Development of a Data Exchange Protocol between EMME/2 and ArcInfo

   network data modelArcInfo supports many data models (coverage, grid, triangulated irregular network, CAD, etc.) to represent geographic information. A coverage is for vector data, and supports georelational models, that is, it contains both the spatial and attribute data for geographic features. The feature classes, used in the coverage to store geographic features, are:

• points for storing punctual features;

• arc, node and route-system for storing linear features;

• polygon and region for storing areal features.

ArcInfo stores coordinates only for points, arcs, and nodes, and uses topological relationships for defining networks and polygons. Here are the three topological concepts used to define features:

• The arc-node topology defines the connectivity of arcs; arcs are composed of two nodes and up to 500 vertices, and are connected at nodes; a set of connected arcs can define a network (streets and intersections);

• A polygon is defined as an ordered series of connected arcs, but the first and the last arcs must connect (area definition topology); for each arc, the left and right polygons are identified (left-right topology).

Networks and polygons form the framework for defining the two other feature classes:

• Route-systems are defined as an ordered series of arcs, however the first and last arcs need not connect. They are composed of:
  • Routes, which are linear features composed of one or more sections;

  • Sections, which may be an arc or portion of an arc used to define a route; a section is the most basic component of a route-system.

  In the dynamic segmentation model, route-systems are used to model linear features using route-measures and events, and to associate multiple sets of attributes to any portion of a linear fea

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