5.4. Alignments and Profiles

5.4.1. Horizontal Alignments

A horizontal alignment defines the centreline geometry of a road, railway, pipeline, or other linear infrastructure project. The alignment represents the designed path in plan view (the horizontal plane) and serves as the reference axis for stationing, profile views, and cross-sections.

5.4.1.1. Geometry Elements

Every alignment is built from a sequence of geometric elements placed end-to-end. The alignment engine computes the precise geometry from PI (Point of Intersection) data that you provide.

Element	Description
Tangent	A straight segment connecting two consecutive PIs, or connecting a curve end to a PI. Tangents have constant bearing along their length.
Circular Curve	A constant-radius arc that rounds the angle between two tangents. Defined by the curve radius and the deflection angle at the PI. The curve produces a smooth transition from one tangent direction to the next.
Spiral (Clothoid)	An Euler spiral where curvature increases linearly with arc length. Clothoid spirals provide a gradual transition between a tangent (zero curvature) and a circular curve (constant curvature), or between two curves of different radii. Specified by either the spiral length (L) or the spiral parameter (A).
Spiral (Cubic Parabola)	A transition curve defined by the equation y = x^3 / (6RL). Used in some European road design standards. Like the clothoid, it can be specified by length (L) or parameter (A).

A typical alignment follows the pattern: Tangent - Spiral In - Circular Curve - Spiral Out - Tangent - … but simpler configurations (tangent-curve-tangent without spirals, or tangent-only) are also supported.

5.4.1.2. Creating an Alignment

There are two ways to create an alignment: interactively by picking PI points, or by converting an existing polyline.

Method 1 — ALIGNMENT command (interactive PI picking)

Type ALIGNMENT (alias ALG) in the command line, or choose Civil > Alignments > Create Alignment from the menu.
Click points on the canvas to place each PI (Point of Intersection). The first click places PI #1, the second places PI #2, and so on. A rubber-band preview line follows the cursor.
Right-click or press Enter to finish. The alignment is created and appears on the canvas with its default style.

The initial alignment has straight tangent segments only (no curves). To add curves and spirals, open the PI Table Editor (see below).

Method 2 — ALIGNFROMPOLYLINE command

Type ALIGNFROMPOLYLINE (alias AFP) in the command line.
Click on an existing polyline or line in the drawing.
The alignment is created using the polyline vertices as PI points. The original polyline remains unchanged.
If the polyline’s vertices carry differing elevations (a 3D polyline with real elevations, or a 2D polyline with per-vertex Z), IQcad asks Create vertical profile from vertex elevations? [Yes/No] <Yes>. Accepting it also asks for a Vertical curve length <0> applied to every interior PVI (0 keeps an angular profile).

Note

When the profile is built from vertex elevations, each PVI is placed at the station where the vertex projects onto the finished alignment, so elevations line up with station queries even where corner curves cut inside the sketched polyline. The profile can be refined afterwards with DESIGNPROFILE.

This is useful when you have already drawn the approximate route as a polyline and want to convert it into a civil alignment for further design.

5.4.1.3. PI Table Editor

The PI Table Editor is the primary tool for fine-tuning alignment geometry. Open it from the Civil ribbon > Edit PIs button, or by double-clicking an alignment in the Civil Toolspace.

The editor has two panels:

Left panel — Alignment list:

Shows all alignments in the drawing with their names.
New — creates a new empty alignment.
Delete — removes the selected alignment.
Rename — changes the alignment name.
Import — imports alignment data from ALM or PSIMO files.

Right panel — PI data grid:

Each row represents one PI. The following columns are available:

Column	Description
PI #	Sequential PI number (read-only).
Easting	X coordinate of the PI point. Editable.
Northing	Y coordinate of the PI point. Editable.
Radius	Radius of the circular curve at this PI (0 = no curve). Editable.
Spiral In	Length or parameter of the entry spiral. Editable.
Type (In)	Spiral type for the entry spiral. Choose from the dropdown: Clothoid L, Clothoid A, Cubic L, Cubic A.
Spiral Out	Length or parameter of the exit spiral. Editable.
Type (Out)	Spiral type for the exit spiral.
Deflection	Deflection angle at this PI (computed, read-only).
Tangent	Tangent distance from PI to curve start/end (computed, read-only).
Curve Length	Arc length of the curve at this PI (computed, read-only).
Station	Station value at this PI (computed, read-only).

