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SUE - Display Existing MX Subsurface Strings

This page describes future development not yet implemented. Documentation for Subsurface Utility Engineering (SUE) is composed of three pages, this is the first page.

Subsurface Utility Engineering (SUE) tools provide the Civil Designer and Utility Coordinator the ability to model underground features for purposes of planning and design decision making. These tools allow plan, profile and 3D modeling of all underground assets.

SUE entities are modeled using Nodes (point type features such as catch basins) and Links (linear features such as pipes). This page describes the steps involved in preparing MX elements to be converted into SUE elements.

It is imperative that the proper DGN model be active. Pay close attention to model references within this document. OpenRoads drawings are seeded with 3 DGN models:

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

Display and Edit Existing MX Subsurface Strings

OpenRoads works with Features. In the future when we use the Survey functionality of OpenRoads, Features will be created instead of MX Strings. Until that time we need to create features from the MX strings as documented in the Importing MX Strings 2 Features page. At this time existing MX Subsurface strings are converted using the Subsurface Utility Engineering tools.

Open the SUE Drawing created in the Create OpenRoads Base Drawings process. If one does not exist, then from the MX menu select File > New Plan Display... Supply the file name to be used for Subsurface Utility Engineering drawing in the format 12345-terrain-SUE. All Utility features will be created in this DGN.

Before attempting to display the MX Subsurface Strings, they need to be separated from the MX feature strings. An MX Input File pdf file has been compiled to accomplish this. It will copy all the subsurface strings from the TOPO model into a new model called TOPO SUBSURFACE. This step should have been done during the Creating the Terrain - Convert MX Point Strings process. Therefore, check your MX model file to see if this was already done. If the TOPO SUBSURFACE model already exists then only do steps 1, 4 thru 6.

Refer to the following steps to generate, display and review the MX Subsurface Strings:

  1. Open this new DGN's MX model.
  2. Copy the Input File text file into your MX project Directory. Name the file Topo-Features.INP. Skip this step and step 3 if the TOPO SUBSURFACE model already exists.
  3. Input this file in MX to create the TOPO SUBSURFACE model. This file will also create a TOPO FEATURES, TOPO POINTS and a TOPO STRUCTURE MX model, these addition models will have future value.
  4. Verify that the Model Default for the TOPO SUBSURFACE model is set to the TOPO style and feature set. If it was not properly set, then you might need a current Defmods.TXT file in the MX project directory.
  5. Display the strings of the new TOPO SUBSURFACE model, do that from the MX menu; select Display > Plan with Style Set... Choose the TOPO SUBSURFACE model and click OK to display (Fit View might also be necessary).
  6. 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 this process is complete.

OpenRoads does not have an equivalent to MX's Null Elevation concept. Therefore all MX Null elevations need to be addressed prior to any OpenRoads procedures. Of course, if we knew the null point's elevation then it wouldn't have been assigned a null elevation. So a plan of action must be determined.

Unlike existing surface detail, subsurface features should not be sectioned to the surface model. For the most part, any valid subsurface elevations will be lost. Assigning a surface elevation to just the null points introduces confusion with other subsurface strings that actually meet the surface.

Most of the strings that are assigned null elevations are the drainage pipes. Survey often locates a valid pipe invert and then a second (null elevated) direction shot. A plan view will allow you to determine if any surveyed pipe's direction shot point to each other. If any of them do, then each pipe invert can be linked together and the null direction shots may be abandoned. To further assist, the linking of pipe ends may have already been done on the MicroStation EXD.DGN drawing. If so, then attach this drawing as reference to act as a guide.

MX Configuration settings

MX Configuration Settings

There is an MX setting which allows MicroStation commands to manipulate MX strings. If it is not already set, select View > Configuration.

At the bottom of the General tab under CAD Manipulation, check the Allow graphic manipulation of MX elements box.

There are three methods for resolving the null elevation. These edits can be captured in a Journal file prior to editing in case there is a need to repeat them in the future.

Option 1

Now the MicroStation Modify Element command may be used to grab one of the pipe null direction ends and snap it to the invert of the pipe that the direction shot was pointing to. The pipe that was snapped to can now be deleted using the Modify > Edit Strings > delete string. Please note that a MicroStation delete will only remove the MicroStation graphics and not the MX data that defines the string.

3d image of drainage

Option 2

Since there is no OpenRoads equivalent to MX's null elevation of -999, a different value can be assigned to represent these unknown elevations. Therefore, let's assign what we will call a Subsurface Unknown Elevation Datum Elevation (or SUEDE for short). Decide on an elevation between 25' to 100' below the general project elevation. This way the horizontal extent is maintained, subsurface items hopefully stay subsurface and all unknown elevations drop to the same consistent datum (making it easier to distinguish them from surveyed detail). Once established, assign this SUEDE value to every null elevation in the TOPO SUBSURFACE model. Refer to the following steps to accomplish this:

  1. Identify every string and point number in the TOPO SUBSURFACE model that has a null elevation. Use either; MX Explorer, MX reports or the on screen Display Status Tooltips, which ever works best for you.
  2. 2.Determine what the SUEDE value will be. Be sure to document the SUEDE value in the Project Journal file.
  3. The safest way to eliminate the null elevations is to copy the Edit Null Elevations text file file to the project directory. Follow the directions in the file to apply the data gathered in Steps 1 and 2.
  4. If an input file was generated in Step #3, then Input this file in MX. Do that from the MX menu, select File > Input... browse for the new Edit Null Elevations.INP and then click Open.
  5. Re-Display the TOPO SUBSURFACE model to confirm that there are no more null elevations.

Option 3

A third alternative to this would be to interactively address the null points. Do this from the MX menu, select Modify > Edit Point > Change String Dimensions... On the Change String Dimensions panel, select the TOPO SUBSURFACE model for the Model Name. Using the rotated display, select a String Name by selecting a string that that extends to the MX defined null elevation. In the Point Selection section, select the Search for a Dimension option with a Dimension Number of 3 and a Dimension Value of "-999". At the bottom of the panel, check the New Value for Dimension 3 box and then enter the determined SUEDE value. Click Apply to process the string dimension change. To address additional strings, place input focus in String Name and then select another string from the screen with a null elevation. Click Apply and repeat as necessary.

To save these edits you can open a journal file prior to editing the strings in case you need to do it again in the future.

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