cong nghe vien tham - pham vong thanh va nguyen truong xuan

8/8/2019 Cong Nghe Vien Tham - Pham Vong Thanh Va Nguyen Truong Xuan

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Cng ngh vin thm

Dng cho hc vin cao hc Trc a1

Li ni u

Vin thm l k thut thu nhn thng tin ca cc i tng m

khng cn tip xc trc tip vi cc i tng . Ngy nay nc ta

cng nh cc nc khc trn th gii, cng ngh vin thm c sdng rng ri trong nhiu lnh vc nh thnh lp, chnh l bn a

hnh, iu tra hin trng s dng t, iu tra thm thc vt, nghin

cu ti nguyn mi trng, nghin cu bin, nghin cu tai bin thin

tai... Vi tm quan trng nh vy cng ngh vin thm c a vo

ging dy trong chng trnh o to sau i hc trong nhng nm

gn y.

Sau 5 nm o to, thng trc Hi ng Khoa hc v o to

trng ra quyt nh p dng khung chng trnh o to mi bt

u t nm 2001. c s phn cng ca Khoa o to sau i hc

v B mn Trc a nh, chng ti bin son gio trnh mn hc

"Cng ngh Vin thm" dng cho hc vin cao hc ngnh Trc a.

Bi ging gm 2 phn chnh:

Phn 1: C s Vin thm cp n cc vn chung ca

Vin thm nh gii thiu chung v vin thm v tinh, l thuyt phn x

ph ca cc i tng t nhin v on c iu v nh vin thm.Phn 2: X l nh Vin thm cp n cc vn x l s

nh vin thm nh tng cng cht lng nh, nn chnh hnh hc nh

vin thm v k thut phn loi trong vin thm.

Ton b ni dung bi ging c chia thnh 7 chng, chng

1, chng 2, chng 3 v 6.4 chng 6 do PGS.TS.Phm Vng

Thnh bin son; chng 4, chng 5, chng 6 v chng 7 do

PGS.TS.Nguyn Trng Xun bin son.

Mc d c nhiu c gng nhng chc chn khng trnh

c cc sai st, rt mong nhn c s ng gp ca ng nghip

v c gi cun sch c hon chnh hn.

Cc tc gi


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Chng 1

GII THIU CHUNG V VIN THM V TINH-----------------------------------------------------

.1.1. nh ngha v phn loi vin thm1. nh ngha

Vin thm c nh ngha nh mt khoa hc cng ngh m nh ncc tnh cht ca vt th quan st c xc nh, o c hoc phn tch mkhng cn tip xc trc tip vi chng.

Sng in t hoc c phn x hoc c bc x t vt th thng lngun ti nguyn ch yu trong vin thm. Tuy nhin nhng nng lng nht trng, trng trng cng c th c s dng.

Thit b dng cm nhn sng in t phn x hay bc x t vt thc gi l b cm.

Phng tin dng mang cc b cm c gi l vt mang. Vtmang gm kh cu my bay, v tinh, tu v tr.

2. Phn loi vin thm theo bc sng

Vin thm c th c phn thnh 3 loi c bn theo bc sng sdng (hnh 1.1) :

a. Vin thm trong di sng nhn thy v hng ngoi.

b. Vin thm hng ngoi nhit.

c. Vin thm siu cao tn.

Ngun nng lng chnh s dng trong nhm a l bc x mt tri. Mt

tri cung cp mt bc x c bc sng u th 500 m. T liu vin thm thuc trong di sng nhn thy ph thuc ch yu vo s phn x t b mt vtth v b mt tri t. V vy cc thng tin v vt th c th c xc nh tcc ph phn x. Tuy nhin, radar s dng tia laze l trng hp ngoi lkhng s dng nng lng mt tri. Ngun nng lng s dng trong nhm bl bc x nhit do chnh vt th sn sinh ra. Mi vt th trong nhit bnh

thng u t pht ra mt bc x c nh ti bc sng 10.000m.

Trong vin thm siu cao tn ngi ta thng s dng hai loi k thutch ng v b ng. Trong vin thm siu cao tn b ng th bc x siu caotn do chnh vt th pht ra c ghi li, trong vin thm siu cao tn ch


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Cng ngh vin thm


ng li thu nhng bc x tn x hoc phn x t vt th.

Vin thm trong di sng

nhn thy v hng ngoi

Vin thm hng

ngoi nhit

Vin thm siu

cao tn

B cm

i tngNgun bc x

Bc x ph

Ph in t

My nh

Photo detector

B cm siucao tn

Mt tri

i tngphn x

B cm

i tngBc x nhit

B cm B cm

i tngBc x siu

cao tn

RadaH s phn

tn li

Bc x phn x Bc x pht x

0,5 3 10 Chiu di sng

UV Nhn thy Hng ngoi Hng ngoi nhit Siu cao tn

0,4 0,7 1 mm

14

0,3 0,9

1 mm

30 cm

Hnh1.1. S phn loi vin thm theo bc sng


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.1.2. B cm v phn loi b cm1. nh ngha

B cm l b phn thu nhn sng in t c bc x, phn x t vtth. Vic phn loi cc b cm c th thc hin theo di sng thu nhn, cng

c th phn loi theo kt cu...

Cc b cm b ng thu nhn cc bc x do vt th phn x hoc phtx, cn cc b cm ch ng li thu c nng lng do vt th phn x tmt ngun cung cp nhn to. Mi loi b cm thuc cc nhm trn cn chiathnh cc h thng qut v khng qut. Sau chng li tip tc c chiathnh loi to nh v khng to nh. Loi b cm s dng nhiu trong vinthm hin nay l cc loi my chp nh, my qut a ph quang c, my qutin t.

Cc b cm quang hc c c trng bi cc tnh cht ph, b cmv hnh hc. Tnh cht ph th hin thng qua cc knh ph v b rng cachng. Cc thit b dng phim c c trng bi nhy ca phim, kh nnglc ca knh lc ph v cc tnh cht quang hc ca h thng thu knh. Ccc trng bc x c xc nh da theo s thay i ca bc x in t trcv sau khi i qua h thng quang hc. Cc c trng hnh hc th hin qua ccthng s nh trng nhn, trng nhn khng i, trng khp gia ccknh, bin dng hnh hc...

Lc phn gii l mt h s cho php xc nh gii hn v mt quantrc khng gian ca thit b quang hc. Gii hn phn gii l khong cch nhnht c th pht hin c gia hai im nh v gi tr nghch o ca n llc phn gii.

Vng nh sng b tr theo th t bc sng gi l ph. Chm tia nhsng trng c tch thnh ph thng qua cc thit b quang hc nh lngknh, knh lc ph.

2. My chp nh

a. My chp nh

Cc my chp nh thng s dng trong vin thm bao gm : mychp nh hng khng, my chp a ph, my chp ton cnh ...

Cc my chp nh hng khng thng c lp trn my bay hoc tuv tr dng vo mc ch chp nh o c a hnh. Nhng my chp nh tiubiu l my RMK do hng CARLZEISS hay my RC do hng LEICA Thu S


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ch to. Nhng my chp nh s dng trong vin thm v tinh gm c :METRIC CAMERA, my chp LFC t trn tu v tr con thoi. My chpKFA - 1000 do Nga ch to t trn v tinh COSMOS.

Cc t liu ca my chp nh thng s dng cho cc mc ch o c

cho nn kt cu ca chng phi tho mn cc iu kin quang hc v hnh hcc bn sau :

* Quang sai my chp nh phi nh.

* phn gii ng knh phi cao v nt ca nh phi c m botrong ton b trng nh.

* Cc yu t nh hng trong phi c xc nh chnh xc, v d:chiu di tiu c, to im chnh nh...

* Trc quang ca ng knh phi vung gc vi mt phng phim.

* H thng chng nho phi kh nng loi tr nh hng cachuyn ng tng i gia vt mang v qu t nht l khi chp nh t vtr.

b. c im ca h thng ghi nh bng vt liu nh

- Trn phim nh cha c lng thng tin ln ti 108 bt.

- Lc phn gii cao v kh nng khi qut ho ln.

- S dng rng ri trong khoa hc v sn xut trn cc loi my truyn

thng.

- Kh nng hin th quan st r rng.

- Trn phim nh c kh nng ghi nhn cng mt lc nhiu i lngvt l khc nhau nh : Mt quang hc, quang lng, hnh hc, nh tnh,nh lng ca cc i tng.

- Tnh n nh ghi nh ca h thng rt cao v c kh nng tnh ccc bin dng trong qu trnh to nh (nh sai s mo hnh knh vt, khnho...).

Tuy nhin h thng ny cng c mt s nhc im:

- Thng tin nh khng s dng trc tip c trong cc h thng mytnh khi cha bin thnh tn hiu in.

- Thng tin trn nh khng vn chuyn c trn khong cch t vtr v tri t theo thi gian m phi gi c cm thit b v phim nh x l


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trn mt t.

3. My qut

a. My qut a ph quang c

My qut quang c v c bn l mt bc x k a ph m nh n mtbc nh hai chiu c thu nhn da trn s phi hp chuyn ng gia vtmang v h thng gng quay hoc lc vung gc vi qu o chuyn ng.

My qut a ph quang c c cu thnh bi nhng phn chnh sau:

*H thng quang hc.

*H thng tch ph.

*H thng qut.

*B d.*H thng kim nh.

Cc h thng qut a ph quang c c th t trn my bay hoc vtinh. My qut a ph MSS v TM ca v tinh Landsat l nhng th d v myqut a ph quang c.

+ Nhng phn chnh ca my qut a ph quang c:

H thng quang hc

H thng knh vin vng phn x kiu Newton, Cassegrain hocRitchay - Chretien nhm hn ch s lch mu n mc ti thiu.

H thng tch ph

Cc h thng gng, lng knh hoc knh lc n ph thng c sdng.

H thng qut

Cc gng quay hoc lc trong h thng vung gc vi ng bay lphn t qut c bn.

B d

Nng lng in t c chuyn i thnh tn hiu in nh b dquang in t. Cc b khuch i quang hc thng c s dng cho cc disng nhn thy v vng tia cc tm. i vi vng sng hng ngoi v vngnhn thy ngi ta thng dng diot silicon, vng sng ngn. Dng Ingiumantimony (Isnb) v o bc x nhit ngi ta dng diot HqCdTe.


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H thng kim nh

Cc tn hiu in o c lun b nh hng bi s bin ng nhyca h thng d, do vy cn phi duy tr thng xuyn mt ngun nh snghoc nhit c cng n nh lm ngun nng lng chun kim nh

thng s b cm.So snh vi h thng qut in t (Pushbroom) th cc h thng qut

quang c c nhng u im. V d trng nhn ca h thng quang hc c thnh hn, trng khp gia cc knh ph cao hn v c th thit k cc hthng c phn gii cao hn. Tuy vy nhc im c bn ca n l t shiu dng tn hiu - nhiu li nh hnso vi h thng qut in t.

b. My qut a ph in t

Cc h thng in t hoc b cm mng tuyn tnh l h thng qut

trong khng c b phn c hc nh gng quay. B phn ghi nhn tn hiuch cht l mng tuyn tnh. Cc b d bn dn cho php ghi li ng thitng hng nh (hnh 1. 2).

Hnh1.2.S ca d liu thu c bi h thng qut in t.

Cc h thng qut in t khng c b phn c hc no nn nnh hot ng ca n rt cao. Tuy vy thng xut hin nhiu trn mt hngnh do chnh lch nhy gia cc b d.

Cp thit b np (CCD) thng c dng trong b cm mng tuyntnh nn i khi ngi ta thng gi chng l b cm tuyn tnh CCD hay my

Dng qut

ng bay ca vt mang

B phn quang hc

B cm mng tuyn tnh


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chp CCD. HRV ca v tinh SPOT, MESSR ca MOS-1 v OPS ca JERS-1l nhng v d v b cm tuyn tnh CCD t trn v tinh.

c. c im ca h thng ghi nh bng my qut a ph

- C kh nng ghi nhn nh theo chu k thi gian, thng tin mang tnh

thi s.

- Lc phn gii cao, khi qut ha ln.

- C th x l tip theo cc thng tin bng phng php tnh ton,cng, tr, chia cc knh ph nn sn phm a dng hn nh chp.

- C th a thng tin ghi nhn c v cc li chiu.

H thng Landsat ca M c b phn qut bng gng xoay sau a thng tin qua ng knh quang hc vo my. H thng SPOT qut bng

mt dy Detector.Ngoi ra h thng my qut nh trn v tinh cng c mt s nhc

im nh:

- Lc phn gii ca nh qut thp hn nh chp.

- Qu trnh truyn thng tin v mt t s b nhiu.

- x l thng tin phi s dng cc h thng my tnh in t phctp.

.1.3. Cc v tinh vin thmV tinh c mang b cm vin thm gi l v tinh vin thm hay v tinh

quan st mt t.

