Adjust Linestring Elevation Command

alan.sharp · June 4, 2020, 12:53pm

Adjust Linestring Elevation

Command Licensing and Default Menu Location

The Adjust Linestring Elevation command is part of the RPS Data Prep Toolbox
The command is located on the Data Prep macros menu ribbon
The command is located in the Modify menu group

Command Description

Provides a quick and easy way to null out or modify VPIs on selected sections of 3D linestrings and to elevate curb and gutter lines to 3D planes or grading framework surfaces. Also provides an effective means to adjust linestrings to match grade at end points or any point in the linestring allowing for delta Z proration over a given distance.

Latest Changes

October 3rd 2022
The command has been completely redesigned to accommodate the new Plane, Surface and Spot modes of adjusting elevations. The existing functionality has been maintained but the user interface has changed to facilitate the additions that have been made.

The new Plane mode allows you to elevate curved sections of linestrings to a 3 point plane, ideal for accurately elevating curb and gutter lines and parking islands that lie on an inclined plane. The method allows you to subdivide arcs into equal segments or to utilize arc to chord settings to subdivide arc elements for elevating purposes. This approach also adds uniformity to the model building process.

The new Surface Mode allows you to elevate curved sections of linestrings to a selected grading framework surface that defines the planar slopes of a parking lot. The method allows you to subdivide arcs into equal segments or to utilize arc to chord settings to subdivide arc elements for elevating purposes. This approach also adds uniformity to the model building process.

The new Plane and Surface modes, eliminate the issues typically associated with elevating curb and gutter using provided elevation call outs that will generate small sags or crests in curb elements due to the linear interpolation methods used to elevate lines between provided 3D points along the line.

The new Spot mode allows you to quickly and easily add elevations to 3D lines as either VPIs or as Horizontal nodes with elevation. You can click and enter elevation values or click and then click an elevation text or other 3D object to define the elevation for the clicked locations.

Command Interface Description

The Adjust Linestring Elevation command dialog looks as follows

The command provides the ability to

Adjust the elevations of the selected line or lines over the entire length of the line or over a selected range of stations along the line (from and to locations).
The elevation adjustment can also be set to Constant, Range or None allowing variable height adjustments to be set over the range of the lines being adjusted. This is applied in addition (compounded solution) to the elevation changes being made.
You can also decide whether or not you want to lock in the elevation at the start and end of the adjustment range or allow it to float - using only the original VPIs or 3D nodes of the selected line(s) to control the vertical on the lines. When you lock the start or end location elevation, the elevation of those points on the line are determined from the original vertical geometry of the line and they are created as VPIs at the start and end locations. The first and last adjustment points are then determined 0.01’ or 0.001m in from those points on the line. When you do not lock the start or end locations, the start and end points are elevated using the adjustment mode selected, and they will connect to the adjacent VPI / elevation points outside the adjustment zone with a straight grade.

Take this simple line as an example (no adjustments applied

If we now apply an absolute adjustment to the elevations between 2 locations with locking applied at the start and end of the adjustment range. We are using an elevation constant of 115’ using a Location 1 and Location 2 for the start and end point of the adjustment range

If we undo that and then do it again and this time we remove the locks at the start and end point we will get this result

If we do the same thing again and this time we apply an elevation adjustment, the adjustment can be applied as None (no adjustment). Constant (a constant adjustment e.g. -2’ to remove a 2’ subgrade adjustment or Range where a value of adjustment is applied at the start and end of the adjustment range e.g. if you want a transitional subgrade adjustment you could add -2 at the start location and -4 at the end location to get a transition from -2 to -4 over the range of the linestring adjustment (this is what was applied below - you can see at the start point the elevation is 113 (115-2) and at the end it is 111 (115-4) and that there is a constant slope between the start and end points.

Now that we have explained the basics of Elevation adjustment and Elevations, we will explain the dialog controls and options in more detail

Elevation Mode

The adjustment of a linestrings elevation can be carried out using one of several options listed below

Absolute
Changes the selected station range of the line to a specified elevation with optional elevation adjustments as described earlier (None, Constant, Range)

Delta
Changes the selected station range of the line by a delta elevation from existing elevations at the start and end points of the selected range. Typically one end of the range will be adjusted to “match grade” and the other end will be locked at existing elevation with a zero delta providing a gradual change in elevation over the selected range allowing the adjusted end to match an existing or required grade. All elevation points of the source line will be adjusted on a prorated basis. For example if you want to modify the end elevation of a linestring to match existing grade while holding a node 200’ from the end of the line fixed yet hold the internal geometry of the selected line section, the Delta function will allow you to do that quickly and easily.

