terrain modeling

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Bentley Inroads Terain modeling

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Page 1: Terrain Modeling

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A terrain model element is part of MicroStation SELECTseries 3 and later. The Terrain Model element is used by the OpenRoads Technology replacing the various TIN and DTM format used by InRoads, GEOPAK, and MXROAD in the past. Because the Terrain Model element is part of MicroStation it can be shared and used by other non-civil disciplines.

Although the Terrain Model element can only be used in SELECTseries 3 and higher software, there is no data loss if a DGN model containing a Terrain Model is opened in SELECTseries 2 software. The Terrain Model will not be visible in SELECTseries 2 but once the file is opened again in SELECTseries 3 everything will function normally.

MicroStation provide the general display controls including contour and spot labeling tools. MicroStation also provides a tool to import LandXML data into a Terrain Model. LandXML is the only format supported by native MicroStation tools. Bentley civil software powered by OpenRoads Technology such as InRoads, GEOPAK, MXROAD, and PowerCivil provide additional tools for creating Terrain Models from native Bentley Civil formats (DTM, TIN, DAT, and FIL) as well as dozens of other common formats such as ASCII, DEM, IMG, Lidar, Graphics, and Point Clouds.

Bentley civil software powered by OpenRoads Technology also includes tools to edit, merge, clip, analyze, and report on terrain models.

Terrain Models are easily shared using standard MicroStation reference functionality. A Terrain Model does not need to be loaded into your drawing to use it. All you have to do is reference the Terrain Model into a drawing and it can be used. The display of the referenced Terrain Model can be defined so you can view the model different than the source is displayed allowing one user to view contours while another views triangles or contours at a different interval. Because everyone using the Terrain Model is referencing it, the updates are automatically propagated to all users.

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Terrain Models are defined by features. There are two types of features, Source Features and Calculated Features. Source Features come from the source data (xml, txt, dtm, graphics, etc.) that was used to create the Terrain Model. Calculated Features are derived or calculated from the Source Features.

Source Features – Breakline, Boundary, Spot, Void, etc.

Calculated Feature – Contours, Triangles, Triangle Vertices, Flow arrow, Low Points, High Points, etc.

Which features are displayed and how they appear is defined by an Element Template. Element Templates are stored in DGN Libraries and allow organizations to setup standard display configurations that can easily be deployed and managed across large groups of users. The Bentley Civil workspace delivered with the software includes Element Templates for common terrain displays including the boundary, contours, and triangles.

Element Templates can be directly linked to Terrain Model Elements as shown with the green line. This technique is most commonly used to control how a Terrain Model is displayed.

Terrain Models also link to a Feature Definition which in turn links to Element Templates. When a Terrain Model is first created it is a good practice to link it to a Feature Definition. The Feature Definition, and linked Element Template, become the default way a Terrain Model displays. The Feature Definition also allows you to define different Element Templates for displaying the Terrain Model in plan and profile views.

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Element Templates are stored in a DGN Library for easy inclusion in corporate standards. When an Element Template is used it is copied to the active DGN model so that model can be used when not connected to the corporate standards.

The terrain Element Template includes parameters for which features (calculated and source) are displayed and the symbology used to display those features. Some features such as contours also have additional parameters such as smoothing, major and minor intervals, and labeling settings. Triangle features include a parameter to include Thematic displays where you can visualize changes in elevation, slope, or height.

If a parameter is not included in an Element Template, right click in the blank grey area at the bottom of the dialog and select Add > Terrain Model > {parameter}.

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The most common workflow is to reference the DGN model that contains the Terrain Model into your active DGN model. When a DGN file containing a terrain model is referenced into another DGN model, you can allow the terrain model to be displayed differently in the other model. This allows the presentation to vary for different purposes, without changing the terrain model display in the original DGN model.