After editing values, click Apply to rebuild the alignment geometry. The canvas updates immediately to show the new alignment shape.

Spiral types explained:

Clothoid L — specify the spiral by its arc length (L).
Clothoid A — specify the spiral by its parameter (A), where A^2 = R * L.
Cubic L — cubic parabola spiral specified by arc length.
Cubic A — cubic parabola spiral specified by parameter.

5.4.1.4. Editing vertexes graphically

Five commands edit alignment vertexes directly on the canvas. ADDPI (API), DELPI (DPI) and EDITPI (EPI) work on the alignment itself: pick the alignment (or pre-select it), then click to insert a PI into the nearest tangent segment, click an existing PI to remove it, or click an interior PI to edit its curve radius and spiral (current values shown as the defaults; end PIs have no curve to edit). ADDPI first prompts once for a default curve radius — and, if greater than 0, a spiral length and type — and applies those defaults to every PI clicked in the run; press Enter through the prompts for sharp radius-0 PIs. ADDPVI (APV) and DELPVI (DPV) work inside a profile view: each click adds a design-profile PVI at the clicked station and elevation, or removes the nearest one. All five repeat until Enter, and every click (or edit) is a single undo step. New PVIs are inserted with vertical curve length 0 — refine them afterwards with DESIGNPROFILE; PIs added with a default of radius 0 (or curves added later) can be refined afterwards with the PI Table Editor or EDITPI.

5.4.1.5. Alignment Properties

When an alignment is selected, the Object Inspector displays the following properties:

Property	Description
Name	The alignment name, displayed in the Civil Toolspace and used to link profile views and cross-sections to the alignment.
Style Name	The named alignment style that controls all visual aspects of the alignment on the canvas (see Alignment Styles below).
Start Station	Station value at the beginning of the alignment. Change this to shift the stationing (e.g., set to `1000` if the alignment starts at station 1+000).
Total Length	Total alignment length in drawing units (read-only).

5.4.1.6. Alignment Commands

Command	Alias	Description
`ALIGNMENT`	`ALG`	Create a new alignment by picking PI points interactively on the canvas. Click to place each PI, right-click or Enter to finish.
`ALIGNFROMPOLYLINE`	`AFP`	Create an alignment from an existing polyline. Click on a polyline to convert its vertices into alignment PIs; optionally builds the vertical profile from a 3D polyline’s vertex elevations.
`ALIGNREVERSE`	(none)	Reverse the direction of an alignment. The start becomes the end and vice versa; stationing is recalculated accordingly.
`ALIGNPROPS`	(none)	Display alignment properties (name, length, PI count, element list) in the command line output.

5.4.1.7. Alignment Styles

Alignment styles control every visual aspect of how an alignment appears on the canvas. Each alignment references a style by name via the Style Name property. Edit styles via Format > Alignment Styles… or right-click an alignment in the Civil Toolspace and choose Alignment Style….

The style editor has three tabs:

Tab 1 — Centerline & Ticks:

Setting	Description
Centerline visible	Show or hide the alignment centerline.
Centerline color / weight / linetype	Visual appearance of the centerline.
Major tick interval / length	Spacing and length of major station ticks (e.g., every 100 m).
Minor tick interval / length	Spacing and length of minor station ticks (e.g., every 20 m).
Tick color / weight	Visual appearance of station ticks.

Tab 2 — PI & Arrows:

Setting	Description
PI markers visible / color / size	Show PI points as markers on the alignment.
Show PI Details	When enabled, geometry tables are drawn at each PI showing the computed curve parameters (see PI Detail Tables below).
PI lines visible / color / weight / linetype	Show the tangent extension lines through each PI.
Direction arrows visible / interval / color / size	Show arrows along the centerline indicating the alignment direction.

