This paper first synthetically analyzes three classical algorithms of constructing Delaunay Triangulation Irregular Net (DTIN),
then uses improved convex hull algorithm to construct non-constrained D-TIN. The non-constrained D-TIN may
cause some Delaunay triangles which span contour lines, so these Delaunay triangles must be dealt with. Then the local
adjusting algorithm based on diagonals changing of the impacted region is used to embed contour lines into D-TIN as
constrained segments and ultimately construct constrained D-TIN (CD-TIN). After constructing CD-TIN which supports
the spatial data mining, it is easy to compute normal vectors of Delaunay triangles in the CD-TIN, and then get their
gradient values. By means of the relationship of gradient values and terrain features, flats and mountain regions can be
distinguished from topographic map based on contour lines. Even the terrain features such as mountain peak can be also
recognized in the recognized mountain regions primarily by Flat-Triangle whose three vertexes have the same digital
elevation.
KEYWORDS: Geographic information systems, Web services, Systems modeling, Data modeling, Internet, Software, Computing systems, Computer networks, Received signal strength, Information security
Over the past decade, GIS technologies have evolved from the traditional model of stand-alone systems to an
increasingly distributed model based on independently provided, specialized, interoperable GIS Web services. But
traditional GIS Web services adopt RPC-based interaction model, this model is not appropriate for the scalability of the
GIS, thus restricts universal application and further development of GIS Web services. REST is an approach for getting
information content from a Web site by reading a designated Web page that contains an XML file that describes and
includes the desired content. REST ignores the details of component implementation and protocol syntax in order to
focus on the roles of components, the constraints upon their interaction with other components, and their interpretation of
significant data elements. Based on the analysis of the characteristics and the defects of the traditional interaction model
and the comparison between the traditional model and REST-based interaction model, this paper discusses a
development direction of GIS Web services interaction model.
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