1. V tinh Landsat

H thng Landsat c phng ln qu o ln u tin nm 1972, chon nay, c 5 th h v tinh c phng. Mi v tinh c trang b mt bqut a ph MSS, mt b chp nh v tuyn truyn hnh RBP. H thngLandsat - 4, 5 cn c trang b thm mt s b qut a ph TM.

T liu v tinh Landsat l t liu vin thm ang c s dng rng ritrn ton th gii v Vit Nam.

a. Qu o v tinh Landsat.

- cao bay: 705km, gc nghing mt phng qu o: 980

- Qu o ng b mt tri v bn lp.


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- Thi im bay qua xch o: 9h39' sng.

- Chu k lp: 17 ngy.

B rng tuyn chp: 185km.

b. B cm:

MSS (Multispectral scanner) v TM (Thematic mapper)

C 2 b cm ny u l my qut quang c.

H thng Landsat MSS hot ng di ph nhn thy v gn hngngoi (bng 1). c im ca MSS l:

- S dng 4 bng ph.

- Mi bng ph c trang b 6 b thu, c s dng si quang hc.

- Ghi tn hiu nng lng phn x t b mt tri t.- Tn hiu c m thnh 64 cp sng.

- phn gii mt t 80m.

- Gc qut t ng sang Ty l 11,60

- Thi gian l quang 33 mili giy.

- rng mi ng qut 185 km

Bng 1

Knh ph Dng phn x ph Bc sng ()

1 Nhn thy - xanh 0.5 - 0.6

2 Nhn thy - 0.6 - 0.7

3 Hng ngoi 0.7 - 0.8

4 Hng ngoi 0.8 - 1.1

H thng Landsat TM s dng vng th nhn thy, gn hng ngoi vhng ngoi nhit (bng 2)

Cc c im ca nh TM:

- rng cc ng qut: 185 km.

- Gc qut: 14.80

- phn gii mt t: 30 m.

Bng 2


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Knh ph Bc sng ()1 0 45 - 0.522 0.52 - 0.603 0.63 - 0.69

4 0.76 - 0.905 1.55 - 1.756 10.4 - 12.57 2.08 - 2.35

2. V tinh SPOT

H thng SPOT c Php phng nm 1986. Cho n nay c bnth h v tinh c phng ln qu o. Mi v tinh c trang b mt b quta ph HRV.

T liu v tinh SPOT l t liu vin thm hin ang c s dng rngri trn th gii v Vit Nam.

a. Qu o.

- cao bay 830km, gc nghing ca mt phng qu o 98,7o

- Thi im bay qua xch o: 10 gi 30 sng.

- Chu k lp: 26 ngy trong ch quan st bnh thng.

Bng 3

Cc c trng ca HRV Dng a ph Dng ton sc0.50 - 0.59 0.5 1 - 0.730.61 - 0.68

Band

0.79 - 0.89Trng nhn 4. 1 3 4. 1 3 phn gii 20 x 20 m 10 x 10mS Pixel trn mt hng 3.000 6.000 rng ng qut 60 km 60 km

b.B cm.B cm HRV khng phi l my qut quang c m l my qut in t

CCD. HRV c th thay i gc quan st nh mt gng nh hng. Gngny cho php thay i hng quan st + 270 so vi trc thng ng nn c ththu c nh lp th.

Cc thng s ca nh SPOT ch ra bng 3.


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3. V tinh COSMOS

T liu v tinh Cosmos l t liu vin thm c s dng rng ri trn

th gii v nc ta. nh v tinh ca Lin X c hai loi.

a.nh c phn gii cao.

cao bay chp: 270 km

Tiu c my chp f = 1.000mm

Kch thc nh: 30 x 30 cm

phn gii mt t: 6 - 7 m.

Chp hai knh ph.

ph dc > 60 % .

b.nh c phn gii trung bnh:

cao bay chp 250 km

Tiu c my chp f = 200mm

Kch thc nh: 18 x 18 cm

phn gii mt t: 30 m.

Chp ba knh ph 510 - 600m.

600 - 700m

700 - 850 m

ph dc > 60%.

.1.4. Tliu s dng trong vin thmKt qu ca vic thu nhn nh t v tinh hay my bay ta s c nhng

tm nh dng tng t hay dng s, lu tr trn phim nh hoc trn bng t.

1. nh tng t

nh tng t l nh chp trn c s ca lp cm quang halogen bc,nh tng t thu c t cc b cm tng t dng phim ch khng s dngcc h thng quang in t. Nhng t liu ny c phn gii khng gian caonhng km v phn gii ph. Ni chung loi nh ny thng c mohnh ln do nh hng ca cong b mt tri t. V tinh Cosmos ca Ngathng s dng loi b cm ny.


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2. nh s

nh s l dng t liu nh khng lu trn giy nh hoc phim. Nc chia thnh nhiu phn t nh thng c gi l pixel. Mi pixel tngng vi mt n v khng gian. Qu trnh chia mi nh tng t thnh cc

pixel c gi l chia mu(Sampling) v qu trnh chia cc xm lin tcthnh mt s nguyn hu hn gi l lng t ha. Cc pixel thng c dnghnh vung. Mi pixel c xc nh bng ta hng v ct. H ta nhthng c im 0 gc trn bn tri v tng dn t tri sang phi i vi chs ct v t trn xung i vi ch s hng. Trong trng hp chia mu mtnh tng t thnh mt nh s th ln ca pixel hay tn s chia mu phic chn ti u. ln ca pixel qu ln th cht lng nh s ti, cn trongtrng hp ngc li th dung lng thng tin li qu ln. Hnh 3 ch ra s nguyn l chia mu v lng t ha.

a. Khi nim chia mu

S phn b lin tc cacp xm hay mu

S pixel

Sdng

Tc chia mu

Chia mu

nh tng t nh s

pixel

Vf

fd

f: tng t

fd: lng t hoV: n v cng n: S nguyn(n-0,5)V f < (n+0,5)V fd =nSai s lng t ho: f-fd (Phn bng)

b. Khi nim lng t ho


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c. Lng t ha trong trng hp tn hiu c cha nhiu

Hnh1.3.S nguyn l chia mu v lng t ha

nh s c c trng bi mt s thng s c bn v hnh hc bc xbao gm:

- Trng nhn khng i l gc khng gian tng ng vi mt n vchia mu trn mt t. Lng thng tin ghi c trong trng hnh khng itng ng vi gi tr pixel.

- Gc nhn ti a m b cm c th thu c sng in t gi l trngnhn. Khong khng gian trn mt t do trng nhn to nn chnh l b rngtuyn bay.

- Vng b nht trn mt t m b cm nhn c gi l phn giimt t. i khi hnh chiu ca mt pixel ln mt t c gi l phngii. Bi v nh s c ghi li theo nhng di ph khc nhau nn ngi ta gil t liu a ph (hnh 1. 4).

Nng lng sng in t sau khi ti b d c chuyn thnh tn hiuin v sau khi lng t ha tr thnh nh s. Trong ton b di sng tng tthu c ch c phn bin i tuyn tnh c lng t ha. Hai phn bin catn hiu khng c xt n v chng cha nhiu nhiu v khng gi c

quan h tuyn tnh gia thng tin v tn hiu. Xc nh ngng nhiu l mtvic ht sc cn thn. Cht lng ca t liu c nh gi qua t s tnhiu/nhiu. T s tn hiu/nhiu c nh ngha thng qua biu thc sau:

S = 20*lg (S/N)[dB]. Nratio

Thng tin c ghi theo n v bit. Trong x l s, n v x l thngl byte. Do vy i vi t liu c s bit nh hn hoc bng 8 th c lu

Vo

Ra


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dng 1 byte (v 1 byte bng 8 bit) v t liu s c s bit ln hn 8 c lu dng 2 byte hay trong 1 t. Trong 1 byte c th lu c 256 cp xm, cntrong 1 t c th lu c 65536 cp xm.

Ngoi cc thng tin nh, trong mi ln lu tr ngi ta phi lu thm

nhiu thng tin b tr khc nh : s hiu ca nh, ngy, thng, nm, cc chtiu cht lng.

Hnh 1.4.S m t mi tng quan gia cc khi nim

3. S liu mt t.

S liu mt t l tp hp cc quan st m t, o c v cc iu kinthc t trn mt t ca cc vt th cn nghin cu nhm xc nh mi tngquan gia tn hiu thu c v bn thn cc i tng. Ni chung cc s liumt t cn phi c thu thp ng thi trong cng mt thi im vi s liuv tinh hoc trong mt khong thi gian sao cho cc s thay i ca cc itng nghin cu trong thi gian khng nh hng ti vic xc nh miquan h cn tm.

S liu mt t c s dng cho cc mc ch sau:

- Thit k cc b cm

- Kim nh cc thng s k thut ca b cm.

4 3 2 1

H thng quang hc

1 2 3 4

B knh tch sng I

B knh tch sng J

Chiu rng chuyn bay

Trng nhn

Trng nhn khng i

phn gii mt t


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- Thu thp cc thng tin b tr cho qu trnh phn tch v hiu chnhs liu.

Khi kho st thc a ta cn thu thp cc s liu :

a. Cc thng tin tng quan v thng tin chi tit v i tng nghin

cu nh chng loi, trng thi, tnh cht phn x v hp th ph, hnh dng bmt, nhit ...

b. Cc thng tin v mi trng xung quanh, gc chiu v cao mttri, cng chiu sng, trng thi kh quyn, nhit , m khng kh,hng v tc gi.

Do vic thu thp s liu mt t l cng vic tn km thi gian v kinhph cho nn ngi ta thng thnh lp cc khu vc th nghim trong c y cc i tng cn theo di v o c.

4 . S liu nh v mt t

c th t c chnh xc trong qu trnh hiu chnh hnh hccn phi c cc im nh v trn mt t c ta a l bit. Nhng imny thng c b tr ti nhng ni m v tr ca n c th thy c d dngtrn nh v bn .

Hin nay ngi ta s dng h thng nh v ton cu GPS vo mcch ny.

5. Bn v s liu a hnh phc v cho cc cng tc nghin cu ca vin thm cn phi c

nhng ti liu a hnh v chuyn sau :

-Bn a hnh t l 1/25.000 hoc 1/50.000.

Trn bn a hnh c th ly c to cc kim tra phc v vichiu chnh hnh hc hoc cc thng s cao nhm khi phc li m hnhthc a.

-Bn chuyn

Cc bn chuyn s dng t, rng, a cht... t l khong1/5.000 n 1/25.000 rt cn cho vic nghin cu chuyn ,chn vng muv phn loi. Nu cc bn ny c s ha v lu trong my tnh th c thc s dng xy dng c s d liu h thng tin a l.

-Bn kinh t x hi


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Cc ranh gii hnh chnh, h thng giao thng , cc ch s thng kcng nng nghip... cng l cc thng tin quan trng c th c khai thctrong vin thm.

-M hnh s a hnh

Bn cnh cc dng bn truyn thng, trong vin thm cn s dngmt dng s liu khc l m hnh s a hnh hay m hnh s cao cto ra t ng bnh , li s liu cao phn b u, li s liu caophn b ngu nhin hay cc hm m t b mt.


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Chng 2

L THUYT PHN X PH CA CCi TNG T NHIN

---------------------------------.2.1. Bc x in t1. Bc x in t

Bc x in t truyn nng lng in t trn c s cc dao ng catrng in t trong khng gian hoc trong lng cc vt cht. Qu trnh lantruyn ca sng in t tun theo nh lut Maxwell. Bc x in t c tnhcht sng v tnh cht ht.

Tnh cht sng c xc nh bi bc sng, tn s v tc lan

truyn, tnh cht ht c m t theo tnh cht quang lng t hay pho ton.Bc x in t c 4 tnh cht c bn l tn s hay bc sng, hng lantruyn, bin v mt phn cc.

Bn thuc tnh ca bc x in t lin quan n cc ni dung thng tinkhc nhau, v d nh tn s hay bc sng lin quan ti mu sc, s phn cclin quan n hnh dng ca vt th.

Tt c cc vt th u phn x v hp th, phn tch v bc x sngin t theo cc cch khc nhau v c trng ny thng c gi l c trng

ph.Hin tng phn x ph c lin quan mt thit vi mi trng m

trong mi trng sng in t lan truyn, v nng lng truyn trong khng

gian dng sng in t. Di sng in t c coi l di sng t 0,1 n10km.

Hnh 2.1 ch ra s phn loi sng in t v cc knh ph s dngtrong vin thm.

Di sng nhn thy cn gi l vng sng chp nh c tc l sngin t vng ny c th ghi nhn c ln phim nh. Trong phng phpvin thm cc thng tin vng ph nhn thy c th ghi ln phim nh nh lti liu gc o trc tip nng lng phn x ph dng lin tc.

Ngoi di ph nhn thy, thng tin v nng lng phn x ph ca cci tng c ghi nhn bng s ri rc v c hin th tip theo di dngnh qua thit b bin i thng tin ri rc thnh thng tin lin tc.


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2. Ngun chiu sng v th phn x ph nng lng mt tri

Ta bit rng mi i tng t nhin u phn x nng lng mt trichiu ln chng mt cch xc nh, c trng cho trng thi v bn cht cci tng .

