173, cc i tng khc c gii on c s lng

pixel khng ng k. Nguyn nhn l do s phn loi khng kim tra ch da vo

gi tr s v tn s xut hin ca cc i tng nn c nhng i tng hon ton khc

nhau nhng li c gi tr sng gn bng nhau sc phn thnh mt nhm. T

chng ta c th thy c trn nh s phn x ca cc i tng ch tp trung 4

nhm tng ng 4 c

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