An InRoads user asked for Mark's thoughts on this question :

What's the overall process for creating an InRoads surface model from a graphical topo file containing contours and spot elevations? I'm just doing some preliminary earthwork and don't have an existing surface except for this 3D MicroStation contour file. (I'm also working in ProjectWise if that makes a difference.)

Here is the Zen Dude's response:

Here is a quick run-through of the method that is acceptable in cases like this.

1)  Open the file with MicroStation

2)  Set up the DGN file to:

a.      Create a view that isolates only the contours (no text)

b.      Create a view that isolates only the spot elevations (no text)

3)  Open InRoads

4)  Open up the Custom Toolbar (TBR) called Build DTM From Contours that I attached. (This is optional and will just help with the workflow and finding the commands)

5)  If this is the first time on this project verify that the InRoads Project Defaults are properly set up

6)  Create a new placeholder for the surface data

a.      InRoads > File > New > Surface

7)  Import Contours into the DTM: (This process was more completely described in The Zen Guide to InRoads Essentials reference book, published in 2003).

a.      Put a fence around all the contours

b.      File > Import > Surface > From Graphics

 i.      No Thinning 

 ii.      Densify to 10 (or some appropriate density that fits the level of site detail

 iii.      Check Results

c.      Verify the import by viewing Features in a "clean model"

d.      Triangulate the surface (Optional)

e.      Save (Save As) the Surface to ProjectWise

8)  Import Points into the DTM

a.      Put a fence around all the contours

b.      File > Import > Surface > From Grapics 

i.      Check Results

c.      Verify the import by viewing Features in a "clean model"

d.      Triangulate the surface

e.      Save (Save As) the Surface to ProjectWise

9)  Surface Data Clean-up (you will have to address any areas that do not accurately represent the topography that you are working with using one or all of the methods below.)

a.      Contours:

i.      Delete data (Contours) that should not be in the DTM (remove any contour data that you don't need or want)

ii.      Partial Delete data (Contours) that should not be in the DTM (there may be contours passing through buildings or other structures that shouldn't be used)

b.      Points:

 i.      Delete data (Points) that are inappropriate for the DTM (inaccurate spot elevations, zero elevations, or other elevational anomalies.)

c.      Breaklines:

i.      Add additional breaklines as needed (do this wherever you know something should exist because of your interpretation of the contours or because of your familiarity with the site itself.)

d.      Address any crossing segments in the DTM as needed

 i.      Surface > View Surface > Crossing Segments

ii.      Surface > Utilities > Resolve Crossing Segments

10)  Add any additional necessary breaklines:

a.      To define 'hard' edges where contours have been pieced together

b.      To refine the surface model where a toe or top of slope should occur

c.      At the out limits of the model where an edge should exist but currently doesn't

11)   Apply the InRoads > Surface > Utilities > Generate Inferred Breaklinescommand. (It's important not to generate the Inferred breaklines until the surface model contours and breaklines have been cleaned up. If the clean up is not done first then the inferred breaklines will connect themselves to any invalid contours or spot shots.)

12)  Compress the surface under InRoads > Surface > Utilities > Compress Surface

13)  Delete Triangles in any inappropriate areas of the model

14)  Add an Exterior Boundary to the surface model (See my InRoads Survey book, Appendix A for detail on this procedure.)

a.      View Perimeter

b.      Import from Graphics

c.      Triangulate

15)  Lock Triangles on the Surface Properties dialog box

16)  Save the Surface to ProjectWise

17)  If you have to lower the surface because of asphalt removal use the Surface > Edit Surface > Transform Surface tool

a.      Use Relative Elevation for the Method and define the 'delta' Elevation at the bottom right (-) (+)

b.      Select the Features to Include in the transformation

c.      Use the Surface > Utilities > Compare Surfaces tool, Interactive mode to verify the transformation

I hope this help a little.

Civilly yours,  

-zen