Phng php th ng ghi nhn nh l thu nhn nh sng phn x ti tng do mt tri chiu xung. Hin nay a s cc h thng thu nhn nhv tr (tr h thng raa) hot ng theo phng php th ng. V vy khinghin cu ngun sng trong h thng vin thm ta ch yu xt n mt tri.

Lp di sng Tn s

T ngoi 100A0 ~ 0,4 750~ 3.000THz

Nhn thy 0,4 ~ 0,7 430 ~ 750THzCn hng ngoi 0,7 ~1,3 230 ~ 430THz

Hng ngoi ngn 1,3 ~ 3 100 ~ 230THz

Gia hng ngoi 3 ~ 8 38~100THz

Hng ngoi nhit 8 ~ 14 22 ~ 38THz

Hng ngoi

Hng ngoi xa 14 ~ 1mm 0,3 ~ 22THz

0,1 ~ 1mm 0,3 ~ 3THzMilimet (EHF) 1 ~ 10m 30 ~ 300GHz

Centimet (SHF) 1 ~ 10cm 3 ~ 30GHzSngMicro

Decimet (UHF) 0,1 ~ 1m 0,3 ~ 3GHz

Sng cc ngn (VHF) 1 ~ 10m 30 ~ 300MHz

Sng ngn(HF)

10 ~ 100m 3 ~ 30MHz

Sng trung(MF)

0,1 ~ 1km 0,3 ~ 3MHz

Sng di(LF)

1 ~ 10km 30 ~ 300KHz

Sng Radio

Sng rt di(VLF)

10 ~ 100km 3 ~ 30KHz


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quyn v b mt i tng cng nh bn thn cc i tng.

1. Mt s khi nim c trng phn x ph cc i tng t nhin

Sng in t chiu ti mt t, nng lng ca n s tc ng ln bmt tri t v s xy ra cc hin tng sau:

- Phn x nng lng.

- Hp th nng lng.

- Thu quang nng lng.

Nng lng bc x s chuyn i thnh ba dng khc nhau nh trn.Gi s coi nng lng ban u bc x l EO th khi chiu xung cc i tng

n s chuyn thnh nng lng phn x E, hp th E v thu quang E. Cth m t qu trnh trn theo cng thc:

Eo = E+ E+ E (a) .

Trong qu trnh ny ta phi lu hai im:

Th nht l khi b mt i tng tip nhn nng lng chiu ti, tythuc vo cu trc cc thnh phn, cu to vt cht hoc iu kin chiu sng

m cc thnh phn E, E, E s c nhng gi tr khc nhau i vi cc itng khc nhau. Do vy ta s nhn c cc tm nh ca cc i tng khcnhau do thu nhn nng lng phn x khc nhau. Ph thuc vo cu trc bmt i tng, nng lng phn x ph c th phn x ton phn, phn xmt phn, khng phn x v mt hng hay phn x mt phn c nh hng(hnh 2.2) .

a - Phn x ton phn

b - Phn x mt phn


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c - Tn x ton phn

( Khng phn x v mt hng)

d - Tn x mt phn

(Phn x mt phn c nh hng)

Hnh 2.3Mt s phn x

Cc dng phn x t cc b mt nh trn cn c lu khi on ciu v cc nh v tr v cc nh my bay nht l khi x l hnh nh thiu ccthng tin v cc khu vc ang kho st. iu c ngha l phi bit r ccthng s k thut ca thit b c s dng, cc phn chp, iu kin chpnh, v nhng yu t ny c vai tr nht nh trong vic on c iu v nh.

Th hai l nng lng chiu ti i tng c phn x khng nhngph thuc vo cu trc b mt i tng m cn ph thuc vo bc sng canng lng chiu ti. Do vy m trn nh ta thy hnh nh i tng do ghinhn c kh nng phn x ph ca cc bc sng khc nhau s khc nhau.

1 - ng c trng phn x ph ca thc vt.

2 - ng c trng phn x ph ca t kh.

3 - ng c trng phn x ph ca nc.

20

40

60

0

0,6 1,0 1,4 1,6 2,0 2,4

()

r(%)

0,8 1,2 1,8 2,2 2,6

2

1

3

Hnh 2.4c tnh phn x ph ca mt s i tng t nhin


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Cc h thng vin thm ch yu ghi nhn nng lng phn x ph nncng thc (a) c th vit li l:

E = Eo - (E+ E) (b)

Nng lng phn x bng tng nng lng bc x tr nng lng hp

th v nng lng thu quang.

nghin cu s ph thuc ca nng lng phn x ph vo bcsng in t ta a ra khi nim kh nng phn x ph. Kh nng phn x phr ca bc sng c nh ngha bng cng thc :

%)100.()(

)(

0

E

Er = (c)

thy r c tnh phn x ph ph thuc vo bc sng ta xt th

sau (hnh 1.8)2. c tnh phn x ph ca cc i tng t nhin

a. c tnh phn x ph ca thc vt:

Kh nng phn x ph ca thc vt xanh thay i theo di bcsng. Trn th (hnh 2.5) th hin ng c trng phn x ph thc vtxanh v cc vng phn x ph chnh.

()

20

40

60

0 0,6 1,0 1,4 1,6 2,0 2,4

(%) r

0,8 1,2 1,8 2,2 2,6

Sc t hp th Nc hp th

Nhn thyCn hng ngoi

Hng ngoi

Phn x ph hng ngoi

Sc tCu trct bo Thnh phn nc

Cc yu t chnh nhhng n kh nng

phn x ph ca l cy

Nhng di ph hp th

Hnh 2.5c tnh phn x ph ca thc vt.


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Trong vng sng nh sng nhn thy cc sc t ca l cy nh hngn c tnh phn x ph ca n, c bit l cht clorophin trong l cy, ngoira cn mt s cht sc t khc cng ng vai tr quan trng trong vic phnx ph ca thc vt.

Hnh 2.6. c tnh hp th ca l cy v ca nc

Theo th trn ta thy sc t hp th bc x vng sng nh sng nhnthy v vng cn hng ngoi, do trong l cy c nc nn hp th bc xvng hng ngoi. Cng t th trn ta c th thy kh nng phn x ph cal xanh vng sng ngn v vng nh sng l thp. Hai vng suy gim kh

nng phn x ph ny tng ng vi hai di sng b clorophin hp th. haidi sng ny, clorophin hp th phn ln nng lng chiu ti, do vy nnglng phn x ca l cy khng ln. Vng sng b phn x mnh nht tng

ng vi sng 0,54. tc l vng sng nh sng lc. Do l cy ti cmt ta cm nhn c mu lc. Khi l a hoc c bnh, hm lng clorophintrong l gim i lc kh nng phn x ph cng s b thay i v l cy sc mu vng .

vng hng ngoi nh hng ch yu ln kh nng phn x ph ca

l cy l hm lng nc trong l. Kh nng hp th nng lng (r) mnhnht cc bc sng 1,4 ; 1,9 v 2,7. Bc sng 2,7 hp th mnh nhtgi l di sng cng hng hp th, y s hp th mnh din ra i vi

sng trong khong t 2,66 - 2,73.

Trn hnh 10 cho thy di hng ngoi kh nng phn x ph ca l

mnh nht bc sng 1,6 v 2,2 - tng ng vi vng t hp th ca nc.

()0 0,5 1,3 2,1 2,5

0,9 1,7

20

40

60

%

80

100r

........ Hp th ca ncPhn x ca l cy


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Khi hm lng nc trong l gim i th kh nng phn x ph ca lcy cng tng ln ng k (hnh 2.7).

Hnh 2.7. c tnh phn x ph ca thc vt.

Tm li: Kh nng phn x ph ca mi loi thc vt l khc nhau vc tnh chung nht v kh nng phn x ph ca thc vt l:

- vng nh sng nhn thy, cn hng ngoi v hng ngoi kh nngphn x ph khc bit r rt.

- vng nh sng nhn thy phn ln nng lng b hp th biclorophin c trong l cy, mt phn nh thu qua l cn li b phn x.

- vng cn hng ngoi cu trc l nh hng ln n kh nng phn

x ph, y kh nng phn x ph tng ln r rt.- vng hng ngoi nhn t nh hng ln n kh nng phn x ph

ca l l hm lng nc, vng ny khi m trong l cao, nng lng hp

th l cc i. nh hng ca cc cu trc t bo l vng hng ngoi i vikh nng phn x ph l khng ln bng hm lng nc trong l.

b. Kh nng phn x ph ca th nhng

ng c trng phn x ph ca a s th nhng khng phc tpnh ca thc vt. Hnh 2.8 th hin kh nng phn x ph ca ba loi t

trng thi kh.

c tnh chung nht ca chng l kh nng phn x ph tng theo

di bc sng, c bit l vng cn hng ngoi v hng ngoi. y ch cnng lng hp th v nng lng phn x, m khng c nng lng thuquang. Tuy nhin vi cc loi t ct c thnh phn cu to, cc cht hu cv v c khc nhau, kh nng phn x ph s khc nhau. Ty thuc vo thnh

()

1

0,5 1,3 2,1 2,5

0,9 1,7

20

40

60

80

r(%)

23

4

1. m < 40%

2. m 40 54%

3. m 54 66%4. m >66%

0,7 1,1

1,5

1,9

2,3


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phn hp cht m bin ca th phn x ph s khc nhau. Cc yu tch yu nh hng n phn x ph ca t l cu trc b mt ca t, mca t, hp cht hu c, v c.

Hnh 2.8.c tnh phn x ph ca th nh

ng.Cu trc ca t ph thuc vo t l st, bi, ct. St l ht mn ng

knh nh hn 0,002mm, bi c ng knh 0,002mm - 0,05mm, ct c ngknh 0,05mm - 2mm. Ty thuc t l thnh phn ca ba loi t c bn trnm to nn cc loi t c tn khc nhau.

Vi t ht mn th khong cch gia cc ht cng nh v chng stgn nhau hn. Vi ht ln khong cch gia chng ln hn, do vy kh nngvn chuyn khng kh v m cng d dng hn. Khi m t, trn mi ht

ct s bc mt mng mng n

c, do vy m v l

ng n

c trong loi tny s cao hn v do m cng s nh hng ln n kh nng phn xph ca chng,

Hnh 2.9. Kh nng phn x ph ca t ph thuc vo m

0 0,5 1,3 2,1 2,5

0,9 1,7

20

40

60

80

r(%)

........ t mnt bit ct

()0 0,5 1,3 2,1 2,5

0,9 1,7

20

40

60

80

r(%)

1. ............... m 04%

2. m 512%

3. m 2232%

100


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Khi m tng kh nng phn x ph cng s b gim (hnh 2.9). Dovy khi ht nc ri vo ct kh ta s thy ct b thm hn, l do s chnhlch r rt gia cc ng c trng 1, 2, 3. Tuy nhin nu ct m m cthm nc cng s khng thm mu i my (do s chnh lch t gia ng 2v ng 3).

Mt yu t na nh hng n kh nng phn x ph l hp cht huc trong t. Vi hm lng cht hu c t 0,5 - 5,0% t c mu nu xm.Nu hm lng hu c thp hn t s c mu nu sng.

xt st cng nh hng ti kh nng phn x ph ca t. Kh nngphn x ph tng khi hm lng xt st trong t gim xung, nht l vngph nhn thy (c th lm gim ti 40% kh nng phn x ph khi hm lng xt st tng ln).

Khi b xt st ra khi t, th kh nng phn x ph ca t tng lnr rt di sng t 0,5 - 1,1 nhng vi bc sng ln hn 1,0 hu nhkhng c tc dng.

Nh trn ni c nhiu yu t nh hng n kh nng phn x phca t, tuy nhin chng c lin quan cht ch vi nhau. Cu trc, m, mn b mt, hm lng cht hu c v xt st l nhng yu t quan trng.Vng phn x v bc x ph c th s dng ghi nhn thng tin hu ch vt cn hnh nh hai vng ph ny l du hiu on c iu v cc ctnh ca t.

Mt im quan trng cn lu l mc d bin th kh nngphn x ph ca cc loi t c th khc xa nhau nhng nhn chung nhngkhc nhau ny n nh nhiu di sng khc nhau. i vi thc vt chng taphi nh kh nng phn x ph ph thuc bc sng (tc l on c iu v cc knh khc nhau), nhng vi th nhng khng th lm c nh vy,mc d s khc bit v kh nng phn x ph l quan trng nhng nhiu ctnh phn x ph ca chng phi on c iu v cc di sng nhn thy.

c. Kh nng phn x ph ca nc

Cng nh trn, kh nng phn x ph ca nc thay i theo bcsng ca bc x chiu ti v thnh phn vt cht c trong nc. Kh nngphn x ph y cn ph thuc vo b mt nc v trng thi ca nc.Trn knh hng ngoi v cn hng ngoi ng b nc c pht hin rt ddng, cn mt s c tnh ca nc cn phi s dng di sng nhn thy nhn bit.


