Road Cross-Section Coordinates
Calculate the signed offsets and elevations of lane and shoulder edges from a centreline and user-entered dimensions.
Check a proposed section before transferring its break points into CAD. The diagram, coordinate table and CSV share the same results.
- •ERA Geometric Design Manual (2013), Chapter 6 §§6.2–6.3, cross-section context
- •Highway designers
- •CAD technicians
- •Engineering students
Rise = width × crossfall / 100Width and rise are in metres. Crossfall is in percent, positive when elevation increases moving outward.Use these outputs for preliminary checks. They do not constitute official engineering approval. Verify the inputs, method and results against the project criteria before using them for design or construction.
Section inputs
Enter widths in metres. A negative crossfall falls away from the centreline on either side.
Section coordinates
Scroll the table sideways to see every column.
| Side | Point | Offset (m) | Rise from centreline (m) | Elevation (m) |
|---|---|---|---|---|
| left | Shoulder edge | -5 | -0.13 | 99.87 |
| left | Lane 1 edge | -3.5 | -0.07 | 99.93 |
| centre | Centreline | 0 | 0 | 100 |
| right | Lane 1 edge | 3.5 | -0.07 | 99.93 |
| right | Shoulder edge | 5 | -0.13 | 99.87 |
Cross-section method and worked example
Begin at the centreline. For each side, accumulate widths outward to locate the next edge. Add width × crossfall ÷ 100 to the previous elevation. Use negative offsets on the left and positive offsets on the right. Crossfall has the same outward sign convention on both sides.
With a centreline elevation of 100.000 m, a 3.5 m lane at −2% falls 0.070 m to 99.930 m. A further 1.5 m shoulder at −4% falls 0.060 m to 99.870 m. In the symmetric example the lane edges are at ±3.5 m and the shoulder edges are at ±5.0 m. If only the right lane crossfall changes to +2%, its edge rises to 100.070 m. A zero crossfall preserves the previous elevation.
ERA Geometric Design Manual with appendices 080213.pdf (2013), Chapter 6 §§6.2–6.3, printed pages 6-1–6-2, PDF indices 82–83 (zero-based), provides the lane and shoulder context. The coordinate calculation is a geometric derivation. The worked dimensions are synthetic. The tool handles one section with up to eight lanes and one optional shoulder per side. Project criteria, median geometry, daylighting and quantities require separate checks.
Check side, units and the elevation datum before transferring the CSV to a drawing. For a related coordinate-order and datum workflow, see the survey point and surface tutorial.