Spatial Query
A GIS let you retrieve information pertaining to a geographic entity on the map. This function is sometimes referred to as Spatial Query. You can use the spatial query tools (such as the i button in the Tools box) to review and edit the entity's attribute data.
1.4 Formulate Attributes
After you finish editing the network, you need to calculate the free flow travel time for both directions of a street. It is easier to do this task in a Dataview (a table that displays data for the entire layer) than using the info tool, because you are now dealing with all streets, not just some of them. To open the Dataview of the Miasma network, make sure the Highways/Streets is the working layer. Click at the New Dataview button. A data window will show up. Examine the data. The attributes data shown in Highways/Streets dataview should correspond to those in Table 1.
GIS Concepts
Link Direction
In the dataview of the Miasma network, Dir stands for direction and is used to indicate if the street is one-way of two-way. In Miasma Beach, [Page]Dir link values are all 0 indicating that they are all two-way streets. Therefore, on the record (i.e., a row in the dataview) of a street, there are two fields correspond to one attribute (e.g., speed, capacity, or number of lanes). While AB_SPEED contains free flow speed of one direction, BA_SPEED contains that of the opposite direction. This could be useful, for example, when each direction has different speed limit or capacity. To know whi