Before:

After a -1’ adjustment to start of line:

Plane
Changes the elevations of the curved sections of the selected station range of the source line to match the elevations defined by a plane created from 3 elevated points. The elevation points around the curved sections are computed using one of several options including number of intervals e.g. 4, arc to chord tolerance e.g. 0.02, angular interval e.g. 5 degrees or arc distance e.g. 2.0’ rather than the locations at which the arcs cross the triangle sides of the planar surface. This mode will typically be used to elevate the curved sections of curb and gutter lines in parking lot models.

Spot
Provides a quick and easy way to add elevations to 2D lines at provided spot elevation locations in the plans / CAD files. The elevation points can be created as VPIs (Vertical Points only on a linestring) or as Horizontal Nodes (3D nodes of a linestring in Horizontal control). Elevations can be entered by hand or can be selected by clicking on a piece of text or another 3D object that has the desired elevation.

Surface
Changes the elevations of the curved sections of the selected line or lines to the elevation of a surface model. The elevation points around the curves are defined using one of several options including number of intervals e.g. 4, arc to chord tolerance e.g. 0.02, angular interval e.g. 5 degrees or arc distance e.g. 2.0’ rather than the locations at which the arcs cross the triangle sides of the 3D surface. This mode will typically be used to elevate curved sections of curb and gutter lines in parking lot models to a grading framework surface that defines the engineers intended planar surface model for the parking lot.

Elevations - Adjustment mode

This function applies to all modes other than Spot mode. There are three options of adjustment available

None:
Applies no additional elevation adjustment to the computed elevations

Constant:
Applies a constant elevation adjustment to the computed elevations, allowing you to make a vertical adjustment to account for e.g. subgrade adjustments.

Enter the Constant value in the data entry field provided.

Range:
Applies a transitional adjustment between the selected start and end locations of the linestring adjustment process. You can enter a different value for the start and end points e.g. -2’ at the start and -5’ at the end and all vertical nodes will be adjusted by a prorated amount based on how far they are along the line from the selected start point.

Enter the adjustment value for the start and end of range positions in the data entry fields provided.

Elevations

This function applies to the Absolute mode only. There are three options of adjustment available

Constant
This allows you to enter a single elevation value that will be applied to the entire range (from start to end location) of the selected linestring. The end result will also depend on whether or not you select to Hold elevation at the beginning and or end of the range. If you Hold the elevations at the start or end locations, this will have the effect of putting a step up or step down to the entered constant elevation at that location. If you do not hold the elevations at the start or end locations then the start and end points will be adjusted to the constant elevation value entered (+/- the elevation adjustment being applied) and will connect to the previous (start) or subsequent (end) elevation point on the source line creating a slope in and out of the constant elevation portion of the line (as described earlier).

Range
This allows you to enter an elevation value at the start and end locations of the range selected allowing the line to slope between the start and end points of the range. The Hold elevation / No Hold elevation controls will have the same Step / Slope functions as described for the constant mode above. The elevation adjustment options can also be used to further adjust the elevations of the line.

Undefined
This allows you to set all of the nodes / VPIs of the line between the selected start and end locations to undefined elevation, the line will slope from the start to end location based on the elevations of those locations in the source line.

Linestring

Select the linestring or Linestrings (See All Below) that you wish to modify using the currently selected mode of adjustment.

You can turn on the show line direction markings using the button next to the line selector control.

If you activate the auto advance button on the line selector control (ON = orange tinge) you will not be asked to select a line after each execution - the process will assume that the next set of locations will be on the same line that you have currently selected.

Portion:
In this command all lines are treated in the same way, they have a Start Point, End Point and a Location (1 or 2) that can fall anywhere between the start and end point of the line.

You can choose to adjust a line in one of the following ways

All
From Start to Location
From Location to Location (1 to 2)
From Location to End

When you have selected the range of the line that you wish to adjust, select the locations in the Location range fields provided. Note that Start and End are already known and cannot be modified.

The All mode will select the line from its start to end point. Note that when you are in Surface adjustment mode, selecting All mode will allow you to select multiple lines (and their entire length) for the adjustment in one pass.

Hold elevation at the beginning of the range checkbox:
Check this checkbox if you want to lock the lines elevation at the original line elevation at that location. This will interpret the elevation of that point in the source line and add a VPI at that location with that elevation value to lock it in.

Hold elevation at the ending of the range checkbox:
Check this checkbox if you want to lock the lines elevation at the original line elevation at that location. This will interpret the elevation of that point in the source line and add a VPI at that location with that elevation value to lock it in.

