Network Features of Space ry

The network features mentioned here refer to the features in the geometric network structure advocated by ESRI. The relationship between the network elements is the relationship between the geometric network and the logical network. String 7

During modeling (such as Geodatabase), ry networks create tables from a geographical perspective, such as highway tables, city tables, and railway tables. The logical network requires three tables: edge element table, join element table, and connection table (which describes how the first two are connected ). The edge element table and the joined element table provide the unique identifier of the element. For more information about edge and join, see ESRI online help.

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I. Composition of network features

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There are four main features in the geometric Network: simple side, simple joint, complex side and complex joint. (Edge: edge, join: junction) string 1

1. A simple edge (feature layer) is associated with an independent GPS edge (element layer, without geographic concepts or geometric coordinates) in a logical network, that is, a one-to-one relationship.
2. A simple set is associated with a single node in the logical network. It is also a one-to-one relationship.
3. A complex edge feature can be associated with any number of edges in a logical network. These edges must be organized in a chain structure. (For example: junction1-edge1-junction2-edge2-junction3-edge3-junction4, apparently, they are not necessarily on a straight line)
4. A complex joining feature is associated with a group of joining and edge in a logical network. These edges are connected to each other and can be organized into any topology. From the abstract and concrete point of view, we can abstract such a small network into an independent joint and form an internal network in the substantive sense. Not exactly, when we look at the Earth from space, a small county can only be understood as a point. And complex edge features Different Yes, this internal network is usually mesh, of course, it can also be a chain. String 7

In this way, you can write complex feature classes as needed during development. However, if you do not write software code in the class extension architecture as required, you cannot create a type Extension in ArcInfo. String 9

2. Understand these members and their relationships

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From the perspective of the relationship between the geometric network and the logical network, simple and simple joins correspond one-to-one. In this case, segmentation is required in some cases. If there is a wire Branch, in order to add the joint between the branch lines, it cannot be divided into multiple independent wire features.

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Unfortunately, for data query and maintenance, a wire is often treated as an independent feature. When using simple edges, You have to divide each segment. If there are hundreds of GIS branch routes on one of the main lines in the above cases, data aggregation and maintenance are quite complicated. However, a complex edge can create multiple edge elements for each complex edge element and allow the joint to exist in any position in the edge direction.

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It should be noted that a complex edge is not a set of edge features, but a feature. It only contains multiple elements and can separate each element. Management . This is also one of the main advantages of dividing networks into two layers: geometric networks and Logical Networks. When the features in the geometric network are modified, the elements in the logical network should also be changed accordingly. String 9

Complex joint features share the same with complex edge features, but they can abstract a more complex structure (such as a network) into a joint, manage the internal network through the relationship constraints between the geometric network and the logical network. The most typical example is the distribution box.

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There is a common feature between the complex edge type and the complex joint type, that is, the change to the element table, which reflects the one-to-many relationship mentioned above. For example, for the distribution box S1, there is not just one record as there is a simple and simple joined element table, but a subid is assigned to each record by multiple records, to indicate multiple elements in the internal network. If this complex join type has four edge elements and five joining elements, a total of nine records are required, which are four edge records (1, 2, 4) and five joining records (, 8, 9 ). In the network, these elements can be understood as (s1-1 )~ S1-9 ).

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Iii. Conclusion

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Understanding network features is conducive to the rational design of the object structure during development. Objects in the real world are far more complex than the dot and wire planes. Therefore, mastering the design tools does not mean that a good structure can be designed. Network features are only a part of the design process. I am confident that it is necessary to take time for application development to deeply understand each stage and get twice the result with half the effort.

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