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Create Existing Terrain Features - Introduction

OpenRoads works with Civil Geometry Features in the MicroStation drawing file and not with conventional MX models and strings. Survey is processed and MX models and strings are created, these strings ultimately need to be brought into MicroStation drawings as OpenRoads Features. These Features will have properties defined which tell OpenRoads and the other Civil Tools how to interact with and display (plan, profile, cross section, as well as 3D views).

OpenRoads drawings are seeded with 3 DGN models:

  1. Default
  2. Default-3D
  3. MX

It is imperative that the proper DGN model be active.


Before opening MX and creating terrain features

Before starting this process, the style set variables need to be set correctly as described here to override some default values.

To do this from the Workspace menu, select Configuration... Then select Category All (Alphabetical) from the Category area. From the View/modify all configuration variables box, select the variable MX_DEFAULTCIVILSTYLESET_PSS. Click the Edit... button to get the Edit
Configuration Variable
panel. Change the New Value from $(NH_MX)/Imperial_Styles/Road.pss to $(NH_MX)/Imperial_Styles/TOPO.pss. Click OK and then repeat the process to edit the variable MX_DEFAULTCIVILSTYLESET to the same value of $(NH_MX)/Imperial_Styles/TOPO.pss.

Click OK on the Configuration panel and then Save the changes when prompted. For these changes to take effect, Exit this MX session and reopen MX.

When finished working with the terrain models, go back into Workspace > Configuration and
Delete the two variables edited above. This will set them back to Road.pss. Once again,
Exit MX and then reopen MX for these changes to take effect.


Separating the TOPO detail strings for processing

Open the 12345-Terrain.dgn in MX. If it does not exist, then refer to Create OpenRoads Base Drawings to created it.

An MX Input File has been compiled to copy all the TOPO strings from the TOPO model into a several new MX models. These strings need to be separated so different tasks can be preformed on the different stings. The commands in this file, TOPO-FEATURE.txt, can be copied and pasted into a topo-features.inp file or Right-Click on the link and use the Save Target as option to create a copy in the project's MX directory.

Next, Input this file in MX which will create the TOPO FEATURES, TOPO POINTS, TOPO SUBSURFACE and TOPO STRUCTURE MX models. Each of these MX model's Model Defaults should be set to OpenRoads.pss.

Open the 12345-terrain.dgn's MX model. From the MX menu select File > Input > topo-features.inp to input the file.

Strings in the TOPO FEATURES and TOPO POINTS models will need to be draped over the Triangles model to remove null elevations. The TOPO STRUCTURE strings represent the bridge structure which (we expect) is suspended above the ground and should not be draped. See Generating Existing Bridge Terrain for the processing of the TOPO STRUCTURE strings.

Evaluate and Eliminate Null Elevations - TOPO FEATURES

Refer to the following steps to evaluate and address the null elevations in the MX strings:

  1. Verify that the Model Defaults for the TOPO FEATURES model is set to the OpenRoads.pss style and feature sets.
  2. Display the strings of the new TOPO FEATURES model by selecting Display > Plan with Style Set... from the MX menu. Specify the TOPO FEATURES model, click OK to display (a Fit View might also be necessary).
  3. Use Rotate View with the method set to Dynamic in order to inspect the model at a perspective orientation. This will allow a visual confirmation of any of the model's null elevations. If you believe that there are no null elevations then advance to Step #5.
  4. The easiest way to eliminate the null elevations is to run NHdraper which is found on the MX menu. Select Add-Ins > Personal Add-Ins > NHdraper. Supply the String Model Name; TOPO FEATURES. This program can be run on an individual string (much faster) or all strings by specifying the sring label ????. Supply the Triangulation Model Name; TRIANGLES. Also check the Add elevations only to existing points check box. Click OK to run NHdraper. An alterative option to address null points is to Long Section every string that contains a null elevation over the MX triangulation model. This option is best done with a Longsection Input File text file. Directions on how to edit this file are embedded in the file. Check your work, re-Display the TOPO FEATURES model to confirm that there are no more null elevations. The third option if necessary, is to individually edit the null points with a derived elevation.
  5. From the MX menu select Display > Erase Display...
  6. Repeat steps 1 thru 5 for the TOPO POINTS MX model.

Text File Format symbol Text File Format (.txt). Visit for a list of free .txt readers for a variety of operating systems.

New Hampshire Department of Transportation
PO Box 483  |  7 Hazen Drive  |  
Concord, NH  |  03302-0483
Tel: 603.271.3734  |  Fax: 603.271.3914