Clear Linestring after applying changes checkbox:
Check this checkbox if you want to clear the current line selection after each execution in readiness for a new line to be selected. This works well when elevating islands in a parking lot to a Plane defined by 3 points, where each execution will expect a different line selection to be made, thereby stopping the command from applying a second set of corrections to the same line inadvertently.

In the following sections we will provide specific details for each adjustment mode along with a training video showing how each mode is designed to function.

Absolute Mode

This mode has been well covered by the documentation above. The video below shows how to use the Absolute Mode in detail.

Video Demonstration

Delta Mode

This mode has been well covered by the documentation above. The video below shows how to use the Delta Mode in detail.

Video Demonstration

Plane Mode

The Plane mode, as has been described earlier will elevate curved sections of a selected linestring range to a planar surface defined using 3 points.

When modeling curb and gutter lines in 3D, you will often be provided with elevation spots at the PC and PT points of the curves. In some cases you may also be provided with elevations at mid curve or interval points around the curve also. In the latter cases, the curve sections will be elevated correctly when using the PC, PT and mid curve points, however where you are provided with the PC and PT points only, you will often find that the elevations along the curve will not create the surface as intended by the engineer.

This is because the curve was designed to fall on a grade plane and the elevations have been interpreted at the PC and PT points only on that grade plane, however when interpreted just from the PC and PT points around the curve (how TBC interpolates elevations of a line between provided vertical controls on a line by linear interpolation) you will find that you get a small sag or crest in the curve vs the intended planar grade for the curve.

Take the following example

The parking island was designed to lie on a plane defined by a rectangle where the south side is at elevation 100 and the North side is at elevation 101.50. The arcs are 4’ radius, and the elevations at the PC and PT points are all computed correctly. However when you look at the surface model generated using just this line where all the elevations are correct, clearly shows a warping of the plane at each of the arc corners (the non linear nature of the color bands across the island. This is caused by the fact that the elevation interpolation for the line is along the line between the PC and PT points rather in the N-S and E-W axes of the plane that was used to define the island.

In this exaggerated oblique view of the island you can see the problem more clearly

The Plane mode and Surface mode of Adjust Linestring Elevation is designed to help you correct these issues on either individual elements (an arc return or a single island) (Plane Mode) or all lines of a parking lot to a grading framework surface (Surface Mode).

Filled out command dialog looks as follows

In this case we are using the following settings

Elevation adjustment = None (we are not making any additional adjustment to line elevations
Plane definition - requires 3 3D points to define the plane, so we selected three of the provided PC/PT points that define the plane (two on the North side and one on the South side of the island). When selecting the 3D points, if the locations are 2D you can enter an elevation or click a piece of text or a 3D object that provides the required elevation information.
Reset plane after adjusting linestring checkbox - if after each line execution you want to reset the plane and start over, check this checkbox. Leave the checkbox unchecked, if you will be adjusting multiple lines to the same plane.
Linestring - select the linestring representing the island. Note that this is already a linestring and that the PC / PT point elevations have already been applied to the line using the Spot Mode. If the line is e.g. a Polyline, you can convert it to a linestring using the Convert to Linestring command available from the command header bar icons.
For the Portion of the line to adjust we selected All
We are not holding any elevations at the start or end of the line, all 3D nodes that already exist are left unadjusted by this mode of the command, additional vertical controls are added between the PC and PT points if the PC and PT points are already elevated.
The clear Linestring after applying changes checkbox is currently unchecked, however if you are executing this process on multiple islands sequentially, we recommend that this checkbox is checked.
Arc Points mode is currently set to Number of Segments and that is set to 4. This will divide the arcs into 4 segments with VPIs at each of the segment end points. The more segments you use, the closer the curb line will be to the designers intended planar grade. You can choose Arc to Chord if you wish the number of segments to be increased with tighter radius curves and with longer curved sections. There are other modes also that allow you to subdivide by angle interval (in degrees of arc) or Arc distance (distance around the curve) as needed.

You click apply when the settings and controls are as you need them and the additional elevation points are added to the curves and the surface is updated according to those changes - see below.

You can clearly see that the warping at each curved corner has now been corrected and that the plane has now been supported through al of the arc sections through the addition of the extra vertical controls to the curved sections of the line. Note that the additional vertical controls are equally spaced around the curved sections resulting an more uniformity in the surface model created from the line.

