Geological, 40m EDM, forest stands and land use data 
were in digital format. These data were converted into 
Transverse Mercator projection, which was the standard 
projection for Taiwan. A boundary coverage of Der-Chi 
watershed, which was digitized from 1:10000 
topographic maps, was used to clip these data to ensure 
they had the same spatial coverage. 
Sub-watersheds for the area were delineated manually 
using 1:100000 topographic maps and digitized. The 
coverage was cross checked with the DEM data. 
Several data layers were generated using ARC/INFO 
functions. Taiwan's soil conservation regulations use soil 
depth and slope as key factors in determining land use 
restriction for sloped land. The soil coverage was derived 
for soil sample points using kriging. The DEM was used 
to generate a TIN for the region. Slope coverage was then 
derived from the TIN. 
A 100 meter protection zoné around the reservoir was 
generated using buffer function. 
Cadastral Data Set 
Cadastral data record the ownership and the zoning 
restrictions for each parcel and is a vital part of the 
environmental database for decision support. 
The cadastral information of Der-Chi watershed 
consisted of 189 cadastral maps and related records. 
These maps were based on a local coordinate system. No 
exact mathematical relationship existed between the 
coordinate system and Transverse Mercator coordinate 
system, which was used for other data. 
Several steps had been taken to integrate these maps with 
other data. First, a set of points was identified on the 
cadastral maps as candidate control points. The positions 
of these candidate points were located in field and 
differential GPS was used to obtain the coordinates of 
these points. Finally, these control points were used to 
transform the cadastral maps. The accuracy of the 
transformed cadastral maps was checked by overlapping 
the roads and rivers on cadastral maps and those on the 
physical environmental data set. The results indicated 
that the transformed cadastral data was suitable for 
environmental monitoring purpose. 
Image Data Set 
Image data set includes two types of data. The first type 
is satellite images, including raw images and classified 
land use maps. The second type is photos taken in the 
field to record land use. The photos were scanned and 
stored in jepg format. 
  
sytem 
funciton 
requirements 
  
  
  
  
system 
development 
  
  
  
  
  
system 
testing 
  
  
  
  
Figure 4 Monitoring System Development Procedures 
Environmental Decision support System Development 
The purpose of the environmental monitor system was to 
build a decision support system which enables 
researchers and land managers to query and retrieve 
information from environmental database and to perform 
analysis required by management tasks. The procedures 
used to develop the system is shown in Figure 4. 
First, a series of interview with agencies involved in the 
land management of the Der-chi area was taken to 
understand each agency's responsibility and requirements. 
The results of interview were used to formulate the initial 
system function requirements. The system was developed 
according to these requirements. The system was 
delivered to the agencies and tested. Feedback from users 
was use to modified the system 
The system is developed using Arcview/Avenue in MS 
Window environment. All functions are menu or icon 
driven. The system is still under development. At the 
present, the system includes the following modules. 
Data Access and Data Management 
Users could retrieve data by various location schemes, 
Such as political boundaries, sub watershed units, parcels, 
134 
or by subjects, such as geology, land use, slope and soil. 
The system uses optical disks to store large quantity of 
image data. The information on these optical disks is an 
integrated part of the database system and can be 
accessed easily from query menu. New images can be 
added to the image database quickly. 
Map Production 
The system provides predefined layouts for map and/or 
attribute data output. Users can quickly generate maps 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996 
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