# Volume Presets

The Volume Definition Editor includes a **Preset** dropdown that populates the term builder with common volume configurations. Presets provide a quick starting point -- after applying a preset, you can modify the terms, change line selections, or add additional terms to customize the definition.

## Available presets

### Overbreak

Measures the excess excavation beyond the design template -- the area of the measured profile that extends outside the theoretical line.

- **Formula:** `Area(Excavation, Template)`
- **Term type:** Area (intersection)
- **Lines:** first measured line definition + first template line definition
- **Use case:** quantifying over-excavation for cost analysis and shotcrete consumption

```{note}
The intersection-based `Area()` function captures only the overlapping region. To measure specifically the area outside the template, use `DiffArea(Excavation, Template)` instead.
```

### Underbreak

Measures the area of the design template that was not excavated -- the violation zone where the measured profile falls inside the theoretical line.

- **Formula:** `Area(Template, Excavation)`
- **Term type:** Area (intersection)
- **Lines:** first template line definition + first measured line definition
- **Use case:** identifying zones where the tunnel profile does not meet the design specification

### Full Excavation

Measures the total area enclosed by the measured excavation profile.

- **Formula:** `EnclosedArea(Excavation)`
- **Term type:** EnclosedArea (single polygon)
- **Lines:** first measured line definition
- **Use case:** total cross-sectional area for material quantity estimation

### Shotcrete Thickness

Measures the area between two measured lines -- typically the excavation line and a shotcrete line. This represents the cross-sectional area of the applied shotcrete layer.

- **Formula:** `Area(Excavation, Shotcrete)`
- **Term type:** Area (intersection)
- **Lines:** first and second measured line definitions
- **Use case:** shotcrete volume computation for material tracking

```{tip}
For shotcrete thickness, the intersection of the two measured lines gives the area of the shotcrete layer. If you need the full ring between the two lines, use `DiffArea(Excavation, Shotcrete)` instead.
```

### Invert Area

Measures the area at the bottom of the tunnel section, below a specified elevation level.

- **Formula:** `EnclosedArea(Excavation)` with **Down** clipping level enabled at 0.0
- **Term type:** EnclosedArea (single polygon) with clipping
- **Lines:** first measured line definition
- **Use case:** invert concrete volume, drainage channel area

After applying this preset, adjust the **Down** clipping level to the actual invert elevation for your tunnel.

### Crown Area

Measures the area at the top of the tunnel section, above a specified elevation level.

- **Formula:** `Area(Excavation, Template)` with **Up** clipping level enabled at 0.0
- **Term type:** Area (intersection) with clipping
- **Lines:** first measured line definition + first template line definition
- **Use case:** crown shotcrete area, arch support zone analysis

After applying this preset, adjust the **Up** clipping level to the actual springline or crown elevation for your tunnel.

## Modifying presets

When you select a preset from the dropdown, it replaces the current term configuration entirely. The preset dropdown then resets to "Custom" to indicate that any further changes create a custom definition.

You can freely modify a preset after applying it:

- Change the line selections to reference different measured or template lines
- Add additional terms with the **Add Term** button
- Adjust clipping levels or the additive constant
- Switch the computation method between Applicable Length and Average Areas

## Creating custom definitions

If none of the presets match your needs, leave the preset dropdown on "Custom" and build the formula manually using the term builder. Common custom definitions include:

- **Net lining area:** `DiffArea(Final Lining, Excavation)` -- the designed lining zone
- **Combined area:** `Area(Excavation, Template) + DiffArea(Excavation, Shotcrete)` -- multiple terms combined
- **Side-specific analysis:** any term with Left/Right clipping to analyze one side of the tunnel independently