Non-collinear/coincident - what's the harm?

IR XM

Are there any destructive implications for running an alignment in the Roadway Designer that has non-collinear or non-coincident elements ? What is the inherent harm with having elements that don't check out OK in the Check Integrity tool? Is it just a best practice to have these elements perfectly coincident or collinear, or does it impact the design? Just curious...

BTW, I worked with a user who received those errors in some of his alignments, even though the start/end coordinates and bearings were the same. I cranked up the NE and Angular precisions to 7 places and found slight deviations. But I don't think that these minor tolerance problems would cause problems later in the process - could they?

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  • I try to avoid these but 7 decimal places would be a little extreme for any civil application. We usually run coordinates out 4 places but even then the surveyors can usually just get buy with 2 decimal places. The larger the discrepencey the more chance you have of coming up with odd errors in your roadway design though.

    I do not like to have either error but if I do I would rather have non-collinear because some times there is a need to have a slight angle point between a tangent and a curve especially if you have to work around existing structures.

  • I routinely have non-collinear alignments on edges of pavements and such where there is the need for the angle points also.  It seems to function fine in general.  Once I had a single cross section that had a point control that wasn't properly working...and I realized it was due to a tiny non-coincident point on the edge of pavement. 

    The only annoying thing is that IR won't allow editing of non-collinear alignments...why, I don't know.  I am not sure why the Add, Move, and Edit PI's won't work with non-collinear.

    As far as centerline geometry, I've always used cogo classic for 10 years now and have never had a geometric problem.  The ics input files provide good documentation to quality control how all geometry is established and related, control monuments used, etc.

    HTH.  Chris

     

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  • I routinely have non-collinear alignments on edges of pavements and such where there is the need for the angle points also.  It seems to function fine in general.  Once I had a single cross section that had a point control that wasn't properly working...and I realized it was due to a tiny non-coincident point on the edge of pavement. 

    The only annoying thing is that IR won't allow editing of non-collinear alignments...why, I don't know.  I am not sure why the Add, Move, and Edit PI's won't work with non-collinear.

    As far as centerline geometry, I've always used cogo classic for 10 years now and have never had a geometric problem.  The ics input files provide good documentation to quality control how all geometry is established and related, control monuments used, etc.

    HTH.  Chris

     

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