Topology and DNC (Maritime Charting)
Topology is a set of rules that allows you to accurately model geometric relationships. Topology enforces spatial integrity by defining relationships between features.
Topology is only enforced when you validate it. When the topology is validated, the following occur:
- Clustering—The cluster tolerance is the minimum distance between vertices of features that are not coincident. Vertices that fall within the cluster tolerance are defined as coincident and snapped together during the clustering process.
- Cracking—Cracking adds vertices at the intersection of feature edges.
- Rule validation—Once the data has been clustered and cracked, the topology rules are validated and errors are logged.
Validation
Validation takes the longest when you run it for the first time. The first validation checks every feature in the database. Subsequent validations only check dirty areas (areas where edits took place).
DNC Rule base
If you have rules that require specific features to exist to validate another feature, you get false errors. For example, if a rule depends on the existence of Dqyarea but you validated before that feature was created, you have a lot of errors that would not exist if you created the feature first.
A rule in DNC that almost always has an exception is that the boundary of GroundSurfaceElementAS in Ecrarea must be covered by CoastL. Where the GroundSurfaceElementAS meets the Dqyarea edge, there is no coastline, so this error is marked as an exception.
Depending on what stage of production you are in, you may or may not want to correct the error when it is identified. The context menu gives correction options that automatically fix the problem when chosen.
注:You should only validate after your chart has been collected and you have made topological edits.
Error Inspector
Once you have made edits to a feature that participates in a topology and validated your edits, you may see one or more topology errors. You can manage topology errors with Error Inspector.
使用“错误检查器”可在一个表中查看拓扑错误，该表显示违反的规则、错误中涉及的一个要素类或多个要素类、错误的几何、错误中涉及的要素的要素 ID 以及错误是否已被标记为异常。可以按表中的任意字段对错误进行分类，以便可以处理给定类型的所有错误。还可将表中显示的错误限定为给定类型的错误、在当前可见地图范围中发生的错误或已被标记为异常的错误。
除了可以对错误进行查看和分类之外，“错误检查器”还可用于选择错误、平移或缩放至所选错误，以及对错误应用各种类型的拓扑修复方法。“错误检查器”还允许您使用键盘快捷键。