Updating Network Objects from the Ground Model

Sampling of a ground model can be used to update network object data. The objects that can be updated by ground model sampling are:

Line section elevation data can be updated by sampling a ground model. Elevations at existing vertices can be updated and new vertices inserted between existing vertices.

To update a section by sampling a ground model:

  1. Select the sections to be updated on the GeoPlan Window.
  2. Select Update from ground model from the Model menu. The Update from Ground Model dialog is displayed.
  3. Set parameters in the dialog:
    • Insert vertices on lines to give a maximum spacing of - check this option to insert vertices between existing points if they are separated by a spacing greater than that specified. Vertices will be inserted at regular spacings between existing vertices with the elevation of the new vertices determined from the selected ground model.
    • Do not insert vertices on lines between existing vertices with elevations - check this option to prevent new vertices being inserted between vertices that already have elevation values. (Intended for use when extending a river line. Insertion of vertices and ground model sampling can be carried out for the extended parts of the line leaving the original part of the river line unchanged.)
    • Overwrite existing elevations - check this option to overwrite elevation values at existing vertices. If this option is unchecked, existing elevation values at existing vertices will be retained. (Existing vertices with no elevation specified will be updated from the ground model.)
    • Ground Model - select the ground model to be sampled. If a ground model is currently loaded onto the GeoPlan, this selection box will be automatically populated.
  4. Click OK to carry out the update operation.

The river line elevations will be updated from the Ground Model. If a river line vertex is located outside of the ground model, or in a location where the ground model has undefined height, the elevation of the vertex will be set to null. A message will be displayed warning the user that the elevation of one or more vertices will be set to null.

It is also possible to update cross section line elevations for existing vertices by sampling the ground model from the Section Editor. See Updating cross section lines for details.

The level-area table of a storage node or pond node with an associated storage area polygon can be updated by sampling a ground model.

To update a node by sampling a ground model:

  1. Select the nodes to be updated on the GeoPlan Window
  2. Select Update from ground model from the Model menu. The Update from Ground Model dialog is displayed.
  3. Select an option from the dialog:
    • Reset existing storage array tables - select this option to recalculate level-area values in the storage array table. Existing level-area values will be removed prior to update. Set parameters for setting level-area values:
      • Storage node level interval - determines the increment in level values in the level-area table.
      • Minimum storage node level - the lowest level to be set in the level-area table. By default, this level will be the lowest ground model height within all storage polygons associated with selected nodes.
      • Maximum storage node level - highest level to be set in the level-area table. By default, this level will be the highest ground model height within all storage polygons associated with selected nodes.
    • Update existing storage array tables - Select this option to recalculate the area value for existing levels in the storage array table.
  4. Select the Ground Model to be sampled. If a ground model is currently loaded onto the GeoPlan, this selection box will be automatically populated.
  5. Click OK to carry out the update operation.

The level-area table of the node will be updated according to the option chosen in the update dialog. The area corresponding to level values in the storage array table will be calculated from the ground model. The degree of accuracy of the area calculation will depend on the type of ground model used.

TIN ground model

The TIN ground model provides an exact solution based on the ground model data. This is, of course, subject to the accuracy of the TIN data and the level interval chosen for the calculation. Resolution is improved by setting a smaller level interval.

For each level in the level-area table, InfoWorks ICM calculates a level contour from the ground model for the area surrounding the storage node. InfoWorks then calculates the intersection between the storage area polygon and the level contour to give the area of the storage area for this level value.

Grid ground model

The method used with a gridded ground model is, because of limitations within the ground model, only a best estimate. The accuracy of the estimate falls as cell size within the grid increases.

Essentially, for each level in the level-area table, InfoWorks identifies all the grid cells that fall within the storage area perimeter and have an appropriate Z value:

  • a cell falls within the perimeter if its bottom left corner falls within the perimeter
  • a cell is included if its Z value is greater than or equal to the lower stage for this height band.

The area for this stage is then the sum of the areas of all the cells that meet these criteria.

Base linear structures and bridge linear structures can be updated by sampling a Ground Model. Elevations at existing vertices can be updated and new vertices inserted between existing vertices.

  • Only base linear structures with Crest level set to Irregular can be updated
  • Only bridge linear structures with Invert level set to Irregular can be updated
  • When updating a bridge linear structure, if vertices are inserted between existing vertices, Opening height and Deck thickness values will be calculated by linear interpolation.

To update a linear structure by sampling a ground model:

  1. Select the linear structures to be updated on the GeoPlan Window
  2. Select Update from ground model from the Model menu. The Update from Ground Model dialog is displayed.
  3. Set parameters in the dialog:
    • Insert vertices on lines to give a maximum spacing of - check this option to insert vertices between existing points if they are separated by a spacing greater than that specified. Vertices will be inserted at regular spacings between existing vertices with the elevation of the new vertices determined from the selected ground model.
    • Do not insert vertices on lines between existing vertices with elevations - check this option to prevent new vertices being inserted between vertices that already have elevation values. (Intended for use when extending a line. Insertion of vertices and ground model sampling can be carried out for the extended parts of the line leaving the original part of the line unchanged.)
    • Overwrite existing elevations - check this option to overwrite elevation values at existing vertices. If this option is unchecked, existing elevation values at existing vertices will be retained. (Existing vertices with no elevation specified will be updated from the ground model.)
    • Ground Model - select the ground model to be sampled. If a ground model is currently loaded onto the GeoPlan, this selection box will be automatically populated.
  4. Click OK to carry out the update operation.

The linear structure elevations will be updated from the Ground Model. If a linear structure vertex is located outside of the ground model, or in a location where the ground model has undefined height, the elevation of the vertex will be set to null. A message will be displayed warning the user that the elevation of one or more vertices will be set to null.

Cross section line elevation data can also be updated by sampling a ground model from the Section Editor. Only elevations for existing vertices are updated.

Tips

If you also want to insert new vertices between existing vertices, use the Update from ground model option from the Model menu.

To update elevations at existing vertices for cross section lines by sampling a ground model:

  1. Ensure that a ground model is loaded on the GeoPlan.
  2. Use the Properties tool () to select the cross section line to be updated on the GeoPlan Window.
  3. In the Section data field, click to display the cross section line data in the Section Editor.
  4. Click Update from Ground Model. The cross section line levels will be updated from the ground model, and an Update from Ground Model Report is displayed.
  5. Click OK to save the updates.

An elevation will not be assigned to a cross section line vertex that is located outside of the ground model, or in a location where the ground model has undefined height. A message will be included in the report if this occurs.

Update from Ground Model Dialog

River Lines

Nodes

Base Linear Structures (2D)

Bridge Linear Structure (2D)

2D Meshes

Ground Model