Geometric network
The so-called geometric network network is a collection of topological relationships between elements of elements. Each element plays a certain role in the geometry network, such as one or one intersection. Multi-feature classes may be the same role in a single geometric network.
Establish the most basic method of geometry network to determine the elements of the geometric network and the roles played by these feature classes. A series of network weights and other advanced parameters are also determined.
There are two ways to establish a network: establish a new empty network, establish a network for existing simple elements.
Create a new empty network
ArcCatalog allows you to create new geometry networks from nothing, and then design the network from head. You can use the editing tools in ArcMap, customize VB, VBA, or C code to increase the elements of the geometry network.
The steps to establish a network are as follows:
1. ???????? Use arccatalog to establish an elements set, this elements sets the geometric network and his elements.
2. ???????? Using ArcCatalog creates a new feature class in the elements, and assigns their roles.
3. ???????? Use arccatalog to establish a connectivity rule for the geometry network.
4. ???????? Use a custom script or an ArcMap editor to add a feature for the geometry network.
Establish a geometry network based on existing data
You may have data to create geometric networks in your database, all of ArcCatalog and Arctoolbox contain tools that use ready-made data to establish geometry networks.
The steps to establish a network from existing data is as follows:
1. ???????? Use ArcCatalog or Arctoolbox to import your data into the geodatabase.
2. ???????? Using ArcCatalog or ArctOOLBOX to establish a geometry network with an existing feature class.
3. ???????? Using ArcCatalog to add additional feature classes for the geometry network.
4. ???????? Using ArcCatalog to establish connectivity for the geometry network.
How to build a network
Establishing a geometric network from existing data is an extremely high-cost CUP operation, which costs a lot of time and computer system resources, and the amount of data is also important. If the elements need to be captured, the network establishment operation will spend a lot of time during the element steps.
The process of network establishment is described in the following steps:
1. ???????? If it is determined that the capture is determined, the simple feature is captured.
2. ???????? If you specify the capture, capture complex elements.
3. ???????? Establish an empty logical network.
4. ???????? Create a network architecture in the database.
5. ???????? From the input elements class, calculate the extract attribute for weight.
6. ???????? Establish a topology.
7..???????? Establish an isolated intersection, enter the elements of the intersection to the geometry network, and initialize the value of the intersection.
8. ???????? Set the weight for the intersection element.
9. ???????? Adding a side for the geometry network.
10. ???? Set the weight of the edge element.
11. ???? Relocating all the necessary indexes in the database.
Network capture model
Ideally, your data should be "clean" before establishing a geometry, "clean" means that the elements that should be connected in the geometric network should be geographically consistent, that is, there is no fake association and hang intersection. . However, if not this, the data is to be captured during the network establishment process.
In the process of understanding, it is important to establish a similarity in the process of capturing, how to establish a connectivity, and how the elements collection is adjusted, and below is in a particular case, how to establish an example of a similarity.
Among these schematic diagrams, use the following keywords to indicate what type of feature in each scene is displayed.
Simple side along with model
Simple side: Simple side connecting can only be built at the endpoint of each side feature. Uncorted across connectivity, even if there is a node on the simple side.
Complex side communication model
Complex side: The endpoints on the complex edge can be established on the endpoint and middle of the side. In the place where connecting is established, if there is no node exists, a new node will produce. When capturing complex edges, connectivity is to be built on the endpoint of one side, without establishing both of the intermediate points. Node group communication model
Node Group: When capturing two elements, if the captured place is more than one node within the capture tolerance, then these nodes are called node groups. The capture will occur above a node of the node group, but does not have to be on the nearest node.
Consistent intersection communication model
Consistency intersection: When the network establishment process encounters consistent intersections, or when the capture process creates a consistent integration point, connectivity does not result. That is, connectivity can only be established above a node in the connectivity node.
Adjusting elements
When capturing elements during network establishment, it is important to understand how geometric elements are adjusted during capture. In establishing a geometry network wizard, a feature class is specified as adjustable, then all or part of the elements will be automatically adjusted, and those that are not specified as a certain feature will be fixed during network establishment. .
Network establishment error
When establishing a geometry network from an existing simple feature class, in some input elements class, there is an illegal network geometry. When an illegal geometric element is generated, the establishment process does not fail, and it will establish a "suggested" element as a network element, but will not establish network connectivity for which feature is established. If this happens, after the network establishment process, a warning message will be issued while generating a data sheet for logging error messages in the database.
Warning information will report the total number in each illegal network feature class. The name of the wrong table can be:
_builder
. The structure of the network error table is as follows:
Field Name
Error Information
Errorid
The id of the error Object
ClassID
The Object Class ID of The Feature Class Containing The ILLEGAL Geometry
ObjectID
The Object id of the feature with iLlegal Geometry
ErrorType
The Error for this feature
ArcMap has tools that use the network to establish an error table to discover illegal errors. (See Identify Network Build Error). Once you have discovered these errors, and fix them, you can use rebuild network connectivity tools to repair network connectivity for these features (see About EDITING Network Feaures).
This built-in error table shows only features that have illegal network geometry when establishing a network. If you fix these elements, or other elements have errors when they are built in the network, this error table is not updated. Once you fix the elements geometry in this table, it is not needed, and you can delete it with ArcCatalog.
There are some tools and commands in ArcMap to help you identify and fix the illegal geometry entities or inconsistent network connectivity of the network element. To use these tools and commands, see Editing Network Features and Network Verification Tools and Commands.
Architecture lock
When establishing a geometry network, a row lock is required on all input feature classes. If any feature class has a shared lock, the network will not be established.
If any of the elements in the network has a shared lock or a locking lock, this lock will be propagated to other feature classes in the network. For more information on the lock and architectural locks, please see the geographic data project.