In this second example (shown below) we are given spot elevations at the PT / PC on the bullnose of an island at the end of a parking bay and additional spot elevations at the IP point of the curves and then a further elevation point at the back of the parking bay. The intent of the engineer is clear that there is a slope of 0.4’ over the 20’ from the nose of the island to the back of the parking bay. The arc radius is 4’ so at the PC / PT points of the arcs not provided, the elevations should be 100.08 (4’ x 0.4/20), however if we query the line at those same locations having been elevated as provided, the elevation at those points is 100.11 i.e. 0.03 higher than the engineers intent. In addition that difference also shows up in the curved sections as a crest or sag in the same way as in the previous example.

So the filled out dialog for Plane mode in this example will look as follows

On execution the result is as shown below

Here is the colored elevation view of the island surface - again showing that the warping of the surface around the curved sections has been corrected.

Before correction

After correction

Video Demonstration

Spot Mode

The Spot mode has been developed to make elevating lines faster and easier than using the edit linestring command. The tool has less overhead to deal with when adding spot elevations to lines to convert them from 2D to 3D lines.

The command dialog looks as follows

Elevation Mode:
Select Spot mode from the pull down list of options.

Linestring:
Select the linestring that you wish to add spot elevations to. Note that if the line is not already a linestring, you will need to convert it to a linestring before you can add the spot elevations. Use the Convert to Linestring command from the command header bar to achieve that.

You can switch the line direction arrows On and Off using the show direction button at the end of the linestring selector field.

Set the Auto advance button at the end of the line selector field to enabled (orange tinge), that way each elevation entered will be for the same line until you change lines on completion of the line.

Location:
Click the location on the line that you wish to add an elevation.

Note that your Snap modes are going to be important in this process. Typically you will need End Point, Near Point and Intersection Point snaps running to create elevations at the correct locations along the line. Click Snap in the toggle buttons at the base of the graphics screen area of TBC to access the point snap modes.

Elevation:
Enter the elevation for the location that you selected, you can type in a value or click a piece of text that contains the value or click a 3D object that has the required elevation. You can also use the right click options to extract elevations from other lines or locations e.g. Along Line snap etc…

Use elevation formula checkbox:
If the elevations that are provided on the plans are e.g. for Top Back of Curb (TBC) and you are elevating e.g. Flow Line (FL) that is 0.5’ below TBC, you can enter an elevation formula {Z}-0.5 to auto correct the entered or clicked elevation values by -0.5’ automatically.

Auto apply on elevation change checkbox:
If the elevation that you enter or click is different from the previously entered value (at the last location) when this checkbox is checked, the elevation will be automatically applied on accepting the entry with Enter or clicking the elevation text etc. When not checked, you will press Enter to accept each value selected or entered. If there are two successive points with the same elevation value, you will need to press enter to accept the second value manually.

Point type:
When adding elevations to linestrings you have two options as to how the elevations are stored.

The first option is to store the elevation as a VPI (Vertical Point of Intersection) which is a location defined by distance along the line and elevation. These types of node have no horizontal XY location. These types of node will show up in the vertical tab of the linestring editor command.
The second option is to store the elevation along with an XY location i.e. it is stored as a 3D node in the line. If a node does not already exist in the source line at the clicked location, one will be created and the elevation applied. These nodes will show up in the horizontal tab of the linestring editor command.

Note: The VPI method stores the elevation based on distance along the line from the origin of the line. There are some situations in TBC where if the line length changes (caused by e.g. a joining of two lines or the editing of a line using grips that the position of the VPIs along the lines can change. Creating 3D nodes is a more secure solution to locking in both the location of the elevation points and the elevation of the locations.

User Tips

When you have completed elevating one line and you want to select a new line to start elevating, press the N key on your keyboard.

While moving along a line you can use the WASD keys to Pan the screen Up, Down, Left and Right rather than using your mouse controls.

Video Demonstration

Surface Mode

The Surface Mode has been created to elevate lines to a surface model, however in this process rather than draping the line over the surface model and elevating all of the straight and curved sections where the lines cross the Triangle sides of the surface model, we create a uniform number of points in the curved sections of the lines only to elevate the line to the surface but only the curved sections and only at the interval or arc to chord etc. locations.

This process has been created to improve modeling of curb and gutter lines in parking lots, where the engineers intended surface shape is defined by a “Grading Framework” that represents the planar surfaces and slopes intended by the engineer.

First step in this process is to visualize the engineers intent and to use the elevation call outs to draw the grading framework lines in 3D, and then to create a surface from those grading framework lines.

The second step is to elevate the Curb and Gutter lines to the grading framework surface which will ensure that the vertical shape of the curb lines is following the grading framework

Final step of the process is to use the multi offset line command to create the Flow Lines (FL) and Top Back of Curb Lines (TBC) from the Edge of Pavement Lines (EOP).

