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Building Widening Surfaces

  • 1.  Building Widening Surfaces

    Posted 09-19-2022 08:16

    Okay, so I'm trying to find the best way to build widening surfaces. These are projects where you have to project out the existing slope for the widening. I have all RPS tools and I know some of them are needed. For sure the offset slope command. 

    Here's my biggest pain point though. Usually we can't trust the engineer's original ground surface to be accurate to the field conditions created by the contractors actual survey. So, right now, the best method I've found is to require the contractor to topo two shots to project the slope of existing, but every 25'. If we do every 50' our surface is going to have 50' chords which will not fair well with the machine control. It won't match in the middle of those 50' chords. 25' is much better but also time consuming for the contractor, especially on large roadway projects. 

    Here is my thought: how can we use the engineer's existing shots, say every 50', combined with the vertical geometry of the engineer's OG surface? Also, how could we make it so they don't have to topo both spots on the road for the slope. Generally the engineer's surface is sufficient for the cross slope of the existing road, it's just the varying of the elevation as you go down the road and they used different control. So, can we easily extract the slopes from the OG surface, then adjust just the lines to the asbuilt survey, maybe just using the RPS "Adjust LS Elevation" command? Combine that with the RPS "Optimize Linestring" command maybe? So there is less data to work with? Engineer OG surfaces often have a lot of detail in them so elevating based on those surfaces creates a lot of VPIs. 

    I really can't figure out an efficient way to model widening jobs when it's all based off existing.



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    Adam Bower
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  • 2.  RE: Building Widening Surfaces

    Posted 09-19-2022 14:34
    Hi Adam,
    Take one of your "existing" Strings and convert it to the Alignment.
    Then in the Profile View you will see the vertical profile chorded every 50 freedom units of yours.
    Now in the alignment editor you can add new Vertical Alignment, this time try to run a manual best fit by applying vertical curves etc.

    Alternatively, export your shots with chainage (stationing) as Easting and with elevation as Northing. Reimport them to the Plan View and connect the dots.
    This way you can move Vertical Profile to the Plan View. In the Plan View you can use which ever "best fit" "optimize" "make it smooth" command that you prefer. Then by using Corridor -> Copy to Profile you can "move it back" to the profile view and this way recreate your new Vertical alignment without guess work.

    With this step done, create a corridor with your new VAL as centre Line, and slope node-to-node between two "existing strings".

    I hope that my answer doesn't violate the Code Of Conduct.



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    Marian
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  • 3.  RE: Building Widening Surfaces

    Posted 09-19-2022 14:45
    Regarding: Also, how could we make it so they don't have to topo both spots on the road for the slope?


    Draft two lines where you would expect your "slope shots" to be.
    Drape them onto OG surface using "vertices only"

    Now you have two lines that represent fragment of the OG, but most importantly, they have the same cross fall as OG.

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    Marian
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    Original Message