Mesh Zones
Mesh Zone objects are used as part of the mesh generation process carried out when undertaking 2D Modelling. They can be used to divide a 2D Zone into regions of different mesh resolution.
When using the Classic method of mesh generation (InfoWorks networks only), Mesh Zones can be used to specify larger or smaller triangles than the 2D Zone. However when using the Clip meshing method (InfoWorks or SWMM networks), only smaller triangles can be achieved. If it is necessary for a Mesh Zone to have larger simulation elements than the surrounding 2D Zone, then you can use the Override 2D zone minimum element area setting and the Minimum element area properties to aggregate small triangles into larger elements. See the Mesh Zone Data Fields (InfoWorks) and Mesh Zone Data Fields (SWMM) for further information about Mesh Zone properties.
Mesh Zones, in InfoWorks networks, can also be used to define zones in which ground level modification is required (see below). In addition, if a Ground level modification property is specified for the mesh zone in an InfoWorks network, mesh zone boundaries will be enforced as break lines during the mesh generation process when using the clip meshing method of mesh generation. When using the classic method, mesh zone boundaries are automatically enforced as break lines during the mesh generation process, even if a Ground level modification property is not specified.
Mesh Zones can be imported via the Open Data Import Centre or, for InfoWorks networks, generated via intersection. Zones can also be digitised directly on the GeoPlan Window.
Mesh Zone parameters are edited in the Mesh Zone Grid Window of the Polygons Grid or the Mesh Zone Property Sheet. For further information on creating and editing polygons, see the Digitising Network Objects section.
Using Mesh Zones for Ground Level Adjustment in InfoWorks networks
In InfoWorks networks, Mesh Zones can be used to define specific zones in which ground levels are to be adjusted in the 2D mesh; to correct for road channels and kerb depths for example.
Tip Mesh Level Zone objects provide greater flexibility in modifying mesh elevations than Mesh Zones. Use Mesh Level Zones to define roads channels and so on in more detail.
The ground level of elements within the Mesh Zone is determined from the Ground Model used during the meshing process. Adjustment to ground model level is applied to mesh elements within the Mesh Zone without modifying the source ground model.
The criteria to adjust element ground level are defined in the Ground level modification, Raise by and Level fields of the zone. See the Mesh Zone Data Field topic for full details.
The method of adjustment is selected in the Ground level modification field:
- None: no modification applied.
- Raise or lower: adjust the element level by the value specified in the Raise by field. To lower the ground level, specify a negative value in the Raise by field.
- Level: set the element level to the value specified in the Level field.
- Upper limit: set the maximum element level to the value specified in the Level field. If the ground level of an element (before modification) exceeds the value in the Level field, element level will be set to the value in the Level field.
- Lower limit: set the minimum element level to the value specified in the Level field. If the ground level of an element (before modification) is less than the value in the Level field, element level will be set to the value in the Level field.
The adjusted ground level is displayed in the Ground Level field of the 2D Zone Mesh Element Properties Dialog.
In previous versions of InfoWorks ICM, ground level adjustment was carried out during simulation and not during the meshing process. For meshes created prior to version 3.0, level adjustment will still be carried out during simulation. In these cases, the adjusted ground level of a mesh element will be displayed in the simulation results, but not in the network prior to simulation.