The command dialog looks as follows for the Surface Mode of operation

Elevation Mode:
Select Surface mode of operation

Elevation adjustment:
You can choose

None for no additional elevation adjustment
Constant for a constant elevation adjustment over the adjustment range of the selected line or over the entire length of all selected lines
Range to apply an elevation adjustment at the start of the line and a different adjustment at the end of the adjustment range to apply a transitional adjustment over the adjustment of a single line. The range mode makes little sense in most situations where you are adjusting multiple lines at the same time.

Elevation from surface:
Select the surface model from which the elevations will be determined. This will be the grading framework surface in most situations.

Linestring:
If you have the Portion setting below set to All then you will be able to select multiple lines here. If the Portion setting is set to Start to Location, Location to Location or Location to End you will only be able to select a single line here.

Portion:
The portion refers to the range of a line or lines that you want to adjust. The options are

All - the entire length of a line or a number of lines that you select
Start to Location - the start of the line to a point along the line
Location to Location - a range between two points along the line e.g. from station 300 to 600
Location to End - from a point along the line to the end of the line

The mode that you select here determines whether you can select a single line or multiple lines for adjustment at the same time. When All is selected you will be able to select multiple lines for adjustment. When All, or any of the other options is selected you can select a single line only for adjustment.

Hold elevation at the beginning of the range checkbox:
Check this checkbox if you want to lock the lines elevation at the original line elevation at that location. This will interpret the elevation of that point in the source line and add a VPI at that location with that elevation value to lock it in.

Hold elevation at the ending of the range checkbox:
Check this checkbox if you want to lock the lines elevation at the original line elevation at that location. This will interpret the elevation of that point in the source line and add a VPI at that location with that elevation value to lock it in.

Clear Linestring after applying changes checkbox:
Check this checkbox if you want to clear the current line selection after each execution in readiness for a new line to be selected. This works well when elevating islands in a parking lot to a Plane defined by 3 points, where each execution will expect a different line selection to be made, thereby stopping the command from applying a second set of corrections to the same line inadvertently.

Arc Points:
This will divide the arcs of the selected lines into a number of segments with VPIs at each of the segment end points based on the mode selected. The more segments you use, the closer the curb line will be to the designers intended planar grade.

You can choose one of the following modes to determine the intervals for each arc segment

None - this will not subdivide the arcs of the selected lines
Angle - this will subdivide the arcs into segments of equal angle e.g. 5 degrees
Arc distance - this will subdivide the arcs into segments of equal length e.g. 1.0’
Arc to chord - this will subdivide the arcs into segments where the chord is always less than a specified tolerance from the arc segment at its mid point. This increases the number of segments when the radius gets smaller or the arc gets longer.
Number of segments - this divides the arc into a defined number of segments of equal length e.g. 4 segments.

Note that with Angle and Arc distance mode, there will always be the potential for one segment that is shorter than the others, this is the “remainder” segment i.e. if the Arc angle of the source line is 92 degrees and you choose a 10 degree angle then one segment will be 2 degrees. Similarly if the Arc length is 103.5’ and you choose 10’ then one arc segment will be 3.5’ long.

Video Demonstration
In the following video we show how to create the Grading Framework lines and surface for a Parking Lot, how to build a surface model from those lines and then how to elevate the Curb and Gutter lines to that grading framework surface. We also show how to use the Multi-Offset Line command to create the other lines of the curb and how to make a surface from the overall results.

Use Case Notes

The location fields allow math functions, so for example for location 2 you could click on the end of the line to derive the lines total length and then enter -200 after the displayed value to move location 2 200’ back up the line.
The WASD keys are activated for panning the plan view while working in e.g. Spot mode for elevating linestrings.
The N key can be used to select a new line when working in Spot mode to change from one line to another without having to move the cursor over to the dialog area to click the line selection control.

Header Bar Commands

The following commands have been added to the header bar of the command dialog providing you with quick access to the tools that you will likely need when working with the adjust linestring command

Help
RPS Settings
Convert to Linestring
Edit linestring
Create Point
Break Line
Smart Join
Explore Object
New Profile View

Note that if you hold the Shift key down when you click the New Profile View command, the currently selected line will be computed in the plane of the currently open profile view allowing you to see two or more lines projected into the plane of the original line used to create the profile view.

Apply
When you tap apply, the linestring elevations will be adjusted and the command will ready itself for another selection set and repeat process execution. If you do not want to make a second selection and repeat the process tap Close to finish the process.

Close
Closes the command with no further execution.

Feedback and Enhancement Requests

If you would like to provide feedback on the use of the Adjust Linestring Elevation command or to request enhancements or improvements to the command please reply below!