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Trong iu kin t nhin, mt nc hoc mt lp mng nc s hpth rt mnh nng lng di cn hng ngoi v hng ngoi (hnh 2.10) dovy, nng lng phn x rt t. V kh nng phn x ph ca nc di sngdi kh nh nn vic s dng cc knh sng di chp cho ta kh nng on

c iu v thy vn, ao h... di sng nhn thy kh nng phn x ph canc tng i phc tp. Vit phng trnh cn bng nng lng v nghincu kh nng phn x ph ca nc di sng nhn thy:

E() = E() + EH() + ET()

E() = E() + E() + E

Hnh 2.10.Kh nng phn x v hp th ca nc.

Nh hnh 2.11nc ct b hp th t nng lng di sng nh hn

0,6 v thu quang nhiu nng lng di sng ngn. Nc bin, nc ngtv nc ct c chung c tnh thu quang, tuy nhin thu quang ca ncc gim r rt v bc sng cng di c thu quang cng ln.

Hnh 1.11.Kh nng phn x ph ca mt s loi nc.

0,4 0,5 0,6 0,7

10

20

30

50

40

2

1

1- Hp th2- Phn x

( )

r(%)

0,4 0,5 0,6 0,7

21 1- Nc sng

2- Nc i dng3- Nc gn b4- Nc vnh

( )0,250,51

50

2,5

r(%)

0,1

51025

3

4


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Kh nng thu quang cao v hp th t di sng nhn thy chng trng i vi lp nc mng (ao, h nng) v trong th hnh nh vin thm ghinhn c di sng nhn thy l nh nng lng phn x ca cht y: ct,...

thu quang ca nc ph thuc vo bc sng nh sau:Bng 4

Bc sng thu quang

0,5 0,6 n 10m

0,6 0,7 3m

0,7 0,8 1m

0,8 1,1 Nh hn 10cm

Tuy nhin trong iu kin t nhin khng phi lc no cng l tngnh nc ct. Thng thng trong nc cha nhiu tp cht hu c v v c vvy kh nng phn x ph ca nc ph thuc vo thnh phn v trng thica nc. Cc nghin cu cho thy nc c c kh nng phn x ph caohn nc trong, nht l nhng di sng di. Ngi ta xc nh rng vi suti thiu l 30m, nng tp cht gy c l 10mg/ lt, th kh nng phn xph lc l hm s ca thnh phn nc ch khng cn l nh hng cacht y.

Ngi ta chng minh rng kh nng phn x ph ca nc ph

thuc rt nhiu vo c ca nc, di sng 0,6 0,7 ngi ta pht hinrng gia c ca nc v kh nng phn x ph c mt mi lin h tuyntnh.

Hm lng clorophin trong nc cng l mt yu t nh hng ti khnng phn x ph ca nc. N lm gim kh nng phn x ph ca nc bc sng ngn v tng kh nng phn x ph ca nc bc sng c muxanh l cy.

Ngoi ra cn mt s yu t khc c nh hng ln ti kh nng phnx ph ca nc, nhng cng c nhiu c tnh quan trng khc ca nckhng th hin c r qua s khc bit ca ph nh mn ca nc bin,hm lng kh mtan, xi, nit, cacbonic... trong nc.

.2.3. Mt s yu t chnh nh hng ti kh nng phn xph ca cc i tng t nhin


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on c iu v cc i tng t nhin c hiu qu ta phi xcnh nh hng ca cc yu t khng gian - thi gian, kh quyn n kh nngphn x ph ca cc i tng t nhin trn mt t.

1. nh hng ca cc yu t khng gian - thi gian ln kh nng

phn x ph ca cc i tng t nhin.

a. Yu t thi gian.

Thc ph mt t v mt s i tng khc thng hay thay i theothi gian. Do vy kh nng phn x ph cng thay i theo thi gian. V dcy rng l vo ma ng v xanh tt vo ma xun, ma h, hoc la c mubiu hin b mt khc nhau theo thi v. V vy khi on c iu v nh cnbit r thi v, thi im ghi nhn nh v c im ca i tng cn onc iu v.

b. Yu t khng gian.

Ngi ta chia thnh hai loi: yu t khng gian cc b v yu t khnggian a l. Yu t cc b th hin khi chp nh cng mt loi i tng, vd cy trng theo hng, lung v cng cy nhng trng theo mng ln thkh nng phn x ph ca hai loi trng ny s em li kh nng phn x phkhc nhau.

Yu t a l th hin khi cng loi thc vt nhng iu kin sinhtrng khc nhau theo vng a l th kh nng phn x ph khc nhau. Yu

t thi gian cng c th th hin. Khi gc mt tri h thp ta s c hnh nhni c bng v cng mt i tng trn hai sn ni, mt bn c chiu sngv mt bn khng c chiu sng to nn kh nng phn x ph khcnhau...

c th khng ch c nh hng ca yu t khng gian, thi giann kh nng phn x ph ta cn thc hin theo mt s phng n sau:

- Ghi nhn thng tin vo thi im m kh nng phn x ph ca mti tng ny khc xa kh nng phn x ph ca mt i tng khc.

- Ghi nhn thng tin vo nhng lc m kh nng phn x ph ca mti tng khng khc bit my.

- Ghi nhn thng tin thng xuyn, nh k qua mt khong thi giannht nh.

- Ghi nhn thng tin trong iu kin mi trng nht nh, v d gcmt tri ti thiu, my t hn 10%, qua mt s ngy nht nh ...


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2. nh hng ca kh quyn

Khi xem xt h thng ghi nhn cc s liu v thng tin vin thm tathy rng nng lng bc x t mt tri chiu xung cc i tng trn mtt phi qua tng kh quyn, sau phn x t b mt tri t nng lng li

c truyn qua kh quyn ti my ghi thng tin trn v tinh. Do vy khquyn nh hng rt ln ti kh nng phn x ph ca cc i tng t nhin.

B dy kh quyn (khong 2.000km) nh hng ti nhng tia sng tmt tri chiu xung, cn i vi cc v tinh vin thm th b dy ca khquyn nh hng ti s liu thng qua tham s cao bay ca v tinh.

Kh quyn c th nh hng ti s liu v tinh vin thm bng hai conng tn x v hp th nng lng. S bin i nng lng bc x mt tritrong kh quyn l tn x v hp th sng in t bi cc thnh phn kh

quyn v cc ht ion kh. V qu trnh ny m s phn b ph, phn b gc vphn b khng gian do vic pht x ca cc i tng ang nghin cu yu i.

Sau y chng ta xem xt nh hng ca kh quyn c hai con ngtn x v hp th.

Hin tng tn x ch lm i hng tia chiu m khng lm mt nnglng. Tn x (hay phn x) c c l do cc thnh phn khng kh hoc ccion c trong kh quyn phn x tia chiu ti, hoc do lp kh quyn dy c cmt khng kh cc lp khng ng nht nn khi tia chiu truyn qua cc

lp ny s gy ra hin tng khc x.Hin tng hp th din ra khi tia sng khng c tn x m nng

lng c truyn qua cc nguyn t khng kh trong kh quyn v nung nnglp kh quyn. Hin tng tn x tuyt i xy ra khi khng c s hp thnng lng. Trong h thng vin thm khi nng lng tia sng b tn x v cchng, nu trng thu ca ng knh my ghi thng tin tht rng th s thuc ton b nng lng tn x, ngc li nu trng thu nh qu th s thuc mt phn nng lng.

Cc nguyn nhn chnh gy ra hin t

ng tn x v hp th nnglng nh sng mt tri l:

- Do s hp th, khc x nng lng mt tri ca cc phn t trong khquyn.

- Do s hp th c chn lc bc sng ca hi nc, ozon v cc hpcht khng kh trong kh quyn.


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- Do s phn x (tn x nng lng chiu ti, do s khng ng nhtca kh quyn v cc ht nh trong kh quyn).

Nu gi Eo l nng lng bc x ton phn chiu ti, E l nng lng

b hp th, E l nng lng tn x, E l nng lng cn li lt qua c nh

hng ca tng kh quyn th ta c th xc nh c h s hp th h s phnx v trong sut T ca dy lp kh quyn theo cng thc :

=oE

E ; =oE

E ; T =oE

E

+ + T = 1

i vi vt th trong sut :

T = 0 ; + = 1

i vi vt th t hp th: + T = 1

Hin tng tn x, bc x trong kh quyn cn ph thuc kch thcht gy tn x. Khi nng lng t ngun chiu qua kh quyn vo nhng vngm kch thc ht nh v gn bng bc sng th hin tng tn x cn phthuc bc sng.

Nu nhng vng kch thc ht ln hn bc sng rt nhiu nh htma th nh sng tn x bao gm:

- Phn x trn b mt ht n

c.- Xuyn qua ht nc hoc phn x nhiu ln trong ht nc.

- Khc x qua ht nc.

Trong trng hp ny hin tng phn x ph khng ph thuc vobc sng ca bc x m ph thuc vo thnh phn khng kh, nn sng mdy c ta s lm cho nng lng b tn x ht cho nn nh c mu trng(nng lng khng li c my thu thng tin). Do trn nh t hp mumy lun c mu trng.

Kh quyn tc ng n bc x mt tri qua 3 con ng phn x, hpth v cho nng lng truyn qua. i vi cng tc vin thm phn nnglng truyn qua l rt quan trng.

Sau y ta xt th c trng cho s tc ng ca kh quyn n bc

x nng lng (hnh 2.12).


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Hnh 2.12.Ca s kh quyn

Trn th trc honh biu th di bc sng , mt trc biu thh s phn x nng lng ngun theo phn trm (%).

r = =oE

E x 100%

vng nh sng nhn thy nng lng phn x ph ln nht c gn

60% nng lng chiu ti c phn x. th cho thy rng mi di sngkhc nhau nng lng bc x c mc phn x v hp th khc nhau : mts bc sng b hp th t, mt s vng khc nng lng b hp th nhiu.y l "ca s kh quyn".

H thng chp nh v tr th ng s s dng hu hiu "ca s khquyn", cn cc h thng chp nh v tr ch ng s s dng cc ca s

vng sng 1mm 1m. Ca s ca kh quyn bc x mt tri gm (bng 5).

Cc ca s ny tnh cho lp kh quyn nm ngang dy nh mt lp c

hai mt song song. Khi tia chiu xin, hoc ng knh gc rng c tnh cacc ca s kh quyn cng s thay i.

Cc knh sng ca h thng vin thm l cc di sng ph hp, cngha l chn cc knh sao cho c th thu c cc sng nhng ca s nitrn.

25

5075100

0,3 1,0 10 100

1mm1m

Ngun nng lngr(%)

Vng nhn thy

Hng ngoi nhitChp nh

Qut a ph Radio v sng ngn

0,3 1,0 10 100 1mm 1m


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Bng 5S ca s Bc sng ()

1 0,3 1,32 1,5 1,8

3 2,0 2,64 3,0 3,65 4,2 5,06 7,0 15,0

H thng vin thm a ph thng s dng cc ca s 1 , 2, 3 v 6 v nh hng phn x v bc x rt r rng.


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Chng 3

ON C IU V NH Vin thm---------------------------------------

on c iu v nh vin thm l qu trnh tch thng tin nh tnhcng nh nh lng t nh da trn cc tri thc chuyn ngnh hoc kinhnghim ca ngi on c iu v. Vic tch thng tin trong vin thm cth phn thnh 5 loi:

- Phn loi a ph.

- Pht hin bin ng.

- Chit tch cc thng tin t nhin.

- Xc nh cc ch s.

- Xc nh cc i tng c bit.

Phn loi a ph l qu trnh tch gp thng tin da trn cc tnh chtph, khng gian v thi gian ca i tng. Pht hin bin ng l pht hinv phn tch cc bin ng da trn t liu nh a thi gian. Chit tch ccthng tin t nhin tng ng vi vic o nhit trng thi kh quyn, caoca vt th da trn cc c trng ph hoc th sai ca cp nh lp th. Xcnh cc ch s l vic tnh ton cc ch s mi, v d ch s thc vt.

Xc nh cc c tnh hoc hin tng c bit nh thin tai, cc cutrc tuyn tnh, cc biu hin tm kim kho c.

Qu trnh tch thng tin t nh c th c thc hin bng mt ngihay my tnh.

Vic on c iu v bng mt c u im l c th khai thc ccc tri thc chuyn mn v kinh nghim ca con ngi, mt khc vic onc iu v bng mt c th phn tch c cc thng tin phn b khng gian.Tuy nhin phng php ny c nhc im l tn km thi gian v kt quthu c khng ng nht.

Vic x l bng my tnh c u im l nng sut cao, thi gian x lngn, c th o c cc ch s c trng t nhin nhng n c yu im lkh kt hp vi tri thc v kinh nghim ca con ngi, kt qu phn tch ccthng tin km. khc phc nhc im ny, nhng nm gn y ngi taang nghin cu cc h chuyn gia, l cc h chng trnh my tnh c kh


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nng m phng tri thc chuyn mn ca con ngi phc v cho vic on ciu v t ng.

