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EVALUATION OF A GIS RULE-BASED MODEL TO MAP FORESTED WETLANDS IN MAINE 
By Wen-Shu Liou; Steven A. Sader 
Commission VII, Working Group 5 
KEY WORDS: GIS, Rule-Based Model, Forested Wetlands 
ABSTRACT 
The objectives of this research were to analyze, revise, and test a Geographic Information System (GIS) rule-based model to improve 
the mapping of forested wetlands at two study sites in Maine. To determine the performance of satellite mapping techniques, three 
conventional image classification methods (unsupervised, tasseled cap, and hybrid classification) and a revised GIS rule-based model 
were evaluated. Accuracy assessment was conducted by cross tabulation of classification results to photo interpreted random sample 
plots. 
The GIS model incorporated hydric soils, slope, National Wetland Inventory, and hydrography layers. After the GIS layers were 
analyzed statistically, a integrated model was formulated. The new integrated GIS model offered a greater degree of versatility and 
automation for a less subjective classification approach in the forested wetland mapping application. 
The model had the highest classification accuracy among all tested methods at both study sites. Pairwise significance tests indicated 
that the integrated model was significantly better than unsupervised and tasseled cap classification methods at both study sites. The 
Kappa coefficients for the integrated model were slightly higher compared to the hybrid classification approach, however the 
significance test indicated no difference between the two methods at either study site. 
The results suggest that the physical characteristics of the two study sites may have had more influence on the conventional 
classification methods than on the integrated model because the model incorporated the physical variables into the decision rule. 
Evaluation of new variables in the model (e.g. topographic position) and the effect of spatial error propagation in developing the GIS 
data base need to be investigated further. 
1.0 INTRODUCTION 1) Compare three conventional techniques of land cover 
classification including unsupervised, tasseled cap 
Forested wetlands are abundant in Maine and provide valuable transformation, and hybrid (unsupervised and supervised) 
services including moderation of downstream flooding, for delineating forested wetlands and understanding the 
maintenance of water quality. provision of diverse habitats for limitations of spectral image classification. 
wildlife, and pollution control (Wharton et al, 1982) The 2) Apply statistical analyses to evaluate the contribution of 
forested wetlands are described as lands transitional between selected GIS layers in the prediction of forested wetland 
terrestrial and aquatis systems where the water table is usually at locations and determine the optimal model. 
or near the surface or the land is covered by shallow water and 3) Develop a formulated rule in an integrated remote sensing 
dominated by trees 20 feet or taller. and GIS model. 
The first simple model to integrate remote sensing and GIS to 4) Verify the accuracy of forested wetland classification results 
address forested wetland identification was developed by Ahl using aerial photographs and field data as a reference 
(1994). This model consisted of a land cover classification source. 
(representing forest and non-forest) derived from satellite 5) Develop the model on one study site (Acadia) and test the 
imagery and four hierarchical GIS lavers National Wetland formalized model in a second study area (Orono) to 
Inventory (NWI), hvdric soil, slope, and hydrological data. compare the results with a previous model (Ahl, 1994). 
However, the four GIS layers were assigned arbitrary weights 
based on their presumed contribution to identifying wetlands and 
this created some ambiguity in the model. 2.0 LITERATURE REVIEW 
This research attempts to develop an improved GIS model. To 
avoid subjective criteria, the presumed weights for each GIS 2.1 Federal Wetland Mapping Programs in the U.S.A. 
layer needed to be carefully examined. A data analysis procedure 
and non-site specific rule needed to be formulated to provide The interpretation of aerial photography is the most widely used 
consistent results. method of deriving wetlands maps. In producing wetland maps 
The specific objectives of this research were to analyze, revise, (e.g. NWD, wetland types are identified primarily from aerial 
and test a rule-based model to identify forested wetlands in two photographs by skilled interpreters using stereoscopic techniques. 
Maine study sites. An integrated model was developed to weight The NWI project claimed that leaf-off color infrared photography 
selected attribute data residing m a GIS. Analyses were from early spring was the best for detecting forested wetland, 
performed to: especially for deciduous forested wetland. Furthermore, the 
419 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996