International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
limited. And the flood water depth or the necessary 
information on regional base is not easily acquired by the 
remote sensing data. Then it should be very convenient that the 
above mentioned information can be uploaded into the web 
servers which exist at hand, but the client of disaster 
information unconsciously and seamlessly can access such 
kind data on the distributed and cooperated web servers 
through the Internet. Recently, the discussion of the 
international standard for such distributed and cooperated 
server design is progressing at ISO, OGC, etc. 
Mathematical morphology procedure should be suitable 
for the method of SAR data analysis for such kind of disaster 
data server. Because this image processing procedure will 
have advantage over the flood disaster monitoring using SAR 
satellite data in some points. 
The authors plan to make rapidly flood extent mapping 
server on the Internet for the early warning system of regional 
and agricultural flood damage. 
2. FLOOD EXTENT MAPPING METHOD IN 
HI dilation dilation 
— — 
  
  
  
  
  
  
  
  
  
  
erosion erosion 
—- — 
Fig.1 The results of dilation and erosion 
22 Terrain feature recognition method for SAR imagery 
in paddy field areas during flood 
If the farm lane or levee is above the water surface 
otherwise it is an ordinary inundation or flood, the flood 
PADDY FIELD AREAS 
2.1 Interaction between SAR data and ground features 
Computational mathematical morphology operations, 
such as erosion, dilation, opening, closing and directional 
filters, provide image feature measurements. By using 
conventional method, they can detect the flood extent from the 
low backscattering value of each pixel for the water surface. 
But it will be very difficult to distinguish the flood areas from 
the ordinary paddy fields especially in the early growing stage 
of rice plants. But SAR signal intensity for each pixel 
includes some interactive information between microwave and 
terrain feature on the ground. Then morphological processing 
procedures are one of the methods for detecting such spatial 
information. For example, if the Levee of paddy fields is 
above the inundated water surface, the paddy fields should be 
almost without damages in the consolidated farm lands. If the 
region of the low backscattering intensity level occupy large 
area, that can be most likely large water surface, 
flood-inundated areas. These calculations require only a 
snapshot of SAR image. 
  
"Morphological operators 
S#B= {z: B+z#S} ; erosion operation 
S @ B=#{B+x:x#S} ; dilation operation 
S $ B = (S # B) @ B ; opening operation 
S Y B = [ S @ (-B)] # (-B) ; closing operation 
  
  
  
damage to paddy rice is assumed as no damage. Because 
usually, paddy fields have the water surface of its swamp and 
the water level is under the top of the levee or farm lane. 
  
  
rice crop 
  
  
water lebel 
  
  
  
  
  
  
an inundated paddy field lot 
  
  
  
  
Fig2 Cross section of paddy fields 
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