Trong chng ny s cp n cng tc on c iu v bng mtv on c iu v nh bng x l s trn my tnh.

A. ON C IU V NH BNG MT.

on c iu v nh bng mt c th p dng trong mi iu kintrang thit b. on c iu v bng mt l vic s dng mt ngi cng vicc dng c quang hc nh knh lp, knh lp th, my tng hp mu xcnh cc i tng. C s on c iu v bng mt l cc chun onc iu v v mu on c iu v.

.3.1. Cc chun on c iu v nh v tinh v muon c iu v

Nhn chung c th chia cc chun on c iu v thnh 8 nhmchnh sau:

1. Chun kch thc

Cn phi chn mt t l nh ph hp on c iu v. Kch thcca i tng c th xc nh nu ly kch thc o c trn nh nhn vimu s t l nh.

2. Chun hnh dng

Hnh dng c ngha quan trng trong on c iu v nh. Hnhdng c trng cho mi i tng khi nhn t trn cao xung v c coi lchun on c iu v quan trng.

3. Chun bng

Bng ca vt th d dng nhn thy khi ngun sng khng nm chnhxc nh u hoc trng hp chp nh xin. Da vo bng ca vt th cth xc nh c chiu cao ca n.

4. Chun en en trn nh en trng bin thin t trng n en. Mi vt th

c th hin bng mt cp sng nht nh t l vi cng phn x nhsng ca n. V d ct kh phn x rt mnh nh sng nn bao gi cng cmu trng, trong khi ct t do phn x km hn nn c mu ti hntrn nh en trng. Trn nh hng ngoi en trng do cy l nhn phn x


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mnh tia hng ngoi nn chng c mu trng v nc li hp th hu ht bcx trong di sng ny nn bao gi cng c mu en.

5. Chun mu sc

Mu sc l mt chun rt tt trong vic xc nh cc i tng. V d

cc kiu loi thc vt c th c pht hin d dng ngay c cho nhng ngikhng c nhiu kinh nghim trong on c iu v nh khi s dng nh hngngoi mu. Cc i tng khc nhau cho cc tng mu khc nhau c bit khis dng nh a ph tng hp mu.

6. Chun cu trc

Cu trc l mt tp hp ca nhiu hnh mu nh. V d mt bi ckhng b ln cc loi cy khc cho mt cu trc mn trn nh, ngc li rnghn giao cho mt cu trc sn si. ng nhin iu ny cn ph thuc vo t

l nh c s dng.

7. Chun phn b

Chun phn b l mt tp hp ca nhiu hnh dng nh phn b theomt quy lut nht nh trn ton nh v trong mi quan h vi i tng cnnghin cu. V d hnh nh ca cc dy nh, hnh nh ca rung la nc, cci trng ch... to ra nhng hnh mu c trng ring cho cc i tng .

8. Chun mi quan h tng h

Mt tng th cc chun on c iu v, mi trng xung quanhhoc mi lin quan ca i tng nghin cu vi cc i tng khc cung cpmt thng tin on c iu v quan trng.

Nhm tr gip cho cng tc on c iu v ngi ta thnh lp ccmu on c iu v cho cc i tng khc nhau. Mu on c iu v ltp hp cc chun dng on c iu v mt i tng nht nh. Kt quon c iu v ph thuc vo mu on c iu v. Mc ch ca vic sdng mu on c iu v l lm chun ha kt qu on c iu v canhiu ngi khc nhau. Thng thng mu on c iu v do nhng ngic nhiu kinh nghim v hiu bit thnh lp da trn nhng vng nghin cuth nghim c iu tra k lng. Tt c 8 chun on c iu v cngvi cc thng tin v thi gian chp, ma chp, t l nh u phi a vo muon c iu v. Mt b mu on c iu v bao gm khng ch phn nhm cn m t bng li na.

.3.2. nh tng hp mu


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T liu nh v tinh dng on c iu v bng mt tt nht l ccnh tng hp mu.

c im c bn ca nh tng hp mu l s m ha bng mu sc

cc khc bit v ph ca cc i tng. y chun on c iu v chnh

l tng phn mu c nhn mnh nh s la chn mt cch c thcphng n tng hp mu. Trong trng hp t liu gc tho mn cc iu kink thut nu s dng phng n tng hp mu chun v iu kin x l hanh cht ch th mu l mt chun on c iu v tng i n nh.

Nh kh nng phn bit cao ca mu sc m n c th truyn t cckhc bit v ph ca i tng, nh tng hp mu c tnh trc quan sinh nghn nh ph trng en.

i vi nh ph chp vng hng ngoi, nh tng hp mu cho ta bc

tranh mu gi khng c thc trong t nhin.V mu sc, nh tng hp mu so vi nh mu v tinh chp trn phim

mu 3 lp c nhiu mu sc hn vi tng phn mu cao hn. So vi nhph th nh tng hp mu cng c nhiu mu sc hn v tng phn caohn, nhng lc phn gii li km hn nh ph mu. Kh nng on c iuv cc i tng trn nh tng hp mu ph thuc vo phng n la chnmu. Vic la chn cc phng n tng hp mu ph thuc vo nhim von c iu v, kh nng ng dng ca nh tng hp mu on c iuv cc i tng c th.

La chn knh ph tng hp mu l mt cng vic quan trngquyt nh cht lng thng tin ca kt qu tng hp mu. Vic la chn knhph c xc nh trn c s nh sau:

- c tnh phn x ph ca cc i tng cn on c iu v.

- Nhim v on c iu v.

- Yu cu i vi lc phn gii.

- c im ca vng cn tng hp mu...

c tnh phn x mu ca cc i tng c biu th trn th cc phn trc. chn knh ph mang tnh thng tin cao cn phn loinhm i tng chnh cn on c iu v hoc cc i tng ch th chnh.

Trn c s cc knh ph mang thng tin ta chn ra knh chnh v knhph. Trong bng 6 a ra mt s v d v kh nng phn x ph ca mt s


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i tng tng knh ph. Nhng bng nh th ny thng dng la chnknh ph tng hp mu.

Bng 6: V d v m t kh nng thng tin ca cc knh a ph.

Knh a phBM

MKF - 6 Cc thng tin chnh trn knh ph(Nhn bit c bng mt)

460 500m

tng phn thp vi cc nhm i tng chnh.on c iu v c ranh gii m ly, c, phnbit c rng, c ct v t, vng h nc c thon c iu v n su 20m.

510 560m 520 560m

Cc i tng k trn c tng phn tt hn,phn bit tt ct v t, thc vt vi nc, trm tch t v.v... Thu vn on c iu v n su

15m.

600 700m560 620m

v

640 680m

tng phn ln i vi cc nhm i tng, cutrc nh r nt. Thc vt c tng phn cao vimt s loi, ct th hin nh cc knh trn. C thon c iu v cc i tng kch thc nh vhnh tuyn, cc thng tin v cu trc a cht v amo. Thu vn on c iu v c n su10m.

700 850m695 745m

v

790 890m

i vi knh 695 745m tng phn thp. C

th on c iu v vng b n

c, vng c mcao. Thm thng tin v loi thc vt l rng. Rngl rng v l kim, b mt nc l nhng i tngc tng phn cao. C th on c iu vvng nc n su 1m, cc thng tin v cu trca cht...

Bn cnh vic s dng bng ny la chn knh cn s dng c th phn x ph ca ring tng nhm i tng nu phn trc.

Mt khc la chn knh ph c th s dng biu sng

(histogram), khi dng biu cn s dng phim tng hp mu.

Cc thit b dng cho tng hp mu nh a ph thng dng trn thgii v nc ta l:

- My chiu hnh a ph chuyn dng MSP - 4C (c) v AC - 90B(Nht).

- My nn Rectimat - C, Dust 2000 c gn u mu.


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- Cc my vi tnh PC c mn hnh mu VGA v cc trm lm vic WS.

.3.3. on c iu v nh v chuyn kt qu on ciu v ln bn nn

Sau khi nghin cu ch th on c iu v, nghin cu b nh mu,

nh v tinh v cc ti liu khc ta tin hnh cng tc on c iu v nh.Kt qu on c iu v bao gi cng c chuyn ln bn nn. Bn nn th hin kt qu on c iu v phi tha mn cc iu kin sau:

- C mt t l ph hp v chnh xc.

- Cc h thng nh v ta a l phi c th hin y .

- Nn bn phi sng v cc thng tin c bn phi c in sao chokhng gy kh khn cho vic th hin cc kt qu on c iu v.

Thng thng bn a hnh cc t l, s quy hoch v bn trc nh c s dng lm bn nn cho cng tc on c iu v nh. Bn t l 1/50.000, 1/100.000 v 1/250.000 ph hp cho vic on c iu vnh v tinh phn gii trung bnh cng phn gii nh cao. Cc bn trc nh rt ph hp cho vic chuyn kt qu on c iu v thm thc vtln bn nn.

C 4 phng php chuyn kt qu on c iu v ln bn nn.

1. Can v

Kt qu on c iu v c t trn bn sng v bn nn ct ln trn sao cho cc a hnh a vt trng nhau v sau thao tc vin chc can li nhng g cn thit.

2. Chiu quang hc

nh c on c iu v c chiu ln bn thng qua mt hthng quang hc. H thng ny cho php thc hin mt s php hiu chnhhnh hc c bn nh hiu chnh t l, xoay trong khng gian v trong mtphng. Da theo nguyn tc nn phn vng phng php ny cho kt qu

tng i tt so vi phng php can v.3. S dng li vung.

Trong trng hp khng c thit b chiu hnh hoc thit b nn chnhhnh hc theo nguyn l quang hc c th s dng phng php li vung.Bng phng php nn hnh hc n gin c th to c hai h li trn bn


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v nh v cn c vo v tr tng i ca i tng trong h li c thchuyn ni dung on c iu v t nh ln bn .

4. S dng cc thit b o nh

Trong trng hp c cc thit b o nh hin i nh cc my nn nh

quang c my o v nh hng khng vic hiu chnh hnh hc s t kt quchnh xc hn so vi cc phng php khc. Nguyn l ca phng php nyl da vo vic dng li m hnh chp nh v thc hin vic chuyn v thngqua cc m hnh .

S tng qut ca vic on c iu v nh v tinh bao gm ccbc c bn sau:

- Chun b t liu nh.

- c thng tin b tr v nh v nh theo bn .

- To kha on c iu v.

- o c cc yu t nh lng.

- Phn tch nh v on c iu v cc i tng.

- Thnh lp bn chuyn .

B. ON C iU V NH BNG X L S

.3.4. Khi nimCc t liu thu c trong vin thm phn ln l di dng s cho

nn vn on c iu v nh bng x l s trong vin thm gi mt vai trquan trng v c l cng l phng php c bn trong vin thm hin i.on c iu v nh bng x l s trong vin thm bao gm cc giai onsau :

- Nhp s liu .

C hai ngun t liu chnh l nh tng t do cc my chp nhcung cp v nh s do cc my qut cung cp. Trong trng hp nh s th t

liu nh c chuyn t cc bng t lu tr mt cao HDDT v cc bng tCCT. dng ny my tnh no cng c c s liu. Cc nh tng t cngc chuyn thnh dng s thng qua cc my qut.

- Khi phc v hiu chnh nh.

y l giai on m cc tn hiu s c hiu chnh h thng nhm tora mt t liu nh c th s dng c. Giai on ny thng c thc hin


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trn cc my tnh ln ti cc Trung tm thu s liu v tinh.

-Bin i nh.

Cc qu trnh x l nh tng cng cht lng, bin i tuyn tnh... lgiai on tip theo. Giai on ny c th thc hin trn cc my tnh nh nh

my vi tnh trong khun kh ca mt phng th nghim.

-Phn loi.

Phn loi a ph tch cc thng tin cn thit phc v vic theo dicc i tng hay lp bn chuyn l khu then cht ca vic khai thc tliu vin thm.

-Xut kt qu.

Sau khi hon tt cc khu x l cn phi xut kt qu.

.3.5. Cc h nhp s liui vi nh s th t liu nh c chuyn t bng t lu tr mt

cao HDDT vo bng t CCT. dng ny my tnh no cng c c s liu.V vy, h nhp nh m t trong phn ny c coi nh mt h chuyn i ccnh tng t en trng hay mu v dng s.

Chc nng c th ca tng h phc thuc vo nhng yu t sau:

- Kch thc ca phim: Kch thc ti a m thit b c th chuyn i

c.- phn gii: Mt im/inch (DPI).

- Thang cp xm: Bao nhiu cp sng c th chuyn i chay ni cch khc mi pixel u ra c m my bt.

- Tc chuyn i.

- iu kin mi trng: Yu cu lm vic trong bng ti hon ton,trong nh sng m...

- chnh xc.Loi nh c th chuyn i c: Film hoc giy.

