TPC allows you to insert vertical curves into any traverse. The elevations of the traverse points that fall between the BC (Beginning of Curve) and EC (Ending of Curve) are automatically updated according to their respective vertical curves.

When you work with vertical curves, you would like to:

- Automatically identify grade breaks that could require a vertical curve.
- Automatically assign the curve length based on the grade change.
- Compute a single vertical curve or compute all of them in the alignment.
- Specify the vertical alignment (station/elevation) for a traverse and automatically compute the vertical curves and tangent grades between the curves.
- Insert BC/EC points into the traverse.
- Allow unbalanced vertical curves (L1 not equal to L2).
- View the original vertical curve tangents along with the vertical curve.
- Label the vertical curves in a drawing.

The Vertical Curve View displays the vertical curve data associated with a traverse. You can enter VPI's (Vertical Points of Intersection), grades, stations, etc.

To access the Vertical Curve View, open a traverse and choose Windows | Vertical Curve View.

If your traverse (alignment) already has grade breaks in it, TPC can automatically identify the grade breaks and insert vertical curves with the appropriate lengths. This is typical of road design where you have identified the vertical tangents and are ready to refine the alignment with vertical curves.

- Station your alignment with points at specified intervals for tangents and curves. Only the elevations of existing points will be modified to conform to the vertical curves.
- From the Vertical Curves Screen, choose Edit | Update Vertical PIs.
- Enter the Min Change percent. This is the smallest change in grade that will be considered eligible for a vertical curve.
- Enter up to 5 grade change / curve length combinations. If a grade change equals or exceeds the Change value, the total curve length will be equal to the Length you specify. In the example shown here, a grade change of 7% would get a curve length of 100, while a grade change of 12% would get a curve length of 200.
- Choose OK.

TPC will insert the VPIs into the Vertical Curve Screen and compute all of the curve values. It will not update the traverse. You can choose to update the traverse based on the vertical curve values after you have had a chance to review and/or edit them.

*If you don’t specify any Change/Len combinations, the VPIs will still be identified, but no curve data will be inserted - you will need to enter the data for each curve manually.*

You can enter your own vertical curve information. If the traverse already has some vertical alignment, it will be overwritten (updated) by the information you enter here when you compute vertical curves. You can even update the elevations of the points on the tangents between the vertical curves.

- Highlight a blank line in the Vertical Curve View.
- Enter the station and elevation of the VPI, the curve lengths and grades. The BC, EC and their elevations will be updated automatically as you enter your data.

You can insert and delete VPIs or go back and change any of the values.

The VPIs are stored with the traverse data. If you save this survey, you can come back and review or edit your vertical curve information any time.

Once you have confirmed that the VPIs are where you want and the curve lengths meet the specifications of the project, you are ready to compute the elevations inside the vertical curves.

- Station the traverse so that you have points every 25, 50 or 100 units along the alignment. You can choose different intervals for horizontal tangents and curves/spirals.
- From the Vertical Curves Screen, choose Tools | Compute.
- If you want to insert the BC and EC for each curve, turn on [X] Insert BC/EC. You will also need to specify a tolerance. If an existing traverse point is already within the tolerance you specify, the BC or EC will not be added. If the BC or EC is inserted, it can be identified by a “BC” or “EC” in the Type column.
- Edit the options you want and choose OK.

One of the important rules of computing vertical curves is that only existing traverse points are adjusted. If an existing point lies within a vertical curve, its elevation will be adjusted based on its location (stationing) in the curve. If the traverse does not have any points between the BC and EC, no points will be added.

At times, you will want to update the tangent (constant grade) points, proportioning their elevations based on their distance from the previous EC and the next BC. In effect, this causes the entire vertical alignment of the traverse to be controlled by the VPIs in the Vertical Curve Screen.

- Choose Tools | Compute Vertical Alignment.
- Turn on [X] Update Tangents Between Curves.
- Choose OK.

You can update a single vertical curve or selected curves.

- In the Vertical Curve Screen, select the VPI(s) you want to compute.
- Choose Tools | Compute.
- Select the other options you want and choose OK.

If you use the Update Tangents options, the points on the tangents will be adjusted based on the vertical curve computations and grades.

If you update VPIs manually based on the grade breaks in the current traverse, L1 and L2 are assumed to be equal. You can, however, enter different values for L1 and L2.

If the values for L1 and L2 are different, the high or low point of the curve is still computed at the VPI station, but the BC and EC are computed at their respective distances (stations) from the VPI.

Vertical curves are viewed along with the profile for the traverse or alignment.

- Right click a blank spot in the Drawing View and choose Profile View. You may also need to choose View | Zoom | Zoom Extents.
- In the Miscellaneous tab, turn on [X] Include Vertical Curves.
- Choose OK.