# Vertical points of intersection (VPI) entry method

To add an element to the alignment:

1. Select the Element. If you select:

   - Point, enter the Station and Elevation to define the VPI.

   - Circular arc, enter the Station and Elevation to define the VPI and enter the Radius of the circular arc.

   - Symmetric parabola, enter the Station and Elevation to define the VPI and enter the Length of the parabola.

   - Asymmetric parabola, enter the Station and Elevation to define the VPI and enter the In length and Out length of the parabola.

   The Slope in field shows the calculated slope value.

   The Length, K factorand Slope out fields update when the next element is added. The exact fields shown depend on the selected element.

2. Tap Store.

- A vertical alignment defined by VPIs must end with a point.
- When you edit an element, only the selected element is updated. All adjoining elements remain unchanged.