Cc h nhp nh nhn chung c thit k da trn nhng phngphp qut nh chnh sau:

a. Qut c hc


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Bc nh c t trn mt ng hnh tr v qu trnh qut c thchin bng vic quay ca ng v mt tia sng chiu t bn trong ra. Tc qut theo phng php ny ni chung khng cao nhng n c s dng rngri v n cho php thc hin vic chuyn i vi chnh xc cao v phngii ln.

b. My quay v tuyn

My quay v tuyn i khi cng c s dng v gi thnh ca n rtr. Tuy vy nhc im ca n l phn gii thp, chnh xc v tr khngcao v phn gii v mu cng khng cao.

c. Bung chp CCD

Cc bung chp CCD c u th hn cc my quay v tuyn v chngc phn gii cao hn, chnh xc hn v kch thc cng b hn. ng

nhin gi thnh ca chng l t hn nhiu ln.

d.Bung chp CCD mng tuyn tnh

Bung chp CCD mng tuyn tnh lm vic trn nguyn l chia itng nghin cu thnh nhiu hng nh v vic chuyn i c thc hintun t theo tng hng mt. Cc my qut lm theo nguyn l ny hin nay rtph cp v gi thnh r, cht lng li cao.

.3.6. Hiu chnh nh1. Hiu chnh nhTt c cc t liu s hu nh bao gi cng chu mt mc nhiu x

nht nh. loi tr cc nhiu ny cn phi thc hin mt s php tin x l.Khi thu cc bc x t mt t trn cc vt mang v tr, ngi ta thy chng cmt s khc bit so vi trng hp quan st cng i tng khong cchgn. iu ny chng t khong cch xa nh vy tn ti mt lng nhiunht nh do gc nghing v cao mt tri, mt s iu kin quang hc khquyn nh s hp th, tn x, m gy ra... Chnh v vy bo m cs tng ng nht nh v mt bc x cn phi hiu chnh nh.

Cc ngun nhiu bc x gm 3 nhm chnh sau :

a. Cc ngun nhiu do bin i nhy ca b cm

Trong trng hp cc b cm thun tu quang hc bao gi cng xy ratrng hp cng bc x ti tm nh ln hn ti cc gc. Hin tng nygi l hin tng lm m nh. y l mt sai lch khng th trnh khi chocc h quang hc. Khi s dng cc b cm quang in t th s chnh lch


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gia cng bc x trc ng knh v cng m thit b thc s ghi nhncng l mt i lng cn a vo qu trnh hiu chnh.

b. Cc ngun nhiu do gc chiu ca mt tri v do a hnh

- Bng chi mt tri

Bn thn mt tri to bng chi ca mnh trn mt t di dng mtvng sng hn nhng vng khc. Bng chi mt tri c th c loi tr cngvi hin tng lm m nh trn nguyn l ng dng chui Furie.

-Bng che

Bng che l hin tng che khut ngun bc x do bn thn a hnh. c th loi tr n cn c s liu m hnh s a hnh v to vt mang tithi im thu tn hiu.

c. Cc ngun nhiu do trng thi kh quynRt nhiu cc hiu ng kh quyn khc nhau nh hp th, phn x, tn

x... nh hng ti cht lng nh thu c. Ngi ta thng s dng cc mhnh kh quyn m phng trng thi kh quyn v p dng cc qui lutquang hnh hc v quang kh quyn gii quyt vn ny.

2. Hiu chnh kh quyn

Bc x mt tri trn ng truyn xung tri t b hp th, tn x mtlng nht nh trc khi ti mt t v bc x, tn x t vt th cng b hp

th hay tn x trc khi ti c b cm. Do vy bc x m b cm thu ckhng ch cha ring nng lng hu ch m cn cha nhiu thnh phn nhiukhc na. Hiu chnh kh quyn l mt cng on tin x l nhm loi trnhng thnh phn bc x khng mangthng tin hu ch.

C 3 nhm phng php chnh s dng trong hiu chnh kh quyn l:phng php s dng hm truyn kh quyn, phng php s dng s liuquan trc thc a v cc phng php khc.

-Phng php s dng hm truyn kh quyn

Phng php s dng hm truyn kh quyn l gii php gn ng hayc s dng. Mi thng s da trn trng thi trung bnh ca kh quyn k chm lng cc ht bi l lng v hi nc.

-Phng php s dng cc s liu quan trc thc a

Trong phng php ny ngi ta tin hnh o c bc x cc itng cn nghin cu ngay ti thi im bay chp. Sau da trn s khc


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bit cng bc x thu c trn v tinh v gi tr o c ngi ta tinhnh hiu chnh bc x. Phng php ny cho kt qu rt tt nhng khngphi lc no v u cng thc hin c.

- Cc phng php khc.

Mt s v tinh c trang b cc b cm c bit chuyn thu nhn cctham s trng thi kh quyn ng thi vi cc b cm thu nhn nh v vichiu chnh kh quyn c tin hnh ngay trong qu trnh bay.

3. Hiu chnh hnh hc

Mo hnh hnh hc l sai lch v tr gia ta nh thc t o c vta nh l tng thu c t b cm c thit k hnh hc l tng v trongcc iu kin thu nhn l tng. Mo hnh hnh hc gm mo hnh ni sai vmo hnh ngoi sai. Mo hnh ni sai sinh ra do tnh cht hnh hc ca b cm

v mo hnh ngoi sai gy ra do v tr ca vt mang v hnh dng ca vt th. a cc ta nh thc t v ta nh l tng phi hiu chnh hnh hc.Bn cht ca hiu chnh hnh hc l xy dng c mi tng quan gia hta nh o v h ta qui chiu chun. H ta qui chiu chun c thl h ta mt t (h ta vung gc hoc h ta a l) hoc h ta nh khc.

Cc trnh t c bn ca hiu chnh hnh hc bao gm :

a. Chn la phng php

Phng php c chn la phi da trn bn cht mo hnh ca tliu nghin cu v s lng im khng ch c th c.

b. Xc nh cc tham s hiu chnh

Vic xc nh cc tham s hiu chnh thng thng da trn vic thitlp cc m hnh ton hc v cc h s ca m hnh ny c tnh theo phngphp bnh sai trn c s cc im bit ta nh v ta cc im kimtra. Nhng bin i thng s dng trong thc t l :

Bin i Helmert :x = au + bv + c S n s l 4

y = - bu + av + d

Bin i Affine :

x = au + bv + c S n l 6

y = du + ev + f


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Bin i theo php chiu hnh.

x =1aua

auava

87

321

++++

S n l 8

y = 1aua

avaua

87

654

++

++

Bin i a thc :

x = aijui-1vj-1

y = bijui-1vj-1 S n ph thuc vo bc a thc

.3.7. Bin i nh1. Tng cng cht lng v chit tch c tnh

Tng cng cht lng nh l thao tc chuyn i nhm tng tnh dc, d hiu ca nh cho ngi on c iu v. Cn chit tch c tnh lthao tc nhm phn loi, xp xp cc thng tin c sn trong nh theo cc yucu hoc ch tiu a ra di dng cc hm s.

a.Tng cng cht lng nh

Nhng php tng cng cht lng nh thng c s dng l bini cp xm, bin i histogram, t hp mu, bin i mu gia hai hRGB v HSI...

b.Chit tch c tnh

Chit tch c tnh c thc hin i vi 3 loi c tnh chnh:

- c tnh ph: Cc mu sc c bit, gradient, tham s ph.

- c tnh hnh hc: Cc cu trc ng, hnh dng, kch thc...

- c tnh cu trc: Mu, tn sut phn b khng gian, tnh ngnht...

2. Bin i cp xm

Bin i cp xm l mt k thut tng cng cht lng nh ngin nhm bin i khong gi tr cp xm m thit b hin th c kh nngth hin c. Bng cch bin i ny hnh nh trng s r hn. C th thchin php bin i ny da theo quan h y = f(x)

Trong y l gi tr cp xm sau bin i v x l gi tr cp xmnguyn thu. Hm s f c th l tuyn tnh hoc phi tuyn tnh. Thng ngi


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ta s dng php bin i tuyn tnh v php bin i da vo gi tr trungbnh.

3. Th hin mu trn t liu nh

th hin mu trn t liu nh vin thm ngi ta phi t hp mu

v hin mu gi.

a. T hp mu

Mt bc nh mu c th c t hp trn c s gn 3 knh ph no cho 3 mu c bn. C hai phng php trn mu l cng mu v tr mu.Trn hnh 3.1 ch ra s nguyn l ca vic trn mu.

Hnh 3.1S nguyn l ca vic trn mu.

Nu ta chia ton b disng nhn thy thnh 3 vng c bn l , lc,chm v sau li dng nh sng trng chiu qua knh lc , lc, chmtng ng ta thy hu ht cc mu t nhin u c khi phc li. Phngphp t hp mu c gi l phng php t hp mu t nhin.

Trong vin thm, cc knh ph khng c chia u trong di sngnhn thy nn khng th ti to li c cc mu t nhin mc d cng sdng 3 mu c bn , lc, chm. T hp mu nh vy c gi l t hp mugi. T hp mu gi thng dng nht trong vin thm l t hp mu gi khign mu cho knh hng ngoi, mu lc cho knh v mu chm cho

knh lc. Trn t hp mu ny cc i tng c th hin theo cc gam muchun nh thc vt c mu . Vi cc mc khc nhau ca mu thhin mc dy c ca thm thc vt.

b. Hin mu giT hp mu ch thc hin c trong trng hp c 3 knh ph tr ln.

Trong trng hp ch c mt knh ph, c th th hin c trong khnggian mu ngi ta s dng phng php hin mu gi, trong phng php nyng vi mt khong cp xm nht nh s c gn mt mu no . Cch

Chm

Lam

Trng

Tm

LcVng

a. T hp cng mu

Lam

Lc

en

Chm

Vng

Tm

b. T hp tr mu


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gn mu nh vy khng c qui lut no c v hon ton ph thuc vo ngithit k. Thng thng cch ny hay c s dng cho nh sau phn loi, nhch s thc vt, nh nhit... Hnh 3.2 minh ho vic t hp v hin mu gi.

Hnh 3.2

4. Cc php bin i gia cc nh

Cc php bin i gia cc knh ca mt nh hoc gia cc nh chpti nhiu thi im khc nhau rt hu ch cho vic tng cng cht lng vchit tch c tnh. C hai nhm bin i chnh l bin i s hc v bin ilogic.

a.Bin i s hc

Cc php bin i s hc da trn cc php tnh cng, tr, nhn, chiav s phi hp gia chng c s dng cho nhiu mc ch k c loi tr mts loi nhiu. Kt qu ca mt s php bin i thng khng l s nguynm l s thc, cho nn li phi chuyn chng v khng gian s nguyn datrn cc php tng cng cht lng.

b. Cc php bin i logic

Phn x ph ca thc vt

Chm Lc Hng ngoi

Chm Lc Mu

0 0 0 en127 127 127 Xm255 255 255 Trng255 0 0 Chm

0 255 0 Lc0 0 255

255 255 0 Lam255 0 0 Tm

0 255 255 Vng

V d v t hp mu

Tng mu

Lam Lc Vng lc Vng Da cam Tm

V d v hin mu gi

chi

ChmLc


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Cc php bin i logic s dng cc ton t OR v ton t AND nhiutrong vic phn tch t liu a thi gian hoc chng nh ln bn .

5. Phn tch cu trc

Cu trc l mt tp hp lin kt ca cc hnh mu nh c lp li mt

cch u n. Trong thc t on c iu v bng mt, ngi on c iuv thng cm nhn c cc cu trc mn, trn hoc sn si khi on ciu v cc thm rng hoc cc cu trc cnh cy khi on c iu v mngli thu vn...

Phn tch cu trc l vic phn loi hay chia tch cc c tnh cu trctrn nh trong mi lin quan ti hnh dng cc hnh mu c bn, mt vlng phn b ca chng.

Trong on c iu v bng mt, vic cm nhn cc cu trc v phn

loi chng do ngi on c iu v thc hin. B c ngi c kh nng khiqut, nhn bit v tng hp cc cu trc mt cch tuyt vi cho nn kt quthng c chp nhn. Trong khi vic on c iu v bng my tnh dokh nng nh ngha cc cu trc v mt ton hc gp rt nhiu kh khn, khnng lu tr thng tin trong b nh cn hn ch, kh nng cc ngn ng lptrnh cho php thc hin cc t duy tng t con ngi trong qu trnh khiqut, tng hp cn qu t cho nn vic t ng phn tch cu trc trn mytnh t nhiu vn cha mang li kt qu nh mong mun.

Tuy vy, ngi ta vn thc hin vic phn loi cu trc da trn cc kthut phn tch thng k v phn tch chui ph.

a. Phn tch thng k da trn ma trn n*n

Cc ch s sau ca ma trn c coi nhcc thng tin cu trc.

- Khong cp sng ca histogram.

- Ma trn phng sai - hip phng sai.

- Ma trn nn ct chy.

Cc tham s ny c s dng chung vi cc thng tin ph khc trongqu trnh phn loi.

b.Phn tch chui ph

Cc cu trc c phn tch da trn vic ng dng chui Furie nhmtm ra cc thnh phn phn b theo cc hng, mt .