1. Use the Element Information tool to define how the terrain model is displayed.

2. If the Terrain Model is in a reference, set the Override Symbology to Yes in the Reference section. After changing the Override Symbology to Yes you must unselect the Terrain Model or clear the selection set so that it is no longer displayed in the Element Information window and then select it again. This is required to get the Template parameter to become active. If the Terrain Model is in the active DGN model, skip this step.

3. Select the desired Element Template from the Template option in the General Section.

4. To override which features are displayed by the Element Template, expand the Calculated Features Display or Source Feature Display section and set the desired features to On or Off.

Note: If the type of feature displayed is not defined in the active Element Template built in symbology and settings will be used to display the feature. A good practice when setting up Element Templates is to define the “How” for all feature types even though many of them will not be displayed by default when that Element Template is used. That way if someone turns on a feature it will use your standards, not the standards built into the software.

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Terrain Models are created by importing source data from graphics, files, point clouds, or from a Survey field book. Creating Terrain Models from Survey field books is covered in the survey training, all of the other types are discussed in this course.

File – Creates a terrain model from common file formats include InRoads DTMs, GEOPAK .tin or .dat files, MXROAD .fil files, text, LandXML and many others.

ASCII – Creates a terrain model from text files using a text import wizard. The wizard is used to define the format of the text file being read.

Graphical Filter – Creates a terrain model from 3D graphical elements. The filter defines which graphics to import based on their symbology. The advantage of the Create Terrain by Graphical Filter tool is that numerous terrain features can be imported simultaneously; the user does not have to select each feature individually, as with the Create Terrain by Elements tool. However, there must be consistency in the source data to utilize this tool.

Point Cloud – Creates a terrain model from point cloud data that has been processed with MicroStation, Descartes, and Pointools.

Elements – Creates a terrain model from 3D graphical elements selected individually or with a selection set. This tool is most useful if the elements do not have consistency symbology or attributes.

Some data types include an option to Filter the data as it is imported. Filtering eliminates unnecessary points to reduce the size of the Terrain Model. There are two filtering options,

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Tin and Tile. Both filter points but they use different algorithms and will produce slightly different results. The tiling algorithm is faster and typically provides a 30-50% reduction in file size. The TIN algorithm is slower but typically provides 70-90% reduction in file size. Details of each method are provided in the Help.

Some data types also include an option to specify a Geographical Coordinate System. The Geographical Coordinate System allows data collected in a different coordinate system to be converted to the coordinate system of the active DGN model during import.

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There are two parts to the Terrain Filter Manager, Filters and Filter Groups.

Filters define the feature type (break line, spot, void, etc) and the filter selection criteria. Elements that meet all of the filter selection criteria pass the filter and are created in the terrain model with the designated feature type. The filter selection criteria includes color, level, element type, line style, line weights, cell names, feature name, transparency, element template, and elevations. A minimum of one selection criteria must be defined.

Filter Groups are a combination of individual Filters that will be processed in a single Create Terrain operation. For example, a Filter Group might contain three filters. One for break lines, one for spot points, and one for void areas. Complex filter groups could contain dozens of filters.

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Terrain Models created using the OpenRoads Technology tools add a level of intelligence to the Terrain Model call rules. The rules allow the Terrain Model to preserve a link to the source data so it can be updated when revisions are made to the source data. This has very powerful implications for both existing ground and design Terrain Models. For example, as survey data is enhanced and corrected the Terrain Model can automatically update to the newest information. Terrain Models of a design are automatically updated as changes are made such as geometry and templates changing. Unlike the past when DTMs and TINs were a result of a design process, Terrain Models are a dynamic representation of the current source data.

Lock• Temporarily deactivate rules.• Rules can be deactivated when the Edit Terrain Model tools need to be used.• Edits to source data do not update terrain model.

Unlock• This is the default state of a Terrain Model with the rules linking to the source data.• Edits to source are updated in terrain model either automatically or using the with

Update from Source tool.• Edit Terrain Model tools are not available.• If previous edits were made with the Edit Terrain Model tools they will be lost when

the Terrain Model is unlocked and the rules activated again.

