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Monitoring of shoreline change by using satellite images in Cuulong river estuaries

Nguyen Dinh Duong,Vo Duc Tuyen
Centre of Geography and Natural Resources
NCSR of Vietnam


Absract
In the presented paper authors describe a methodology using satellite image for shoreline change monitoring. There are submitted two methods: graphic and digital. Both methods were used and their advantages were also compared. The paper includes and FORTRAN program AutoCAD programme.

List of Appendix
Appendix No. 1. Listing of programme TRANSF
Appendix No. 2. shoreline change detection map-Cuulong river's delta.

Introduction
One of problems. which must b solved in the coastal zone research subproject sponsored by the UNDP/ESCAP Regional Remote Sensing program is a trial application of remotely sensed data to detect and evaluate shoreline change in areas of Red river's delta and Cuulong rivers one.

Yearly shoreline change affected by river action in those areas is very great Frequent observation and timely detection of erosion areas play important role in national economy.

An application of modern survey methods to solved this problem is being carried out at the present time. One of the most successful direction is a utilization of satellite remotely sensed data especially high resolution for this purpose.

In this paper we submit shortly an experimental application of remotely sensed data in shoreline change detection mainly used methodology and gained results.

Used Materials
To evaluate exactly a shoreline change the first thing to be done is a collection of different materials the first requirement of collected data are multitemporality and second is that collected data must enable evaluate exactly, unambigously shoreline change.
Following materials should be used:
  • Topographic and thematic maps in apropriate scales edited in different times.
  • High resolution data for example SPOT, TM in different series
  • Aerial and field trips photos
  • Historic documentation
Complete acquisition of those data is very important for correct and accurate evaluation of shoreline change. We have used only LANDSAT 2,3,4 and SPOT images. we have collected satellite images that are already in Vietnam and some images supplied by ESCAP.

For this study we have used following materials (see tab .1)
  • LANDSAT MSS images with resolution 80 m
  • SPOT images with resolution 20 m
  • SOJUZ photos with resolution 30 m
  • Topographic map UTM 1: 250 000 edited in 1966.
Table 1.
Materials Cuulong river's delta
LANDSAT
MSS		 2/1/1973
31/12/1981
SUJUZ
KATE 140		 1/06/1983
SPOT 7/03/1986
8/02/1987
Topographic
Map		 1: 250 000
edited in 1966

Methodology
Shoreline in this study is understood as a mean high water line. For coast, where is there a mangrove a outward boundary is considered to be a shore line.

Because of different spectral characteristics of water, land and vegetation we can discern very well water from other objects in infrared band. Hence for this study we used mainly LANDSAT band? and SPOT band 2. Naturally the rest bands also give a lot of use full information.

Because satellite sensors are not in the same geometric construction and photographic products contain much distorsion, geometric processing is very important in drafting shoreline from images into map. We have attempted to use both graphic and digital methods for transfering of interpreted shoreline from image prints into maps. Both methods are described in detail as following.
  1. Graphic method
    Used graphic method is so called a local transformation one. Sufficient numbers of topographic control features were selected on both maps and prints. Control points have to be distincly observed on both prints and maps and they have been chosen like crossing of transportation network. Crossing of canal network atd. By this way system of control points new shore lines were transferred from prints into maps part by part on ZOOMTRANSFERSCOP. These land water boundaries of maps and prints will contain the erosion and accretion area of the change detection maps.

  2. Digital method
    In order to applicant this method it is necessary to have a pc computer with the following configuration.


    Fig. 1. PC - computer configuration used for digital method

    There are so many ways to executive it but following approach is applied jointly with the AutoCAD programme package. Whole transformation is divided into four steps.

    1. step - Control point four steps
      Do the same as described in the graphic method

    2. step - Shoreline digitalization by digitizer

    3. step - Digital processing
      This step is done by three separate programmes: FDXFOUT, TRANSF and FDXFIN. First thing to be done is convertion from AutoCAD file. DWG by command DXFOUT to file. DXF and by FDXFOUT programme coordinates x, y, are extracted and stored in appropriate files ready for transformation. The chosen transformation is based on planne affine one and it is programmed in FORTRAN 77. This programme can process unlimited number of coordinates. Listing of programme can TRANSF is given in Appendix 1. After transformation all corrected coordinates are stored back into AutoCAD file. DWG by FDXFIN programme and DXFIN command.

    4. Step - Ploting
      Corrected shoreline can be regenerated on screen and plotted on plotter by using utilities of AutoCAD.

      Advantages of the above described methodology are that all powerfull graphic abilities of AutoCAD can be used either during digitizaing or in editting and plotting. Further more all results are stored and they can be replotted or edited comfortably at any time.

Results
With the help of upper described methods and collected images shoreline change detection maps for Cullong river's delta was compiled and presented in Appendix 2. For better study we have choosen two places where the change is very distinct. In the place number 1 the action of nearshore streams has connected the island and main - land and under the action of stream is Cua tieu and Cha Dai mouth there is a trend off accretion in both mothern and southern direction. The chosen place number 2 is Cu Lao dung that is into he between of Dinh an and Tran De mouth. The accretion was permanent and it develops mainly into northern direction. Accretion speed is calculated for one profile and shown on graph in appendix 2.

Appendix No. 2


Conclusion
Survey method using satellite image has conformed its precedence in solving such a problem like monitoring shoreline change. Its results are not only objective detailed but very qualitative (for convenient scale) as well.