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.3.8. Phn loi a ph1. Khi nim

Mc ch tng qut ca phn loi a ph l t ng phn loi tt c

cc pixel trong nh thnh cc lp ph i tng. Thng thng ngi ta s

dng cc d liu a ph phn loi v tt nhin, mu ph trong c s d liu

i vi mi pixel s c dng lm c s phn loi. C ngha l, cc kiu

c trng khc nhau biu th cc t hp DN da trn s bc x ph v c

trng bc x vn c ca chng. V vy mt "mu ph" khng ni n tnh

cht hnh hc m ng hn, thut ng "ph" y ni n mt tp hp gi tr

o bc x thu c trong cc knh ph khc nhau i vi mi pixel. Vic

nhn bit mu ph cp n mt s phng php phn loi c s dng thng

tin ph trn cc pixel lm c s t ng phn loi cc lp i t

ng.Nhn bit mu ph theo khng gian bao gm phn loi pixel hnh nh

da trn c s quan h khng gian ca chng vi cc pixel bao quanh. Vic

phn loi khng gian c th xem xt nhng kha cnh nh cu trc ca hnh

nh tnh cht gn gi ca pixel, kch thc nt, hnh nh, tnh nh hng, tnh

lp li v bi cnh c th. Nhng dng phn loi ny c mc ch l ti to

loi hnh tng hp theo khng gian do ngi gii on tin hnh trong qu

trnh on c nh bng mt. Do phng thc nhn bit mu theo khng

gian c xu hng phc tp hn v i hi i su vo tnh ton hn.

Nhn bit mu theo thi gian s dng thi gian nh mt cng c tr

gip trong vic nhn dng cc c trng. Trong vic kho st cc cy trng

nng nghip chng hn, nhng thay i khc bit v ph v khng gian trong

mt v canh tc c th cho php phn bit trn cc hnh nh a thi gian

nhng khng th phn bit c nu ch cho mt d liu m thi. Chng hn,

mt rung la nng c th khng th phn bit c vi t hoang nu va

mi gieo xong ma ng v v phng din ph n s tng t nh bi thoang ma xun. Tuy nhin nu c phn tch t hai d liu th rung la

nng nhn bit c, bi v khng c lp ph no khc hoang v cui

ng v c mu xanh lc cui ma xun.

Vi vic khi phc li hnh nh v cc k thut tng cng, vic phn

loi hnh nh c th s dng kt hp theo kiu lai to. Do vy, khng c mt


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cch "ng n" n l no c th p dng cho vic phn loi hnh nh. Vic

p dng phng php phn loi ny hay phng php phn loi khc ph

thuc vo tnh cht ca d liu ang phn tch v vo kh nng tnh ton.

C hai phng php phn loi a ph, l phng php phn loi c

kim nh v phng php phn loi khng kim nh.

Trong phng php phn loi c kim nh ngi gii on nh s

"kim tra" qu trnh phn loi pixel bng vic quy nh c th theo thut ton

my tnh, cc ch s m t bng s cc th loi lp ph mt t khc nhau c

mt trn mt cnh. lm vic ny, cc im ly mu i din ca loi lp

ph bit (gi l cc vng mu) c s dng bin tp thnh mt "kha

gii on" bng s m t cc thuc tnh ph cho mi th loi in hnh. Sau

mi pixel trong tp hp d liu s c so snh vi mi chng loi trongkha gii on v c gn nhn bng tn ca chng loi m n "c v ging

nht".

Cnphng php phn loi khng kim nh khng ging nh phng

php phn loi c kim nh, quy trnh phn loi khng kim nh gm hai

bc ring bit. im khc bit c bn gia hai phng php ny l ch

phng php phn loi c kim nh bao gm bc ly mu v bc phn

loi, cn trong phng php phn loi khng kim nh, trc tin d liu nh

c phn loi bng cch nhm chng thnh cc nhm t nhin hoc thnh

cc cm c mt trn cnh. Sau ngi gii on nh s xc nh tnh ng

nht ca lp ph mt t ca cc nhm ph ny bng cch so snh cc d liu

hnh nh phn loi vi cc d liu tham kho mt t.

2. Phn loi c kim nh

Hnh 3.3 tm tt 3 bc c bn trong phng php phn loi c kim

nh. Trong giai on ly mu ngi gii on s nhn dng cc vng i din

v nghin cu cch m t bng s cc thuc tnh v ph ca mi loi lp phmt t trong cnh ny. Tip theo, trong giai on phn loi mi pixel trong

tp hp d liu hnh nh c phn thnh cc loi lp ph mt t m n gn

ging nht. Nu pixel khng ging vi bt k tp d liu no th n c gn

nhn "cha bit". Nhn phn loi gn cho mi pixel trong qu trnh ny c

ghi li trong tng ng ca tp d liu gii on. Nh vy, ma trn nh


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nhiu chiu ny c s dng xy dng mt ma trn tng ng ca cc loi

lp ph mt t cn gii on. Sau khi phn loi ton b d liu, cc kt

qu c trnh by trong giai on a ra kt qu. Do vic phn loi bng s,

cho nn kt qu c th s dng theo nhiu cch khc nhau. Ba dng in hnh

ca kt qu u ra l bn chuyn , bng thng k din tch ton cnhhoc phn cnh cho cc loi lp ph mt t khc nhau, v cc file d liu

bng s a vo h thng thng tin a l GIS, khi "kt qu u ra" ca

vic phn loi tr thnh "u vo" ca GIS.

a. Giai on ly mu

Trong khi vic phn loi d liu nh a ph l mt qu trnh t ng

ha cao th vic lp rp thu thp cc d liu mu cn cho vic phn loi l mt

cng vic khng c tnh cht t ng. Vic ly mu cho vic phn loi c

kim nh va c tnh cht ngh thut va c tnh cht khoa hc. N i hi

mt d liu tham kho ng k v mt tri thc su sc ton din v khu vc

m d liu s p dng. Cht lng ca qu trnh ly mu s quyt nh

thnh cng ca giai on phn loi.

Mc ch chung ca qu trnh ly mu l thu thp mt tp hp thng

k m t mu ph cho mi loi lp ph mt t cn phn loi trong mt nh.

Giai on a ra kt qu (3)

Kt qu a ra:- Bn - Bng d liu- Cc file d liu s.

Hnh 3.3. Cc bc c bn trong phng php phn loi c kim nh.

Knh 1

5

23

4

F F F F F F F F F FF F F F F F F F F C

F F F F F F F C C

S S F F F F F U C C

W W S F F F U U C C

W W S F F F F U C C

W W W S F F F U U C

W W W S F F F F U F

W W W W S F F F F F

W W W W S F F F F F

F

Nc (W)

Ct (S)

Rng (F)

th (U)

Ng (C)

C CN(H)

DN1DN2DN3DN4DN5

Tp hp phn loi(Nhm s c t bng loi)

Tp hp d liu nhnhm s/1 pixel

Giai on ly mu (1)

Thu thp d liu s tvng mu phn x phca cc loi i tng

Giai on phn loi (2)

So snh cc pixel cha bitvi mu ph; Quy v chngloi gn ging nhau

Pixel (3,7)

F


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c c kt qu phn loi ng, d liu mu cn phi va c

trng va y . C ngha l, ngi gii on nh cn phi nghin cu xy

dng cc s liu thng k mu cho mi loi ph to thnh mi lp thng tin

cn phn bit bng phng php phn loi. Chng hn, trong kt qu phn loi

cui cng, ngi ta mun ch ra mt loi thng tin l "nc", nu hnh nhang phn tch ch cha c mt vng nc v nu n c cng c trng ph

thu nhn trn ton b din tch ca n, khi ch cn mt vng ly mu l

biu th l nc. Tuy nhin, nu vng din tch nc li cha nhng khu

vc khc nhau: ni th nc rt trong, ni th nc rt c, th ti thiu phi

cn t nht l 2 loi ph lm mu thch hp cho nt c trng ny. Nu c

nhiu vng nc xut hin trn nh, th cc thng k vng mu cn thit i

vi mi loi ph khc c th c mt trong cc vng ph nc. Theo , ch

ring loi thng tin v "nc", c th c i din bi 4 hoc 5 loi ph. Khi 4 hoc 5 loi ph ny c th c s dng phn loi tt c cc vng

nc xut hin trn nh.

By gi ta thy r ly mu l qu trnh hon ton khng th thiu

c. Chng hn, mt loi thng tin nh "t nng nghip" c th cha nhiu

loi cy trng v mi loi cy trng c th c i din bi mt s loi ph.

Nhng loi ph ny c th bt ngun t nhng ngy (thng) trng cy khc

nhau, cc iu kin m t ai, cch canh tc, cc chng loi ging, cciu kin a hnh, cc iu kin kh quyn hoc t hp cc yu t . im

cn nhn mnh l tt c cc loi ph to thnh mt loi thng tin cn phi

c i din thch hp trong cc thng k ca tp hp vng mu s dng

phn loi hnh nh.

Qu trnh la chn b mu i vi ngi gii on nh cha c kinh

nghim thng l mt nhim v kh khn. Ngi gii on xy dng, nghin

cu cc s liu thng k i vi cc loi ph khng "chng ph" ln nhau c

mt trong mt cnh tng t kh khn hn. Nu c vn , th thng l do bt

ngun t cc loi ph trn ranh gii gia "cc loi qu " hoc cc loi

"chng ph". Trong nhng trng hp , tc ng ca vic xa b hoc tp

hp cc th loi mu c th kim tra bng cch th - tm sai st (th, tm sai

st li tin hnh th, tm r sot c th tip tc). Trong qu trnh ny kch

thc ca mu, cc phng sai v ph, tnh chun v c tnh nhn dng ca


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cc b mu cn phi c kim tra li. Cc chng loi rt t xut hin trn nh

b loi b khi b mu cho chng khng b nhm ln vi cc loi xut hin

ph bin trn din rng. C ngha l, ngi gii on nh c th chp nhn

phn loi sai i vi mt loi him xut hin trn nh m bo chnh

xc phn loi ca mt loi tng t v ph thng xut hin trn nhng dintch rng. Ngoi ra, phng php phn loi c th u tin nghin cu xy

dng bng cch chp nhn mt tp hp cc loi c thng tin chi tit. Sau khi

nghin cu cc kt qu phn loi thc t, ngi gii on nh c th tng hp

mt s loi chi tit thnh loi c tnh khi qut hn (v d loi "cy xoan" v

"cy bng" c th tng hp li thnh loi cy "rng l v ma ng" hoc t

trng "ng" v "c chn nui" thnh t canh tc).

Lu , vic chn lc b mu l bin php nng cao chnh xc

phn loi. Tuy nhin, nu mt lo lp ph no xut hin trn mt nh c

nhng mu phn x ph tng t, th khng th dng vng mu hoc chn

lc lm cho chng c th tch bit v ph. Khi phn bit cc loi lp

ph ny phi on c bng mt hoc kim tra ngoi nghip. Cc quy trnh

on c mu a thi gian v khng gian cng c th p dng trong nhng

trng hp ny.

b. Giai on phn loi

Bn cht ca qu trnh ny l so snh cc pixel cha bit vi mu ph

ca cc i tng c xy dng giai on ly mu, sau quy cc pixel

ny v loi i tng m chng gn ging nht.

Vic phn loi a ph trong phng php phn loi c kim nh

thng dng cc thut ton sau:

- Thut ton phn loi theo xc sut cc i.

- Thut ton phn loi theo khong cch ngn nht.

- Thut ton phn loi hnh hp.

Cc thut ton ny s c gii thiu t m trong chng 6.

3. Phn loi khng kim nh

Cch phn loi khng kim nh khng s dng d liu mu lm c s

phn loi, m dng cc thut ton xem xt cc pixel cha bit trn mt


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nh v kt hp chng thnh mt s loi da trn cc nhm t nhin hoc cc

loi t nhin c trong nh. Nguyn l c bn ca phng php ny l cc gi

tr ph trong mt loi lp ph phi gn ging nhau trong khng gian o, trong

lc cc d liu ca cc loi khc nhau phi c phn bit r vi nhau v

phng din ph.

Cc loi thu c do vic phn loi khng kim nh gi l cc lp

ph. Do ch chng ch da trn cc nhm t nhin c trong nh, c im

nhn dng ca cc loi ph lc ban u cha bit nn ngi gii on phi so

snh cc d liu c phn loi vi mt dng no ca d liu tham kho

(chng hn nh t l ln hn hoc bn ) xc nh c im nhn dng v

gi tr thng tin ca cc loi ph. Nh vy, trong phng php phn loi c

kim nh, chng ta xc nh cc loi thng tin hu ch v sau xem xt kh

nng phn tch ph ca chng cn trong phng php phn loi khng kim

nh chng ta xc nh cc loi tch c ph v sau xc nh thng tin

hu ch ca chng.

