OBSERVATIONS OF COASTAL CHANGES ON TAIWAN USING A 10 YEARS TIME SERIES ERS

SAR IMAGESHsiu-Wen Wang, Kun-Shan Chen, and Chih-Tien Wang

Institue of Space Science & Center for Space and Remote Sensing Research, National Central University

Chung-Li, Taiwan

OutlineINTRODUCTION

DATA AND METHOD

VALIDATION

OBSERVATIONS AND

RESULTS

DISCUSSIONS

CONCLUSION

INTRODUCTIONEsat China Sea longshore current

South Sea of current of seasonal winds

The structure for western coast is mainly sandy shore, while eastern

coast mainly rocky shore.Characteristics of ocean currents surround

Taiwan

Kuro

shio

DATA AND METHOD (1/3)ERS-1&2 SAR Images SPOT-2&5 Images

2007/07/23

2007/08/23

1997/10/24

1. 2 times observation data set of 1997 and 2007

2. Same tidal datum.3. Cloud-free images

Trac

k

Range

Local Time: 10:30 a.m.Tidal station

1. 55 times observation data set of 1996, 1999, 2003, 2005, and 2010

2. descending orbits

DATA AND METHOD(2/3)1996/01/31 Waisanting

ERS-1 SAR image

1996/01/31 WaisantingWaterline

FilteredSAR images

Average filter

w1xw1

Average filter

w2xw2

Average filter

w3xw3

Edge detection Edge detection Edge detection

waterline

correlator

Multi-scale edge detection

Red Green Near infrared

Shortwave infrared

Panchromatic Fusion

Fusion band 1

Edge detection

Correlator operation

waterline

DATA AND METHODS(3/3)

Red Green

NIR SWIR

Fusion Red Fusion Green

Fusion NIR Fusion SWIR

Multi-scale edge detection

Image data: ERS-2Local time: 2007/04/19 a.m. 10:30Location: Waisanting sandbank in Chayi county

under 10

11-20 21-40 41-600

102030405060

22

57

17

4

GPS vs. Waterline Extraction

Difference(m)

coun

t(%

)

Waterline extraction from SAR imageWaterline indication survey from GPS

RMS: 23m

VALIDATION(1/3)

VALIDATION(2/3)

R: 2003/10/02 G: 2003/07/24B: 2003/04/10

Waterline overlaid on a color composite SAR image in 2003

Depth data integration from sonar measurement on July, 2003

Survey MarkReference pointWaterline extraction from SPOT-5

2(0.5m)

3(0.5m)

4(2.5m)

5(1m)

6(2.5m)

1(0.5m)

Image data: SPOT-5Local time: 2008/09/06 a.m. 10:14~10:17Location: Da-Fu coastline in Yilan county

RMS: 1.5m

Datum: TWD97 E N HLand

administration, M.O.I. (station:

2080)

332369.52

2742704.52 23.26

Measurement result

(AM.9:00~AM.12:00)

332369.54

2742704.55 23.34

Measurement error -0.02 -0.03 -0.08

VALIDATION(3/3)

OBSERVATIONS AND RESULTS(1/7)

Western coastline from SAR image extraction in 1996 to 2005

Eastern coastline from SPOT image extraction in 1997 and 2007

OBSERVATIONS AND RESULTS(2/7)

Nanliao

Siangshan wetland

Fangyuan

OBSERVATIONS AND RESULTS(3/7)

Haifengdaosandbank

Waisantingsankbank

Yunlin offshore industrial park

OBSERVATIONS AND RESULTS(4/7)

Chigu lagoon

Kaohsiung

OBSERVATIONS AND RESULTS(5/7)

Gongliao beach

Wushin port

OBSERVATIONS AND RESULTS(6/7)2004年 12月 06日 11時 2004年 12月 06日 11時2002/05/16 a.m.12:00

The northward shore at Wushin port The southward shore at Wushin port

OBSERVATIONS AND RESULTS(7/7)

Hualien port

Chihpen

DISCUSSIONS(1/2)

　 Data

Tide statio

n Haifengdao

Tide(m)

Area(ha.)

Erode or heap(ha.)

Distance

1996/4/11(11:00)

-0.64 1380 － -

1999/8/19(10:30)

-0.67 2173 793 500

2004/1/15(13:24)

-0.7 1681 -492 2000

2005/7/28(10:00)

-0.62 1400 -281 100

2010/9/30(10:30)

-0.57 1750 350 500

1996 1998 2000 2002 2004 2006 2008 20101000

2000

3000

:實

際觀

測面

積公

頃

年份1996 1998 2000 2002 2004 2006 2008 2010

0

2000

4000

:累

積距

離變

化公

尺

Haifengdao sandbar change between 1996 and 2010

Haifengdaosandbank

Yunlin offshore industrial park

Juoshui River

Year

Are

a o

f sa

nd

ban

k (

ha.)

Accu

mu

latio

n d

istan

ce(m

ete

r)

　 Data

Tide station Waisating Sandbar

Tide(m) Area(ha.) Erode or heap(ha.) Distance

1996/10/3(10:30)

0.25 2340 － －

1999/5/6(10:30)

0.15 1673 -667 90

2004/4/29(10:30)

-0.04 1636 -37 320

2005/4/14(10:30)

0.062 1400 -236 100

2010/4/8(10:30)

0.06 1568 168 300

Waisanting sandbar change state from 1996 and 2010

1996 1998 2000 2002 2004 2006 2008 20101400

1600

1800

2000

2200

2400

:實

際觀

測面

積公

頃

年份1996 1998 2000 2002 2004 2006 2008 2010

0

200

400

600

800

1000

:累

積距

離變

化公

尺

Waisantingsankbank

Year

Are

a o

f sa

nd

ban

k (

ha.)

Accu

mu

latio

n d

istan

ce(m

ete

r)

DISCUSSIONS(2/2)

CONCLUSIONWestern coastline changes greatly while relatively small in

Eastern coast. The time series observations by SAR images clearly reveals

exposed or submerged sandbank size and moving distance of the coastline change situation

Optical image for a long time observation limits to small areas.

Sandbank waterline and depth data integration was verified and the data can be used for inter-tidal zones estimation.

satellite remote sensing by SAR, aided by ground tidal data, bathymetric mapping, and optical images, is an effective and efficient tool for mapping the changes of coastlines and sandbanks over long periods of time.