Tab 3 — Labels:

Setting	Description
Text height / color	Base text properties for all labels.
Station labels (major / minor + offset)	Station values at major and minor tick marks.
PI labels (radius, tangent, deflection, spiral length + offset)	Curve parameter labels placed near each PI.
Curve labels (length, chord, degree + offset)	Arc geometry labels placed along curves.
Name label	The alignment name displayed at the start of the alignment.
Station equation labels	Labels at station equation points (if any).

Four built-in styles are provided: Standard (centerline, ticks, PI markers and PI lines), Centerline Only (ticks, PI markers, and arrows hidden), Design Phase (includes PI detail tables, PI lines, and full labels), and Empty (all components hidden — use to suppress an alignment from display without deleting it).

5.4.1.8. Alignment Label Styles

Labels are part of the alignment style (Tab 3 in the style editor). The following label categories can be independently enabled or disabled:

Station labels — placed at major and minor tick positions along the centerline. Major labels show the full station value (e.g., 0+100.000); minor labels show an abbreviated value. The label offset controls how far the text sits from the centerline.
PI data labels — placed near each PI marker. They can show radius, tangent distance, deflection angle, and spiral lengths. Useful during design to see curve parameters directly on the plan.
Curve data labels — placed along circular curve arcs. They can show curve length, chord length, and degree of curvature.

All label text respects the text height and color settings from the style.

5.4.1.9. PI Detail Tables

When Show PI Details is enabled in the alignment style, geometry tables are drawn at each PI showing the computed parameters:

Start / End PIs — PI number and coordinates (X, Y).
Symmetric curves (equal entry and exit spirals) — single column showing: deflection angle, radius, arc length, spiral parameter (A), spiral length (L), shift (epsilon), and tangent distance (T).
Asymmetric curves (different entry and exit spirals) — two columns showing A1/A2, L1/L2, epsilon1/epsilon2, and T1/T2.

Tables are placed on alternating sides of the alignment with leader lines connecting the table to the PI point. Tables auto-hide when you zoom out and PIs are too close together on screen, keeping the display uncluttered.

The tables take the colour of the alignment’s PI layer, or the style’s PI marker colour when that layer is left at its default, so they read on the black model background and on the white sheet of a layout alike. They are part of the plot: a layout exported to PDF draws the same tables, with the auto-hide rule measured on paper instead of on screen.

5.4.1.10. Import Formats

Alignments can be imported from several external formats:

Format	Description
LandXML	International standard for civil engineering data exchange. Imports horizontal geometry (lines, curves, spirals) and vertical profile. Use File > Import LandXML.
ALM	Alignment Solver format. Reads both geometry elements and PI data including spiral parameters. Use the Import button in the PI Table Editor.
PSIMO	Greek road design format (`.S01` for horizontal, `.S02` for vertical alignment). PI-based with spiral parameters. Use the Import button in the PI Table Editor.

5.4.1.11. Station Format

Station display format is configurable in Civil Settings (Civil ribbon > Settings):

Station Index Increment — 1000 for metric notation (e.g., 0+300.000) or 100 for imperial notation (e.g., 3+00.000).
Station Precision — 0 to 4 decimal places.

5.4.2. Profile Views

A profile view is a graph that shows elevation along the length of a reference line. The horizontal axis represents station (distance along the alignment or polyline), and the vertical axis represents elevation. Profile views are used to visualise existing ground levels, design vertical alignments, and compare surfaces.

Profile views can contain two types of profiles:

Sampled profiles — elevation data sampled from a TIN surface along the alignment at regular intervals. These represent existing conditions (e.g., natural ground, rock surface).
Design profiles — manually defined vertical alignments consisting of PVI (Point of Vertical Intersection) points connected by straight grades and optional vertical curves.

5.4.2.1. Creating a Profile View

Method 1 — CREATEPROFILEVIEW command (from alignment)

Use this when you have an alignment and want to see how it crosses one or more surfaces.