Trong phng php phn loi c kim nh chng ta khng xem xt

n vic ly mu cho loi i tng b phn loi sai. iu cho thy u

im ca phng php phn loi khng kim nh l xc nh r cc loi khc

nhau c mt trong d liu hnh nh. Nhiu trong s cc loi ny c th u

tin cha xut hin i vi ngi gii on dng phng php phn loi ckim nh. Cc loi ph trong mt cnh tng c th c qu nhiu lm cho ta

gp kh khn khi ly mu cho tt c cc loi ca chng, cn trong phng

php phn loi khng kim nh cc loi ny c t ng tm thy.

C nhiu thut ton nhm chng li nhm xc nh cc nhm ph

t nhin c trong tp d liu. Mt dng thut ton ph bin do ngi gii on

chp nhn v s lng cc nhm c trong d liu gi l phng php gi tr

trung bnh K. Khi thut ton s la chn hoc pht hin v tr cc trung tm

ca nhm trong khng gian o nhiu chiu. Lc mi pixel trong nh c

gn cho nhm m vc t trung bnh ty chn l ngn nht. Sau khi tt c cc

pixel c phn loi theo cch , cc vc t trung bnh i vi mi nhm

s c tnh ton li. Sau cc gi tr trung bnh c tnh ton li ny s

c s dng lm c s phn loi li cc d liu ca hnh nh. Quy trnh

ny tip tc cho n lc khng cn thay i trong vic nh v cc vc t trung


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bnh ca loi gia cc ln lp ca thut ton. Khi , ngi gii on s xc

nh c c im nhn dng lp ph ca mi loi ph.

Do thut ton gi tr trung bnh K c tnh lp cho nn phi tnh ton

nhiu v vy, n thng ch s dng cho cc vng din tch nh ca nh. Cc

vng din tch nh thng gi l cc vng mu khng kim nh v khng

nn nhm ln vi cc vng mu s dng trong phng php phn loi c kim

nh bi v trong khi cc vng mu c kim nh nm trong cc min c

chng loi lp ph ng nht th cc vng mu khng kim nh li c

chn cc a im khc nhau trn ton cnh c cha nhiu loi lp ph.

iu ny m bo cho mi loi ph trong cnh tng c i din mt

cch c lp v cc loi ph ca cc vng khc nhau c phn tch xc

nh c im nhn dng chng. Cc nhm tng t ging nhau biu th cc

loi lp ph ging nhau c kt hp li vi nhau khi thch hp. Cc s liu

thng k c nghin cu cho cc nhm kt hp s dng phn loi ton b

cnh tng (v d bng thut ton khong cch ti thiu hoc xc sut cc

i). Do phng php phn loi ny i hi cc yu t ca phn tch c kim

nh cng nh khng kim nh cho nn n c gi l phng php phn

loi hn hp.

Cch phn loi hn hp c bit c gi tr trong nhng phn tch m

trong c bin thin phc tp trong cc mu phn x ph i vi cc loi lpph. Nhng iu kin ny hon ton c tnh ph bin trong thc t nh lm

bn thc vt cc vng ni. Trong nhng iu kin , kh nng bin

thin v ph trong phm vi cc loi lp ph thng bt ngun t thay i cc

loi lp ph theo ging loi v t cc iu kin a l khc nhau (th nhng,

dc). Cch phn loi hn hp gip ngi gii on nh x l kh nng thay

i . Mt cch tip cn chung khc na i vi phn loi khng kim nh

l s dng cc thut ton a vo nhy cm i vi "cu to b mt" hoc

" th" ca hnh nh lm c s xc lp cc tm ca nhm. Cu to b mt

c xc nh bng phng sai nhiu chiu quan trc trn mt "ca s"

chuyn ng i qua nh (chng hn mt 3 x 3). Ngi gii on s t mt

ngng phng sai m di ngng mt c xem l ng nht v trn

ngng n c xem l khng ng nht. S trung bnh ca ca s trn

u tin gp trn nh s tr thnh tm ca nhm u tin. S trung bnh ca


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ca s trn th hai gp trn nh s tr thnh tm ca nhm th hai v c th

tip tc. Khi t ti s lng ti a (chng hn 50), th ngi gii on s xem

cc khong cch gia cc tm nhm trc trong khng gian tr o v nhp

hai nhm gn nht ng thi kt hp cc s liu thng k ca chng.

Ngi gii on tip tc kt hp hai nhm gn nht sau cho n khi tonb nh c phn tch xong. Sau phn tch cc tm nhm mi xc nh

kh nng phn loi chng trn c s khong cch thng k do ngi gii on

qui nh. Nhng nhm c tch ra do nh hn khong cch c kt

hp li v s liu thng k ca chng c nhp li vi nhau. Cc nhm cui

cng thu c t kt qu phn tch nh trn c s dng phn loi hnh

nh (chng hn, vi phng php phn loi dng khong cch ti thiu hoc

xc sut cc i).

D liu t cc vng mu c kim nh i khi c s dng tng

thm cc kt qu ca phng php nhm li ni trn khi mt s loi lp ph

cha c trng trong phn tch thun tu khng kim nh. ng x v cc

c trng hnh tuyn khc khng c hin th trong thng k to nhm lc

ban u nu cc c trng ny khng c p ng tiu chun trn trong

ca s chuyn ng.

Cn lu l kt qu ca vic lm ny ch l s nhn dng ng cc

loi khc nhau v phng din ph trong d liu hnh nh. Ngi gii onvn cn phi s dng d liu tham kho lin kt cc loi ph vi cc th

loi lp ph cn quan tm. Qu trnh ny, ging nh bc chn lc b mu

trong phn loi c kim nh.

.3.9. Giai on a ra kt quCng dng ca bt k phng php phn loi hnh nh no cui cng

s ph thuc vo sn phm cc kt qu a ra m chuyn ti mt cch hu

hiu thng tin

c gii on cho ng

i s dng. y, ranh gii gia vinthm, bn my tnh, lm bn s v h thng thng tin a l b xa

nha. C th la chn mt cch khng hn ch cc sn phm u ra. Ba dng

tng qut thng c s dng, bao gm cc sn phm "bn " ha, cc

bng s liu thng k khu vc v cc file d liu bng s.

1. Cc sn phm ha


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Bi v cc d liu c phn loi nm di dng mng d liu hai

chiu, kt qu ha d dng c a ra bng my vi tnh bng cch hin

th cc mu cc tng hoc cc ch cho mi trong mng theo loi lp ph i

tng c gn cho. C th s dng mt lot thit b cho mc ch ny nh

cc mn hnh th hin mu, cc my in, cc my ghi phim v cc my qut cln. Nhng cch hin th trnh by cc kt qu phn loi mt cch rt hu

hiu v ngi phn tch c th chn cch hin th mt cch tng tc ch cc

tp con (tp hp con) ca file ban u hoc d dng thay i cch gn mu

sc, to nhm cc loi... Khi mun c sn phm u ra copy giy i vi cc

d liu trn c th s dng my in tnh in hoc in laze. Cc bn in ra c th

l trng en hoc in mu. Ta cng c th s dng my chp phim mu hoc

scanner laze sn xut cc bn in cng c chnh xc cao v mu v hnh

hc.

2. Cc d liu a ra bng bng

Mt hnh thc chung na v kt qu u ra l dng mt bng lit k

tm tt cc s liu thng k v din tch ca cc loi lp ph c mt trn cnh

tng hoc trong cc din tch nh hn cnh tng m ngi s dng xc

nh. Ta c th rt ra cc s liu thng k v din tch t file d liu gii

on da theo tng li.

Trc ht ranh gii ca mt vng ang quan tm (nh l mt lu vc,

thung lng hoc mt tnh) c s ha i vi cc ta ma trn nh. Trong

ranh gii , s lng cc trong mi loi lp ph s c lp bng v nhn

vi din tch mt t ca mt tng ng. Qu trnh ny n gin hn vic o

th cng cc vng trn mt bn v l u im ch yu ca x l d liu lp

ph mt t di dng s.

3. Cc file thng tin bng sMt th loi cui cng a ra kt qu l cc file d liu gii

on cha cc kt qu phn loi c ghi li trn mt s phng tin lu trbng my tnh (chng hn CCT hoc a). D liu c gii on di dngny, c th d dng nhp vo h thng GIS ha nhp vi cc file d liu al khc.


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Chng IV

tng cng cht lng nh vin thm--------------------------------------------------------------

.4.1 nh s trong vin thm1. Khi nim v nh s

nh s c to bi mng hai chiu ca cc phn t nh c cng kchthc c gi l Pixel. Mi pixel c xc nh bi to hng (m), ct (n)v gi tr xm (g) ca n l g(m, n) bin i theo to im (x, y). To hng v ct ca mi pixel u l cc s nguyn. Cn gi tr xm ca pixelnm trong thang xm t 0255 (thang xm 256 bc theo n v thngtin 8 bit). To s ho ch l cc gi tr ri rc m, n v c biu th:

x = x + m.x

y = y + n.y

Trong :

m = 0, 1, 2 ... M

n = 0, 1, 2 ... N

x, y l bc nhy s ho.

Khi ly x = y v N = M ch ra cc gi tr ri rc c gn vo ccgi tr xm g(m, n) tng ng ca cc pixel, lc chng ta ni rng nh

c ly mu (Sampling) v cc gi tr xm ca n c lng t ho.Cc phn t ca ma trn xm g(m, n) c dng:

( ) ( ) ( )

( ) ( ) ( )

( ) ( ) ( )

g g g N

g g g N

g M g M g M N

0 0 0 1 0 1

1 0 11 1 1

1 0 11 1 1

, , ... ,

, , ... ,

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

, , ... ,

(4-1)

i vi nh v tinh dng s th mi phn t nh ca pixel th hin mt

khu vc b mt trn tri t. Gi tr xm ca pixel c tnh bng tr trungbnh ca phn x ph ca ton b khu vc nm trong phm vi ca pixel. Tac th thu c nh s nh cc thit b s ho, c th l my qut nh. Qutrnh s ho bao gm 2 vn quan trng l nh mu nh v lng t hohnh nh, hay c th ni rng:

Qu trnh s ho = Qu trnh nh mu + Qu trnh lng t ho


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Cng ngh vin thm


Qu trnh nh mu nh c s dng to ra s ri rc ho khnggian hnh hc lin tc ca nh. Thng thng n c thc hin nh h thngquang hc vi kch thc no c chn chuyn ng dc theo ngqut trn tm nh, cng ti thi im n tin hnh o, ghi (thi gian c nh trc hoc di ca bc nhy) phn x hoc bc x gi tr en ca tng vng vi i tng tng ng. Vic nh mu nh cho tng v trca m ca h thng quang hc l gi tr thch hp ca ton gi tr entrong khong ca m (kch thc). Theo lut nh mu, bc nhy nh mul tng T tho mn iu kin:

Tfc

1

2 (4.2)

Trong :

fC - L tn s cao nht ca php bit n FURIER ca vic nh munh, tc l tn s ct.

Qu trnh lng t ho c s dng to ra s ri rc khng gian en lin tc ca nh. Lng t ho c th thc hin bng hai phng php ltuyn tnh hoc khng tuyn tnh nhch ra hnh 4-1 v hnh 4-2.

Hnh 4-1Lng t tuyn tnh

Hnh 4-2Lng t khng tuyn tnh

Theo phng thc tuyn tnh, cng thc lng t ho c th biu din

di dng sau:( ){ }( )

I Integer I I I

I I

A=

min

max min

(4.3)

Trong :

IA

0 i2i1 imaximin

i

I

N-1

bc

M bc

IA

N i

N-1


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Cng ngh vin thm


N - L thang cng (bc en) lng t ho v thng t 0255.

Imax, Imin- L gi tr cng cc i v cc tiu trong nh mu nh.

Ngoi ra nh s c th thu nhn trc tip nh h thng Sensor t trncc thit b bay. Phng thc thu trc tip ny c s dng trong k thut

vin thm nh l h thng MSS, TM t trn v tinh Landsat ca M hoc hthng CDD t trn v tinh Spot ca Php...

2. Cc c trng c bn ca nh s trong vin thm

Trong vin thm, vic thu nhn nh s c thc hin nh cc h thngSensor t trn cc v tinh hoc trn con tu v tr. Cc Sensor ny qut vnh mu nng lng phn x b mt tri t ti vng m v tinh bay qua.Trong cng mt thi im cc nng lng ph thu nhn c phn tch lintc nh h thng lng knh tch tia c bit v c ghi li sau khi lng t

ho thnh cc bng ph khc nhau to ra nh s vin thm hay gi l nh sa ph. Loi nh ny c c trng ring ca chng l c trng ph, c trngkhng gian v c trng thi gian.

a. c trng ph

Cc i tng khc nhau di mt t s phn x cc bc sng in tkhc nhau. V th cc i tng mt t thuc cng mt lp s c ph (en) khc nhau trong cc bng ph khc nhau v cc i tng thuc cc lpkhc nhau cng s c

cong nghe vien tham - pham vong thanh va nguyen truong xuan

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