PI-7-5 
Fig-4 Computer Extracted Watersheds and river systems 
connection to ocean must have drainage direction to 
reach the ocean, solving concave and flat land 
problems. This solution is not necessary for the inland 
isolated Area-A. 
e) Buffer area with 5 pixels distance from DCW 
streamlines, but without Area-A is created(Area-B). 
Drainage directions of pixels in Area-B are defined. 
All pixels in Area-B with connection to ocean or Area- 
A must have drainage direction to reach ocean or 
Area-B, solving the problems of concave and flat area. 
But Pixels in inland isolated are not necessary to solve 
the problems. 
f) Drainage directions for pixels not belonging Area-A 
nor Area-B are defined. All pixels in this area should 
have drainage direction to reach ocean, Area-A or 
Area-B, by solving the problems of concave and flat 
area. 
4. RESULT & DISCUSSION 
Global Drainage Direction Matrix(DDM) with 30 
seconds arc grid is produces using GTOPO30, DCW 
streamlins, WBDb-II streamlines and USGS Land 
Cover Data. The generated DDM and extracted 
streamlines from the DDM have following 
characteristics: 
(1) The extracted river systems have consistent 
structure with existing streamline data such as DCW 
and WBDb-II. 
(2) The extracted streamlines runs adequate position of 
topographic condition derived from GTOPO30 DEM 
data. 
(3) Inland isolated watersheds are delineated using 
existing streamlines data of DCW and WBDb-II. 
(4) The consistency of water body distribution between 
computer derived and satellite image classified can be 
seen. 
Moreover, the global DDM covering most of the 
continents is the first product opened on WWW. 
And, the developed algorithm and computer program 
which generate DDM by using DEM and streamline 
information can be adapted for any scale data, and 
areas, and they can produce a consistent DDM and 
river network systems based on existing streamlines 
prepared, independent of the accuracy of DEM.