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ArcGIS 9 - Arcgis Network Analyst Tutorial
The elevation field contains logical elevation values for establishing connectivity only and does not provide height information for the feature. ArcGIS Network Analyst can use this data to modify the connectivity settings established in the previous step. ArcGIS Network Analyst automatically searches and maps the relevant fields.
The ArcGIS Network Analyst analyzes the source shapefile and looks for common fields like Meters, Minutes (FT_Minutes and TF_Minutes, one for each direction), and Oneway. Once it finds these fields, it automatically creates the corresponding network attributes and assigns the respective fields to them. (This can be viewed by clicking the Evaluators button.)
ArcGIS Network Analyst supports turns in a shapefile based network. Turn information (such as turning restrictions and delays) enhance the quality of network analysis. Earlier versions of ARC/INFO and ArcView GIS used turn tables. These turn tables can be converted into turn features and used in the network dataset. You will use turn features in Exercise 2.
Elevation fields have been used since the earlier versions of ARC/ INFO and ArcView GIS to model connectivity. ArcGIS Network Analyst supports this connectivity model. Each feature in a shapefile or a coverage would be assigned two Z-elevation values, one for each endpoints. If the endpoints of line features have the same Z-elevation value, connectivity is established. If the values are different, they do not connect (e.g. in the case of bridges or tunnels). The elevation field contains logical elevation values for establishing connectivity only and does not provide height information for the feature.
Source: nature.berkeley.edu
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