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29.2.5. Complemento Comprobador de Topología

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Figura 29.14 El complemento Comprobador de Topología

La topología describe las relaciones entre puntos, líneas y polígonos que representan las características de una región geográfica. Con el complementoComprobador de Topología, puede revisar sus archivos vectoriales y verificar la topología con varias reglas de topología. Estas reglas verifican con las relaciones espaciales si sus entidades “Igual”, “Contener”, “Cobertura”, “CoveredBy”, “Cross”, son “Disjoint”, “Intersect”, “Overlap”, “Touch” o son “Within “ El uno al otro. Depende de sus preguntas individuales qué reglas de topología aplica a sus datos vectoriales (por ejemplo, normalmente no aceptará sobrepasos en las capas de línea, pero si representan calles sin salida, no las eliminará de su capa vectorial).

QGIS tiene un función constructora de edición topológica incorporada, que es ideal para crear nuevas funciones sin errores. Pero los errores de datos existentes y los errores inducidos por el usuario son difíciles de encontrar. Este complemento lo ayuda a encontrar tales errores a través de una lista de reglas.

To enable the Topology checker plugin:

  1. Go to Plugins menu

  2. Open showPluginManager Manage and Install plugins and choose pluginInstalled Installed

  3. Enable checkbox topologyChecker Topology checker

  4. Close the Plugin manager dialog. A topologyChecker Topology checker entry is added to the Vector menu.

After you enabled topologyChecker Topology checker open it and choose options Configure to create your topology rules.

En ** capas de puntos **, están disponibles las siguientes reglas:

  • Must be covered by: Here you can choose a vector layer from your project. Points that aren’t covered by the given vector layer occur in the “Error” field.

  • Must be covered by endpoints of: Here you can choose a line layer from your project.

  • Must be inside: Here you can choose a polygon layer from your project. The points must be inside a polygon. Otherwise, QGIS writes an “Error” for the point.

  • Must not have duplicates: Whenever a point is represented twice or more, it will occur in the “Error” field.

  • Must not have invalid geometries: Checks whether the geometries are valid.

  • Must not have multi-part-geometries: All multi-part points are written into the “Error” field.

En ** capas de línea **, están disponibles las siguientes reglas:

  • End points must be covered by: Here you can select a point layer from your project.

  • Must not have dangles: This will show the overshoots in the line layer.

  • Must not have duplicates: Whenever a line feature is represented twice or more, it will occur in the “Error” field.

  • Must not have invalid geometries: Checks whether the geometries are valid.

  • Must not have multi-part geometries: Sometimes, a geometry is actually a collection of simple (single-part) geometries. Such a geometry is called multi-part geometry. If it contains just one type of simple geometry, we call it multi-point, multi-linestring or multi-polygon. All multi-part lines are written into the “Error” field.

  • Must not have pseudos: A line geometry’s endpoint should be connected to the endpoints of two other geometries. If the endpoint is connected to only one other geometry’s endpoint, the endpoint is called a pseudo node.

En ** capas de polígono **, están disponibles las siguientes reglas:

  • Must contain: Polygon layer must contain at least one point geometry from the second layer.

  • Must not have duplicates: Polygons from the same layer must not have identical geometries. Whenever a polygon feature is represented twice or more it will occur in the “Error” field.

  • Must not have gaps: Adjacent polygons should not form gaps between them. Administrative boundaries could be mentioned as an example (US state polygons do not have any gaps between them…).

  • Must not have invalid geometries: Checks whether the geometries are valid. Some of the rules that define a valid geometry are:

    • Los anillos poligonales deben cerrarse.

    • Los anillos que definen los agujeros deben estar dentro de los anillos que definen los límites exteriores.

    • Los anillos no pueden cruzarse a sí mismos (no pueden tocarse ni cruzarse entre sí).

    • Los anillos no pueden tocar otros anillos, excepto en un punto.

  • Must not have multi-part geometries: Sometimes, a geometry is actually a collection of simple (single-part) geometries. Such a geometry is called multi-part geometry. If it contains just one type of simple geometry, we call it multi-point, multi-linestring or multi-polygon. For example, a country consisting of multiple islands can be represented as a multi-polygon.

  • Must not overlap: Adjacent polygons should not share common area.

  • Must not overlap with: Adjacent polygons from one layer should not share common area with polygons from another layer.

When you create a New rule click on the symbologyAdd Add rule to include it to the Current rules. You can enable or disable individual rules by clicking on the checkbox. Right-clicking over a rule provides the following options:

  • Select All the rules

  • Activate or Deactivate the selected rules

  • Toggle activation of selected rules

  • Delete selected rules. This can also be achieved with the symbologyRemove Delete selected rules button.

Press OK and then choose from the Topology checker panel:

  • validateAll Validate All: applies the active rules to all the features of the involved layer(s)

  • or validateExtent Validate Extent: applies the active rules to the features of the involved layer(s), within the current map canvas. The button is kept pushed and the results will update as the map canvas extent changes.

Errors will show up in the table of results containing type of error, layer and feature ID. Use Filter errors by rule menu to filter the errors to a specific error type.

Check checkboxShow errors on the canvas to show error location on the canvas. Clicking a row in the table will zoom the map canvas to the concerned feature, where you can use QGIS digitizing tools to fix the error.