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

   is composed of an i-node (from-node) and a j-node (to-node) - a node is created by the CLEAN command when two arcs crossover (polygon topology) - links can pass one over another - bus stops can be stored as point events which are not necessarily represented by nodes at the arc-node level - bus stops must be represented by a node - all feature attributes are stored in a relational-like data base ("horizontal" structure) that is managed by the INFO information manager (or other external relational data base managers) - element attributes are stored in a "vertical" structure - tables are mostly user-defined depending of the user applications and data needs - many of the attributes are already defined (standard attributes)

[Page]

D) The communication process

Although it seems natural to consider a direct communication process between an ArcInfo workspace (Master GIS) and an EMME/2 data bank, there are several difficulties involved. For example, given an ArcInfo workspace where there are a road network and a transit network, we still have to define traffic zones and decide on a certain aggregation of the network representation for some specific applications. This can only be carried out by the transportation planners and not by an automatic process. In order to establish an automatic process that can exchange information between the two software packages, we decided to establish an EMME/2 coverage in ArcInfo with a "one-to-one" relationship with the EMME/2 network elements. The communication paths are shown in Figure 1. Note that there is no specific sequence in this figure.

Figure 1 - General components involved in

上一页  [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]  ... 下一页  >>