Remove Rule• Removing the rules will improve the performance of a terrain model and is

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recommended for all large terrain models.• Features can still be added, removed and modified in a terrain model after the rules

have been removed.• Terrain models with the rules removed can be merged and appended into complex

terrain models.• Once removed, rules cannot be reactivated, the link to the source is broken

permanently.• Removing the rules is recommended when sharing a terrain model with non-civil users

such as MicroStation, plant, or building.

Update from Source• The Terrain Model is updated from its source data.

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When the source is imported (from graphics, text, etc.), rules are created that link the terrain model to the source data.

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All edits and updates should be made to the source data (text, graphics, or survey field book).

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The updates are propagated to the terrain model either automatically or using the Update from Source tool.

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Once all of the updates are complete you are ready to clean up the edge triangles.

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The Edge Method defines which triangles around the edge of a Terrain Model get created. There are two options to control the edge triangles. The terrain model is updated dynamically when the Edge Method changes so if the results are not acceptable, change the value until the results are acceptable. Only triangles along the edge of a terrain model are affected by this parameter. Interior triangles are never removed.

Slivers – long narrow ‘sliver’ triangles along the edge of a terrain model are removed. There are no parameters to control what is a sliver triangle.

Max. Triangle Length – triangles along the edge of a terrain model whose edge is longer than the specified length are removed.

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After the Edge Method is defined to produce acceptable edge triangles you have two options. For most, the terrain model is ready for use.

Optionally additional terrain model editing may be done.

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The Edit Terrain Model tools provide limited editing without returning to the source data. It is always recommended to make edits to the source data whenever possible. These tools should only be used for minor edits and when returning to the source data is not possible.

The Edit Terrain Model tools should be used on un-ruled Terrain Models. The Lock –Deactivate Rule tool on the heads up menu is used to set a Terrain Model into an un-ruled state.

When the source is imported the terrain model remains linked to the source data. All edits and updates should be made to the source data (text, graphics, or survey field book) and the updates propagate to the terrain model.

Rules linking to source data takes a higher priority than manual edits with the Edit Terrain Model Tools.

Note: Terrain Models created from Survey field books have a slightly different locking process. Instead of locking the terrain you need to deactivate the survey processing rules. To do this, go to the Survey tab in the Project Explorer. Right-click on the survey project and select Deactivate Survey Processing Rules.

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Civil Message Center – The Civil Message Center displays errors, warnings, and messages related to OpenRoads Technology elements including terrain model elements. Geometry and other design warnings are also displayed here. By default the Civil Message Center is docked in the lower left corner. If the Civil Message Center is not visible, select the Civil Message Center tool (red flag icon) from the General Geometry task menu.

The source data for the terrain model may be incomplete or incorrect thus requiring features to be added to, removed from, or redefined in the terrain model. The Add Feature, Remove Feature, and Change Feature Type tools are used for this.

The Report Crossing Features and Report Conflicting Points tools identify potential problems. Points or linear features that conflict with one another are reported. An Elevation Tolerance can be specified to limit the number of conflicts reported. Only points or linear features that are at the same X and Y position and gave a difference in elevation greater than the specified Elevation Tolerance are reported as conflicts. Right click on conflicts listed in the window to zoom to the location of the conflict and to be presented with options to correct the conflict.

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Terrain models can be combined into Complex Terrain models. The complex Terrain model is not only a combination of Terrain Models but a combination that remembers the order in which terrain models are combined and how they are combined. Terrain Models can be combined by merging or appending them together.

Merge – The data from the primary terrain model is discarded and replaced with the data from the merge terrain model in the area where the two overlap. The two terrain models must overlap with at least one point.

Append – The combined data from both terrain models is retained in the areas where the terrain models overlap. The two terrain models can overlap or be adjacent to one another.

The Edit Complex Terrain Model tool is used to make changes to complex terrain models such as changing the order of the terrain models or the merge/append action.

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