In the case the collection of satellite data is complete , unintermitten and with appropriate resolving power there is ability to evaluat the shoreline change not only qualitatively but quantitatively as well. On the whole remote sensing methods bring more economical advantages than traditional ones because they reduce field trips that often need high finance expenditure. they can be used for forecasting shoreline erosion and in protection against it.

Acknowledgemnt
Many thanks belong to ESCAP organizations for their supplements of satellite images and all members of research group who has taken part in solving this study problem.

Reference
  • James collins The national ocean survey coastal mapping program, Coastal zone 78. San Francisco. California 1978.
  • Albertz/Kreiling Photogram metric guide. Image technology Institute Co. Ltd.
Appendix No 1. Listing of Programme TRANSF 

C    PLANE AFFINE TRANSFORMATION WITH OVERDETERMINATION
C    DETERMINATION OF TRANSFORMATION COEFFICIENTS
	    REAL A(40), AA (40), C(6), MTH (12) , AAT (12)
	 1AAS (36), AAS1(36), BAS(2), BAS 1 (6) , BAS2 (36)   	
	   CHARACTER*13 ITEN 
   REAL MO, MP
   DATA A/40*-9999999,/ , AA/40*-9999999,/MTH,12*0/, 
   1AAS1/36*0./,BAS2/6*0,/ 
              EOFD=-9999999.0
C
C    READING FILE NAME OF MEASURED COORDINATES
C
C         WIRTE(*,*)'FILE NAME OF MEASURED COORDINATES?
	  READ (*,'(A13)') ITEN 
	  OPEN (2, FILE =ITEN, STATUS = 'OLD') 
	  ICH=ICH*2
	  DO 88888 N=1, ICH, 2
	  READ (2,*) AA (N0, AA (N+1) 
88888 continue
C
C    READOMG FO;E MA,E PF GOVEM COORDINATES
C 	
	  WRITE (*,*)(A13)') ITEN
	  OPEN (1, FILE =TTEN, STATUS='OLD
	  READ (1,*) ICH
	  ICH = ICH*2
	  DO 5004 II-1, ICH, 2
	  READ (1,*) A (II), A (II+1) 
5004	CONTINUE
C
C    ESTABLISHING OF NORMAL EQUATIONS 
C	
  	   II=1
10	   MTH(1) =1.
   MTH(2)=AA (II) 
   MTH(3)=AA (II*A) 
   MTH (10)   = 1 
   MTH (11) = AA (II+1)
   MTCH (12) = AA (II+1)
   CALL TRAM (MTH, AAT, 2,12)
   CALL NASM (AAT, MTH, AAS, 12, 12, 36)
   CALL SOUM (AAS, AAS1, AAS1, 36)
   BAS (1) = A (II)
   BAS (2) =A (II+1)
   CALL NASM (AAT, BAS, BAS1, 12, 2, 6)
   CALL SOUM (BAS1, BAS2, BAS2, 6)
   II = II +2 
   IF (AA(II), NE, EOFD) GOTO 10

C
C    SOLUTION OF NORMAL EQUATIONS
C
	 CALL INVMCAAS1, AAS2, 36)
	 IF (AAS2(1), EQ (EOFD) GO TO 1000
	 CALL NASM (AAS2, BAS2, C, 36, 6,6,)
	 I = 1
 SUM = O
11	 X = (1) +C (2) * AA (I) + C (3) * AA (I+1)
      Y = C (4) +C (5) * AA (I) +C (6) * AA (I+1)
 V X 2 = (A (I) - X) * (A(I) - X) 
 VY2 = (A(I+1) - Y) **2
 SUM = VX2 +VY2 
 I = I + 2
 IF (AA(I), NE, EOFD)  GOTO 11
 TI = 2, * (I-2,) - 6, 
 MO = SQRT (SUM/TI)
 MP = MO*1, 414214
C
C     TRANSFORMATION
C
	 OPEN (11, FILE + RESULT, DAT, STATUS = UNKNOWN)
	 WRITE (*, 200) C (1), C (4), C (2), C (5), C (3), C (6), MO, MP
   200 FOMAT (7X, TRANSF, COEFFICIENTS'/ 
        17X, AO = , E12,5,3 X, 	'BO=, E12,5/
        17X, A1= E12, 5, 3X, 	'B1=, E12, 5,/
        17X, A2= E12,5,3X, 	'B2= , E12, 5/
        17X, MO= E12, 5,3X,	'MP=, E12,5.0
 WRITE (*,*) FILE NAME OF COORDINATES BEFORE    TRANSFORMATOIN? 
 READ (*, (A13) ' ) ITEN
 OPEN (3 FILE=ITEN, STATUS = 'OLD')
 WRITE (*,*) FILE NAME OF COORDINATES AFTER  TRANSFORMATION?
 READ (*, (A13) ') ITEN
 OPEN (4, FILE = ITEN, STATUS = NEW ' ) 
2002	READ (3, *, END = 6000) ICHEK
	WRITE (4,  *) ICHEK
	ICHEK = ICHEK *2
	DO 2000 I = 1, ICHEK, 2
	READ (3, *) X, Y
	BX = C (1) + C (2) * X +C (3) Y 
	BY = C (4) +C (5) *X +C (6) * Y 
2000	WRITE (4,*) BX, BY
	GOTO 2002
2001	CONTINUE
1000	WRITE (11, 1001)
1001	FORMAT (2X, 	*** SINGULAR COEFFICIENT MATRIX ***   '  ) 
1002	CONTINUE
6000	CONTINUE
	CLOSE (1)
	CLOSE (2)
	CLOSE (3)
	CLOSE (4)
	CLOSE (11)
	STOP
	END