String Code Surface Extend

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Introduction

The String Code Surface Extend command is used to create a CSD Surface model related to a selected String, extending outwards from Code/s on that string. 

This functionality is extremely valuable in road reconstruction situations where it is required to widen out at existing (or design) grades - the String Code Surface Extend extends a surface outwards from any selected Code in the cross section (or left and right of a single code for Left/Right Side Method) , providing valuable surface information that designers can use in their Road design.

The String Code Surface Extend functionality would also prove critical in designing off ramps between grade separated roads, where it is required to extrapolate out the pavement crossfalls to match in the off-ramp to the roads at either end.

The String Code Surface Extend command is used to create a temporary model, from which other commands can obtain elevation information at a given (x,y) position.  This (x,y) position will usually be calculated from a given distance and offset on an alignment that is not the same as the alignment used to create the model.

The Surface Name created in this process is set by the designer and will have the prefix 'SE-' automatically added to the name, to easily distinguish it in the Surface Manager.

A key feature of this command is that it allows the designer to extend a surface beyond the Code/s selected.  There are three Side Method modes for controlling this:

• Both Sides
  • You select a code left and right of the centreline, and then offsets to extend a surface outside of these codes. 
  • You can elect to extend at the same crossfall as the section leading to that code, set your own crossfall or add/remove an amount from the calculated crossfall. 
• Left Side
  • You select a left code only, then an offst to extend outwards from that code.  You can also specify an offset to extend inwards from that code (toward the centreline)
  • You can manage the crossfall (both extending outwards and inwards from the code) by selecting to match the section crossfall leading to the code, specifying your own crossfall or adding/removing and amount to the calculated crossfall
• Right Side
  • You select a right code only, then an offst to extend outwards from that code.  You can also specify an offset to extend inwards from that code (toward the centreline)
  • You can manage the crossfall (both extending outwards and inwards from the code) by selecting to match the section crossfall leading to the code, specifying your own crossfall or adding/removing and amount to the calculated crossfall

In the images below, the highlighted part of the section view describes the surface extents for the both, left side and right side methods:

Both Sides	Left Side	Right Side

The surface created updates as the Road String is edited.

For Civil 3D users, the model can be exported to Civil 3D if desired using the   Export CSD Surface to Civil 3D command

String Code Surface Extend - Application to Road Reconstruction

This temporary model is particularly useful when it is required to widen road pavement by extending out from the existing roadway edge and match the existing road crossfalls (or set the crossfall). In this case the designer sets the centreline and edge of roadway elevations, then creates a String Code Surface Extend that extends outwards from the edge of roadway labels well beyond where the new design edge of roadway is required.

Any String can be draped onto this surface, or cross section Codes can be draped directly onto the surface (avoiding the need to create a String) to force the design edge of roadway to match the surface elevations of the String Code Surface Extend, thus guaranteeing the desired crossfall.

Details

Details of the form are as follows:

Models	All created models are listed here.  Users and add, select for editing and delete models from this list.
[List of String Code Surface Extend models]	Click on a named model to select it for edtiing or deletion.
Add Model	Create a new String Code Surface Extend model.  Edit using the Details on the right
Delete Group	Delete a selected String Code Surface Extend model.
Details	Establish the reference string, code/s and extensions to apply.
Model Name	Name the model (surface) to create.  The created surface will have 'SE-' appended to this name.
String	Select the String to use for creating the model.
Start	Type in or use the pick icon to set the start location on the alignment/string.
End	Type in or use the pick icon to set the end location on the alignment/string.
Side Method	Use the pick list to select the side/s to extend from.  Options are Both, Left Side or Right Side.  Image of inputs as shown below: Both Sides Left Side Right Side
Left Side	Extend options from the Code left of the centreline.
Code	Picklist to select the Code to extend from to create a surface model.
Extension	Type in an offset from the selected code.  Behaviour depends on the Side Method:   Both: Offset left of the Left Side Code by the value specified   Left: Offset left of the Left Side Code by the value specified   Right: Offset left of the Right Side Code by the value specified
Crossfall Method	Sets the crossfall to apply when extending from the Code.  Options are:   Code: Apply the crossfall by calculating the crossfall to the selected Left Code   Value:Type in the crossfall for apply   Code + Value: Apply the crossfall by calculating the crossfall to the selected Left Code, and add the Crossfall (%) input
Crossfall (%)	Type in a crossfall value to use in the extension of the code
Right Side	Extend options from the Code right of the centreline.
Code	Picklist to select the Code to extend from to create a surface model.
Extension	Type in an offset from the selected code.  Behaviour depends on the Side Method:   Both: Offset right of the Right Side Code by the value specified   Left: Offset right of the Right Side Code by the value specified   Right: Offset right of the Left Side Code by the value specified
Crossfall Method	Sets the crossfall to apply when extending from the Code.  Options are:   Code: Apply the crossfall by calculating the crossfall to the selected Right Code   Value:Type in the crossfall for apply   Code + Value: Apply the crossfall by calculating the crossfall to the selected Right Code, and add the Crossfall (%) input
Crossfall (%)	Type in a crossfall value to use in the extension of the code
Build Models	Create all Models listed.  Surfaces will be created for each Model.  Surfaces created will use the Model names and have prefix 'SE-' added.
Close	Close the form.