How can you edit terrain model by editing contour lines?

OpenRoads Designer Connnect Edition 2020 Release 3: I would like to edit a terrain model by editing the contour lines. Seems like the only way to edit terrain models is by editing triangles. Is this possible and if so, how? Thank you in advance.

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  • Robert is correct. There is an old POB article written by an Engineer/Surveyor (whose name escapes me) that summed it up in one precise statement: "Contours are Output and Not Input."

    There are many issues when contours are used as input. Ridge Lines and Valley Lines are not picked up, resulting in many zero slope areas where all three triangle points are on the same contour. Top and bottom edges of slopes are also not picked up with similar results. Saddles and localized high and low spots are also missed.

    Before InRoads had some of its enhanced surface and feature editing tools, I wrote a user command (think pre-VBA macro) that assisted in drawing 3D linestrings. Eventually, it was made part of an MDL called Civtools. It prompted for a starting elevation and a delta Z. Then. as you drew a linestring, point by point, it could assign automatic elevations to each point. With it, I could draw a very faithful DTM by drawing the 3D breaklines that would result in contours that matched my source data, and it took at least half the time it would ordinarily take to draw all the contours.

    Now, with Open Roads Tools, you can draw the 2D locations for the breaklines and then use the profiling tools to quickly assign elevations and to tweak them as needed.

    The goal of these tools is to accurately model a 3D design (or existing conditions) and when you do, accurate cross sections and contours will be one of the outputs. 

    I have used USGS DEM files to get my existing elevations with about a 10M or 30' spacing and had to flip triangle faces to try and get a good representation with well-formed ridges, valleys, ditches, etc.. There were times when the surface looked OK until you looked closely, and the contours had little zigzags (which the client apparently hated). The best surfaces come from 3D breaklines with occasional spot elevations to define local high and low spots.  


    Charles (Chuck) Rheault
    CADD Manager

    MDOT State Highway Administration

    • MicroStation user since IGDS, InRoads user since TDP.
    • AutoCAD, Land Desktop and Civil 3D, off and on since 1996
Reply
  • Robert is correct. There is an old POB article written by an Engineer/Surveyor (whose name escapes me) that summed it up in one precise statement: "Contours are Output and Not Input."

    There are many issues when contours are used as input. Ridge Lines and Valley Lines are not picked up, resulting in many zero slope areas where all three triangle points are on the same contour. Top and bottom edges of slopes are also not picked up with similar results. Saddles and localized high and low spots are also missed.

    Before InRoads had some of its enhanced surface and feature editing tools, I wrote a user command (think pre-VBA macro) that assisted in drawing 3D linestrings. Eventually, it was made part of an MDL called Civtools. It prompted for a starting elevation and a delta Z. Then. as you drew a linestring, point by point, it could assign automatic elevations to each point. With it, I could draw a very faithful DTM by drawing the 3D breaklines that would result in contours that matched my source data, and it took at least half the time it would ordinarily take to draw all the contours.

    Now, with Open Roads Tools, you can draw the 2D locations for the breaklines and then use the profiling tools to quickly assign elevations and to tweak them as needed.

    The goal of these tools is to accurately model a 3D design (or existing conditions) and when you do, accurate cross sections and contours will be one of the outputs. 

    I have used USGS DEM files to get my existing elevations with about a 10M or 30' spacing and had to flip triangle faces to try and get a good representation with well-formed ridges, valleys, ditches, etc.. There were times when the surface looked OK until you looked closely, and the contours had little zigzags (which the client apparently hated). The best surfaces come from 3D breaklines with occasional spot elevations to define local high and low spots.  


    Charles (Chuck) Rheault
    CADD Manager

    MDOT State Highway Administration

    • MicroStation user since IGDS, InRoads user since TDP.
    • AutoCAD, Land Desktop and Civil 3D, off and on since 1996
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