Type CREATEPROFILEVIEW (alias CPV) in the command line, or choose Civil > Profile > Create Profile View.
If multiple alignments exist, type the alignment name or click on it. If only one alignment exists, it is selected automatically.
Optionally select a surface to sample. Press Enter to skip if you only want to show a design profile.
Click a point on the canvas to place the profile view.

The command creates a profile view entity at the insertion point. If a surface was selected, the existing ground profile is sampled automatically and displayed as a line in the view. If the alignment has a vertical profile (e.g., imported from LandXML), a design profile is also added.

Method 2 — QUICKPROFILE command (from any line or polyline)

Use this for a quick elevation check along any line or polyline, without needing a formal alignment.

Type QUICKPROFILE (alias QP) in the command line.
If multiple surfaces exist, type the surface name or click on it. If only one surface exists, it is selected automatically.
Click on a line or polyline in the drawing.

The command samples the selected surface along the line/polyline and creates a profile view near the selected entity. This is the fastest way to see a terrain profile.

5.4.2.2. Creating a Design Profile

A design profile represents the proposed vertical alignment (the road grade line). To create one inside an existing profile view:

Type DESIGNPROFILE (alias DP) in the command line.
Click on a profile view in the drawing to select it.
Click points inside the profile view to place PVI (Point of Vertical Intersection) points. Each click defines a station and elevation.
Right-click or press Enter to finish placing PVIs.
For each interior PVI (not the first or last), you are prompted for a vertical curve length. Enter 0 for a sharp grade break, or a positive value for a smooth parabolic vertical curve.

The design profile is added to the profile view and drawn as a line.

5.4.2.3. Profile View Properties

When a profile view is selected, the Object Inspector displays the following properties:

Property	Description
Name	Display name of the profile view.
AlignmentName	Name of the source alignment (read-only for alignment-based views).
Title	Title text displayed above the profile view grid.
StartStation	Start station of the horizontal axis.
EndStation	End station of the horizontal axis.
DatumElevation	Bottom elevation of the vertical axis.
TopElevation	Top elevation of the vertical axis.
ViewWidth	Width of the profile view on the canvas (in drawing units).
ViewHeight	Height of the profile view on the canvas (in drawing units).
VerticalExaggeration	Ratio that stretches the vertical axis relative to the horizontal. A value of `5` means 1 m of elevation is drawn as 5 m on screen. Useful for seeing subtle grade changes on long alignments.
MajorGridX / MinorGridX	Major and minor grid line spacing on the horizontal (station) axis.
MajorGridY / MinorGridY	Major and minor grid line spacing on the vertical (elevation) axis.
GridColor / MinorGridColor	Colors for major and minor grid lines.
ShowAxisLabels	Show or hide station and elevation labels along the axes.

Profile views update automatically when the source alignment PIs are edited or when a source polyline is modified (for quick profiles).

5.4.2.4. Profile View Commands

Command	Alias	Description
`CREATEPROFILEVIEW`	`CPV`	Create a profile view from an alignment and optionally sample a surface along it.
`QUICKPROFILE`	`QP`	Create a quick profile view by sampling a surface along any line or polyline in the drawing.
`DESIGNPROFILE`	`DP`	Add a design profile (vertical alignment) to an existing profile view by clicking PVI points.

5.4.3. Alignment Editor

Open with Civil › Alignment › Edit Alignment PIs… or the ribbon’s Alignment dropdown.

The editor has two tabs:

Horizontal — PI table with Easting, Northing, Radius, Spiral In/Out, computed Deflection, Tangent, Curve Length, and Station. Start Station field at the top sets the initial chainage.
Vertical Profile — VPI table with Station, Elevation, CurveLength, computed Grade (%) and K-Value. Add/Delete VPI buttons.

Import — the Import button is the single entry point for alignment files:

ALM format — reads horizontal PIs, vertical VPIs, start station, superelevation, offsets, widenings, cant, and rail data.
PSIMO format (.S01) — reads horizontal and vertical alignment data.

After import, if a vertical profile is found, the editor offers to create a Profile View entity in the drawing.