Full text: XVIIIth Congress (Part B7)

  
QUANTITATIVE ASSESSMENT OF SHORELINE CHANGES 
USING 
MULTI-TEMPORAL SATELLITE IMAGES 
Liang-Chien Chen 
Professor 
and Jiann-Yeou Rau 
Assistant Research Scientist 
Center for Space and Remote Sensing Research 
National Central University, Chung-Li, Taiwan 32054, R. O. C. 
E-mail: lcchen(gcsrsr.ncu.edu.tw 
Commission VII, Working Group 8 
KEY WORDS: Multi-Temporal Satellite Images, Surface Reconstruction , Coast. 
ABSTRACT: 
We present here a new scheme that performs surface reconstruction and coastline change detection for tideland 
areas using multi-temporal satellite images and tidal measurements. The basic idea of this investigation is to 
reconstruct a reference DTM for a tideland area of interest from a set of multi-temporal SPOT images and tidal 
measurements first. Then, the coastlines on a historical target satellite images are extracted and compared to the one 
predicted from the reference DTM according to the associated tide elevations. The variations of shorelines between 
the reference image set and the historical images may thus be assessed quantitatively. À self-consistency check may 
also be performed to evaluated the quality for predicted shorelines. Experimental results indicate that the relative 
error is smaller than 5% as far as the area variation is concerned. The largest sand bar of Taiwan ,Wai-San-Ting, has 
lost its area about 37% during the last eight years. 
1. INTRODUCTION 
Detection of landcover changes for coastal areas is 
an important task in environmental monitoring 
[Hull ,1978]. The variations of shorelines have direct 
impacts on the economy development, land planning , 
and land management. Thus, The terrain changes of 
tideland have attracted world-wide interests.[Welch et 
8l.,1992 ; Stokkom et al., 1993] 
Carter[1978] investigated the applicability of satellite 
images in the data acquisition for wetlands. The 
spatial resolution of the satellite images i.e., Landsat 
MSS, is limited to 80M at the time. Frihy et al., [1994] 
identified the pattern of shoreline changes for Nile 
Delta. However, the tidal variation is not rigorously 
treated. In addition, three dimensional terrain analysis 
for shore areas is no considered. 
The spatial, spectral , and temporal resolutions of 
satellite images have significantly improved in recent 
years. Hence, combining multi-temporal satellite 
images and tidal measurements , through image 
interpretation and analysis, make the detection of 
dynamic changes for shorelines possible. The basic 
idea of this investigation is to reconstruct a reference 
DTM for a tideland area of interest from a set of multi- 
temporal SPOT images and tidal measurements first. 
Then, the coastlines on a historical target satellite 
image are extracted and compared to the one traced 
from the reference DTM according to the associated 
tide elevations. The variations of shorelines may thus 
be assessed quantitatively. 
The structure of this paper is as follows. In the next 
section ,we give a brief introduction to the techniques 
118 
for the proposed scheme, Section 3 provides the 
experimental results. Finally, section 4 offers some 
conclusions. 
2. THE PROPOSED SCHEME 
The proposed scheme comprises two major 
components. The first is to derive a reference DTM for 
tideland areas from a set of reference satellite images 
incorporating different tide elevations. The second 
component predicts the shoreline for a given tide 
elevation from the reference DTM. Then a change 
detection for the shoreline may be performed with 
respect to a historical data set. The flow chart of the 
proposed scheme is shown in figure 1. 
2.1 Generation of a Reference DTM 
The procedure for derivation of a reference DTM 
includes: 
(1)collecting a series of SPOT data as reference 
images which are associated with different tide 
elevations over a short period of time, when 
insignificant variations for a tideland area of interest 
are assumed, 
(2)performing geometrical registrations among the 
reference images,[Chen & Lee, 1992] 
(3)Extracting shorelines from each of the reference 
images, 
(4)assigning elevation for each point on the extracted 
shorelines according to tidal measurements, 
(5)superimposing all layers of the extracted shorelines 
with different elevations, 
(6)generating a reference grid DTM through an 
interpolation procedure. [Lee & Chen 1990] 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996
	        
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